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Gravid oviposition sticky trap and dengue non-structural 1 antigen test for early surveillance of dengue in multi-storey dwellings: study protocol of a cluster randomized controlled trial

Gravid oviposition sticky trap and dengue non-structural 1 antigen test for early surveillance of... Background: Dengue is a global disease, transmitted by the Aedes vectors. In 2018, there were 80 615 dengue cases with 147 deaths in Malaysia. Currently, the nationwide surveillance programs are dependent on Aedes larval surveys and notifications of lab-confirmed human infections. The existing, reactive programs appear to lack sensitivity and proactivity. More efficient dengue vector surveillance/control methods are needed. Methods: A parallel, cluster, randomized controlled, interventional trial is being conducted for 18 months in Damansara Damai, Selangor, Malaysia, to determine the efficacy of using gravid oviposition sticky (GOS) trap and dengue non-structural 1 (NS1) antigen test for early surveillance of dengue among Aedes mosquitoes to reduce dengue outbreaks. Eight residential apartments were randomly assigned into intervention and control arms. GOS traps are set at the apartments to collect Aedes weekly, following which dengue NS1 antigen is detected in these mosquitoes. When a dengue-positive mosquito is detected, the community will be advised to execute vector search-and-destroy and protective measures. The primary outcome concerns the the percentage change in the (i) number of dengue cases and (ii) durations of dengue outbreaks. Whereas other outcome measures include the change in density threshold of Aedes and changes in dengue-related knowledge, attitude and practice among cluster inhabitants. Discussion: This is a proactive and early dengue surveillance in the mosquito vector that does not rely on notification of dengue cases. Surveillance using the GOS traps should be able to efficiently provide sufficient coverage for multistorey dwellings where population per unit area is likely to be higher. Furthermore, trapping dengue-infected mosquitoes using the GOS trap, helps to halt the dengue transmission carried by the mosquito. It is envisaged that the results of this randomized controlled trial will provide a new proactive, cheap and targeted surveillance tool for the prevention and control of dengue outbreaks. Trial registration: This is a parallel-cluster, randomized controlled, interventional trial, registered at ClinicalTrials.gov (ID: NCT03799237), on 8th January 2019 (retrospectively registered). Keywords: Aedes, Mosquito, Dengue, Dengue NS1 test, Gravid oviposition sticky trap, Cluster randomized controlled trial, Surveillance * Correspondence: [email protected]; [email protected] Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia Full list of author information is available at the end of the article © The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 2 of 12 Multilingual abstracts potential, many of such interventions/products are still Please see Additional file 1 for translations of the ab- under trial [13–17]. Urgent and effective strategies for stract into the five official working languages of the vector surveillance/control are required pending the re- United Nations. sults of the aforementioned trials, since their assess- ments are highly time-consuming. In this matter, Background community support must also be sought. Ultimately, re- Dengue is a major mosquito-borne viral disease world- gardless of whether these novel techniques will eventu- wide, especially in the tropical and sub-tropical coun- ally be implemented, vector surveillance remains an tries. Aedes mosquitoes (mainly Ae. aegypti and Ae. indispensable component of dengue control. Vector sur- albopictus) are the vectors of the disease. Globally, some veillance should be routinely and thoroughly conducted 390 million dengue cases occur annually, 96 million of to prevent dengue epidemics. The World Health which are clinically apparent [1]. In Malaysia, a total of Organization (WHO) has called for the development of 80 615 cases of dengue with 147 deaths were reported in integrated national vector surveillance and health infor- 2018. During the same year, the state of Selangor re- mation systems to guide vector control measures [18]. ported the highest number of cases (45 349 cases) and Many traps of different designs have been tested for deaths (41 deaths) [2]. Subsequently, within the first ten mosquito surveillance [19–21] and the use of sticky weeks of 2019, Selangor accounted for more than half traps to lure and trap gravid adult Aedes females for vec- (16748) of the 28 936 dengue cases in Malaysia [3]. tor surveillance/control appears to be promising in a At present, anti-dengue drugs are not available, while number of countries [22–28]. Moreover, dengue non- dengue vaccine is not efficacious enough to act as a structural antigen 1 (NS1) rapid test is a simple and reli- standalone intervention [4]. Additionally, the current able tool for detecting dengue in mosquitoes caught by vector surveillance/control measures – which are the the sticky traps [27, 29]. In a preliminary study con- hallmark of dengue control programs in many Southeast ducted in an urban area in Selangor, Malaysia, infected Asian nations, including Malaysia [5], usually involve Ae. aegypti mosquitoes could be obtained from sticky house-to-house larval surveys, source reductions, larvi- non-insecticidal gravid oviposition sticky (GOS) traps ciding, and fogging, all of which are riddled with down- [26]. The use of the GOS traps and dengue NS1 rapid sides like non-relevance [6], cost- and labor- test kits allowed the rapid detection of dengue in the intensiveness [7], lack of community participation, as trapped mosquitoes, unlike the more sophisticated re- well as resistance of mosquitoes to insecticides [8–11]. verse-transcription PCR (RT-PCR). Accordingly, the The fact that asymptomatic, dengue-infected individuals health personnel involved in the study have found both are able to spread the disease has also been largely ig- instruments to be an easier method of dengue surveil- nored [12]. These are the likely reasons for the alarming lance rather than labor-intensive larval surveys. Subse- rise in dengue epidemics and the struggle to control quently a prospective, longitudinal phase 2 study found them. Accordingly, proactive and sensitive methods dengue cases to occur around one week following the which facilitate the early detection of dengue are desper- detection of infected mosquitoes, with a peak lag of 2–3 ately needed to pre-empt dengue outbreaks. weeks [27]. Thus, this method of surveillance is likely to Besides the mentioned flaws of the dengue control be feasible for incorporation into dengue control pro- program, the correlations of larval indices/adult mos- grams. Also, control methods such as search-and-des- quito emergence with dengue cases and the proportion troy measures, should be initiated whenever positive of people who seek medical care post-infection are poor mosquitoes are detected. In short, GOS traps and rapid [6]. Furthermore, due to the passive nature of the dengue NS1 detection in mosquitoes offer a potentially current surveillance system, vector control activities comprehensive, early-warning surveillance system that is mainly prevent further transmission of dengue from capable of pre-empting the occurrence of dengue index cases rather than eliminate the disease. Therefore, epidemics. the existing, reactive programs lack sensitivity and pro- Hence, the current phase of the research is aimed to activity, and hence lack the ability to curb dengue epi- determine if this adult Aedes surveillance/control demics. In view of all these shortcomings, more sensitive method (using GOS traps and dengue NS1 antigen test) and proactive methods involving the early detection of can actually reduce the occurrence of dengue outbreaks. dengue that can potentially stave off dengue outbreaks The proposed novel approach entails the active monitor- are desperately needed. ing of adult Aedes populations using easily constructed, Although novel techniques, such as the release of gen- inexpensive, reusable traps as well as rapid dengue-diag- etically-modified mosquitoes (release of insects carrying nostic kits. Vector surveillance is required to detect dominant lethality; RIDL) and the use of Wolbachia bac- changes in vector abundance, evaluate control pro- teria to control Ae. aegypti populations, have great grammes, obtain spatial and temporal information of Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 3 of 12 vector populations, as well as facilitate timely evidence- The study procedure is demonstrated in Fig. 1. based interventions. In resource-limited settings, vector control/surveillance practices must be both efficient and Study setting efficacious [30]. If this paradigm is proven to be effect- This trial is conducted at Damansara Damai in ive, a very viable alternative for curbing dengue will be Petaling Jaya Utara 10 (3.1930°N, 101.5923°E), Petal- made available not only to Malaysia, but to other low- ing district, Selangor, Malaysia (Fig. 2). Of the nine to-middle-income countries as well. districts, Petaling district is the major contributor to the dengue cases in Selangor [3]. Following discus- Design sions with the Petaling Jaya City Council, Damansara Aims Damai was chosen in view of its “closed” area (there This parallel-cluster randomized controlled trial is de- is only one main entrance and exit to this area), its signed with the aim of measuring the efficacy of a new, status as a dengue hotspot and it having sufficient proactive paradigm (i.e. GOS traps and dengue NS1 number of high-rised apartments. rapid tests) to (i) reduce the occurrence of dengue cases In 2018, Damansara Damai has approximately 61 615 vis-à-vis conventional vector surveillance measures; (ii) inhabitants in an area of 3.45 km , translating into a provide the community with early information of dengue population density of approximately 17 859 inhabitants/ transmission in the area, which will in turn provide km (Development Planning Department, Petaling Jaya more time for concise mitigative plans to be adminis- City Council, personal communication). There were 278 tered onto the community by public health authorities; and 227 dengue cases reported respectively in 2018 and as well as (iii) be workable and well-received by the 2017 in this area (Vector Control Unit, Petaling Jaya City management and residents of the housing areas. If its ef- Council, personal comunication). Eight apartments were ficacy and practicability are proven, efforts will be under- selected to be included in the cluster randomized con- taken to effectuate major revamps to the existing trolled trial that is being carried out for 18 months. standard operating procedures through the Ministry of Health Malaysia and other policy makers. Additionally, a Sample size dossier will be submitted to the WHO for adoption by The sample size was calculated based on that for a clus- Southeast Asian countries. ter randomized trial [31] using the Stata 13 statistical Fig. 1 Flow chart of study procedure 7 Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 4 of 12 Fig. 2 Map of study site. Insert: map of Selangor showing the study sites (apartments) in Damansara Damai, Petaling District software (StataCorp, Texas, USA) [32]. The likely inci- Harmoni Apartment, Bayu Apartment, and Park Avenue dence and spatial variation of dengue were determined Condominium were assigned to the intervention arm with reference to the number of confirmed cases in se- while Vista Apartment, Indah Apartment, Lestari Apart- lected localities in Selangor from 2013 to 2017 (Vector ment, and Permai Apartment the control arm. In the Control Unit, Petaling Jaya City Council, personal com- event that an apartment declines to participate or drops munication). Specifically, the variations between local- out of the trial, an apartment which had similar numbers ities in each year were utilized as a guide to estimate the of cases per 1000 units and cases per block will be chosen extent of variations between trial clusters. Each cluster as a replacement. The participants (residents/apartments) contained apartment blocks with similar population and the researchers are not blinded to the intervention. sizes. The minimum sample size required to detect a 60% reduction of dengue in the intervention arm with a Recruitment power of 80% is 20 blocks per arm. From there, the sam- Following the receipt of ethical approval from the Uni- ple size was inflated by 20%. Accordingly, a total of 48 versity Malaya Medical Center Medical Research Ethics blocks is required for the study. Committee, meetings were conducted with the joint For the interventional trial, it was estimated that on management body (JMB) of each apartment, during average, each housing unit will have 2% risk of dengue which written approvals were obtained for house-to- per year. To test the ability of the intervention to reduce house visits as well as deployment of GOS traps. The the number of dengue cases, a sample size of 5710 units JMB is in charge of the management and maintenance (2855 per arm) is required to achieve 80% power at an of an apartment. Concurrently, a complete schedule for alpha of 0.05 (assuming a 50% risk reduction at the end the replacement of the GOS traps was given to the JMBs of the intervention). in an attempt to promote the involvement of the com- munity in the study. Approvals from each JMBs were re- Randomization ceived at different time. Nonetheless, upon receipt of the Initially, eight apartments with 7889 residential units in first approval, the trial started in week 40 of year 2018. a total of 75 blocks were randomly selected and random- All selected apartments provided their consents except ized into the intervention and control arms. Individual for Bayu Apartment. Consequently, Impian Apartment apartment was the item of randomization. The apart- which had similar number of cases per 1000 units and ments were keyed into Microsoft Excel 2010 (Microsoft, cases per block, as well as similar apartment design as Washington, USA), following which they were randomly Bayu Apartment was chosen as the replacement. The de- allocated to the intervention and control arms using tails of the finalized apartments in both arms are pre- computer-generated numbers. Initially, Suria Apartment, sented in Table 1. Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 5 of 12 Table 1 Characteristics of the study arms and the number of traps in each apartment No. blocks Total No. of units No. of floors No. of floors with No. of individual stairway No. traps in Total No. (residential units) in each block traps in each block leading to residential units each block traps Intervention Suria 8 767 (444) 5 2 6–812–16 114 Harmoni 19 2380 (2356) 5 2 NA 6 114 Park Avenue 2 316 (316) 17/18 6 NA 16–17 33 Impian 6 668(660) 5 2 NA 6 36 Total 35 4131 (3776) Control Vista 15 920 (736) 5 1–25–73–566 Lestari 9 2002 (1982) 5–15 2–6NA 2–625 Indah 2 120 (120) 5 2 NA 2 4 Permai 12 1379 (1365) 5 2 NA 2–328 Total 38 4421 (4203) No. Number, NA Not applicable Eligibility criteria 0.375) and is reusable, except for the brown sticky paper All the residents/residential units of the eight sampled which has to be replaced weekly. apartments are eligible for this study. Additionally, people Traps are placed where it is shaded and protected who work at the study sites for at least 40 h per week are from rainfall, and ideally at locations where it is dark also eligible. They are approached via the JMB of each and away from human traffic. The GOS traps are de- apartment, door-to-door visits or community-based ployed continuously and changed weekly for 18 months. events (like clean-ups and annual general meetings). All The placement of traps and the number of traps de- individuals who are 18 years old and above and able to ployed are shown in Table 1. The placement of traps provide informed consent are recruited. Conversely, those varies according to the designs of the individual apart- who are aged below 18 years and unable to provide in- ments. For the intervention arm, GOS traps are placed formed consent are excluded. at the corridors of each block. Generally, for the apart- ments with common corridors, three traps are placed not more than 45 m apart at the corridors at every three Intervention floors (two at each end and one in the middle) [18], Dengue control activities still take place as per the starting from the floor with residential units. As an ex- Ministry of Health’s vector control measures in both ample, a 5-storey block will have traps at two of its intervention and control arms throughout the trial. floors (Ground/Mezzanine and third floor), amounting The measures may consist pyrethroid-fogging at the to a total of six traps per block. There are a few excep- apartments where new dengue cases are reported. tions: (i) If a block has five floors, and residential units Larval surveys may also be conducted depending on are not found starting from the ground floor but the first the severity of the outbreaks and the availability of floor, traps will be set on this floor and on the 3rd floor; manpower [33]. (ii) For the shop apartments (Suria), two traps will be placed on every stairway (Mezzanine/1st floor and 2nd/ Placement of GOS traps 3rd floor) leading to the residential units; (iii) For floors A detailed description of the GOS trap is provided in which are short i.e. corridor is less than 25 m in length reference [18] where it was initially tested as an Aedes (in Park Avenue), only two traps are set on the said surveillance tool for dengue control [18]. In this trial, floors. A manpower of four is enough to cover 19 blocks the outer black container is a 700 ml black, round poly- of an apartment within one hour. propylene plastic container (Diameter 110 mm × Height 87 mm). While the inner container is a 280 ml clear, Detection of dengue non-structural 1 (NS1) antigen in round polypropylene plastic container (Diameter 110 pooled Aedes mosquitoes trapped by the GOS traps mm × Height 46 mm). All traps are filled up till the bot- During collection of the GOS traps, they are examined tom of the inner container with 10% hay infusion water for trapped Aedes and Culex mosquitoes. The numbers made from 1-week-old hay infusion [34]. Each trap costs of missing sticky papers of the traps in each block will about Malaysian Ringgit (MYR) 1.50 (US dollar [USD] be recorded. The Aedes mosquitoes will be identified to Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 6 of 12 species level, and the numbers of each mosquito species single floor/stairway may have zero to two traps. As an of interest in each trap will be recorded. However, only example, a five-storey block in the control arm will have female Ae. aegypti and Ae. albopictus mosquitoes will be two traps (which corresponds to one-third of the six processed as described below. traps to be placed if the block is in the intervention arm) The abdomens of the Aedes mosquitoes will be separated set randomly at either one (Ground/first/Mezzanine or from the thoraxes and pooled. Each head-thorax will be third floor) or two floors (Ground/first/Mezzanine and kept in individual 1.5 ml tubes and stored at − 20 °C. The third floor) of the block. pooled abdomens will be homogenized and tested for the presence of dengue NS1 antigen using the SD Biosensor Outcomes Standard Q Dengue NS1 test kit (Gyeonggi-Do, South The primary outcome of the trial will be measured in Korea). When an abdomen pool is positive, the same test terms of the percentage change in the (i) number of will be repeated for each corresponding head-thorax in an dengue cases and (ii) durations of dengue outbreaks be- attempt to identify the specific/proximal location (trap) tween the control and intervention arms. Data will be where the dengue NS1-positive mosquito was found. collected weekly through study completion for 18 Depending on the number of positive traps and num- months and analysis will be performed thereafter. ber of mosquitoes trapped, the above can be completed The secondary outcome concerns the change in (i) within four hours by four personnel. Overall, setting adult sticky trap index (ASTI; number of traps with traps and collection of traps in 19 blocks of an apart- adult Aedes mosquitoes in total, Ae. aegypti only and Ae. ment; identification and dissection of mosquitoes; and albopictus only every week in each apartment and col- the detection of dengue NS1 antigen in pooled mosqui- lectively in the intervention arm); (ii) adult index (AI; toes require approximately 20 man-hours. number of female adult Aedes mosquito in total, Ae. aegypti only and Ae. albopictus only collected every Notifications of the presence of dengue-positive Aedes week using GOS trap in each apartment and collectively When the test above is positive, flyers and posters will be in the intervention arm); and (iii) dengue-positive trap disseminated within two days to notify the affected index (number of traps with Aedes mosquito positive for apartment’s management and residents that dengue-posi- dengue NS1 per apartment collected every week). The tive mosquito (es) is detected. The Vector Control Unit of numbers of Ae. aegypti and Ae. albopictus will be re- the Petaling Jaya City Council will also be informed. Conse- corded weekly based on the source traps and apartments quently, pyrethroid fogging may be carried out by them. for 18 months until the completion of the study, when The flyers/posters will contain information of (i) the exact analysis will be done. Subsequently, the changes in the block(s) where the dengue-positive mosquito (es) was AI and ASTI throughout the study will be calculated. found, as well as (ii) precautionary measures for residents Other outcomes which will be obtained is change in to protect themselves from mosquito bites. The posters will levels of dengue-related knowledge, attitudes and prac- be put up at strategic locations such as the notice boards of tices (KAP) of the residents using a self-administered each block. The management will also make use of social questionnaire. Levels of KAP will be expressed as per- media such as Whatsapp or Facebook to disseminate the centage of correct answers for each domain. Individuals said information to the residents. Concurrently, mosquito whose scores for each domain exceed 80% will be con- repellants [Fumakilla Nobite Lotion, active ingredient: 10% sidered having good KAP. The level of KAP of residents icaridin (Fumakilla Malaysia Berhad, Penang, Malaysia); in the intervention and control arms will be determined and NATMOS anti mosquito spray, active ingredient: lem- six months after recruitment. Beginning of the 16th ongrassand lemoneucalyptusoil (OPC ResourcesSdn month of the trial (January 2020), a new set of question- Bhd, Penang, Malaysia)] and flyers will be distributed door- naire will be administered to the residents to gauge their to-door. The residents will be educated and reminded to levels of KAP again and their receptiveness towards the take precautionary measures against dengue as well as per- new dengue surveillance method. The levels of KAP be- form mosquito search-and-destroy activities. fore and after will be compared 3 months after recruit- ment for post-trial survey. Control arm In the control arm, a small number of GOS traps are de- Data collection ployed in each block, for entomological survey only. The Adult Aedes surveillance using the GOS traps number of GOS traps placed per block corresponds to As mentioned above, all traps will be replaced weekly. one-third of that in the intervention arm. The traps are The GOS traps and trapped mosquitoes will be proc- only deployed and left for a week once every month at essed in the lab. Mosquitoes caught by these traps will the same location. The traps are placed randomly on be identified by trained researchers. The number of floors as per the intervention arm (Table 1). Thus, a missing traps (missing brown sticky paper) will be Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 7 of 12 recorded for each block. Only the numbers of Ae. IgG seroconversion in paired sera, detection of dengue aegypti, Ae. albopictus and Culex spp. mosquitoes in IgM and IgG in a single sample and PCR, among others each trap will be recorded whereas only the female Ae- [36]. The data obtained will be used for analysis to deter- des mosquitoes will be processed and stored. During dis- mine if the intervention is able to reduce the number section of the mosquito under the stereomicroscope, the and duration of dengue outbreaks. species and number of mosquitoes will be checked again, making sure the records tally and none was Knowledge, attitude and practice (KAP) on dengue and missed during the first round of inspection. Then, the dengue seroprevalence of the residents in the study sites abdomens of the Aedes mosquitoes will be separated Assuming that the baseline knowledge of dengue in the from the thoraxes and up to 5–7 abdomens will be sample population was 50%, the minimum sample size pooled according to species (i.e. one pool of Ae. aegypti, required to attain 80% power at an alpha of 0.05 is 384. another pool of Ae. albopictus). The thorax and head This value was increased to 460 following a 20% infla- will be stored in individual tubes. The pooled abdomens tion. With reference to the dengue seroprevalence study, will be homogenized in 150 μl of phosphate-buffered sa- it was assumed that the baseline seroprevalence of den- line (PBS) using a pellet pestle. The homogenate will be gue in the sample population was 60%. Ergo, the mini- centrifuged at 8000 rpm for 1 min at room temperature. mum sample size needed to achieve the aforementioned One hundred microlitres of the supernatant will be used power and alpha is 369. Following a 20% inflation, the on a SD Biosensor Standard Q Dengue NS1 test kit to value was increased to 443. Therefore, the overall mini- detect dengue NS1 antigen in the pool of abdomens. mum number of residents needed in this part of the re- The presence of a “Test” band — however faint — along search is 460. with a “Control” band, will be regarded as positive. In the initial six months of the interventional trial, Reading is taken after 15–20 min, after which the result KAP questionnaires had been given to the residents at is considered invalid. At least two persons will view the every apartment (both intervention and control arms) result. In the event that there is discordance, a third in- via door-to-door visits. Recruitment was also performed dividual will be sought and the result will be determind during community-based events at the apartments (e.g. by this person. When the abdomen pool is positive, the health screenings, clean-ups, annual general meetings, head and thorax corresponding to the mosquito abdo- etc.). Following receipt of informed consent from indi- mens in that pool, will be homogenized individually in vidual residents, a self-administered KAP questionnaire 120 μl of PBS, centrifuged at 8000 rpm for 1 min and was provided for them to answer on the spot. The ques- tested for dengue NS1 antigen as above. This allows us tionnaire used had been adapted from that of Zaki et al. to identify the GOS trap(s) from which the positive mos- (2019) [37]. This questionnaire had been pilot tested in a quito (es) originated. If a dengue NS1-positive mosquito community similar to the current study population. All is found in the intervention arm, the apartment in ques- sections had Cronbach’s alpha values of more than 0.60 tion will be notified of the result. Steps will be taken, as and are considered acceptable. Test re-test reliability of detailed in the Intervention section. the questionnaire was performed among a sample of 50 participants with intraclass correlation coefficient (ICC) Dengue virus detection and serotyping ranging from 0.6 to 1.0, showing that all items achieved The dengue NS1-positive mosquito abdomen pools will moderate to excellent reliability. The questionnaire has be further analysed using PCR. Viral RNA will be ex- three sections. The first section with eight questions col- tracted from the remaining homogenate using TRIzol, lects personal information such as gender, age, race, edu- following the manufacturer’s protocol. Five μl of RNA cation level, income, history of dengue fever and others. will be used for the first RT-PCR reaction, followed by a The second section gauges the respondent’s knowledge nested PCR using the primers stated by Klungthong et on dengue with 28 dichotomous or single-best-answer al. (2015) [35] for serotyping the dengue virus. questions. The last section assesses attitude and practice of dengue prevention with 16 questions. Upon receipt of Dengue cases in the study sites the completed questionnaires, a code was assigned to The weekly number of notified dengue cases and dur- each. The information was keyed and stored in cloud ation of dengue outbreaks in the study sites will be ob- storage, whereby only the authors have access to. The tained from the District Health office. Dengue fever is a data will be analyzed using IBM SPSS Statistics software notifiable disease in Malaysia, and all suspected/con- version 23 (IBM Corporation, New York, USA). firmed dengue fever cases have to be notified. Confirmed The participants were free to choose to complete the dengue is defined as a case compatible with clinical de- questionnaire survey only, or undergo venepuncture scription of dengue and laboratory-confirmed with any only for dengue seroprevalence, or participate in both. of the following: detection of dengue NS1, dengue IgM/ About 3 ml of venous blood from each consented Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 8 of 12 individual was taken in a plain blood tube for dengue interquartile ranges). Unpaired t-tests will be used to de- seroprevalence by a trained personnel. The blood sample termine the presence of significant differences in the was coded and tallied with that of the questionnaire (if means (or medians). Additionally, the rate of disease and respondent participate in both activities). The blood the rate ratio will also be computed to indicate any dif- tubes were centrifuged at 4000 rpm for 4 min, and the ference in the outcome in both arms, followed by calcu- sera were aliquoted and stored at ≤− 70 °C, until use in lation of the protective efficacy of the intervention. [38] the dengue IgG and IgM ELISA tests. If the sera were For secondary outcomes, the difference and change in not processed on the same day as blood-taking, the adult Aedes density in the intervention arm will be blood tubes were stored at 4 °C and processed the next assesed using the ASTI, AI and dengue-positive trap in- day. ELISA will be performed according to the manufac- dices. The numbers of Ae. aegypti and Ae. albopictus will turer’s protocol in technical duplicates. Results of the be recorded weekly based on the source traps and apart- ELISA test will be informed to the respective partici- ments. All these will be analyzed at the arm and apart- pants via a phone call, text message or verbally in a visit ment level using weekly data. Additionally, the indices to their premises. and cases per week in each apartment will be analysed by generalised linear mixed model (GLMM) as in [27]. Post-interventional survey and measuring dengue The dengue-related KAP of the residents will be seroconversions expressed as percentages of correct answers for each of the At the end of the intervention (at the beginning of the domains. Subsequently, these will be presented in terms of 16th month of trial), a self-administered KAP question- means ± standard deviations. For the intervention arm, naire will be given to the residents of all apartments paired t-test will be performed to determine the presence again. For participants living in the intervention arm, of significant improvement in the mean scores of both do- additional questions will be asked to obtain their feed- mains with regards to the post-interventional survey. On back on this new method of dengue surveillance. The another note, unpaired t-tests will be performed between participants will also be asked if they are willing to pro- (1) the pre-intervention test scores of the intervention arm vide blood to investigate dengue seroconversion. Blood and that of the control arm, as well as (2) the post-interven- will be taken, processed and analysed similarly as stated tion test scores of the intervention arm and the scores of above for the study on dengue seroprevalence. Recruit- the control arm to detect the presence of significant differ- ment and analysis will also be performed as above. ences between them. Individuals whose scores for each do- main exceed 80% will be considered to have good Data management knowledge and/or attitudes/practises accordingly. Subse- Each GOS trap is given an identification number (indicat- quently, the percentages of residents in both arms who ing the apartment and house unit number close by where it have good knowledge and attitudes/practises will be deter- is placed). As stated above, each respondent for the KAP mined. From there, chi-squared tests will be performed to survey and/or dengue seroprevalence was also given a determine the odds ratios (with 95% confidence intervals) unique Identification (ID) number and the samples/data of the occurrence of good knowledge and attitudes/prac- collected from them were labelled with the corresponding tises in the intervention arm with reference to those of the ID numbers. Data from KAP questionnaires, GOS trap col- control arm. Association between KAP with socio-demo- lections and blood samplings is collected on paper forms, graphic variables and past infection (from dengue sero- which is subsequently keyed and stored in cloud storage, prevalence data) will also be determined by calculating the whereby only the authors have access. All hardcopy data is odds ratios and the respective 95% confidence intervals by placed in a locked room. Procedures for data management logistic regression. These analyses will be performed using can be sourced from the corresponding author. IBM SPSS Statistics software version 23. To gauge the receptiveness of the community to this Statistical analyses new intervention, the percentage of respondents whose The effectiveness of the intervention will be determined answers indicate support will be calculated. Chi-squared using two outcome measures, namely percentage change tests and/or logistic regression will also be performed to in number of dengue cases and percentage change in the determine the odds ratios (with 95% confidence inter- duration of dengue outbreaks in the intervention arm vals) to determine any association between receptiveness during the study period as compared to the previous with socio-demographic variables. years; and also compared to that of control arm. The number of dengue cases will be obtained from the Monitoring, harms and auditing Health District Office, where these cases are notified to Data monitoring will be conducted by the research team them. Both measures will be described in terms of that is directly involved in the progress of the trial; draft- means ± standard deviations (or medians and ing and carrying out plans; and solving ethical and Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 9 of 12 unforeseen events. The researchers will meet monthly to to make and deploy, making it more amicable to the discuss progress and any issue that arises. There is no public. In addition, a physical barrier is present to interim analyses and stopping guidelines. prevent emergence of adult mosquitoes if eggs are laid. This trial poses minimal risk to the participants. The Although, double sticky traps collected significantly GOS trap is made of safe material, none which will more adults than standard sticky trap (model similar to cause major harm to any individual. The sticky insect GOS trap) in Trinidad, West Indies [28], this model was glue is non-toxic and can be removed from hands and evaluated in Malaysia, and was found to be inferior com- tools using vegetable oil, followed by soap. Hence, there pared to other models and the standard sticky trap [47]. is no obvious forseeable harm from the intervention. It was found that a small, simple ovitrap with the sticky Only minor discomfort from the venepuncture for den- paper was most attractive to the Aedes. However, it was gue serology is anticipated, which will not impact the felt that it is not practical to use such trap as it can allow routine physical and psychological performance of the larvae to develop and adult mosquitoes to escape. Thus, participants. However, if there should be any adverse the current design of the GOS trap, which is slightly event or complaint, contacts of the investigators have smaller than the earlier version [27] is adopted, similar been given out to the residents in the participant infor- to that currently being used for management of dengue mation sheet and also through correspondence with the clusters in Singapore [22]. JMBs. In view of these, no criteria has been set for ter- Nonetheless, GOS trap, as with other adult traps, do minating or modifying the interventions, nor is there not provide absolute measurement of mosquito abun- any endpoint guidelines. dance as they compete with other natural or cryptic There will be no auditing for this trial. breeding sites. Therefore, this trap is black in colour and also hay infusion water is used. It has been shown that Discussion these factors make the traps more attractive to Aedes Adult mosquito traps have been deployed and tested in mosquitoes [48, 49], thereby increasing the probability various settings. These traps come in different designs. In a of the mosquitoes choosing the GOS trap over other randomized control trial using BG-Sentinel traps, their de- containers. Besides, trap indices rather than mosquito ployment has slightly reduced the density of Aedes in the counts will be the focus for analyses. Still, these traps experimental area as compared to its control counterpart that capture adults can obtain estimates of population [19]. Other autocidal traps such as the In2Care mosquito directly involved in dengue transmission. And because trap [39]and Gravid Aedes Trap [40] which contains insec- gravid mosquitoes are trapped, these mosquitoes which ticides, larvicides and/or biological control agents that kill have taken a previous bloodmeal (possibly an infectious the adults and larvae, have also been found to be useful for one), allow us to survey dengue transmission in the area. vector surveillance/control. Similarly, sticky traps were re- Recent works also encourage using arbovirus prevalence ported to be as effective as [41] or even more sensitive than in mosquitoes as a proxy for human infections [50–52]. standard ovitraps in detecting Ae. aegypti [42]. Variants of Hence, we anticipate the GOS traps to be able to bring the sticky trap, such as AedesTraP [43]and MosquiTRAP down dengue cases, by trapping (infected) gravid Aedes [21] were more sensitive than larval survey at detecting mosquitoes. Although some studies collectively indicate presence of Aedes, besides demonstrating superiority in only a 22% positive correlation between vector indices predicting dengue transmission risks [44]. When compar- and dengue cases [53], other studies found significant ing efficiency of these sticky traps, MosquiTRAP captured correlation between weekly Aedes abundance (in egg a higher number of female Ae. aegypti per trap than counts and ovitrap index) with number of confirmed Adultrap, although both were considered efficient and reli- dengue cases [53, 54]. Increase in Ae. aegypti adult able [45]. In a separate study, all four investigated traps catches, were observed along with increased number of (Adultrap, BG-Sentinel, MosquiTRAP and Ovitrap) rarely dengue cases [53] and adult Ae. albopictus abundance produced null indices and performed better than house was also positively correlated with dengue fever inci- index in estimating seasonal abundance of mosquito [46]. dence, in Zhejiang, China [55]. In addition, average adult Therefore, these adult traps are considered valuable tools mosquito abundance is consistently higher in a dengue and the choice of trap depends on specificity, low cost, ease hotspot compared to a neighbouring low-transmission of use, and consistency [6]. spot, in Taiwan, China [56]. Similarly, mosquito densities However, some of these traps are expensive and may and rates of chikungunya virus detection were signifi- not be cost-effective for a surveillance programme. cantly higher in communities without vector control Others could be relatively labor-intensive, dependent on than in treated communities (using autocidal gravid handler (backpack aspirators), while some uses electri- trap) [50, 51]. A research which employed the Centers city (BG-Sentinel). Being patent-free and insecticide/ for Disease Control (CDC) autocidal gravid trap has also larvicide-free, the GOS trap is a cheap and simple trap reported a significant reduction in the number of dengue Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 10 of 12 cases (by 53–70%) in the interventional area vis-à-vis the apartments where people are living close to each other control area [25]. and thus small number of mosquitoes are sufficient to However, it should be noted that, the GOS trap is not keep the transmission circulating. It is thus envisaged the only intervention of this trial. The intervention in- that the current trial will be able to provide insight and cludes early public alert of the communities and health solutions to reduce the number of dengue outbreaks. authorities, to carry out preventive and protective mea- sures. This may promote the participation of the com- Additional file munity and encourage them to be more responsible in Additional file 1: Multilingual abstracts in the five official working the surveillance of dengue vectors. Knowledge and languages of the United Nations. (PDF 346 kb) awareness are integral parts of a vector control program. Inadequate knowledge and poor practice contribute to Abbreviations the spread of dengue fever [57]. Therefore, engaging the AI: Adult index; ASTI: Adult sticky trap index; GOS: Gravid oviposition sticky; community and educating the public in vector surveil- KAP: Knowledge, attitude, practise; NS1: Dengue non-structural 1 antigen lance/control should be done to ensure in-built sustain- Acknowledgements ability and active health promotion. Additionally, the We would like to thank the Vector Control Unit, Petaling Jaya City Council, GOS traps are very cheap and can be handled by the Selangor, Malaysia for the support and information provided. We are also community with help from the health authorities. In the grateful for the input and fruitful discussion from the meeting with the Selangor State Health Department and District Health Office. We are also future, if this method of surveillance is to be established, immensely grateful to Science Valley Sdn. Bhd., Malaysia for graciously dengue NS1 antigen detection can be performed directly sponsoring the SD Biosensor Standard Q Dengue NS1 test kits for this trial. on the pooled mosquitoes without dissection. Because of We would also like to give thanks to Fumakilla Malaysia Berhad and OPC Resources Sdn Bhd, Malaysia for sponsoring the Fumakilla Nobite Lotion and its simplicity, the detection of dengue antigen in the NATMOS anti mosquito spray. Last but not least, we would like to express mosquitoes can also be carried out by the community. our gratitude to the managements and residents of the apartments of this Thus, making it an integrated vector management sys- trial, for the cooperation and willingnes to have this trial carried out at their premises. tem and not a top-down approach. The study sites are multistorey dwellings where popu- Authors’ contributions lation per unit area is likely to be higher, thus surveil- JWKL, SS, WT, RAZ and IV contributed to writing of the manuscript. IV conceptualized the trial and supervises the progress. RAZ performed the lance should be different than landed properties [58]. In sample size calculation and randomization. JWKL, SS and WT carry out the many urban areas high rise dwellings are becoming trial. All authors read and approved the final manuscript. popular and it will be tedious for the authorities to carry Funding out larval surveys as was done decades ago. Moreover, This work is supported by the Ministry of Higher Education Malaysia (FRGS- the Aedes mosquitoes now have cryptic breeding sites MRSA MO013–2017). The funder has no role in the study design; collection, [59] which makes it even more difficult to adopt the analysis and interpretation of data; writing of the report; and in the decision to submit the article for publication. search and destroy strategy. In this case, surveillance using the GOS traps should be able to efficiently provide Availability of data and materials sufficient coverage. Furthermore, trapping dengue-in- Not applicable. fected mosquitoes using the GOS trap, helps to halt the Ethics approval and consent to participate dengue transmission carried by the mosquito, an added The research protocol has been approved by the Medical Research Ethics benefit of using a capture-kill trap. Committee, University Malaya Medical Center, Malaysia (MRECID. No. It is envisaged that the results of this randomized con- 2018525–6321). The study will adhere to the principles of biomedical research involving trolled trial will provide a new proactive, cheap and tar- human subjects. Specifically, the rights, integrity and confidentiality of the geted surveillance tool for the prevention and control of research subjects, in addition to the credibility and accuracy of the reported dengue outbreaks. It is an added advantage because it will results, will be protected as per the Declaration of Helsinki. Written informed consent will be obtained from participants prior to the administration of the not only control the spread of dengue but also Zika and KAP questionnaire and/or performance of venepunctures by the trained chikungunya viruses. However, some problems have been researchers. The participants will not be reimbursed in any form. encountered, which include, missing traps, tampering of All personal information of the participants will be stored safely in cloud storage, whereby only the authors have access to. All analysis and publication/report will traps, unwillingness of residents to have traps placed dir- not disclose any identifiable information. Only the authors have access to the ectly beside their premises etc. We managed to circum- complete dataset. The data will only be used for analyses related to the trial or vent some of these issues by spending time to explain and dengue/Aedes surveillance by the authors. Results from this study will be published in open access ISI-cited, peer-reviewed interact with the residents. Some of the traps were also journals. Access to the data will be made available after publication and report moved to an adjacent unit or 2–3 m away. or upon getting in touch with the corresponding author. The results of the trial Although the Aedes house index is now much lower will also be updated in ClinicalTrials.gov. Results will also be disclosed to the participant/management of the study sites in simple layman language. Detailed than it was decades ago [35], the number of cases are on reports of the study results will also be presented to the Vector Control Unit of the increase. One plausible reason may be due to the Petaling Jaya City Council and the Selangor State Health Department, and sub- fact that current cases are occurring in high rise sequently the Malaysian Ministry of Health to advocate for the adoption of this Liew et al. 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Practices of dengue fever prevention and the associated factors among the orang Asli in peninsular Malaysia. PLoS Negl Trop Dis. 2015;9:e0003954. 58. World Health Organization. Dengue haemorrhagic fever: diagnosis, treatment, prevention and control. In: World Health Organization, editor. Vector surveillance and control. Geneva: World Health Organisation; 1997. 59. Reiner RC, Jr., Achee N, Barrera R, Burkot TR, Chadee DD, Devine GJ, et al. Quantifying the epidemiological impact of vector control on dengue. PLoS Negl Trop Dis. 2016;10:e0004588-e. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Infectious Diseases of Poverty Springer Journals

Gravid oviposition sticky trap and dengue non-structural 1 antigen test for early surveillance of dengue in multi-storey dwellings: study protocol of a cluster randomized controlled trial

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Springer Journals
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Copyright © 2019 by The Author(s).
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Medicine & Public Health; Infectious Diseases; Tropical Medicine; Public Health
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10.1186/s40249-019-0584-y
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Abstract

Background: Dengue is a global disease, transmitted by the Aedes vectors. In 2018, there were 80 615 dengue cases with 147 deaths in Malaysia. Currently, the nationwide surveillance programs are dependent on Aedes larval surveys and notifications of lab-confirmed human infections. The existing, reactive programs appear to lack sensitivity and proactivity. More efficient dengue vector surveillance/control methods are needed. Methods: A parallel, cluster, randomized controlled, interventional trial is being conducted for 18 months in Damansara Damai, Selangor, Malaysia, to determine the efficacy of using gravid oviposition sticky (GOS) trap and dengue non-structural 1 (NS1) antigen test for early surveillance of dengue among Aedes mosquitoes to reduce dengue outbreaks. Eight residential apartments were randomly assigned into intervention and control arms. GOS traps are set at the apartments to collect Aedes weekly, following which dengue NS1 antigen is detected in these mosquitoes. When a dengue-positive mosquito is detected, the community will be advised to execute vector search-and-destroy and protective measures. The primary outcome concerns the the percentage change in the (i) number of dengue cases and (ii) durations of dengue outbreaks. Whereas other outcome measures include the change in density threshold of Aedes and changes in dengue-related knowledge, attitude and practice among cluster inhabitants. Discussion: This is a proactive and early dengue surveillance in the mosquito vector that does not rely on notification of dengue cases. Surveillance using the GOS traps should be able to efficiently provide sufficient coverage for multistorey dwellings where population per unit area is likely to be higher. Furthermore, trapping dengue-infected mosquitoes using the GOS trap, helps to halt the dengue transmission carried by the mosquito. It is envisaged that the results of this randomized controlled trial will provide a new proactive, cheap and targeted surveillance tool for the prevention and control of dengue outbreaks. Trial registration: This is a parallel-cluster, randomized controlled, interventional trial, registered at ClinicalTrials.gov (ID: NCT03799237), on 8th January 2019 (retrospectively registered). Keywords: Aedes, Mosquito, Dengue, Dengue NS1 test, Gravid oviposition sticky trap, Cluster randomized controlled trial, Surveillance * Correspondence: [email protected]; [email protected] Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia Full list of author information is available at the end of the article © The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 2 of 12 Multilingual abstracts potential, many of such interventions/products are still Please see Additional file 1 for translations of the ab- under trial [13–17]. Urgent and effective strategies for stract into the five official working languages of the vector surveillance/control are required pending the re- United Nations. sults of the aforementioned trials, since their assess- ments are highly time-consuming. In this matter, Background community support must also be sought. Ultimately, re- Dengue is a major mosquito-borne viral disease world- gardless of whether these novel techniques will eventu- wide, especially in the tropical and sub-tropical coun- ally be implemented, vector surveillance remains an tries. Aedes mosquitoes (mainly Ae. aegypti and Ae. indispensable component of dengue control. Vector sur- albopictus) are the vectors of the disease. Globally, some veillance should be routinely and thoroughly conducted 390 million dengue cases occur annually, 96 million of to prevent dengue epidemics. The World Health which are clinically apparent [1]. In Malaysia, a total of Organization (WHO) has called for the development of 80 615 cases of dengue with 147 deaths were reported in integrated national vector surveillance and health infor- 2018. During the same year, the state of Selangor re- mation systems to guide vector control measures [18]. ported the highest number of cases (45 349 cases) and Many traps of different designs have been tested for deaths (41 deaths) [2]. Subsequently, within the first ten mosquito surveillance [19–21] and the use of sticky weeks of 2019, Selangor accounted for more than half traps to lure and trap gravid adult Aedes females for vec- (16748) of the 28 936 dengue cases in Malaysia [3]. tor surveillance/control appears to be promising in a At present, anti-dengue drugs are not available, while number of countries [22–28]. Moreover, dengue non- dengue vaccine is not efficacious enough to act as a structural antigen 1 (NS1) rapid test is a simple and reli- standalone intervention [4]. Additionally, the current able tool for detecting dengue in mosquitoes caught by vector surveillance/control measures – which are the the sticky traps [27, 29]. In a preliminary study con- hallmark of dengue control programs in many Southeast ducted in an urban area in Selangor, Malaysia, infected Asian nations, including Malaysia [5], usually involve Ae. aegypti mosquitoes could be obtained from sticky house-to-house larval surveys, source reductions, larvi- non-insecticidal gravid oviposition sticky (GOS) traps ciding, and fogging, all of which are riddled with down- [26]. The use of the GOS traps and dengue NS1 rapid sides like non-relevance [6], cost- and labor- test kits allowed the rapid detection of dengue in the intensiveness [7], lack of community participation, as trapped mosquitoes, unlike the more sophisticated re- well as resistance of mosquitoes to insecticides [8–11]. verse-transcription PCR (RT-PCR). Accordingly, the The fact that asymptomatic, dengue-infected individuals health personnel involved in the study have found both are able to spread the disease has also been largely ig- instruments to be an easier method of dengue surveil- nored [12]. These are the likely reasons for the alarming lance rather than labor-intensive larval surveys. Subse- rise in dengue epidemics and the struggle to control quently a prospective, longitudinal phase 2 study found them. Accordingly, proactive and sensitive methods dengue cases to occur around one week following the which facilitate the early detection of dengue are desper- detection of infected mosquitoes, with a peak lag of 2–3 ately needed to pre-empt dengue outbreaks. weeks [27]. Thus, this method of surveillance is likely to Besides the mentioned flaws of the dengue control be feasible for incorporation into dengue control pro- program, the correlations of larval indices/adult mos- grams. Also, control methods such as search-and-des- quito emergence with dengue cases and the proportion troy measures, should be initiated whenever positive of people who seek medical care post-infection are poor mosquitoes are detected. In short, GOS traps and rapid [6]. Furthermore, due to the passive nature of the dengue NS1 detection in mosquitoes offer a potentially current surveillance system, vector control activities comprehensive, early-warning surveillance system that is mainly prevent further transmission of dengue from capable of pre-empting the occurrence of dengue index cases rather than eliminate the disease. Therefore, epidemics. the existing, reactive programs lack sensitivity and pro- Hence, the current phase of the research is aimed to activity, and hence lack the ability to curb dengue epi- determine if this adult Aedes surveillance/control demics. In view of all these shortcomings, more sensitive method (using GOS traps and dengue NS1 antigen test) and proactive methods involving the early detection of can actually reduce the occurrence of dengue outbreaks. dengue that can potentially stave off dengue outbreaks The proposed novel approach entails the active monitor- are desperately needed. ing of adult Aedes populations using easily constructed, Although novel techniques, such as the release of gen- inexpensive, reusable traps as well as rapid dengue-diag- etically-modified mosquitoes (release of insects carrying nostic kits. Vector surveillance is required to detect dominant lethality; RIDL) and the use of Wolbachia bac- changes in vector abundance, evaluate control pro- teria to control Ae. aegypti populations, have great grammes, obtain spatial and temporal information of Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 3 of 12 vector populations, as well as facilitate timely evidence- The study procedure is demonstrated in Fig. 1. based interventions. In resource-limited settings, vector control/surveillance practices must be both efficient and Study setting efficacious [30]. If this paradigm is proven to be effect- This trial is conducted at Damansara Damai in ive, a very viable alternative for curbing dengue will be Petaling Jaya Utara 10 (3.1930°N, 101.5923°E), Petal- made available not only to Malaysia, but to other low- ing district, Selangor, Malaysia (Fig. 2). Of the nine to-middle-income countries as well. districts, Petaling district is the major contributor to the dengue cases in Selangor [3]. Following discus- Design sions with the Petaling Jaya City Council, Damansara Aims Damai was chosen in view of its “closed” area (there This parallel-cluster randomized controlled trial is de- is only one main entrance and exit to this area), its signed with the aim of measuring the efficacy of a new, status as a dengue hotspot and it having sufficient proactive paradigm (i.e. GOS traps and dengue NS1 number of high-rised apartments. rapid tests) to (i) reduce the occurrence of dengue cases In 2018, Damansara Damai has approximately 61 615 vis-à-vis conventional vector surveillance measures; (ii) inhabitants in an area of 3.45 km , translating into a provide the community with early information of dengue population density of approximately 17 859 inhabitants/ transmission in the area, which will in turn provide km (Development Planning Department, Petaling Jaya more time for concise mitigative plans to be adminis- City Council, personal communication). There were 278 tered onto the community by public health authorities; and 227 dengue cases reported respectively in 2018 and as well as (iii) be workable and well-received by the 2017 in this area (Vector Control Unit, Petaling Jaya City management and residents of the housing areas. If its ef- Council, personal comunication). Eight apartments were ficacy and practicability are proven, efforts will be under- selected to be included in the cluster randomized con- taken to effectuate major revamps to the existing trolled trial that is being carried out for 18 months. standard operating procedures through the Ministry of Health Malaysia and other policy makers. Additionally, a Sample size dossier will be submitted to the WHO for adoption by The sample size was calculated based on that for a clus- Southeast Asian countries. ter randomized trial [31] using the Stata 13 statistical Fig. 1 Flow chart of study procedure 7 Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 4 of 12 Fig. 2 Map of study site. Insert: map of Selangor showing the study sites (apartments) in Damansara Damai, Petaling District software (StataCorp, Texas, USA) [32]. The likely inci- Harmoni Apartment, Bayu Apartment, and Park Avenue dence and spatial variation of dengue were determined Condominium were assigned to the intervention arm with reference to the number of confirmed cases in se- while Vista Apartment, Indah Apartment, Lestari Apart- lected localities in Selangor from 2013 to 2017 (Vector ment, and Permai Apartment the control arm. In the Control Unit, Petaling Jaya City Council, personal com- event that an apartment declines to participate or drops munication). Specifically, the variations between local- out of the trial, an apartment which had similar numbers ities in each year were utilized as a guide to estimate the of cases per 1000 units and cases per block will be chosen extent of variations between trial clusters. Each cluster as a replacement. The participants (residents/apartments) contained apartment blocks with similar population and the researchers are not blinded to the intervention. sizes. The minimum sample size required to detect a 60% reduction of dengue in the intervention arm with a Recruitment power of 80% is 20 blocks per arm. From there, the sam- Following the receipt of ethical approval from the Uni- ple size was inflated by 20%. Accordingly, a total of 48 versity Malaya Medical Center Medical Research Ethics blocks is required for the study. Committee, meetings were conducted with the joint For the interventional trial, it was estimated that on management body (JMB) of each apartment, during average, each housing unit will have 2% risk of dengue which written approvals were obtained for house-to- per year. To test the ability of the intervention to reduce house visits as well as deployment of GOS traps. The the number of dengue cases, a sample size of 5710 units JMB is in charge of the management and maintenance (2855 per arm) is required to achieve 80% power at an of an apartment. Concurrently, a complete schedule for alpha of 0.05 (assuming a 50% risk reduction at the end the replacement of the GOS traps was given to the JMBs of the intervention). in an attempt to promote the involvement of the com- munity in the study. Approvals from each JMBs were re- Randomization ceived at different time. Nonetheless, upon receipt of the Initially, eight apartments with 7889 residential units in first approval, the trial started in week 40 of year 2018. a total of 75 blocks were randomly selected and random- All selected apartments provided their consents except ized into the intervention and control arms. Individual for Bayu Apartment. Consequently, Impian Apartment apartment was the item of randomization. The apart- which had similar number of cases per 1000 units and ments were keyed into Microsoft Excel 2010 (Microsoft, cases per block, as well as similar apartment design as Washington, USA), following which they were randomly Bayu Apartment was chosen as the replacement. The de- allocated to the intervention and control arms using tails of the finalized apartments in both arms are pre- computer-generated numbers. Initially, Suria Apartment, sented in Table 1. Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 5 of 12 Table 1 Characteristics of the study arms and the number of traps in each apartment No. blocks Total No. of units No. of floors No. of floors with No. of individual stairway No. traps in Total No. (residential units) in each block traps in each block leading to residential units each block traps Intervention Suria 8 767 (444) 5 2 6–812–16 114 Harmoni 19 2380 (2356) 5 2 NA 6 114 Park Avenue 2 316 (316) 17/18 6 NA 16–17 33 Impian 6 668(660) 5 2 NA 6 36 Total 35 4131 (3776) Control Vista 15 920 (736) 5 1–25–73–566 Lestari 9 2002 (1982) 5–15 2–6NA 2–625 Indah 2 120 (120) 5 2 NA 2 4 Permai 12 1379 (1365) 5 2 NA 2–328 Total 38 4421 (4203) No. Number, NA Not applicable Eligibility criteria 0.375) and is reusable, except for the brown sticky paper All the residents/residential units of the eight sampled which has to be replaced weekly. apartments are eligible for this study. Additionally, people Traps are placed where it is shaded and protected who work at the study sites for at least 40 h per week are from rainfall, and ideally at locations where it is dark also eligible. They are approached via the JMB of each and away from human traffic. The GOS traps are de- apartment, door-to-door visits or community-based ployed continuously and changed weekly for 18 months. events (like clean-ups and annual general meetings). All The placement of traps and the number of traps de- individuals who are 18 years old and above and able to ployed are shown in Table 1. The placement of traps provide informed consent are recruited. Conversely, those varies according to the designs of the individual apart- who are aged below 18 years and unable to provide in- ments. For the intervention arm, GOS traps are placed formed consent are excluded. at the corridors of each block. Generally, for the apart- ments with common corridors, three traps are placed not more than 45 m apart at the corridors at every three Intervention floors (two at each end and one in the middle) [18], Dengue control activities still take place as per the starting from the floor with residential units. As an ex- Ministry of Health’s vector control measures in both ample, a 5-storey block will have traps at two of its intervention and control arms throughout the trial. floors (Ground/Mezzanine and third floor), amounting The measures may consist pyrethroid-fogging at the to a total of six traps per block. There are a few excep- apartments where new dengue cases are reported. tions: (i) If a block has five floors, and residential units Larval surveys may also be conducted depending on are not found starting from the ground floor but the first the severity of the outbreaks and the availability of floor, traps will be set on this floor and on the 3rd floor; manpower [33]. (ii) For the shop apartments (Suria), two traps will be placed on every stairway (Mezzanine/1st floor and 2nd/ Placement of GOS traps 3rd floor) leading to the residential units; (iii) For floors A detailed description of the GOS trap is provided in which are short i.e. corridor is less than 25 m in length reference [18] where it was initially tested as an Aedes (in Park Avenue), only two traps are set on the said surveillance tool for dengue control [18]. In this trial, floors. A manpower of four is enough to cover 19 blocks the outer black container is a 700 ml black, round poly- of an apartment within one hour. propylene plastic container (Diameter 110 mm × Height 87 mm). While the inner container is a 280 ml clear, Detection of dengue non-structural 1 (NS1) antigen in round polypropylene plastic container (Diameter 110 pooled Aedes mosquitoes trapped by the GOS traps mm × Height 46 mm). All traps are filled up till the bot- During collection of the GOS traps, they are examined tom of the inner container with 10% hay infusion water for trapped Aedes and Culex mosquitoes. The numbers made from 1-week-old hay infusion [34]. Each trap costs of missing sticky papers of the traps in each block will about Malaysian Ringgit (MYR) 1.50 (US dollar [USD] be recorded. The Aedes mosquitoes will be identified to Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 6 of 12 species level, and the numbers of each mosquito species single floor/stairway may have zero to two traps. As an of interest in each trap will be recorded. However, only example, a five-storey block in the control arm will have female Ae. aegypti and Ae. albopictus mosquitoes will be two traps (which corresponds to one-third of the six processed as described below. traps to be placed if the block is in the intervention arm) The abdomens of the Aedes mosquitoes will be separated set randomly at either one (Ground/first/Mezzanine or from the thoraxes and pooled. Each head-thorax will be third floor) or two floors (Ground/first/Mezzanine and kept in individual 1.5 ml tubes and stored at − 20 °C. The third floor) of the block. pooled abdomens will be homogenized and tested for the presence of dengue NS1 antigen using the SD Biosensor Outcomes Standard Q Dengue NS1 test kit (Gyeonggi-Do, South The primary outcome of the trial will be measured in Korea). When an abdomen pool is positive, the same test terms of the percentage change in the (i) number of will be repeated for each corresponding head-thorax in an dengue cases and (ii) durations of dengue outbreaks be- attempt to identify the specific/proximal location (trap) tween the control and intervention arms. Data will be where the dengue NS1-positive mosquito was found. collected weekly through study completion for 18 Depending on the number of positive traps and num- months and analysis will be performed thereafter. ber of mosquitoes trapped, the above can be completed The secondary outcome concerns the change in (i) within four hours by four personnel. Overall, setting adult sticky trap index (ASTI; number of traps with traps and collection of traps in 19 blocks of an apart- adult Aedes mosquitoes in total, Ae. aegypti only and Ae. ment; identification and dissection of mosquitoes; and albopictus only every week in each apartment and col- the detection of dengue NS1 antigen in pooled mosqui- lectively in the intervention arm); (ii) adult index (AI; toes require approximately 20 man-hours. number of female adult Aedes mosquito in total, Ae. aegypti only and Ae. albopictus only collected every Notifications of the presence of dengue-positive Aedes week using GOS trap in each apartment and collectively When the test above is positive, flyers and posters will be in the intervention arm); and (iii) dengue-positive trap disseminated within two days to notify the affected index (number of traps with Aedes mosquito positive for apartment’s management and residents that dengue-posi- dengue NS1 per apartment collected every week). The tive mosquito (es) is detected. The Vector Control Unit of numbers of Ae. aegypti and Ae. albopictus will be re- the Petaling Jaya City Council will also be informed. Conse- corded weekly based on the source traps and apartments quently, pyrethroid fogging may be carried out by them. for 18 months until the completion of the study, when The flyers/posters will contain information of (i) the exact analysis will be done. Subsequently, the changes in the block(s) where the dengue-positive mosquito (es) was AI and ASTI throughout the study will be calculated. found, as well as (ii) precautionary measures for residents Other outcomes which will be obtained is change in to protect themselves from mosquito bites. The posters will levels of dengue-related knowledge, attitudes and prac- be put up at strategic locations such as the notice boards of tices (KAP) of the residents using a self-administered each block. The management will also make use of social questionnaire. Levels of KAP will be expressed as per- media such as Whatsapp or Facebook to disseminate the centage of correct answers for each domain. Individuals said information to the residents. Concurrently, mosquito whose scores for each domain exceed 80% will be con- repellants [Fumakilla Nobite Lotion, active ingredient: 10% sidered having good KAP. The level of KAP of residents icaridin (Fumakilla Malaysia Berhad, Penang, Malaysia); in the intervention and control arms will be determined and NATMOS anti mosquito spray, active ingredient: lem- six months after recruitment. Beginning of the 16th ongrassand lemoneucalyptusoil (OPC ResourcesSdn month of the trial (January 2020), a new set of question- Bhd, Penang, Malaysia)] and flyers will be distributed door- naire will be administered to the residents to gauge their to-door. The residents will be educated and reminded to levels of KAP again and their receptiveness towards the take precautionary measures against dengue as well as per- new dengue surveillance method. The levels of KAP be- form mosquito search-and-destroy activities. fore and after will be compared 3 months after recruit- ment for post-trial survey. Control arm In the control arm, a small number of GOS traps are de- Data collection ployed in each block, for entomological survey only. The Adult Aedes surveillance using the GOS traps number of GOS traps placed per block corresponds to As mentioned above, all traps will be replaced weekly. one-third of that in the intervention arm. The traps are The GOS traps and trapped mosquitoes will be proc- only deployed and left for a week once every month at essed in the lab. Mosquitoes caught by these traps will the same location. The traps are placed randomly on be identified by trained researchers. The number of floors as per the intervention arm (Table 1). Thus, a missing traps (missing brown sticky paper) will be Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 7 of 12 recorded for each block. Only the numbers of Ae. IgG seroconversion in paired sera, detection of dengue aegypti, Ae. albopictus and Culex spp. mosquitoes in IgM and IgG in a single sample and PCR, among others each trap will be recorded whereas only the female Ae- [36]. The data obtained will be used for analysis to deter- des mosquitoes will be processed and stored. During dis- mine if the intervention is able to reduce the number section of the mosquito under the stereomicroscope, the and duration of dengue outbreaks. species and number of mosquitoes will be checked again, making sure the records tally and none was Knowledge, attitude and practice (KAP) on dengue and missed during the first round of inspection. Then, the dengue seroprevalence of the residents in the study sites abdomens of the Aedes mosquitoes will be separated Assuming that the baseline knowledge of dengue in the from the thoraxes and up to 5–7 abdomens will be sample population was 50%, the minimum sample size pooled according to species (i.e. one pool of Ae. aegypti, required to attain 80% power at an alpha of 0.05 is 384. another pool of Ae. albopictus). The thorax and head This value was increased to 460 following a 20% infla- will be stored in individual tubes. The pooled abdomens tion. With reference to the dengue seroprevalence study, will be homogenized in 150 μl of phosphate-buffered sa- it was assumed that the baseline seroprevalence of den- line (PBS) using a pellet pestle. The homogenate will be gue in the sample population was 60%. Ergo, the mini- centrifuged at 8000 rpm for 1 min at room temperature. mum sample size needed to achieve the aforementioned One hundred microlitres of the supernatant will be used power and alpha is 369. Following a 20% inflation, the on a SD Biosensor Standard Q Dengue NS1 test kit to value was increased to 443. Therefore, the overall mini- detect dengue NS1 antigen in the pool of abdomens. mum number of residents needed in this part of the re- The presence of a “Test” band — however faint — along search is 460. with a “Control” band, will be regarded as positive. In the initial six months of the interventional trial, Reading is taken after 15–20 min, after which the result KAP questionnaires had been given to the residents at is considered invalid. At least two persons will view the every apartment (both intervention and control arms) result. In the event that there is discordance, a third in- via door-to-door visits. Recruitment was also performed dividual will be sought and the result will be determind during community-based events at the apartments (e.g. by this person. When the abdomen pool is positive, the health screenings, clean-ups, annual general meetings, head and thorax corresponding to the mosquito abdo- etc.). Following receipt of informed consent from indi- mens in that pool, will be homogenized individually in vidual residents, a self-administered KAP questionnaire 120 μl of PBS, centrifuged at 8000 rpm for 1 min and was provided for them to answer on the spot. The ques- tested for dengue NS1 antigen as above. This allows us tionnaire used had been adapted from that of Zaki et al. to identify the GOS trap(s) from which the positive mos- (2019) [37]. This questionnaire had been pilot tested in a quito (es) originated. If a dengue NS1-positive mosquito community similar to the current study population. All is found in the intervention arm, the apartment in ques- sections had Cronbach’s alpha values of more than 0.60 tion will be notified of the result. Steps will be taken, as and are considered acceptable. Test re-test reliability of detailed in the Intervention section. the questionnaire was performed among a sample of 50 participants with intraclass correlation coefficient (ICC) Dengue virus detection and serotyping ranging from 0.6 to 1.0, showing that all items achieved The dengue NS1-positive mosquito abdomen pools will moderate to excellent reliability. The questionnaire has be further analysed using PCR. Viral RNA will be ex- three sections. The first section with eight questions col- tracted from the remaining homogenate using TRIzol, lects personal information such as gender, age, race, edu- following the manufacturer’s protocol. Five μl of RNA cation level, income, history of dengue fever and others. will be used for the first RT-PCR reaction, followed by a The second section gauges the respondent’s knowledge nested PCR using the primers stated by Klungthong et on dengue with 28 dichotomous or single-best-answer al. (2015) [35] for serotyping the dengue virus. questions. The last section assesses attitude and practice of dengue prevention with 16 questions. Upon receipt of Dengue cases in the study sites the completed questionnaires, a code was assigned to The weekly number of notified dengue cases and dur- each. The information was keyed and stored in cloud ation of dengue outbreaks in the study sites will be ob- storage, whereby only the authors have access to. The tained from the District Health office. Dengue fever is a data will be analyzed using IBM SPSS Statistics software notifiable disease in Malaysia, and all suspected/con- version 23 (IBM Corporation, New York, USA). firmed dengue fever cases have to be notified. Confirmed The participants were free to choose to complete the dengue is defined as a case compatible with clinical de- questionnaire survey only, or undergo venepuncture scription of dengue and laboratory-confirmed with any only for dengue seroprevalence, or participate in both. of the following: detection of dengue NS1, dengue IgM/ About 3 ml of venous blood from each consented Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 8 of 12 individual was taken in a plain blood tube for dengue interquartile ranges). Unpaired t-tests will be used to de- seroprevalence by a trained personnel. The blood sample termine the presence of significant differences in the was coded and tallied with that of the questionnaire (if means (or medians). Additionally, the rate of disease and respondent participate in both activities). The blood the rate ratio will also be computed to indicate any dif- tubes were centrifuged at 4000 rpm for 4 min, and the ference in the outcome in both arms, followed by calcu- sera were aliquoted and stored at ≤− 70 °C, until use in lation of the protective efficacy of the intervention. [38] the dengue IgG and IgM ELISA tests. If the sera were For secondary outcomes, the difference and change in not processed on the same day as blood-taking, the adult Aedes density in the intervention arm will be blood tubes were stored at 4 °C and processed the next assesed using the ASTI, AI and dengue-positive trap in- day. ELISA will be performed according to the manufac- dices. The numbers of Ae. aegypti and Ae. albopictus will turer’s protocol in technical duplicates. Results of the be recorded weekly based on the source traps and apart- ELISA test will be informed to the respective partici- ments. All these will be analyzed at the arm and apart- pants via a phone call, text message or verbally in a visit ment level using weekly data. Additionally, the indices to their premises. and cases per week in each apartment will be analysed by generalised linear mixed model (GLMM) as in [27]. Post-interventional survey and measuring dengue The dengue-related KAP of the residents will be seroconversions expressed as percentages of correct answers for each of the At the end of the intervention (at the beginning of the domains. Subsequently, these will be presented in terms of 16th month of trial), a self-administered KAP question- means ± standard deviations. For the intervention arm, naire will be given to the residents of all apartments paired t-test will be performed to determine the presence again. For participants living in the intervention arm, of significant improvement in the mean scores of both do- additional questions will be asked to obtain their feed- mains with regards to the post-interventional survey. On back on this new method of dengue surveillance. The another note, unpaired t-tests will be performed between participants will also be asked if they are willing to pro- (1) the pre-intervention test scores of the intervention arm vide blood to investigate dengue seroconversion. Blood and that of the control arm, as well as (2) the post-interven- will be taken, processed and analysed similarly as stated tion test scores of the intervention arm and the scores of above for the study on dengue seroprevalence. Recruit- the control arm to detect the presence of significant differ- ment and analysis will also be performed as above. ences between them. Individuals whose scores for each do- main exceed 80% will be considered to have good Data management knowledge and/or attitudes/practises accordingly. Subse- Each GOS trap is given an identification number (indicat- quently, the percentages of residents in both arms who ing the apartment and house unit number close by where it have good knowledge and attitudes/practises will be deter- is placed). As stated above, each respondent for the KAP mined. From there, chi-squared tests will be performed to survey and/or dengue seroprevalence was also given a determine the odds ratios (with 95% confidence intervals) unique Identification (ID) number and the samples/data of the occurrence of good knowledge and attitudes/prac- collected from them were labelled with the corresponding tises in the intervention arm with reference to those of the ID numbers. Data from KAP questionnaires, GOS trap col- control arm. Association between KAP with socio-demo- lections and blood samplings is collected on paper forms, graphic variables and past infection (from dengue sero- which is subsequently keyed and stored in cloud storage, prevalence data) will also be determined by calculating the whereby only the authors have access. All hardcopy data is odds ratios and the respective 95% confidence intervals by placed in a locked room. Procedures for data management logistic regression. These analyses will be performed using can be sourced from the corresponding author. IBM SPSS Statistics software version 23. To gauge the receptiveness of the community to this Statistical analyses new intervention, the percentage of respondents whose The effectiveness of the intervention will be determined answers indicate support will be calculated. Chi-squared using two outcome measures, namely percentage change tests and/or logistic regression will also be performed to in number of dengue cases and percentage change in the determine the odds ratios (with 95% confidence inter- duration of dengue outbreaks in the intervention arm vals) to determine any association between receptiveness during the study period as compared to the previous with socio-demographic variables. years; and also compared to that of control arm. The number of dengue cases will be obtained from the Monitoring, harms and auditing Health District Office, where these cases are notified to Data monitoring will be conducted by the research team them. Both measures will be described in terms of that is directly involved in the progress of the trial; draft- means ± standard deviations (or medians and ing and carrying out plans; and solving ethical and Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 9 of 12 unforeseen events. The researchers will meet monthly to to make and deploy, making it more amicable to the discuss progress and any issue that arises. There is no public. In addition, a physical barrier is present to interim analyses and stopping guidelines. prevent emergence of adult mosquitoes if eggs are laid. This trial poses minimal risk to the participants. The Although, double sticky traps collected significantly GOS trap is made of safe material, none which will more adults than standard sticky trap (model similar to cause major harm to any individual. The sticky insect GOS trap) in Trinidad, West Indies [28], this model was glue is non-toxic and can be removed from hands and evaluated in Malaysia, and was found to be inferior com- tools using vegetable oil, followed by soap. Hence, there pared to other models and the standard sticky trap [47]. is no obvious forseeable harm from the intervention. It was found that a small, simple ovitrap with the sticky Only minor discomfort from the venepuncture for den- paper was most attractive to the Aedes. However, it was gue serology is anticipated, which will not impact the felt that it is not practical to use such trap as it can allow routine physical and psychological performance of the larvae to develop and adult mosquitoes to escape. Thus, participants. However, if there should be any adverse the current design of the GOS trap, which is slightly event or complaint, contacts of the investigators have smaller than the earlier version [27] is adopted, similar been given out to the residents in the participant infor- to that currently being used for management of dengue mation sheet and also through correspondence with the clusters in Singapore [22]. JMBs. In view of these, no criteria has been set for ter- Nonetheless, GOS trap, as with other adult traps, do minating or modifying the interventions, nor is there not provide absolute measurement of mosquito abun- any endpoint guidelines. dance as they compete with other natural or cryptic There will be no auditing for this trial. breeding sites. Therefore, this trap is black in colour and also hay infusion water is used. It has been shown that Discussion these factors make the traps more attractive to Aedes Adult mosquito traps have been deployed and tested in mosquitoes [48, 49], thereby increasing the probability various settings. These traps come in different designs. In a of the mosquitoes choosing the GOS trap over other randomized control trial using BG-Sentinel traps, their de- containers. Besides, trap indices rather than mosquito ployment has slightly reduced the density of Aedes in the counts will be the focus for analyses. Still, these traps experimental area as compared to its control counterpart that capture adults can obtain estimates of population [19]. Other autocidal traps such as the In2Care mosquito directly involved in dengue transmission. And because trap [39]and Gravid Aedes Trap [40] which contains insec- gravid mosquitoes are trapped, these mosquitoes which ticides, larvicides and/or biological control agents that kill have taken a previous bloodmeal (possibly an infectious the adults and larvae, have also been found to be useful for one), allow us to survey dengue transmission in the area. vector surveillance/control. Similarly, sticky traps were re- Recent works also encourage using arbovirus prevalence ported to be as effective as [41] or even more sensitive than in mosquitoes as a proxy for human infections [50–52]. standard ovitraps in detecting Ae. aegypti [42]. Variants of Hence, we anticipate the GOS traps to be able to bring the sticky trap, such as AedesTraP [43]and MosquiTRAP down dengue cases, by trapping (infected) gravid Aedes [21] were more sensitive than larval survey at detecting mosquitoes. Although some studies collectively indicate presence of Aedes, besides demonstrating superiority in only a 22% positive correlation between vector indices predicting dengue transmission risks [44]. When compar- and dengue cases [53], other studies found significant ing efficiency of these sticky traps, MosquiTRAP captured correlation between weekly Aedes abundance (in egg a higher number of female Ae. aegypti per trap than counts and ovitrap index) with number of confirmed Adultrap, although both were considered efficient and reli- dengue cases [53, 54]. Increase in Ae. aegypti adult able [45]. In a separate study, all four investigated traps catches, were observed along with increased number of (Adultrap, BG-Sentinel, MosquiTRAP and Ovitrap) rarely dengue cases [53] and adult Ae. albopictus abundance produced null indices and performed better than house was also positively correlated with dengue fever inci- index in estimating seasonal abundance of mosquito [46]. dence, in Zhejiang, China [55]. In addition, average adult Therefore, these adult traps are considered valuable tools mosquito abundance is consistently higher in a dengue and the choice of trap depends on specificity, low cost, ease hotspot compared to a neighbouring low-transmission of use, and consistency [6]. spot, in Taiwan, China [56]. Similarly, mosquito densities However, some of these traps are expensive and may and rates of chikungunya virus detection were signifi- not be cost-effective for a surveillance programme. cantly higher in communities without vector control Others could be relatively labor-intensive, dependent on than in treated communities (using autocidal gravid handler (backpack aspirators), while some uses electri- trap) [50, 51]. A research which employed the Centers city (BG-Sentinel). Being patent-free and insecticide/ for Disease Control (CDC) autocidal gravid trap has also larvicide-free, the GOS trap is a cheap and simple trap reported a significant reduction in the number of dengue Liew et al. Infectious Diseases of Poverty (2019) 8:71 Page 10 of 12 cases (by 53–70%) in the interventional area vis-à-vis the apartments where people are living close to each other control area [25]. and thus small number of mosquitoes are sufficient to However, it should be noted that, the GOS trap is not keep the transmission circulating. It is thus envisaged the only intervention of this trial. The intervention in- that the current trial will be able to provide insight and cludes early public alert of the communities and health solutions to reduce the number of dengue outbreaks. authorities, to carry out preventive and protective mea- sures. This may promote the participation of the com- Additional file munity and encourage them to be more responsible in Additional file 1: Multilingual abstracts in the five official working the surveillance of dengue vectors. Knowledge and languages of the United Nations. (PDF 346 kb) awareness are integral parts of a vector control program. Inadequate knowledge and poor practice contribute to Abbreviations the spread of dengue fever [57]. Therefore, engaging the AI: Adult index; ASTI: Adult sticky trap index; GOS: Gravid oviposition sticky; community and educating the public in vector surveil- KAP: Knowledge, attitude, practise; NS1: Dengue non-structural 1 antigen lance/control should be done to ensure in-built sustain- Acknowledgements ability and active health promotion. Additionally, the We would like to thank the Vector Control Unit, Petaling Jaya City Council, GOS traps are very cheap and can be handled by the Selangor, Malaysia for the support and information provided. We are also community with help from the health authorities. In the grateful for the input and fruitful discussion from the meeting with the Selangor State Health Department and District Health Office. We are also future, if this method of surveillance is to be established, immensely grateful to Science Valley Sdn. Bhd., Malaysia for graciously dengue NS1 antigen detection can be performed directly sponsoring the SD Biosensor Standard Q Dengue NS1 test kits for this trial. on the pooled mosquitoes without dissection. Because of We would also like to give thanks to Fumakilla Malaysia Berhad and OPC Resources Sdn Bhd, Malaysia for sponsoring the Fumakilla Nobite Lotion and its simplicity, the detection of dengue antigen in the NATMOS anti mosquito spray. Last but not least, we would like to express mosquitoes can also be carried out by the community. our gratitude to the managements and residents of the apartments of this Thus, making it an integrated vector management sys- trial, for the cooperation and willingnes to have this trial carried out at their premises. tem and not a top-down approach. The study sites are multistorey dwellings where popu- Authors’ contributions lation per unit area is likely to be higher, thus surveil- JWKL, SS, WT, RAZ and IV contributed to writing of the manuscript. IV conceptualized the trial and supervises the progress. RAZ performed the lance should be different than landed properties [58]. In sample size calculation and randomization. JWKL, SS and WT carry out the many urban areas high rise dwellings are becoming trial. All authors read and approved the final manuscript. popular and it will be tedious for the authorities to carry Funding out larval surveys as was done decades ago. Moreover, This work is supported by the Ministry of Higher Education Malaysia (FRGS- the Aedes mosquitoes now have cryptic breeding sites MRSA MO013–2017). The funder has no role in the study design; collection, [59] which makes it even more difficult to adopt the analysis and interpretation of data; writing of the report; and in the decision to submit the article for publication. search and destroy strategy. In this case, surveillance using the GOS traps should be able to efficiently provide Availability of data and materials sufficient coverage. Furthermore, trapping dengue-in- Not applicable. fected mosquitoes using the GOS trap, helps to halt the Ethics approval and consent to participate dengue transmission carried by the mosquito, an added The research protocol has been approved by the Medical Research Ethics benefit of using a capture-kill trap. Committee, University Malaya Medical Center, Malaysia (MRECID. No. It is envisaged that the results of this randomized con- 2018525–6321). The study will adhere to the principles of biomedical research involving trolled trial will provide a new proactive, cheap and tar- human subjects. Specifically, the rights, integrity and confidentiality of the geted surveillance tool for the prevention and control of research subjects, in addition to the credibility and accuracy of the reported dengue outbreaks. It is an added advantage because it will results, will be protected as per the Declaration of Helsinki. Written informed consent will be obtained from participants prior to the administration of the not only control the spread of dengue but also Zika and KAP questionnaire and/or performance of venepunctures by the trained chikungunya viruses. However, some problems have been researchers. The participants will not be reimbursed in any form. encountered, which include, missing traps, tampering of All personal information of the participants will be stored safely in cloud storage, whereby only the authors have access to. All analysis and publication/report will traps, unwillingness of residents to have traps placed dir- not disclose any identifiable information. Only the authors have access to the ectly beside their premises etc. We managed to circum- complete dataset. The data will only be used for analyses related to the trial or vent some of these issues by spending time to explain and dengue/Aedes surveillance by the authors. Results from this study will be published in open access ISI-cited, peer-reviewed interact with the residents. Some of the traps were also journals. Access to the data will be made available after publication and report moved to an adjacent unit or 2–3 m away. or upon getting in touch with the corresponding author. The results of the trial Although the Aedes house index is now much lower will also be updated in ClinicalTrials.gov. Results will also be disclosed to the participant/management of the study sites in simple layman language. Detailed than it was decades ago [35], the number of cases are on reports of the study results will also be presented to the Vector Control Unit of the increase. One plausible reason may be due to the Petaling Jaya City Council and the Selangor State Health Department, and sub- fact that current cases are occurring in high rise sequently the Malaysian Ministry of Health to advocate for the adoption of this Liew et al. 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