Dengue surveillance using gravid oviposition sticky (GOS) trap and dengue non-structural 1 (NS1) antigen test in Malaysia: randomized controlled trial

Dengue remains a major public threat and existing dengue control/surveillance programs lack sensitivity and proactivity. More efficient methods are needed. A cluster randomized controlled trial was conducted for 18 months to determine the efficacy of using a combination of gravid oviposition sticky (GOS) traps and dengue non-structural 1 (NS1) antigen for early surveillance of dengue among Aedes mosquito. Eight residential apartments were randomly assigned into intervention and control groups. GOS traps were placed at the intervention apartments weekly to trap Aedes mosquitoes and these tested for dengue NS1 antigen. When dengue-positive pool was detected, the community were notified and advised to execute protective measures. Fewer dengue cases were recorded in the intervention group than the control. Detection of NS1-positive mosquitoes was significantly associated with GOS Aedes index (r_s = 0.68, P < 0.01) and occurrence of dengue cases (r_s = 0.31, P < 0.01). Participants' knowledge, attitude, and practice (KAP) toward dengue control indicated significant improvement for knowledge (P < 0.01), practice (P < 0.01) and total scores (P < 0.01). Most respondents thought this surveillance method is good (81.2%) and supported its use nationwide. Thus, GOS trap and dengue NS1 antigen test can supplement the current dengue surveillance/control, in alignment with the advocated integrated vector management for reducing Aedes-borne diseases.

Improved Aedes/dengue field surveillance using Gravid Oviposition Sticky trap and dengue NS1 tests: Epidemiological, entomological outcomes and community acceptance

The aim of this study is to investigate the feasibility and outcomes of using Gravid Oviposition Sticky (GOS) trap and dengue NS1 antigen tests for indoor and outdoor dengue/Aedes surveillance in the field. A one-year community-based study was carried out at Sungai Buloh Hospital Quarters, Selangor, Malaysia. GOS traps were first placed outdoors in three apartment blocks (Anggerik, Bunga Raya and Mawar). Beginning 29th week of the study, indoor traps were set in two apartment units on every floor in Anggerik. All female Aedes mosquitoes caught were tested for the presence of dengue NS1 antigen. Dengue seroprevalence and knowledge, attitude and practices on dengue prevention of the community and their reception to the surveillance approach were also assessed. Dengue-positive mosquitoes were detected at least 1 week before a dengue onset. More mosquitoes were caught indoors than outdoors in block Anggerik, but the total number of mosquitoes caught in all 3 blocks were similar. There was a significant difference in distribution of Ae. aegypti and Ae. albopictus between the 3 blocks. 66.1% and 3.4% of the community were positive for dengue IgG and IgM, respectively. Most respondents think that this surveillance method is Good (89%) and support its use nationwide. Dengue case ratio in the study apartment blocks decreased from year 2018 to 2019. This study demonstrated the practicality of performing proactive dengue/Aedes surveillance inside apartment units using the GOS traps. This surveillance method can be performed with immediate result output in the field.

Knowledge, attitude and practice on dengue prevention and dengue seroprevalence in a dengue hotspot in Malaysia: A cross-sectional study

Dengue has become a global public health problem. Despite reactive efforts by the government in Malaysia, the dengue cases are on the increase. Adequate knowledge, positive attitude and correct practice for dengue control are essential to stamp out the disease. Hence, this study aims to assess the factors associated with dengue knowledge, attitude and practice (KAP), as well as the association with dengue IgM and IgG seropositivity. A community-based cross-sectional study was conducted in a closed, dengue endemic area with multi-storey dwellings . Five hundred individuals (aged 18 years and above) were approached for pre-tested KAP and seroprevalences assessment. The study showed only half of the total participants have good knowledge (50.7%) but they had insufficient knowledge about dengue during pregnancy. 53.2% of people had poor attitude and 50.2% reported poor practice for dengue control. Out of 85 respondents who agreed to participate in the dengue seroprevalence study, 74.1% (n = 63) were positive for dengue IgG and 7.1% (n = 6) were positive for dengue IgM. Among all sociodemographic variable, race is the only independent predicator for all KAP levels (P < 0.05). In conclusion, proactive and sustainable efforts are needed to bring a behavioural change among communities in order to fight dengue outbreaks in endemic areas.

Inapparent dengue in a community living among dengue-positive Aedes mosquitoes and in a hospital in Klang Valley, Malaysia

The public health burden of dengue is most likely under reported. Current dengue control measures only considered symptomatic dengue transmission. Hence, there is a paucity of information on the epidemiology of inapparent dengue. This study reports that many people have been unknowingly exposed to dengue infection. Almost 10% and 70% of individuals without any history of dengue infection and living in a dengue hotspot, in Selangor, Malaysia, were dengue IgM and IgG positive respectively. When dengue-positive mosquitoes were detected in the hotspot, 11 (6.3%) of the 174 individuals tested were found to have dengue viremia, of which 10 were asymptomatic. Besides, upon detection of a dengue-infected mosquito, transmission was already widespread. In a clinical setting, it appears that people living with dengue patients have been exposed to dengue, whether asymptomatic or symptomatic. They can either have circulating viral RNA and/or presence of NS1 antigen. It is also possible that they are dengue seropositive. Collectively, the results indicate that actions taken to control dengue transmission after the first report of dengue cases may be already too late. The current study also revealed challenges in diagnosing clinically inapparent dengue in hyperendemic settings. There is no one best method for diagnosing inapparent dengue. This study demonstrates empirical evidence of inapparent dengue in different settings. Early dengue surveillance in the mosquito population and active serological/virological surveillance in humans can go hand in hand. More studies are required to investigate the epidemiology, seroprevalence, diagnostics, and control of inapparent dengue. It is also crucial to educate the public, health staff and medical professionals on asymptomatic dengue and to propagate awareness, which is important for controlling transmission.

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

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).

Electronic supplementary material

The online version of this article (10.1186/s40249-019-0584-y) contains supplementary material, which is available to authorized users.