Parasitology: Bacteria may control malaria parasite infection in mosquitoes

Infection of Anopheles mosquitoes - a major malaria vector - with Wolbachia bacteria correlates with reduced presence of malaria parasites in the mosquitoes, reports a study published in Nature Communications. The findings suggest that Wolbachia bacteria may have an important role in malaria transmission and support their use as a potential tool to reduce the spread of malaria.

Wolbachia bacteria naturally infect many insects, impacting their physiology and reproduction, leading to the longstanding notion that that they could potentially be used to control populations of mosquitoes that transmit pathogens such as dengue or Zika viruses, or malaria parasites (Plasmodium). However, the use of bacteria to block malaria spread has not been fully explored.

Flaminia Catteruccia and colleagues collected over 600 Anopheles mosquitoes in Burkina Faso - a country with high malaria burden - between 2011 and 2014, and found that 19% to 46% (depending on the year) were infected with a particular Wolbachia strain called wAnga. They also collected mosquito eggs and larvae and bred them in the laboratory; they then showed that the wAnga-infected mosquitoes laid eggs more quickly than the uninfected insects. Finally, they screened 221 Anopheles female mosquitoes for Plasmodium and Wolbachia infections, finding Plasmodium in 12 mosquitoes (at a frequency of about five percent, consistent with previous studies) and Wolbachia in 116 mosquitoes. Only one of the insects tested positive for both Wolbachia and Plasmodium infections.

The results of the study are consistent with the hypothesis that Wolbachia is currently naturally controlling malaria transmission. However, further research is required to confirm whether Wolbachia-Plasmodium co-infections are rare in Anopheles mosquitoes in other areas, and to determine the underlying mechanisms.