BIRD FLU INFECTS CATS, TOO, STUDY FINDS
In an experiment, cats caught the H5N1 flu virus by breathing it in and by eating infected chicks, the team of virus experts at Erasmus Medical Center in Rotterdam said.
"This is extraordinary because domestic cats are generally considered to be resistant to disease from influenza A virus infection," the researchers reported in Friday's issue of the journal Science.
The H5N1 strain of bird flu virus has killed 27 people in Vietnam and Thailand in 2003 and 2004. It has also killed or forced the destruction of millions of birds, many of them small flocks kept by farmers.
It pops up in unexpected places and has been recently found in Malaysia and Indonesia, spread by unknown means.
H5N1 influenza frightened officials from the moment it sprang up in Hong Kong in 1997, killing six people and forcing the cull of 1.5 million birds. Health experts said right away it was just the kind of flu that could jump to humans and cause a global epidemic, like the 1918 flu that killed an estimated 20 million people.
So far, H5N1, one of several varieties of influenza affecting flocks worldwide, remains unable to spread from one person to another and only rarely jumps from birds to people. But it has been found in pigs and now in cats, reported flu expert Albert Osterhaus and colleagues.
Most human flu epidemics are believed to begin in birds, with the virus mutating slightly as it infects other animals such as pigs and then acquiring the ability to infect and spread among people. Pigs can carry human flu viruses, which can meet up with the avian viruses, swap genes, and create virulent new strains.
Cats have never before been implicated.
Osterhaus' team infected cats through several routes and found them highly susceptible to H5N1 but not to the common human flu strain H3N2.
"We experimentally infected 4- to 6-month-old European shorthair cats with H5N1 virus by different routes and examined them by virological and pathological techniques," they wrote.
Three cats exposed to H5N1 virus by air became ill and three more became ill after being fed infected chicks. Two more were infected by other infected cats. They were killed for examination and all had damaged lungs.
"The implications of the above findings are first that, during H5N1 virus outbreaks, domestic cats are at risk of disease or death from H5N1 virus infection, either due to feeding on infected poultry or wild birds, or due to contact with infected cats," the researchers wrote.
"Second, the role of cats in the spread of H5N1 virus between poultry farms and from poultry to humans needs to be reassessed. Third, cats may form an opportunity for this avian virus to adapt to mammals, thereby increasing the risk of a human influenza pandemic."
