for National Geographic News
A bird flu virus killed 26 people in Asia and led to the vast slaughter of poultry several months ago. Now a new study says the flu can also infect cats, and that cats can spread the flu to other cats. The finding raises the possibility that they may eventually spread the flu to other mammals, including humans.
Scientists previously believed domestic cats were resistant to diseases from influenza A virus, to which the bird flu virusalso known as H5N1belongs.
The new research suggests that domestic cats are at risk of disease or death from the avian virus. The cats can also play a role in the transmission of the virus, scientists say.
"That cats could so easily be infected and could transmit the infection to other cats means that in areas where poultry are infected with H5N1 virus, cats could act as vectors," said Thijs Kuiken, a veterinary pathologist in the department of virology at the Erasmus Medical Center in Rotterdam, Holland.
"Cats could transmit the virus from one poultry farm to another, or could transmit the virus to people," said Kuiken, an author of the study described in tomorrow's issue of the journal Science.
The avian influenza A virus was responsible for massive poultry slaughters in eight Asian countries in 2003 and 2004. Thirty-seven cases of direct bird-to-human transmission, 26 of them fatal, were officially reported. Anecdotal reports of fatal infections in cats also emerged during the outbreak.
Kuiken and his colleagues investigated whether the virus could make cats sick when the pathogen was introduced into their airways or when the cats ate infected chickens.
The researchers introduced the H5N1 virus into the airways of three cats. Three other cats were fed an infected chick. Finally, two cats were exposed to the virus by being placed in the same cage as the first three cats.
The cats soon showed signs of disease: raised body temperature, decreased activity, and labored breathing. All developed severe lung disease. One cat died after six days of infection.
"Were we surprised? Yes!" Kuiken said. "Although we had expected to see some pathologic change in the lungsbecause of the anecdotal reports of cats dying from H5N1 virus infection in Thailandwe didn't expect them to be so severe and present in all animals."
"Often an infectious agent that causes mortality in the field has a much less severe effect when the infection is performed in the laboratory," Kuiken added. "With H5N1 virus, the experimental infection also resulted in severe lesions."
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