Monday, 9 January 2012

Helping Mosquitoes Fight Off Malaria

Anybody who knows anything about malaria knows that one catches it from a mosquito bite. Mosquitoes don’t just physically carry the parasite from person to person: they are a required host for Plasmodium spp., the agents of malaria. In the mosquito, the parasites multiply sexually, producing tiny forms called sporozoites which are injected into the next person the mosquito bites.

[caption id="attachment_382" align="alignleft" width="300" caption="Anopheles stephensi feeding; CDC, public domain image"]Anopheles stephensi transmits malaria[/caption]

Clearly, the mosquitoes are infected just as people are, but we seldom feel sorry for the poor mosquitoes because, well, we hate them for all sorts of reasons. The mosquito, however, does have an immune system which tries to fight off invading Plasmodium sp. parasites; Mosquitoes don’t mean to transmit these dangerous parasites.

Humans have had a long and costly battle with malaria which, so far, we have not won. Though not self-evident perhaps, it makes sense that we might be able to enlist the help of the lowly mosquito to our mutual benefit, and that’s what some researchers at Johns Hopkins University have done. Yuemei Dong et al. have genetically modified the immune system of a mosquito species, Anopheles stephensi, giving it an enhanced ability to fight off invading Plasmodium falciparum, the worst of the malaria parasites in humans.

In order for this research to prove useful in the real world, the modified mosquitoes would have to be released into the wild and allowed to breed with wild populations (and hopefully do better than the wild type). Aside from the obvious need for caution when releasing a genetically modified organism into the wild, at this point we still don’t know whether:

  • the resistant mosquitoes will do as well in the wild, faced with different A. falciparum strains

  • other Anopheles spp., also malaria vectors, can be similarly modified (there are about 40)

  • Plasmodium falciparum will develop resistance to the mosquito resistance

  • all other species of Plasmodium infecting humans can be targeted this way

This breakthrough is not the answer to the battle against malaria yet, but it may be part of the answer.

Read the paper:

Dong Y , Das S , Cirimotich C , Souza-Neto JA , McLean KJ , et al. 2011 “Engineered Anopheles Immunity to Plasmodium Infection” PLoS Pathog 7(12): e1002458. doi:10.1371/journal.ppat.1002458

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