House cats and ferrets can get the SARS virus and pass it to other animals, a new study shows, raising the obvious question: Can they give it to people?
“You might want to quarantine the pets as well as the people,” suggested Dr. Robert Shope, an expert on emerging diseases at the University of Texas Medical Branch in Galveston. “If it’s been shown that the virus can transmit from cat to cat, it doesn’t take much of a leap of faith that it will transmit to humans.”
Other scientists who have studied SARS say pet owners shouldn’t overreact, however.
“These animals in all likelihood did not play a significant role in spread of (SARS) to humans,” said Dr. Klaus Stohr, the World Health Organization’s chief SARS scientist.
Besides, said Dr. Jeffrey Koplan, the former head of the U.S. Centers for Disease Control and Prevention, “we still don’t know if they can pass the virus to people.”
Researchers discovered the vulnerability of cats and ferrets to SARS while searching for animals to test potential vaccines.
Their study, which will appear in Thursday’s issue of the journal Nature, also notes a separate report that cats were found infected with the virus in a Hong Kong apartment complex where residents contracted SARS last year.
Cats and ferrets are the first pets included on an exotic list of animals scientists think may be able to harbor the virus. However, the virus seems to be so versatile that it could have jumped to humans from a variety of animals, co-author Albert D.M.E. Osterhaus said.
“Cats and ferrets are only distantly related,” he said. “So this demonstrates the promiscuous nature of the virus.”
The origin of the virus that killed 774 people remains unknown. Scientists believe people may have gotten the virus from animals that were infected by another source.
In China, where SARS festered for months before it grew into a worldwide menace this year, exotic raccoon-dogs, ferret badgers and civets imported into markets have been found harboring a germ that’s almost identical to the SARS virus.
The exotic animals were taken off the market for several months, but some markets have begun selling them again, said Dr. Henk Bekedam, the WHO’s representative in Beijing.
Because of the possibility that animals can spread the respiratory virus, WHO has suggested that animals in China and elsewhere be tested for SARS and other diseases before they are eaten.
“We should stay away from animals who are known or likely to transmit the SARS coronavirus,” Stohr said.
A SARS infection can cause flu-like symptoms, including a high fever, head and body aches, congestion and breathing trouble. About 8,100 people are thought to have been sickened by the virus between November 2002 and July, according to the WHO.
For the Nature study, researchers inoculated six cats and six ferrets with the virus cultured from a person who died of SARS, adding drops that contained the virus into their trachea, eyes and nose.
The cats and ferrets began to show their infection two days later in excretions from the throat, and researchers found they produced antibodies within 28 days. When the animals were later euthanized, the virus also was found in their respiratory tract.
The cats did not appear to be affected by the virus, but they did develop a mild case of pneumonia. The ferrets became lethargic, and one of them died four days after it was inoculated.
Scientists also placed two healthy cats and two healthy ferrets with the infected animals. The healthy ferrets showed signs of SARS infection after two days. The ferrets became emaciated and eventually died about two weeks later, though Osterhaus said he is uncertain whether this was due to the virus.
Stohr and Koplan both questioned the results of the study. Stohr said the healthy animals were infected so quickly that he wondered whether the cultured virus was simply rubbed onto them from close contact with their recently inoculated cage mates.
Koplan said too few animals were used to reach a firm conclusion about how cats and ferrets become infected.