Domestic cats can become infected with the bird flu virus H5N1, by feeding on infected birds or by being around an infected cat, findings from a new study indicate.

This could have important implications for transmission of the virus in humans.

During the 2003-2004 outbreak of the H5N1 virus in Asia, there were word-of-mouth stories of fatal infection in domestic cats. This contradicted earlier research suggesting that felines are resistant to disease caused by the virus.

To get a better understanding of the ability of H5N1 to cause illness in cats, Dr. Thijs Kuiken and colleagues, from Erasmus Medical Center in Rotterdam, the Netherlands, tested various ways of transmitting the virus to European short-haired domestic cats.

The team reports in the journal Science that inoculating the windpipe of cats with a virus isolated from a fatal human case resulted in fever, lethargy, labored breathing, and, in one animal, death.

In additional studies, uninfected cats were exposed to infected cats or fed infected birds. In both cases, the researchers report, the virus was transmitted to the previously uninfected animal.

“The role of cats in the spread of H5N1 virus between poultry farms, and from poultry to humans, needs to be re-assessed,” Kuiken’s group concludes.

In addition, “cats may form an opportunity for this avian virus to adapt to mammals, thereby increasing the risk of a human influenza pandemic.” Until now, pigs have been viewed as the most likely stepping-stone for this to occur.

SOURCE: Science, online edition for September 2, 2004.