Spatial repellents: from discovery and development to evidence-based validation

Abstract

International public health workers are challenged by a burden of arthropod-borne disease that remains elevated despite best efforts in control programmes. With this challenge comes the opportunity to develop novel vector control paradigms to guide product development and programme implementation. The role of vector behaviour modification in disease control was first highlighted several decades ago but has received limited attention within the public health community. This paper presents current evidence highlighting the value of sub-lethal agents, specifically spatial repellents, and their use in global health, and identifies the primary challenges towards establishing a clearly defined and recommended role for spatial repellent products in disease control.

Figure 1

The general concept of spatial repellency is clear: to prevent an arthropod from entering a space occupied by a potential human host to reduce encounters between humans and vectors thereby eliminating or reducing the probability (risk) of pathogen transmission to either insect or human.

Figure 2

The fundamental choice between killing mosquitoes and deterring them: mosquitoes that abort attacks on humans because of sub-toxic exposure are, by definition, not exposed to toxic levels that kill them (Killeen GF and Moore SJ with permission).

Figure 3

An outdoor role for spatial repellents? Mathematical models show that the best strategy for application of spatial repellents depends on the vector. Indoors and outdoors use is best for those vectors least susceptible to LLINs/IRS, while use of spatial repellents outdoors is best to complement LLINs/IRS in areas where vectors feed indoors on humans (Killeen, GF and Moore, SJ with permission).