Bacterial larvicides used for malaria vector control in sub-Saharan Africa: review of their effectiveness and operational feasibility

Yahya A Derua,William N Kisinza,Eliningaya J Kweka,Andrew K Githeko,Franklin W Mosha

doi:10.1186/s13071-019-3683-5

Abstract

Several trials and reviews have outlined the potential role of larviciding for malaria control in sub-Saharan Africa (SSA) to supplement the core indoor insecticide-based interventions. It has been argued that widespread use of long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) interventions in many parts of Africa result in many new areas with low and focal malaria transmission that can be targeted with larvicides. As some countries in SSA are making good progress in malaria control, larval source management, particularly with bacterial larvicides, could be included in the list of viable options to maintain the gains achieved while paving the way to malaria elimination. We conducted a review of published literature that investigated the application of bacterial larvicides, Bacillus thuringiensis var. israelensis (Bti) and/or Bacillus sphaericus (Bs) for malaria vector control in SSA. Data for the review were identified through PubMed, the extensive files of the authors and reference lists of relevant articles retrieved. A total of 56 relevant studies were identified and included in the review. The findings indicated that, at low application rates, bacterial larvicide products based on Bti and/or Bs were effective in controlling malaria vectors. The larvicide interventions were found to be feasible, accepted by the general community, safe to the non-target organisms and the costs compared fairly well with those of other vector control measures practiced in SSA. Our review suggests that larviciding should gain more ground as a tool for integrated malaria vector control due to the decline in malaria which creates more appropriate conditions for the intervention and to the recognition of limitations of insecticide-based vector control tools. The advancement of new technology for mapping landscapes and environments could moreover facilitate identification and targeting of the numerous larval habitats preferred by the African malaria vectors. To build sustainable anti-larval measures in SSA, there is a great need to build capacity in relevant specialties and develop organizational structures for governance and management of larval source management programmes.

Highlights

Malaria mosquito vector control in sub-Saharan Africa (SSA) relies on the use of insecticide-treated bednets and/or indoor residual spraying with insecticide
Of the remaining 48 articles, 3, 3 and 32 reported studies that evaluated the activity of larvicides in laboratory, semifield and field settings only, respectively, whereas 10 articles reported a mixture of these types of studies (Table 1)
The findings from the reviewed studies indicated that, at low application rates, bacterial larvicide products based on Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs) were effective against malaria vectors in SSA

Summary

Introduction

Malaria mosquito vector control in sub-Saharan Africa (SSA) relies on the use of insecticide-treated bednets and/or indoor residual spraying with insecticide. These interventions have been shown to be effective and the recent decline in malaria prevalence in many parts of Africa has been attributed in part to their wide-scale use Mosquito larval control interventions have proven records of lowering malaria transmission and even eradication of malaria mosquitoes [8]. Derua et al Parasites Vectors (2019) 12:426 unlike adult mosquitoes, larvae cannot change their behavior to avoid a control intervention targeted at larval habitats [9]. Integrating larval source reduction with adult mosquito control interventions like insecticidetreated bednets has been considered to be a highly effective strategy to control malaria [10]. Preference has been shifted to the use of microbial larvicides Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs), which selectively kill mosquito larvae with negligible effect to nontarget organisms [12]

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