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Dog Flu May Have Been Active as Early as 1999

Canine influenza affecting racing greyhounds closely related to horse virus, study says

TUESDAY, March 25, 2008 (HealthDay News) -- Canine influenza was first identified in 2004, but it has been circulating in the racing greyhound population since at least 1999, a U.S. study reports.

The first recognized outbreak occurred in January 2004 at a dog race track in Florida. Since then, there have been a number of outbreaks at other tracks and at animal shelters, human societies, rescue groups, pet stores, boarding kennels and veterinary clinics.

In this study, a team led by Tara Anderson, of the University of Florida College of Veterinary Medicine, analyzed greyhound blood samples from an animal blood bank in California that uses retired greyhounds as blood donors. The blood samples were collected between 1999 and 2004.

The researchers found that 33 percent of the samples collected in 1999 tested positive for antibodies to the canine influenza virus and concluded that canine influenza was circulating in the racing greyhound population as early as 1999.

The H3N8 influenza virus that causes canine influenza is closely related to the virus that causes equine (horse) influenza. It's believed that the equine influenza virus mutated to produce the canine influenza virus.

Almost all dogs exposed to H3N8 become infected, and about 80 percent develop symptoms but most of the mild form associated with infection of the upper respiratory tract. But some dogs develop a more severe form of influenza that's accompanied by pneumonia. The death rate in these cases is 5 percent to 8 percent.

The research was presented March 18 at the International Conference on Emerging Infectious Diseases in Atlanta.

More information

The American Veterinary Medical Association has more about canine influenza.

SOURCE: American Society for Microbiology, news release, March 18, 2008
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