Increasing the potential for malaria elimination by targeting zoophilic vectors

Abstract

Countries in the Asia Pacific region aim to eliminate malaria by 2030. A cornerstone of malaria elimination is the effective management of Anopheles mosquito vectors. Current control tools such as insecticide treated nets or indoor residual sprays target mosquitoes in human dwellings. We find in a high transmission region in India, malaria vector populations show a high propensity to feed on livestock (cattle) and rest in outdoor structures such as cattle shelters. We also find evidence for a shift in vector species complex towards increased zoophilic behavior in recent years. Using a malaria transmission model we demonstrate that in such regions dominated by zoophilic vectors, existing vector control tactics will be insufficient to achieve elimination, even if maximized. However, by increasing mortality in the zoophilic cycle, the elimination threshold can be reached. Current national vector control policy in India restricts use of residual insecticide sprays to domestic dwellings. Our study suggests substantial benefits of extending the approach to treatment of cattle sheds, or deploying other tactics that target zoophilic behavior. Optimizing use of existing tools will be essential to achieving the ambitious 2030 elimination target.

Priorities for Broadening the Malaria Vector Control Tool Kit

“…While feeds on non-human hosts represent ‘wasted bites’ in terms of acquiring or passing on the malaria parasite, they allow the mosquito to escape the effects of interventions like IRS and LLINs that center on the human host. Targeting these mosquitoes with livestock-based interventions could play an important role in reducing residual transmission [7,8,69]. …”

“…[70]), and many of the challenges that apply to conventional IRS (such as inconvenience of householders having to be available to grant access and remove furniture, concerns over odors or staining of walls etc.) are less relevant [7]. In addition, it might well be possible to use different chemical products than those approved for use in domestic dwellings, providing opportunities for resistance management [7].…”

“…are less relevant [7]. In addition, it might well be possible to use different chemical products than those approved for use in domestic dwellings, providing opportunities for resistance management [7]. Where structures don’t exist, livestock-baited tents [71,72] and use of LLIN fences as livestock enclosures [73] have been shown to kill mosquitoes and reduce mosquito numbers indoors.…”

Insights from agriculture for the management of insecticide resistance in disease vectors

“…On a more basic level, however, it will first require strengthening and diversifying methods of vector control that are complimentary to the core insecticide‐based approaches of indoor residual spraying (IRS) and long‐lasting insecticidal nets (LLINs). Alternative approaches, a number of which are already in the later stages of development, include house screening (Kirby et al., ), eave tubes (Sternberg et al., ), attractive toxic sugar baits (Müller et al., ), spatial repellents (Achee et al., ), entomopathogenic fungus‐impregnated targets (Heinig, Paaijmans, Hancock, & Thomas, ), mass trapping (Homan et al., ), and diverse strategies targeting zoophilic vectors (Chaccour et al., ; Massebo, Balkew, Gebre‐Michael, & Lindtjørn, ; Waite et al., ). These new approaches, together with established strategies of larval source management (Tusting et al., ), could all potentially contribute within an IVM framework.…”

Relative Contributions of Genetic and Non-Genetic Factors on Mosquito Microbiota

“…However, wide-spread use of these approaches, combined with exposure to agricultural pest control chemicals, have led to the emergence and rapid spread of insecticide-resistance alleles in many areas [7,8]. In addition, several populations of mosquitoes have modi ed their behaviors (e.g., the host biting time [9,10] and location [11,12] or the host species preference [13,14]) upon exposure to insecticides. This acquisition of chemical and behavioral resistance to insecticides threatens the advances made in control of mosquito-borne diseases and highlight the need for alternative measures.…”