The mysterious respiratory disease that has swept greyhound
racetracks across the country and also afflicted pet dogs is a type
of flu — an influenza strain that jumped from horses to dogs,
researchers reported Monday.
Such a rapid jump into a new species is rare; the
flu usually evolves into new strains more gradually. But genetic
tests of sick dogs found their disease almost identical to the H3N8
influenza strain that afflicts horses, scientists at the Centers
for Disease Control and Prevention and University of Florida discovered.
Moreover, they found evidence of widespread infection
in race dogs around the country and in pets of various breeds in
Florida and New York.
Since this is a new virus for dogs, they are unlikely
to harbor a natural immunity to it. There are no reports of people
sickened by the new canine flu, which is genetically different from
human flu strains — and from the bird flu that has in Asia.
The results were published online Monday by the
journal Science. This new dog illness made headlines earlier this
year as greyhound racetracks closed to control outbreaks. Veterinarians
struggled to tell if the illness was a new variant of kennel cough
or an entirely new disease. The CDC researchers counted outbreaks
at 14 greyhound tracks in six states from June to August 2004, and
at 20 tracks in 11 states between January and May 2005.
It's not clear how dangerous the new canine flu
is to dogs. Some die, others experience only a fever and cough,
but a large number show no symptoms at all, the researchers report.
While most attention has focused on racing dogs, the researchers
tested 70 dogs of various breeds with respiratory disease in Florida
and New York pet shelters and veterinary clinics. Some 97 percent
showed antibodies to the new canine flu strain.
Tests of blood stored by racetracks suggests the
new flu strain began infecting dogs sometime between 1999 and 2003,
well In 2004, AKC's Compliance department conducted over 5,000 inspections
of dog kennels, individual breeders, and pet stores.