Vector Ecology and Control

Malaria is caused when humans are infected with malaria parasites that are transmitted by mosquito vectors. Vector control interventions that repel or kill mosquitos, such as long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS), are therefore critical tools in reducing the burden of malaria and interrupting its transmission so that countries can reach elimination. IHME researchers are developing models that help to answer key questions about the effectiveness and implementation of vector-based strategies for malaria control and elimination.

Achieving high coverage of these interventions is a fundamental component of current malaria control policy. However, country programs face various financial and operational constraints when it comes to implementing vector control measures, and because malaria transmission can vary so dramatically even within countries, applying single vector-based strategies at a national scale can prove to be an inefficient use of resources. Moreover, malaria transmission often persists even when countries achieve high coverage of LLINs and IRS; their impact is limited by the fact that they can only be used indoors, and resistance of mosquitos to the insecticides used in these interventions is a pressing problem. As a result, novel vector control measures may also be necessary in order to reduce mosquito populations in certain contexts. These new tools, such as attractive toxic sugar baits, larviciding, and mosquito-proofed housing, target mosquitoes both indoors and outdoors, in different habitats, and at various stages in their life cycle – but their potential impact is still being explored.

To provide policy support in response to these challenges, researchers at IHME are developing models that can address a range of important questions related to vector control: How effective are existing vector control interventions, and what will be the impact of achieving certain coverage targets? Which combinations of interventions, either existing or novel, will be needed to reduce the burden of malaria, interrupt transmission, or sustain elimination? When and where should they be deployed?

IHME’s research aims to answer these questions by modeling a number of interrelated components of malaria transmission: mosquito life cycles, feeding, and biting behaviors; parasite incubation and infection; and human behaviors such as mobility patterns and health care seeking. The model ensures that the environment in which these components interact is realistic, taking into account the differences in human and mosquito populations that exist within a particular landscape.

This highly customizable framework enables researchers to model the impact of vector control interventions in specific settings: to compare different interventions in different locations at various levels of coverage and efficacy; to answer key operational questions about how often mosquitoes actually come into contact with these interventions; and to assess the impact of introducing various novel vector control measures, alone and in combination.

Partners: University of California Davis, Durham University, Malaria Elimination Initiative (MEI)