New canine flu is spreading across the U.S.

Virus has been linked to deaths at kennels and tracks

A new, highly contagious and sometimes deadly canine flu is striking kennels and dog tracks around the country, veterinarians said Wednesday.

The virus — which scientists say mutated from an influenza strain that affects horses — has killed racing greyhounds in seven states and has been found in shelters and pet shops, though the extent of its spread is unknown.

Dr. Cynda Crawford, an immunologist at the University of Florida's College of Veterinary Medicine who is studying the virus, said it spreads most easily where dogs are housed together, but it can be passed on the street, in dog runs or even by a human transferring it from one dog to another. Kennel workers have carried the virus home with them, she said.

How many dogs die from the virus is unclear, but scientists said the fatality rate is more than 1 percent and could be as high as 10 percent among puppies and older dogs.

Crawford first began investigating greyhound deaths at a racetrack in Jacksonville, Fla., in January 2004, where eight of the 24 greyhounds who contracted the virus died.

"This is a newly emerging pathogen, and we have very little information to make predictions about it," she said.

She added that because dogs have no natural immunity to the virus, virtually every animal exposed will be infected. About 80 percent of dogs that are infected with the virus will develop some symptoms, Crawford said. She said the symptoms often are mistaken for "kennel cough," a common canine illness caused by the bordetella bronchiseptica bacteria.

Both diseases can cause coughing and gagging for up to three weeks, but dogs with canine flu may have fevers as high as 106 degrees and runny noses. A few will develop pneumonia, which is sometimes fatal. Crawford said antibiotics and fluid cut the pneumonia fatality rate.

Experts said there are no known cases of the canine flu infecting humans. "The risk of that is low, but we are keeping an eye on it," said Dr. Ruben Donis, chief of molecular genetics for the influenza branch of the Centers for Disease Control and Prevention, which is tracking the illness.

But with the approach of the human flu season and fears about bird flu in Asia there is much confusion among some dog-owners who have heard of the disease.

Donis said there currently isn't a vaccine for the canine flu but that one would be relatively easy to develop because a vaccine that prevents the related horse flu exists.