University of California, Davis, March 24, 2006
A lab at the University of California, Davis, has detected canine influenza virus in dogs from three states, using a new test that employs DNA technology to provide rapid, accurate diagnosis of the highly contagious disease.
The School of Veterinary Medicine’s Lucy Whittier Molecular and Diagnostic Core Facility, using a new test developed by the lab, confirmed the canine influenza infections in dogs in the San Francisco area, Colorado and Florida. The new procedure identifies the genetic profile of the virus using polymerase chain reaction, or PCR, technology.
“These results provide accurate diagnoses for the veterinarians treating these animals and demonstrate that this test is capable of detecting the virus even in dogs that have not died from the infection,” said veterinary researcher Christian Leutenegger, who developed the test.
Since November, Leutenegger and colleagues have tested more than 100 samples from dogs suspected of having canine influenza. All of the samples turned out to be negative until Feb. 23, when the first of the three positive samples was diagnosed.
That first case involved a fatal outbreak of disease in a Colorado animal shelter. It was followed by a case in San Francisco, in which an imported puppy became ill but recovered, as did its household-mates. The third case involved a fatal outbreak in a Florida animal shelter.
“There is no reason for dog owners to panic over the confirmation of these cases,” Leutenegger said. “Any dog that exhibits upper respiratory symptoms, such as a persistent cough or nasal discharge, should be routinely examined by a local veterinarian.”
The PCR method is an extremely sensitive test that can detect small amounts of the virus’s genetic material in a sample collected from the dog’s throat on a swab. The process uses an amplification technique that multiplies the existing DNA or RNA so that it can be identified more easily.
This procedure provides a diagnostic tool that is faster and more accurate than other methods. Prior to development of the test, veterinarians relied on serum antibody tests to diagnose canine influenza. The drawback of such blood tests is that they cannot detect the disease until the dog begins to produce sufficient antibodies to the virus, which may be several days after symptoms appear. In contrast, the new PCR-based test can provide results within 24 to 48 hours.
In addition to the canine influenza virus A, this PCR test also is used to detect other infectious diseases in dogs, including Bordetella bronchiseptica, distemper, adenovirus type 2, herpesvirus, and parainfluenza virus, all of which are causes of “kennel cough” in dogs.UC Davis is making it available to veterinarians for $48 per sample for canine influenza alone or $75 per sample for a complete panel of dog respiratory diseases.
“The ability of this assay to detect infectious causes of canine respiratory disease, including canine influenza virus, on a swab collected from the throat of affected dogs, has already impacted our understanding and management of infectious respiratory tract disease in canine populations,” said Jane Sykes, a small-animal veterinary internist specializing in infectious diseases of dogs and cats.
Canine influenza is an upper respiratory disease, first reported in January 2004 in racing greyhounds at a Florida racetrack. To date, antibodies to canine influenza virus have been detected in dogs in animal shelters, adoption groups, pet stores, boarding kennels and veterinary clinics in 19 states. Dogs can also catch the virus from saliva or mucus on shared toys or food dishes. There is no evidence that canine influenza can be passed to humans.
Because this virus is just now emerging, dogs have no natural immunity to it. All dogs exposed will become infected, and about 80 percent of the infected dogs will develop symptoms of the illness.The disease appears to kill 5-8 percent of the infected dogs.
There is currently no vaccine available for canine influenza; veterinarians treat infected dogs with supportive care so that their immune systems can fight off the disease. Antibiotics may be given to deal with secondary bacterial infections, and fluids may be administered to prevent dehydration.