Mosquito transmission plays key role in malaria severity

29 May 2013

Anopheles gambiae mosquito

Image: Anopheles gambiae mosquito©  US Centers for Disease Control and Prevention.

Scientists have discovered that transmission of the malaria parasite via the mosquito regulates its ability to cause disease and therefore affects the severity of the illness. 

This is because parasite gene expression changes during transmission through mosquitoes, which changes the type of immune response generated in a mammal host. This, in turn, reduces parasite growth and associated disease. 

The team also identified parasite genes that may play a role in inducing an effective immune response, and therefore controlling the malaria parasite. By identifying these potential targets of effective anti-malaria immunity, the findings could help drive the development of an effective vaccine. 

The work was led by Jean Langhorne of the MRC's National Institute for Medical Research (now part of the Francis Crick Institute)  and carried out in collaboration with the Wellcome Trust Sanger Institute in Cambridge. 

Malaria is caused by five species of protozoan parasites called Plasmodium. These parasites are spread to people through the bites of infected mosquitoes. 

Laboratory studies to investigate the malaria parasite in the blood are usually done by injecting Plasmodium-infected blood directly into mice. However, for this study the researchers developed an efficient method to transmit the parasites through mosquitoes, by infecting mice via mosquito bites - mirroring the normal way people are infected in real-life. 

Dr Langhorne explained: "Our study shows that the complex interaction between the parasite and the mosquito vector determines the severity of disease caused by the malaria parasite. 

"These findings will influence the ways in which experimental malaria research is performed, and therefore the outcomes of immunity and pathogenesis studies, and shift our focus towards understanding the role of the mosquito vector and the natural route of transmission in the pathogenesis of malaria. 

"This opens up exciting new avenues of research that could help identify protective immune mechanisms and their targets and thus advance the development of an effective anti-malaria vaccine. This work therefore has enormous implications for our long-term goal of malaria control and eradication." 

The paper, Vector transmission regulates immune control of Plasmodium virulence, by Philip Spence, William Jarra, Prisca Lévy, Adam Reid, Lia Chappell, Thibaut Brugat, Mandy Sanders, Matthew Berriman and Jean Langhorne, is published in Nature.

 

  • Transmission of the malaria parasite via the mosquito regulates its ability to cause disease and therefore affects the severity of the disease, according to new research from the MRC's National Institute for Medical Research. 
  • This discovery, and the identification of genes involved, provide potential targets for the development of an effective vaccine against malaria. 
  • Malaria remains one of the most devastating diseases in the developing world - one report showed it caused 1.2 million deaths in 2010 alone. In Africa, a child dies every minute from malaria. The most commonly used drugs are failing rapidly due to resistance, alternatives are expensive and there is no vaccine.