BOSTON — Amateur bird-watcher Joan Trueblood interacts with wild birds at Jamaica Pond in the safest way possible these days: through binoculars and from a distance. Still, she’s not terribly concerned about avian influenza — just yet.
“I know viruses can mutate and that can change the whole picture rapidly,” she said.
That may already be happening. The CDC reports that a Louisiana man severely ill from bird flu he contracted from a backyard flock, is infected with a virus that appears to have mutated to enhance human transmission.
“We always have to keep in mind that, yes, at any point if the avian flu mutates it could cause issues,” said Anne Staudenmaier, VMD. a veterinarian and Exotic Pet and Zoo Medicine specialist at Angell Animal Medical Center. “We don’t want to ignore the risk it carries. But at the same time, it’s not necessarily the average person who is going to get it.”
At this point, exposure to infected animals seems a prerequisite for human infection. And opportunities for such exposure have exploded in the last four months. In Massachusetts, this year, numerous wild birds have been found to be infected with H5N1. The USDA reports that in September, the number of commercial and backyard poultry flocks in the U.S. with avian flu infections stood at three — with 70,000 birds affected. As of this month, more than a hundred flocks have been affected — totaling nearly 17 million birds.
While bird flu is still considered a minimal threat to humans — with the vast majority of cases resulting in mild disease — the same can’t be said for mammals. In fact, the toll has been devastating. Between November and December 20 large felines — including bobcats and a Bengal tiger died from bird flu infections at a wildlife sanctuary in Washington state.
In that case, Staudenmaier said it’s likely infected raw meat killed the cats.
“Right now, we don’t think those cats got it from each other,” she said. “We think they got it because they were all being fed from the same food source.”
Last year, thousands of sea mammals perished in an epidemic likely triggered by ingestion of infected birds. One study reports members of some 48 species have succumbed to H5N1 infection. Another found a 100% mortality rate in ferrets lab-infected with avian influenza from cats.
Domestic cats, in fact, seem particularly vulnerable to the virus. And it’s unknown exactly why.
“Basically, the virus gets in a lot of different, really important organs and causes them to fail,” said Staudenmaier. “Especially the central nervous system and lungs.. If you’re having a lot of inflammation and a lot of disease and a lot of necrosis or death in those organs that’s obviously not amenable to life.”
Staudenmaier said death in mammals can also result from the overwhelming immune response triggered by H5N1 infection.
Could a domestic cat or other pet transmit a bird flu infection to its owner? Possibly, Staudenmaier said, but unlikely.
Still, she recommends taking precautions if a pet seems lethargic or otherwise shows signs of illness — and she said a diet of raw food is risky.
The CDC recommends animals and humans keep their distance from wild birds, be they dead or alive — and avoid contact with bodies of water that birds may have contaminated.
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