HELEN BRANSWELL
A scientist with the UN's Food and Agriculture Organization is setting up a study aimed at trying to determine if cats are playing a role in the spread of the H5N1 avian flu virus, looking at Indonesia where a perplexing pattern of human cases has raised questions about how the disease is transmitting.
Dr. Peter Roeder and Indonesian colleagues will be looking for infected cats in areas with H5N1 outbreaks in poultry. Indonesia is the current hot zone of H5N1 infection, reporting 30 cases - including 23 deaths - since last July.
Experts have been watching the country closely, puzzled by the tenuous and at times seemingly non-existent links between some human cases and infected poultry. Elsewhere investigations have almost always traced human infections back to contact with sick or dead birds.
"The worry is in quite a significant number of human cases in Indonesia that there is no apparent connection between the people and poultry," Dr. Roeder, an animal health officer with the FAO, said in an interview from Beirut, where he was attending a conference.
"Now is it possible that cats could be an intermediary between the two? I'm not wanting to propose that they are, but what I'm saying is I think this raises the question."
Dr. Roeder and some scientists from Erasmus Medical Centre in Rotterdam explored just that issue in a commentary published Wednesday in the journal Nature.
They argued that given the growing number of reports of dying cats in areas with H5N1 outbreaks, and the fact that laboratory experiments have shown cats can become infected and spread the virus cat to cat, it would be imprudent to rule out feline involvement in the spread of virus.
"It's really rather preliminary stuff, although it's been a very consistent story, everywhere we've started asking," Dr. Roeder said.
"As the moment, we have no evidence that they're playing a role in the transmission of infection within poultry flocks, between poultry flocks or between infected chickens and people. But the potential is obviously there."
An American infectious disease expert agrees.
"I think we have to keep every option open and expect the unexpected," said Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.
"That doesn't mean that there are other mechanisms of transmission other than bird to human, but we would be remiss not looking at all other possibilities."
The study Dr. Roeder is setting up will have both virologic and epidemiologic components.
He wants to retrieve virus samples from infected cats and compare their genetic blueprints to those isolated from poultry and human cases of H5N1 in Indonesia.
He also wants to get a better picture of the role cats play in affected villages - how many people own them and whether households have multiple cats.
While the question is being studied, Dr. Roeder and his co-authors have urged that people in H5N1 affected areas keep pet cats indoor, where possible. And they have cautioned against destroying or abandoning companion animals.
"What I don't want is thousands of people taking their cats to the vet to be put down," Dr. Roeder said.
He noted that in many places, cats play a critical role in rodent control. Destruction of cats could lead to a surge in rat and mouse populations and the problems of disease and crop destruction rodents bring with them.
"We could be looking at disturbing an equilibrium which could have a serious result in itself. So we have to be very careful."