Comparison of Novel Sandfly Control Interventions: A Pilot Study in Bangladesh.

Debashis Ghosh,Piero L Olliaro,Christine M Halleux,M Mamun Huda,Axel Kroeger,Abdul Alim,Dinesh Mondal,Greg Matlashewski,Md Almahmud

doi:10.4269/ajtmh.20-0997

Abstract

ABSTRACT.In this pilot comparative study, we investigated and compared the effects of existing vector control tools on sandfly densities and mortality to inform and support the National Kala-azar Elimination Program (NKEP). The interventions included insecticidal wall painting (IWP), reduced-coverage insecticidal durable wall lining (DWL), insecticide-impregnated bednets (ITN), and indoor residual spraying with deltamethrin (IRS). Sakhua union with seven villages was the study area, which was the most highly endemic visceral leishmaniasis union in Trishal upazila, Bangladesh. Each cluster containing the different interventions included approximately 50 households. Study methods included random selection of clusters, collection of sandfly by CDC light trap and manual aspirator to determine sandfly density, and sandfly mortality determined by WHO cone bioassay test. Trained field research assistants interviewed household heads using structured questionnaires for sociodemographic information, as well as safety and acceptability of the interventions. Descriptive and analytical statistical methods measured interventions’ effect and its duration on sandfly density reduction and mortality. We measured the relative efficacy of IWP on sandfly control against DWL, ITN, and IRS by the difference-in-difference regression model. We found that existing interventions were effective and safe for sandfly control with different duration of effect and acceptability. The relative efficacy of IWP for sandfly reduction varied by –59% to –91%, –75% to –81%, and –30% to –104% compared with DWL, ITN, and IRS, respectively, at different time points during the 12-month follow-up. These study results will guide the NKEP for selection of sandfly control tool(s) in its subsequent consolidation and maintenance phases.

Highlights

Visceral leishmaniasis (VL) or kala-azar (KA) is a vectorborne disease caused by Leishmania donovani and is transmitted by female Phlebotomus argentipes sandflies
The only associations between female P. argentipes sandfly densities (FPAD) and HHs socioeconomic demographics were a negative association with a cement floor in the HH was observed in the insecticidal wall painting (IWP) cluster, and a positive association with mud walls and regular use of bednets was observed in the indoor residual spraying with deltamethrin (IRS) cluster (Table 1)
The major findings of the study are that all vector control interventions including insecticideimpregnated bednets (ITN), durable wall lining (DWL) (1-meter high), IWP, and IRS are effective for sandfly control; the strength and duration of efficacy differed considerably, and the IWP had superior performance compared with ITN, DWL, and IRS interventions

Summary

Introduction

Visceral leishmaniasis (VL) or kala-azar (KA) is a vectorborne disease caused by Leishmania donovani and is transmitted by female Phlebotomus argentipes sandflies. In the Indian subcontinent, the disease is endemic, and its presence has been documented since the 19th century where the first reported VL outbreak was in 1824 in the territory of current Bangladesh. During this period, VL caused the deaths of 75,000 people over 3 years.[1] VL peaks periodically, possibly when herd immunity (which is yet to be defined) wanes.[2]. The target of the attack phase is to reduce VL incidence to less than 1 case per 10,000 people at the upazila, block, and district levels, respectively, in Bangladesh, India, and Nepal.[4] Nepal and Bangladesh achieved the elimination target of the attack phase in 2013 and 2016, respectively. India is very close as only 6% of the blocks have a VL incidence of . 1 per 10,000 people.[5]

Methods

Results

Conclusion