The “Vector-based Control of Transmission: Discovery Research” program is an extension of the Grand Challenges in Global Health initiative, aimed at establishing a pipeline of innovative new tools that will be safe, easily deployed, effective and sustainable for use in the control of mosquito-borne diseases. A 5-year $25 million grant was awarded to the FNIH in 2009 by the Bill & Melinda Gates Foundation. The program has subsequently been extended to 2016 with additional funding.

Mosquitoes carry a number of human, as well as animal, diseases. Two of these, malaria and dengue, pose enormous global health problems. Attacking mosquito vectors has historically been one of the most effective ways to reduce transmission of these diseases. However, it is widely acknowledged that currently available vector control methods are not sufficient to do the job against malaria and dengue. For example, in many regions mosquitoes are becoming resistant to widely used insecticides and changing their behavior to avoid bed nets.

Under VCTR, the FNIH has initiated a comprehensive program to discover three different kinds of mosquito control tools and take them through proof-of-principle testing:

• New biological control methods that will either reduce the overall number of mosquitoes or prevent the mosquitoes from transmitting a specific pathogen.  In particular, this research aims to identify long-lasting methods that will be highly cost-effective.

  Under VCTR support, infection with a common bacterium known as Wolbachia has been shown to prevent Aedes aegypti mosquitoes from transmitting dengue virus and other pathogens. In field trials conducted in Australia, the Wolbachia was found to spread rapidly through the local mosquito population, offering the possibility of area-wide protection from dengue transmission. Other VCTR-supported studies are examining how genetic changes can be used to reduce mosquito reproduction.

• Odorant-based methods that will keep mosquitoes away from humans (repellents) or attract mosquitoes into traps.

  New chemical compounds have been identified, with VCTR support, which interfere with the initial steps in the mosquito’s ability to recognize and process environmental cues, including carbon dioxide and other volatile compounds, associated with humans.

• Safer, more effective, and less expensive insecticides to provide much needed alternatives to those that are losing their usefulness.

• Currently available insecticides are limited to a small number of compounds that inhibit just four critical metabolic pathways in the mosquito. Under the ‘New Insecticides for Malaria Control’ program, a component of VCTR, projects are seeking to identify new compounds that target different pathways in order to increase insecticide diversity and thereby limit the impact and spread of insecticide resistance.

The FNIH sponsored a meeting in May 2011 in Seattle on the design of field trials for testing the epidemiologic impact of mosquito-based strategies to control dengue. The convening focused on the approaches being developed by the FNIH grant recipients. Participants included experts in vector biology, epidemiology, infectious disease and clinical trial design. The agenda can be found here.

In November 2012, FNIH sponsored a workshop in Atlanta to explore research needs for tools and strategies to more effectively monitor key parameters involved in malaria transmission by anopheline mosquito vectors.  At this meeting, medical entomologists, modelers and malaria experts reviewed the limitations of current methods, and recommended that improved tools for mosquito species identification, age-grading and measuring the intensity of malaria transmission are required for evaluating the efficacy of vector control interventions.  The agenda can be found here.