Worries about the avian influenza strain, H5N1, that's circulating in Asia have ratcheted up another notch. A paper published online by Science today confirms that the virus can infect cats, and that felines can transmit the virus to other cats as well--and perhaps to humans. Cats' vulnerability to H5N1--which comes on the heels of similar findings in pigs--increases concerns that the virus may evolve into a more dangerous strain that could set off an influenza pandemic.
H5N1 has ravaged poultry farms in nine Asian nations and has claimed the lives of at least 26 people. The virus was first reported in cats in January, when a clouded leopard at a zoo near Bangkok died from an infection; a month later, a sick white tiger at the same zoo tested positive for H5N1. Eating raw, infected poultry was the likely infection route.
To further investigate cats' susceptibility, Thijs Kuiken, a veterinary pathologist at Erasmus University in Rotterdam, the Netherlands, and colleagues inoculated the tracheas of three young domestic cats with H5N1 isolated from a fatal human case. All developed flu symptoms, such as fever and labored breathing, and one died after 6 days. Necropsy of the sick cats revealed lung tissue damage similar to that caused by H5N1 in humans. Two cats living in close contact with an infected animal also became sick, as did three others that each ate an H5N1-infected chick.
The study underscores H5N1's ability to infect multiple mammal species, which is unusual for strains that circulate in birds. Indeed, just 2 weeks ago, director Chen Hualan of China's National Avian Influenza Reference Laboratory in Harbin announced at a meeting in Beijing that H5N1 had also been found to infect pigs as early as last year, a finding that was first reported in January in a Chinese journal. Those results are especially worrisome, flu experts say, because pigs are believed to be mixing vessels in which avian and human flu viruses can combine into new strains.
Klaus Stöhr, a virologist at the World Health Organization in Geneva, Switzerland, says there's no indication so far that H5N1 has become established in pig populations. That's no cause for complacency, however, adds Stöhr, who urges countries where H5N1 has been found to step up surveillance of pigs. And cats with access to poultry should be watched for signs of illness, says Stöhr.
–-MARTIN ENSERINK and JOCELYN KAISER
Related sites
The
Science Express paper
The
World Health Organization's avian influenza page
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