For Bird Flu, Cats Might Be Canary in Coal Mine: Researchers Say Animal Could Be Carrier and Signal Disease’s Arrival

By Susanne Rust, Milwaukee Journal Sentinel

Apr. 6–Although H5N1 avian flu has caused many people to look at migrating birds and domestic poultry in a new, menacing light, it may be time to reappraise the bewhiskered feline serenely licking her paws on your couch.

Danish and Italian researchers are calling on the world’s health organizations and experts to start taking notice of cats. And they’re urging officials to consider these domestic animals as both potential threats to human safety and as possible sentinels for the arrival of the disease.

“We believe that the potential role of cats should be considered in official guidelines for controlling the spread of H5N1 virus infection,” wrote the authors in a commentary in today’s issue of the journal Nature.

But others say too little is yet known about these animals’ role in the spread of the virus. And in North America, where avian flu has not appeared, there is little cause for alarm.

“We believe at the present time a general survey of cats and other carnivores, certainly in North America, and even in H5N1-endemic regions, may not be generally warranted, as the exposure of the cats to infected birds is likely to be low,” said Hon Ip, director of the diagnostic virology laboratory at the U.S. Geological Survey’s National Wildlife Health Center in Madison.

But, he said, if cats begin “showing unusual morbidity or mortality” in areas infected the virus, that stance might have to be reconsidered.

According to the authors, cats have been relatively silent victims in the spread of the flu. As early as February 2004, reports of domestic cats dying from H5N1 started to appear. In a household near Bangkok, Thailand, 14 out of 15 cats “became weak, started vomiting and coughed up blood before dying.”

Tigers and a leopard in two zoos in Thailand also have died after eating fresh chicken carcasses infected with the virus or being exposed to birds with H5N1.

“These reports were surprising because both domestic cats and wild felids were considered to be resistant to disease from influenza A virus infection, of which H5N1 is a subtype,” wrote the researchers, who include Thijs Kuiken and Albert Osterhaus, virologists at the Erasmus Medical Center in Rotterdam, Netherlands, as well as Peter Roeder of the Animal Production and Health Division of the Food and Agriculture Organization of the United Nations in Italy.

Widespread and high mortality of cats has been reported in areas where the disease has become endemic, including Iraq and Indonesia.

Two views on evidence

As of February, the World Health Organization has said “there is no present evidence that domestic cats play a role in the transmission cycle of H5N1 viruses.”

But Osterhaus and his colleagues think there’s increasing evidence to the contrary.

They point to fatal infections in regions where the virus has become endemic, feline deaths where the virus has only recently appeared, and their own laboratory experiments.

The combined evidence, they say, indicates that these animals could provide the material the virus needs to mutate, giving it a chance to become an effective mammal, and human, disease.

Their laboratory work indicates that cats were not only susceptible to the virus but also could pass it between one another, albeit with prolonged exposure.

“Collectively, the data so far show that domestic cats can become infected contact with domestic or wild birds,” eating them or coming into contact with their droppings, the authors wrote.

“Consequently, these data indicate a possible role for cats in the epidemiology of H5N1 in poultry, humans and other species,” they wrote.

And they recommend taking steps to prevent contact between cats and infected birds or their droppings, as well as quarantining and testing cats suspected of such contacts or cats that show symptoms of H5N1 influenza.

The European Center for Disease Prevention and Control recommends keeping cats indoors if they live within about six miles of a verified H5N1 infection in birds.

Ip, of the National Wildlife Center, stressed that no cat-to-human transmission has been documented.

“Cats are clearly potential players” in the possible spread of the disease, said Stanley Temple, professor of wildlife ecology at the University of Wisconsin-Madison. “Because free-ranging cats are likely to prey on sick birds, are susceptible to the virus, live at high densities around people and often have intimate contact with people, they might be the intermediate mammal that allows H5N1 to jump from birds to humans.”

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Copyright (c) 2006, Milwaukee Journal Sentinel

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