Abstract
BackgroundVisceral leishmaniasis (VL) control in the Indian subcontinent is currently based on case detection and treatment, and on vector control using indoor residual spraying (IRS). The use of long-lasting insecticidal nets (LN) has been postulated as an alternative or complement to IRS. Here we tested the impact of comprehensive distribution of LN on the density of Phlebotomus argentipes in VL-endemic villages.MethodsA cluster-randomized controlled trial with household P. argentipes density as outcome was designed. Twelve clusters from an ongoing LN clinical trial—three intervention and three control clusters in both India and Nepal—were selected on the basis of accessibility and VL incidence. Ten houses per cluster selected on the basis of high pre-intervention P. argentipes density were monitored monthly for 12 months after distribution of LN using CDC light traps (LT) and mouth aspiration methods. Ten cattle sheds per cluster were also monitored by aspiration.FindingsA random effect linear regression model showed that the cluster-wide distribution of LNs significantly reduced the P. argentipes density/house by 24.9% (95% CI 1.80%–42.5%) as measured by means of LTs.InterpretationThe ongoing clinical trial, designed to measure the impact of LNs on VL incidence, will confirm whether LNs should be adopted as a control strategy in the regional VL elimination programs. The entomological evidence described here provides some evidence that LNs could be usefully deployed as part of the VL control program.Trial registrationClinicalTrials.gov CT-2005-015374
Highlights
Visceral leishmaniasis (VL), known as kala azar, is a lifethreatening vector-borne disease with a fatal outcome if left untreated
In the absence of an effective vaccine, the program will rely on the active detection and prompt treatment of cases throughout the endemic region, combined with a recurrent indoor residual spraying (IRS) of all villages at risk
Vector control programs based on IRS are notorious for failing to maintain comprehensive spray coverage over time owing to logistical problems and lack of compliance by householders
Summary
Visceral leishmaniasis (VL), known as kala azar, is a lifethreatening vector-borne disease with a fatal outcome if left untreated. A large proportion of the 500,000 annual cases and 60,000 deaths occur in the poor rural communities within the Indian subcontinent [1]. In this region, VL is caused by Leishmania donovani and is transmitted by the sand fly Phlebotomus argentipes [2]. In the absence of a human leishmaniasis vaccine, the elimination program proposes to reduce VL incidence by active case detection and treatment, and the widespread use of residual insecticide spraying (IRS) of houses and cattle sheds with DDT in India and with pyrethroids in Nepal and Bangladesh. We tested the impact of comprehensive distribution of LN on the density of Phlebotomus argentipes in VL-endemic villages
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