Disclosures: Herron reports no relevant financial disclosures.
June 03, 2020
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Q&A: Microbe shows potential as new tool for malaria control

Disclosures: Herron reports no relevant financial disclosures.
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Researchers in Kenya discovered a microbe in Anopheles arabiensis mosquitoes that showed “high levels of impairment” of Plasmodium falciparum, a common malaria parasite in many African countries.

Jeremy K. Herren, PhD, a research scientist at the International Centre of Insect Physiology and Ecology in Nairobi, Kenya, and colleagues said the microbe, Microsporidia MB, has the potential to be a new tool for malaria control.

A naturally occurring microbe impaired malaria transmission among Anopheles arabiensis mosquitoes in Kenya. Credit: CDC/James Gathany
A naturally occurring microbe impaired malaria transmission among Anopheles arabiensis mosquitoes in Kenya. Credit: CDC/James Gathany

Healio spoke with Herren about how the discovery of this microbe could impact efforts to control malaria. – by Ken Downey Jr.

Jeremy K. Herren

Question: What is Microsporidia MB, and where is it found?

Answer: It is a symbiotic microbe found naturally in Anopheles mosquitoes.

Q: How does it impair Plasmodium transmission?

A: We are still figuring out exactly how it blocks transmission. There is evidence to suggest that it primes or “makes the mosquito immune system ready” to fight off Plasmodium.

Q: In the study, the microbe impaired transmission of P. falciparum. What about the other species of Plasmodium that infect humans?

A: We plan to investigate how the microbe interacts with other plasmodium species. In Africa, where Microsporidia MB is found, P. falciparum is the dominant species.

Q: How does this approach compare with other investigational mosquito control efforts, such as gene drives and Wolbachia­-based approaches?

A: There are certainly parallels with Wolbachia-based approaches, where a bacterial symbiont is used for transmission blocking. Wolbachia is transmitted only from mother to offspring mosquitoes, so it necessitates a population replacement. We have recently established that Microsporidia can spread a number of different ways (not just from mother to offspring), so the dissemination strategy for Microsporidia MB might be quite different from that of Wolbachia. There are some conceptual similarities with gene drives, but Microsporidia MB does not change the genetic makeup of the mosquito.

Q: How feasible is this strategy, and how soon could it be implemented in high-burden malaria countries?

A: It is still early stages, but this finding is very promising. It is completely different from all the other methods currently used to control malaria and, therefore, could be used synergistically with them to deal a much more powerful blow against this deadly disease. We are now studying the epidemiology of the microbe in captive mosquito populations. This will allow us to understand the routes and rates of spread, at which point we could design a strategy for deployment. This second phase of the research will certainly be ongoing until late 2021. What is very encouraging is that it is a natural microbe that is already present in some populations of mosquitoes in Africa, and therefore, there is a much lower risk associated with its dissemination (compared with introducing a foreign agent). I think that in light of this, if it spreads well, we could have something useful in a relatively short time frame.