Image: Cat with MRSA
Photo courtesy Lori Spagnoli
Two of Lori Spagnoli's three cats, Dotti, top, Momo, middle, and Fluffy, bottom, contracted MRSA infections. Fluffy's cleared up with antibiotics, but Momo's got worse. Spagnoli makes sure to clean litter boxes daily and to wash her hands frequently to prevent transmission to the people in the family.
By JoNel Aleccia Health writer
updated 3/12/2008 5:00:40 PM ET 2008-03-12T21:00:40

As if all the angst about drug-resistant staph bacteria wasn’t worrisome enough, now it turns out you might get the deadly germ from your cat.

Suspicions about that calico on the couch are being raised this week in the New England Journal of Medicine. German scientists reported that a woman endured a series of nasty abscesses caused by methicillin-resistant Staphylococcus aureus, known as MRSA, until a veterinarian screened — and treated — the family cat.

It’s not an isolated case, or critter, according to researchers in the U.S. and Canada who are studying the connection between pets, people and this dangerous, drug-resistant bug linked to more than 94,000 infections and nearly 19,000 deaths in the U.S. in 2005.

“We’ve found MRSA in dogs, cats, rabbits, pigs — even marine mammals,” said J. Scott Weese, an associate professor of pathobiology at the University of Guelph in Ontario, Canada. Horses and cows also are routinely affected.

Owners should be aware, but not worried, about the possibility of getting MRSA from their pets, said Weese, who is part of a team led by researchers at the University of Missouri, Columbia, studying the prevalence of MRSA in humans and companion animals.

“The big thing we need to get the mindset around is that we’re not a population of dogs, cats and people, we’re a population of animals,” said Weese.

The question perplexing scientists is whether people and pets swap the MRSA germs back and forth, creating a loop of infection and reinfection that could endanger humans and animals alike.

People and pets carry MRSA germs
So far, it’s clear that humans and pets can be colonized with the MRSA bacteria, said John R. Middleton, an associate professor of food animal medicine and surgery at the University of Missouri.  That doesn’t mean they’ve got active infections, just that they’re carriers of the germs that are resistant to most frontline antibiotics.

An ongoing study of some 600 people-pet households across the U.S. showed that staph aureus germs were present in nearly 28 percent of people and about 13 percent of pets. About 10 percent of households had both a human and an animal colonized.

MRSA, the drug-resistant strain, was detected in more than 5 percent of humans and about 3 percent of dogs and cats, Middleton said.

What’s not so clear is whether people got MRSA from their pets — or whether they gave it to them, researchers said. One theory is that pets may pick up the bacteria from people, but then serve as reservoirs, harboring the bugs so they can reinfect humans.

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“Pets could be innocent bystanders, or they could be significant sources of infection,” Weese said. “They’re probably somewhere in between.”

For many people and their pets, the MRSA cycle is not serious. Most MRSA infections are minor skin lesions that are cured quickly with proper hygiene and secure bandages. The bacteria become dangerous when they travel inside the body, where they can lead to bloodstream or surgical site infections or life-threatening pneumonia.

If infections don't heal, test pets
In homes where people are suffering serial MRSA infections or from surgical wounds that just don’t heal, it’s a good idea to consider the non-human family members, scientists said.

“They’ll go ahead and treat all the humans, but they haven’t treated the pets,” Middleton said.

Most vets should be able to conduct the simple swab tests to determine whether a pet is colonized with MRSA, he added.

If the test comes back positive, don't panic, said Lori Spagnoli, 59, of New Jersey. Her oldest cat, Momo, has had a lingering MRSA infection since 2005. Spagnoli's husband, Joe, tested positive for MRSA colonization once, but not again. Spagnoli attributes her family's MRSA-free status to scrupulous sanitation and supplements that boost the immune systems of people and cats alike.

She never considered giving away 15-year-old Momo, or the cat's offspring, Fluffy and Dotti, both 14. Instead she sought advice from the United Kingdom-based Bella Moss Foundation, which helps people whose pets have MRSA.

"I view it as any other bacteria that a family member having it could enter the home," she said. "You're on notice that it might be an issue."

People typically are dosed with stronger-than-normal antibiotics to kick intractable MRSA infections. That’s possible in pets, too, but it appears that animals will shed the bacteria on their own, Weese said, given enough time, good hygiene and no reinfection by a human source.

A good thing, too. One effective cure for animals is a dose of antibiotic nasal cream, which is applied more easily in some species than others, said Middleton.

“You can imagine trying to treat a cat,” he said.

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