Abstract
BackgroundEvidence on the effectiveness of low-cost, sustainable, biological vector-control tools for the Aedes mosquitoes is limited. Therefore, the purpose of this trial is to estimate the impact of guppy fish (guppies), in combination with the use of the larvicide pyriproxyfen (Sumilarv® 2MR), and Communication for Behavioral Impact (COMBI) activities to reduce entomological indices in Cambodia.Methods/designIn this cluster randomized controlled, superiority trial, 30 clusters comprising one or more villages each (with approximately 170 households) will be allocated, in a 1:1:1 ratio, to receive either (1) three interventions (guppies, Sumilarv® 2MR, and COMBI activities), (2) two interventions (guppies and COMBI activities), or (3) control (standard vector control). Households will be invited to participate, and entomology surveys among 40 randomly selected households per cluster will be carried out quarterly. The primary outcome will be the population density of adult female Aedes mosquitoes (i.e., number per house) trapped using adult resting collections. Secondary outcome measures will include the House Index, Container Index, Breteau Index, Pupae Per House, Pupae Per Person, mosquito infection rate, guppy fish coverage, Sumilarv® 2MR coverage, and percentage of respondents with knowledge about Aedes mosquitoes causing dengue. In the primary analysis, adult female Aedes density and mosquito infection rates will be aggregated over follow-up time points to give a single rate per cluster. This will be analyzed by negative binomial regression, yielding density ratios.DiscussionThis trial is expected to provide robust estimates of the intervention effect. A rigorous evaluation of these vector-control interventions is vital to developing an evidence-based dengue control strategy and to help direct government resources.Trial registrationCurrent Controlled Trials, ID: ISRCTN85307778. Registered on 25 October 2015.
Highlights
Evidence on the effectiveness of low-cost, sustainable, biological vector-control tools for the Aedes mosquitoes is limited
Past research Ae. aegypti is highly anthropophilic, endophilic, and endophagic [19]. This partially explains why previous studies showed that household water storage jars contained over 80% of Ae. aegypti larvae in Cambodia, and why these jars became the main target for dengue vector-control activities [20]
This assumption was based on the results from the earlier World Health Organization/Asian Development Bank guppy fish project in the same province [22], and to be conservative assumed no impact from the PPF in arm 1
Summary
Due to the rise in dengue cases [3] and the current lack of effective vaccines and therapeutics, there is an urgent need to develop more effective vector-control methods [22]. Because of the low acute toxicity of PPF it is considered extremely safe and is recommended by the WHO for use in drinking water [44] This trial is designed to measure the reduction in adult and juvenile mosquitoes due to these vector-control methods relative to a control. One limitation is that the study was powered to detect a statistically significant difference between each arm compared with the control, and not between the intervention arms This reduces the ability to see the impact of the PPF. Measurements of guppy fish coverage will be conducted in control villages to identify the extent of any contamination These data are being collected within one province in Cambodia, it is likely that the result of this trial could be generalizable to areas with similar ecology within the country and in neighboring countries.
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