Elaine Thompson  /  AP file
Dutch researchers have discovered cats can spread bird flu to each other.
updated 9/13/2004 3:25:55 PM ET 2004-09-13T19:25:55

Cats not only can catch the deadly bird flu but can spread it to other felines, Dutch researchers reported Thursday, raising important questions about the pets' role in outbreaks.

So far, cats haven't been implicated in the spread of avian flu to people, cautioned World Health Organization's influenza chief Klaus Stohr.

There are two potential reasons, he said: "One is nobody looked. The other is they don't play a role," as infected cats don't shed nearly as much virus as do infected poultry.

Bird flu has caused recurring outbreaks in recent years, including killing 27 people in Asia this year. Human infections until now have been traced to direct contact with infected poultry or poultry waste, and millions of chickens and other fowl have been slaughtered in attempts to stem the disease.

But hearing of the Dutch discovery, the WHO alerted scientists to examine household cats and other mammals whenever they investigate human bird-flu infections. The first such check, in Vietnam last week, found cats in patients' households were healthy, Stohr said.

Because the bird flu is quite different from human influenza strains that typically infect people, scientists fear it eventually could lead to a human flu pandemic. So they are closely watching for the virus among other mammals.

Three house cats killed by disease
Last winter, Thai veterinarians reported that bird flu had killed three house cats. That was a big surprise, because domesticated cats have long been thought resistant to infection from influenza A viruses, the family that harbors bird flu, called H5N1.

The new research, reported Thursday in the journal Science, goes farther to show cats fairly easily spread the disease to each other.

The scientists obtained H5N1 from a fatal human case in Vietnam and sprayed it into the throats of three cats. All became very ill; one died within the week.

Next, they housed two healthy cats with the sick cats. And, they fed three other healthy cats an infected chick apiece. All the cats got sick.

In contrast, cats exposed to a common human influenza A strain weren't infected.

"The role of cats in the spread of H5N1 virus between poultry farms, and from poultry to humans, needs to be reassessed," concluded lead researcher Thijs Kuiken, a virologist at Rotterdam's Erasmus Medical Center.

The discovery isn't as alarming to flu specialists as was China's recent acknowledgment that a few pigs harbored bird flu. Because pigs catch human influenza, too, they are considered the mammal in which genetic mixing to create a super-flu is mostly likely.

Still, Asian farmers battling bird flu should "keep an eye on your other animals in the house," WHO's Stohr said. "If there's any disease, there is reason for concern."

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