Efficacy and community-effectiveness of insecticide treated nets for the control of visceral leishmaniasis: A systematic review

Abstract

Visceral leishmaniasis (VL) has been targeted for elimination from Southeast Asia (SEA). The disease has been endemic in SEA, and in other parts of the world involving both humans and animals. One of the key strategies for combating VL is controlling for the vector sandfly. There are a few vector control strategies that are currently in practice. We sought to assess the efficacy and community effectiveness of insecticide treated nets (ITNs) in controlling the burden of sandfly and the occurrence of VL among humans. We conducted a systematic review following a study protocol and the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) criteria. 6331 initial hits were retrieved from Google Scholar, Lilacs, PubMed, Science Direct, WHOlis, WHOiris and PAHOiris. 25 met the full inclusion criteria. Findings show that the insecticide impregnated bednets and the commercially treated long lasting insecticidal nets (LLINs) are effective in controlling sandflies, with mortalities as high as 75% lasting over a year; although their role in controlling VL in the community was not extensively studied, since effectiveness was usually measured with sandflies densities. Findings also show that insecticide impregnated bednets are low cost and well accepted in the community, however, early erosion of insecticides from nets could occur. Some studies also showed that killing of sandflies may not translate into reduction of VL, therefore sandfly knock down and killing data needs to be interpreted with caution. Conclusions of this review are (1) combining insecticide impregnated bednets, as targeted interventions, with another vector control measure, particularly indoor residual spraying, and in conjunction with case detection, could be the way forward to controlling VL in resource limited settings. (2) Given the current low incidence of VL in SEA, it can be difficult to further research the community effectiveness of those control measures in reducing VL. Author summary Visceral leishmaniasis (VL) is a vector borne disease endemic in Southeast Asia (SEA) and present in other regions of the world. In SEA the disease has been targeted for elimination. VL is transmitted by different species of sandflies and key strategies against VL rely on the control of the vectors. This systematic review assesses the efficacy and community effectiveness of insecticide treated nets (ITNs) in controlling sandflies and VL occurrence among humans. After a revision of 6331 initial hits, 25 studies were included in this systematic review. Main findings indicated that insecticide impregnated bednets and long-lasting insecticidal nets (LLINs) can effectively control sandflies, however, it was not possible to fully assess the role of ITNs in controlling VL transmission. Additional results showed that insecticide impregnated bednets are low cost and well accepted in the community, however early erosion of insecticides from the nets could occur. If insecticide impregnated bednets are combined with other vector control measures, such as indoor residual spraying, and together with case detection, it could be an important strategy to control VL in resource limited settings.