When researchers talk about their biggest bird flu fears, one that typically comes up involves an animal — like a pig — becoming simultaneously infected with an avian and a human flu.
This creature, now a viral mixing vessel, provides the medium for a superbug to develop — one that takes the killer genes from the bird flu and combines it with the human variety's knack for easy infection.
So far, domestic poultry and dairy cows have proved to be imperfect vessels.
So too have the more than 48 other mammal species that have become infected by eating infected birds and then died.
But researchers say there is one population of animal floating under the radar: Pets.
The risk may be low, but the opportunities for transmission are abundant.
"I think companion animals definitely need to be in the picture," said Jane Sykes, professor of medicine and epidemiology at UC Davis School of Veterinary Medicine, describing the viewpoint that diseases such as H5N1 should be viewed from a human, animal and ecosystem lens.
None operates in isolation.
She pointed to our furry friends' penchant for eating dead things, other animals' poop and — in the case of cats — wild birds.
Add to that our primate compulsion to touch, kiss and caress these animals that live in our homes (and sleep on some of our beds), and you've got a situation in which germs could be swapped and mingled.
Now consider the sheer number of companion animals and people in the U.S.
"Two-thirds of households have a dog or a cat," said Sykes.
"That's a lot of companion animals.
There's actually more … in this country than there are people in Australia and the U.K.combined."
She also pointed to new research showing H5N1 antibodies in a group of Washington state hunting dogs trained to retrieve waterfowl, a carrier of the disease.
Ian Redmond, a U.K.based biologist and conservationist, agreed.
"It stands to reason that pathogen spillover (when a virus, bacterium or protozoon is transmitted from one species to another) is most likely when different species are in close contact," he said.
"While traditional companion animals such as dogs, cats and horses have a long history of such close contact with humans, giving thousands of years for us to develop natural immunity to commonly shared pathogens, it is the new situations that carry most risk," he said, including "raw pet food of uncertain origin."
It's an area that epidemiologists, food safety experts and veterinarians are warily watching — a situation akin to the dangers posed by drinking raw milk.
"There's at least one animal a day that we see on our service that's eaten some bizarre raw food diet," Sykes said.
"It did not used to be like that at all."
Raw pet food typically consists of uncooked meat, bones, fruits and vegetables.
The diets are often marketed as "natural" or similar to what animals would eat in the wild.
Calls and inquiries to several raw pet food companies went unanswered.
Jay Van Rein, spokesman for the California Department of Food and Agriculture, said the state's Meat, Poultry and Egg Safety Branch licenses and inspects businesses that produce raw meat — as well as those that import raw products for pet food manufacturing.
"Raw meat pet food legally sold in California comes from USDA-or CDFA-inspected facilities," he said.
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