Last Updated: 19/07/2022
A cluster randomized, placebo control trial to evaluate the efficacy of a spatial repellent (Mosquito ShieldTM) against Aedes-borne virus infection among children ≥ 4–16 years of age in the Gampaha District, Sri Lanka
Objectives
The primary objective of the study is to demonstrate and quantify the protective efficacy (PE) of Mosquito ShieldTM in reducing the incidence of Aedes-borne virus (ABV) infection, as measured by dengue virus (DENV) specific neutralizing antibodies, in children >4-16 years of age whose sero-status to dengue at baseline is seronegative, indicating they have never been exposed to dengue, or monotypic, indicating positive antibodies to a single DENV infection – ‘qualifying participants’- receiving standard entomological surveillance and control procedures by the local Ministry of Health.
Secondary objectives will address key issues related to the optimization and application of spatial repellent (SR) products for public health and confirm the range of contexts within which SR protective efficacy can be achieved.
Secondary objectives are:
1. Estimating PE against aggregated DENV (multitypics), Zika virus (ZIKV), and Chikungunya virus (CHIKV) seroconversion.
2. Estimating the reduction in ABV disease in trial clusters.
3. Estimating the entomological correlates of reduced ABV infection based on measures of adult female adult Ae. aegypti indoor density and blood fed rate (proxy for human-biting rate).
4. Quantifying PE in relation to Mosquito ShieldTM coverage and seasonal effects.
5. Quantifying the total number of infections averted using Mosquito ShieldTM.
Spatial repellents (SRs) have been widely used for the prevention of mosquito bites but their efficacy in reducing ABV has never been tested rigorously in Asia at large scale. To address this knowledge gap, Sri Lanka was selected as a site to estimate the impact of the SR on ABV related outcomes in an area with high baseline dengue transmission. The study will be conducted in the Gampaha district of Sri Lanka across three Medical Officer of Health areas: Negambo, Wattala, Kelaniya. These areas have been selected due to their similar disease ecology, proximity to each other, and ease of access to the implementers of the trial.
A total of 14,430 total subjects across 3,900 households will be enrolled for monitoring for active disease – ‘febrile surveillance cohort’. These households will form 30 clusters (15 intervention, 15 control), each containing ~187 houses. A subset of this cohort, 3,570 (110-120 per cluster) subjects aged ≥4-16 years that test seronegative (naïve) or positive to a previous single DENV infection (monotypic) at baseline sampling will also be enrolled for measuring DENV infection based on laboratory-confirmed seroconversion – ‘longitudinal cohort’. Persons identified positive for antibodies against multiple DENV serotypes (multi-typic) at baseline, indicating more than one previous infection, will be maintained for secondary analyses. Testing for ZIKV or CHIKV infection at baseline and during the intervention phase of the trial will be dependent on circulation history/detection in study area during study period.
Active ABV disease (symptomatic episodes among febrile surveillance participants) will be assessed through an enhanced passive-surveillance system with case ascertainment performed in designated healthcare facilities. Serum samples will be requested from longitudinal cohort participants within 1-2 weeks of when intervention is first deployed (Baseline sample: T0), with two additional follow up samples taken at ~12 (T1), and ~24 months (T2) from baseline sampling. This sampling scheme will coincide with two DENV seasons in Sri Lanka. DENV seroconversion and ABV active disease rates from pre-intervention and follow-up (post-intervention) samples will be compared between SR active intervention and control clusters. All participating houses in each cluster will be monitored entomologically over 3 months before deployment of the intervention and then monthly after the intervention is in place.
Entomological surveys will include monitoring of indoor Aedes aegypti and Anohpeles stephensi adult population densities. Blood-fed status of Ae. aegypti will also be assessed. The incidence of dengue in each cohort will be estimated and compared to determine the benefit of using an SR. Entomological measures will be measured to determine if there are entomological correlates of SR efficacy that may be useful for the evaluation of new SR products.
Jun 2022 — Jun 2024
$3.86M
Related Resources
