A Q&A with Joseph Wagman, PhD, Senior Public Health Entomologist, Malaria and Neglected Tropical Disease Program, Project Director, New Nets Project at PATH on Malaria Vector Control and highlights from the 18th Annual Meeting Vector Control Working Group (VCWG) that took place last month. Questions by Jenny Andrews, Executive Director, Malaria Partners International.
What was the most interesting and/or surprising thing you learned at the conference?
At the beginning of the global pandemic response in 2020, there was genuine concern that malaria control programs and their partners would not be able to adequately maintain services. The need for intense COVID-19 mitigation procedures and the resulting global supply chain disruptions both presented tremendous challenges, and there was a real risk that an epidemic of rising malaria rates would follow on the heels of COVID.
By and large, that did not happen – and one of the main reasons that a malaria crisis was averted was because of the amazing work that National Malaria Control Programs across Africa did to ensure that core vector control interventions were delivered safely, as quickly and to as many people as possible with minimal disruption. It was not a perfect process, but the results are certainly worth celebrating!
What methods are showing the most promise in vector control?
This is a layered response, because the “newest” methods that are generating the most immediate interest from National Malaria Control are the next generation of bed net and IRS products that are really effective at killing pyrethroid-resistant mosquitoes.
The new bed nets are dual-insecticide nets, which contain a pyrethroid plus one other insecticide from a totally different chemical class. This is much like a combination drug therapy. These are the nets that were around 40% – 50% more effective at reducing malaria cases than the older style, pyrethroid-only nets in two recent randomized trials (Tanzania and Benin). Similar results were recently observed by some of our partners in large scale pilot studies in Burkina Faso, Rwanda, and Mozambique.
The new IRS product contains a brand-new insecticide never before used in public health and never sold in Africa for agricultural use, and has been shown to remain effective for 12 or more months after it has been sprayed on walls.
What emerging technologies are on the horizon that could favorably (or unfavorably) impact vector control in the coming years?
The reason the above response is layered, and complex is because even though the new bed nets and new IRS products have produced very exciting results, they are still just updates to the same methods that have been the basis of malaria control for the last 100 years. So even though I am really excited that a better bed net is available, it is still a bed net and still has many of the same limitations. Same for IRS – these new products could have an immediate, positive impact on preventing thousands of extra cases of malaria, but won’t likely be enough to lead to elimination on their own.
That said, some of the other promising, truly novel vector control methods that may be available for large-scale use sometime soon include:
- Spacial repellent
- The use of drones to map mosquito breeding locations to help guide efficient larval source management (in some cases there is proof of concept that drones can actually effectively deliver larvicides to remotely treat hard to reach breeding sites)
- Attractive targets sugar baits (ATSB), which take advantage of natural sugar feeding behaviors in mosquitoes and could be effective against a broader range of vector species that might not necessarily be targeted by bed nets and indoor spraying
- Genetically modified mosquito strains that produce infertile offspring in wild vector populations and can dramatically reduce population densities, making it difficult to maintain transmission
What challenges do you see on the horizon with regard to vector control?
There is a clear need to adapt malaria control responses to local contexts to be more efficient – we often refer to this as sub-national tailoring of malaria control, and involves developing different packages of vector control interventions that will be effective in different settings. This will require the vector control community to think of creative ways to efficiently evaluate the impact of various combinations of interventions in real-time,
so that lessons learned and best practices can be shared quickly. And, of course, this must be done in the most cost-effective way possible to help accommodate shrinking budgets.