GardenDrumTackling malaria by killing ‘grannies’ in Africa

Prosopis juliflora               Photo credit: J.M. Garg

Controlling an invasive species of tree in Africa can significantly reduce the incidence of malaria transmission, a new study has found.  And it’s all to do with killing grannies.

In what’s being billed as ‘extreme gardening’, researchers from the University of Miami as well as the Hebrew University Medical School, Israel, set up a study with Mali locals to test a theory that a widespread species of weed was propping up the local population of malaria-carrying mosquitos.

The fabaceous (pea family) tree, Prosopis juliflora, was introduced to Africa in the 1970s in an attempt to reforest arid areas. It now occupies millions of acres across Africa and is a significant source of nectar for anopheles mosquitos.

The team compared sites where they had pruned off the flower spikes of Prosopis juliflora with sites where they hadn’t, trapping mosquitos on mass to assess population dynamics and the incidence of the malaria virus.

Their article, published in the Malaria Journal recently, found a staggering 60% drop in the population of mosquitos, especially amongst ‘granny’ mosquitos that are the main carriers and transmitters of malaria.

It takes up to ten days for newly-infected juvenile female mosquitos to become mature enough to pass the virus on to humans, by which time they’re actually the grannies of the mosquito world. As mosquitos age, they become less dependent on blood and more likely to forage for nectar to help sustain themselves.

The team has established for the first time that controlling nectar load in local plants may actually help ‘starve’ mosquitos most likely to carry malaria. The results are being billed as a useful management tool for arid areas, where the control of flowering times of shrubs is possible, but less useful in tropical areas.


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