Mosquitoes appear to be acquiring a stronger taste for human blood, out of necessity. A new study out of Brazil suggests that as forests are cut down and wildlife vanishes, local mosquitoes are switching from feeding on animals to feeding on people, reports Popular Science. It's more than an annoyance: The shift has the potential to boost the spread of viruses like dengue, Zika, and yellow fever. The research in the journal Frontiers focused on two areas in Rio de Janeiro state that were part of Brazil's Atlantic Forest, now reduced to about 29% of its original size by deforestation and development. In those previously uninhabited landscapes, human blood turned up in nine mosquito species, the study found.
"Mosquitoes that are normally feeding on other hosts within the habitat can shift to humans if the habitat is no longer suitable for those hosts and they leave," Laura Harrington, an entomology professor at Cornell University, tells ABC News. Co-author Sergio Lisboa Machado of the Federal University of Rio de Janeiro called mosquitoes "opportunists" that rarely travel far, meaning they take what's nearby rather than burn energy searching for wildlife.
Prior research has already linked heavy deforestation to higher mosquito numbers and more mosquito-borne disease, in part because disturbed areas favor hardy species that thrive near people. At the same time, deforestation removes animals that can dilute disease transmission, leaving humans as the main blood source. Of the roughly 3,500 mosquito species worldwide, Harrington notes that only a small number are strongly drawn to humans. But habitat change can tip that balance. "Manipulating the landscape can alter mosquito feeding patterns and sometimes shift feeding patterns towards humans," she says.
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