Canine influenza virus surfaces

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An emerging canine respiratory tract disease, known as canine influenza or canine flu, was found in dogs in shelters, boarding facilities, and veterinary clinics in several areas of Florida, including the southwest counties of Broward, Miami-Dade, and Palm Beach, and in the northeast county of Duval. Cases have also been confirmed in New York and in a dog that resided in Massachusetts.

The disease caused by the highly contagious virus can mimic signs of kennel cough. All dogs, regardless of breed or age, are susceptible to infection and do not have naturally acquired or vaccine-induced immunity, according to the University of Florida College of Veterinary Medicine. The virus can spread by aerosolized respiratory secretions, contaminated inanimate objects, and by people moving between infected and uninfected dogs.


While most dogs that become infected experience a mild form of influenza, some develop a more acute disease with clinical signs of pneumonia. Among the latter group, the fatality rate is 1 percent to 5 percent, the University of Florida reported.

"... Despite the rumors that are out on the Internet and other such sources, this disease is not as deadly as people want to make it," said Dr. Cynda Crawford, a veterinary immunologist at the University of Florida. "Only a minority of dogs, a small number of dogs, experience complications such as pneumonia."

Dr. Crawford was among the group of researchers who identified the virus. The group included staff from the Auburn University College of Veterinary Medicine, Cornell University College of Veterinary Medicine, national Centers for Disease Control and Prevention, Texas A&M University College of Veterinary Medicine, and the University of Wisconsin-Madison School of Veterinary Medicine.

A full report on the group's findings, titled "Transmission of equine influenza virus to dogs," was posted online in the Sept. 26 issue of Science Express Reports, a part of Science magazine.

In April 2004, a group of researchers at the University of Florida reported that preliminary findings suggested equine influenza virus had jumped the species barrier to dogs and caused a respiratory tract disease outbreak, killing eight Greyhounds in January 2004 at a track in Jacksonville, Fla. At the time, the researchers said there was no evidence to suggest the findings extended beyond the particular group of dogs or that it posed a substantial threat to people or their pets.

"... Initially the virus was identified in Greyhounds, and there was some speculation that the virus was exclusively causing disease in Greyhounds," said Dr. Ruben O. Donis, chief of molecular genetics for the influenza branch at the CDC, who was part of the group of researchers.

The group later determined in April to May 2005 that the virus also infected pet dogs when they isolated it from samples sent for diagnostic testing by shelters, boarding facilities, and veterinary clinics, Dr. Crawford said.

"I also want to emphasize that we don't have all the answers to the questions just yet, and we are working diligently on defining this disease syndrome in the dog population, so we have a few numbers to work with, and we are accumulating more data very rapidly on a daily basis," Dr. Crawford said. She also noted that a vaccine for the disease has been in the works for the past few months.

Meanwhile, veterinarians should take precautions when they are told that a client has made an appointment for a dog to be seen because it's coughing. "They may want to not have that dog come in through the waiting room and mix with everyone else's dogs," Dr. Crawford said.

To help researchers better define the clinical signs and risk factors associated with virus infection, veterinarians are encouraged to submit serum samples for canine influenza antibody tests to the Animal Health Diagnostic Center at Cornell University. The samples will also help improve surveillance of the virus in the United States and Canada. For information on sample collecting and shipping, log on to Cornell's Web site at, click on "Emerging Issues," then click on "Canine Influenza Virus."

For a copy of the Science magazine report, click "SCIENCE Magazine Article: Canine Influenza."