Bird flu also kills wild mammals

When a new version of bird flu swept across North America a few weeks ago, researchers began isolating the virus from red foxes, bobcats and other mammals. The reports are only ad hoc for the time being, but the situation should be monitored.

The Dane County Humane Society in Wisconsin received calls last April. At the end of the line, residents of the region reported the strange behavior of foxes, some adults and others younger. The animals were reportedly shaking and struggling to stand. The foxes, too, often lethargic and traveling alone, seemed unusually easy to reach.

Then very soon foxes arrived at the center, most suffering from convulsions before succumbing. Initial analyzes ruled out rabies and other possible causes. Finally, lab tests revealed a much more surprising culprit: a highly virulent strain of bird flu.

Several species affected

The virus, a type of bird flu known as Eurasian H5N1, spread across Europe, Africa, the Middle East and Asia last year. The pathogen then made its way to North America via migratory birds, forcing the culling of hundreds of breeding flocks of poultry in 36 states.

This version of the virus also appears to wreak greater havoc wild birds than previous lines. Ducks, geese, gulls and other terns, many species are affected. The virus would then have infected mammals that fed on these birds, including wild red foxes.

At least seven US states have detected the virus in foxes. Two lynxes in Wisconsin, a baby coyote in Michigan and several skunks in Canada have also tested positive, as have foxes, otters, a lynx, a polecat and a badger in Europe.

Note that two human cases have also been reported (one in the United States and one in the United Kingdom), both in humans who have been in close contact with birds.

A rescued fox. Credit: Dane County Humane Society

Mammals, always a dead end

So far, the virus seems to be causing more damage younger Foxes, probably because they don’t have a fully developed immune system yet. However, the overall infection and death rate is still unknown as reports emerge are anecdotal.

While it’s possible that the virus evolved to better infect mammals, experts note that the most likely explanation for this sudden surge in the number of infected mammals is that this lineage infects large numbers of wild birds, which then kills the Increased chance that scavengers can encounter it.

So far, the virus also doesn’t appear to be causing enough disease or death in wild mammals to endanger these species. And we don’t have that for now no evidence of sustained mammalian to mammalian transmission. ” It’s still a bird virus“Notes Richard Webby, influenza virologist at St. Jude Children’s Research Hospital in Memphis. And mammals are generally considered like dead ends for these viruses.

However, the power of evolution should not be underestimated. The more mammals the virus infects, the more opportunities it has to discover new mutations that could help it spread among foxes, bobcats, or even humans.

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