Gainesville, Fla.-For the first time, University of Florida (UF) veterinary researchers believe they have documented cases of equine influenza virus jumping the species barrier into dogs.

The virus is the likely cause of a respiratory disease outbreak that killed eight racing Greyhounds from kennels in Jacksonville. Although the outbreak has been isolated and quashed, any time a virus jumps species it is considered an important epidemiological event, the university reports.

Dr. Cynda Crawford

Although researchers stress the findings involve only these particular Jacksonville dogs, they will investigate possible connections to similar disease outbreaks that have affected racing dogs in Florida and elsewhere in recent years.

Cynda Crawford, DVM, Ph.D., a UF veterinary immunologist, explains, "I want to stress that our team's findings are preliminary and confined to the dogs affected by an outbreak at one Florida track, an outbreak that occurred three months ago and was contained through a voluntary statewide quarantine, which is no longer in effect."

UF's research team also worked with Cornell University's College of Veterinary Medicine in Ithaca, N.Y., and the Centers for Disease Control and Prevention (CDC). Ed Dubovi, director of virology section at Cornell's Animal Health Diagnostic Lab isolated the virus. CDC was brought in to assess the public health threat and monitor the outbreak.

"The virus found in the canine samples is probably representative of the strain that is circulating now in horses in Florida and elsewhere in the United States," says Ruben Donis, Ph.D. with CDC.

On the basis of genetic sequencing, Donis and colleagues at the Influenza Branch conclude the virus found in canine samples resembled a strain of equine influenza virus that appeared in horses in Wisconsin last year.

The researchers also found that the dogs developed antibodies specific for the influenza virus.

"This implies that the virus replicated enough within the dogs for their immune system to recognize it and form antibodies," Crawford says.

Believed to be a first: Equine influenza virus outbreak struck a Jacksonville, Fla., Greyhound track. The University of Florida spearheaded the investigation working with Cornell University and the Centers for Disease Control and Prevention.

Equine influenza is a disease of horses and is present in North America, Europe and parts of Asia. Horses typically develop a fever and a dry, hacking cough. In the early stages of the disease, horses are reluctant to eat or drink for several days, but usually recover in two to three weeks.

Crawford adds that she is unsure how the Jacksonville Greyhounds could have been exposed to equine influenza virus, and that is one of many questions they intend to pursue through further epidemiological studies.

When Crawford learned about the January outbreak, she visited the Jacksonville track to find 24 dogs affected with symptoms including cough, fever and other more serious symptoms.

Out of the total, eight dogs died and 16 recovered.

Crawford reports she collected blood and nasal fluid samples from 35 dogs, and five of the dogs that died underwent postmortem examinations.

The team also alerted dog owners not to experiment with prevention products approved for other species because of the potential for adverse reactions, including death.

Details of the story provided by Sarah Carey, University of Florida.