Flu Virus Transmitted From Horses to Dogs

An influenza virus has jumped from horses to dogs, causing outbreaks in racing greyhounds and pet dogs in the United States, researchers report in the 30 September 2005 issue of the journal Science.

Flu viruses can transfer to new species in two ways: either the entire virus can directly enter a new species, or a host can be infected with two different viruses, which then combine with each other, producing a new virus with the ability to infect other species. The first type of transfer is rare, but this is what seems to have happened to the equine influenza virus H3N8, according to Patti Cynthia Crawford and colleagues.

In January 2004, an outbreak of respiratory disease occurred in racing greyhounds at a Florida racetrack. Some of the dogs were mildly ill and recovered, while others were much sicker and eventually died. The authors studied genetic samples from the greyhounds and determined that they were infected with a virus that was almost identical to H3N8. They concluded that the entire genome of this virus had been transmitted to the dogs. Further experiments confirmed that this virus was capable of infecting dogs, although it didn’t always cause symptoms. The authors also found evidence of the virus in greyhounds at tracks in several other states and in dogs in shelters in Florida, as well as one in New York.

Kathy Wren

27 September 2005