GAINESVILLE, Fla. --- In what is believed to be the first scientific report of equine influenza virus jumping the species barrier, University of Florida veterinary researchers say the virus is the likely cause of a respiratory disease outbreak that killed eight racing greyhounds from kennels in Jacksonville in January.
Although the 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. These outbreaks could have a significant economic impact on the greyhound racing industry due to track closures and quarantines on dog movement between tracks.
“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track, an outbreak that occurred three months ago and was contained through a voluntary statewide quarantine, which is no longer in effect,” said Cynda Crawford, a UF veterinary immunologist who spearheaded the research funded jointly by the UF College of Veterinary Medicine Racing Laboratory and the state’s Division of Pari-Mutuel Wagering, which regulates greyhound racing in Florida. Her findings are the result of a team effort involving virologists from Cornell University’s College of Veterinary Medicine in Ithaca, N.Y., and the national Centers for Disease Control and Prevention.
“There is absolutely no evidence to suggest that these findings extend beyond this group of dogs affected during that period of time, or that it poses any significant threat to people or their pets,” Crawford said, adding that to make sure the virus was confined to the Jacksonville dogs, blood samples were collected from two additional dog populations in Florida, including randomly selected pets and racing greyhounds from a track in South Florida. Both groups tested negative for equine influenza virus.
Equine influenza is a disease of horses, and the virus is in the same group of viruses that cause flu in people. The disease is present in horse populations throughout Europe, North America and parts of Asia, with horses typically developing 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 and other scientists warn dog owners not to experiment with prevention products approved for other species because of the potential for extremely negative consequences, including death.
With 16 tracks, Florida is the leading state for greyhound racing, according to the National Greyhound Association. Respiratory disease outbreaks appear generally in winter and early spring. The last significant outbreak occurred in March 2003, after which state officials approached UF scientists for help. A respiratory illness also struck greyhounds at tracks across the nation in 1999.
When Crawford learned about the January outbreak, she immediately visited the Jacksonville track, where 24 dogs were affected with symptoms that included cough, fever and other more serious symptoms. Of those, eight died and 16 recovered. Crawford collected blood and nasal fluid samples from 35 dogs, and five of the dogs that died underwent postmortem examinations at UF. She sent the samples for analysis to Ed Dubovi, director of the virology section at Cornell’s Animal Health Diagnostic Lab.
“Cornell’s virology group is one of the best in the country, and Dr. Dubovi cracked this,” Crawford said. “He was able to isolate an influenza-like virus, which he then sent to the CDC, which routinely monitors influenza outbreaks involving interspecies transmission to determine if there is a threat to public health.”
On the basis of genetic sequencing, the CDC’s Ruben Donis and his colleagues at the Influenza Branch concluded the virus found in the canine samples resembled a strain of equine influenza virus that appeared in horses in Wisconsin last year.
“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 U.S.,” Donis said, adding that to strengthen its findings, the CDC plans now to sequence the entire genome of the canine virus.
The scientists report their findings are strong because they also verified 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,” said Crawford, who plans to present the team’s findings later this month at a meeting sponsored by the National Greyhound Association.
The scientists say they have no idea 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.
“The important thing is that now we have something to look for, which will help future efforts to eradicate or prevent these devastating respiratory disease outbreaks that affect racing greyhounds,” said Paul Gibbs, a professor of virology at UF and a co-investigator on the project.
Dave Roberts, director of the Division of Pari-Mutuel Wagering, said the respiratory illness adversely impacts greyhounds as well as the racing industry in many ways.
“In order to better treat the dogs and manage the outbreaks, the division felt it was imperative to investigate the possible causes. We are encouraged by the scientists’ preliminary results and look forward to the university’s future findings as its researchers continue to study the illness,” Roberts said.
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