Lethal virus carried by mosquitoes is too close for comfort

Published: September 26, 2019

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As if mosquitoes haven’t given us enough reasons to loathe them. Globally, there’s yellow fever, dengue fever, Zika, and malaria, of course. Closer to home, we now have West Nile virus. And let’s not ignore just how annoying mosquitoes are with their zzzzzz and their itchy bites.

Recently, though, there’s news about another mosquito-borne disease—a lethal one—that’s a little too close to Canadian cottage country for comfort.

Eastern equine encephalitis (EEE) has killed a number of people in the U.S. this season, including six in the state of Michigan alone. Though EEE is typically an eastern coastal disease—hitting the New England states, those down the coast, and then those along the southern coast to Eastern Texas—it has now surfaced in southern Michigan, where it’s having a particularly deadly season. In fact, six people in that state alone have died of EEE this past summer.

The situation is dire enough that officials in Michigan have released an official plea for people to stay indoors, particularly after dusk.

The culprit appears to be the cattail mosquito, an abundant species and one that bites mammals, including humans. Edward “Ned” Walker, a professor of microbiology and entomology at Michigan State University, says that researchers suspect that the cattail mosquito is the “bridge vector” or secondary factor. They theorize that birds are getting infected with the disease from mosquitoes that feed only on the blood of birds. Then the infected birds get bitten by these cattail mosquitoes, which then carry the virus, transmitting it to horses, white-tailed deer, and even, this past summer in Michigan, a donkey. And, frighteningly, to humans. Horses are particularly susceptible, for reasons that researchers have yet to discern, leading to the “equine” part of the disease’s name.

Should Canadian cottagers be concerned? Should we—gasp!—stay indoors?

Not yet, says Ned Walker, offering up a fascinating (but long) explanation of the glacial history of Michigan, which has created just the kind of habitat where the mosquito species that carries the EEE virus thrives. Lucky for us, these mosquitoes haven’t yet taken up residence in the somewhat different type of bogs and marshes that we have in Canada.

Before you breathe a huge sigh of relief, however, Walker admits that he’s concerned about the impact of climate change and warming temperatures. “It might result in shifts in distributions of mosquitoes,” he says, noting that, occasionally, EEE has surfaced in parts of Michigan with a different ecology than these post-glacial mosquito nirvanas.

One more reason to load up on repellent. And one more reason to hate mosquitoes.

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