Veterinarian Reviewed on January 5, 2008 by Dr. Janice Huntingford
Canine Influenza is caused by type A Orthomyxovirus. This newly emerged pathogen is a highly contagious respiratory infection that spreads through direct contact with a dog’s aerosolized respiratory secretions and with contaminated inanimate objects. Humans may inadvertently spread the infection between infected and uninfected canines. Two clinical syndromes exist: a mild form and a severe form.
In 2004 reported cases of Canine Influenza began with racing greyhounds at a Florida racetrack. Within months, more cases appeared in animal shelters, humane societies, pet stores and veterinary clinics across many states. Although this enveloped RNA virus spreads, this infection is not so common that any alarm should be raised.
Symptoms and Diagnosis
Dogs of any breed and age are susceptible to Canine Influenza. The incubation period is two to five days. Even before showing signs of infection, canines may be most infectious. Approximately 80% of dogs exposed will develop the infection.
Symptoms of the mild form include low-grade fever, and a soft, moist cough that persists for 10-30 days despite antibiotics or cough suppressants. A secondary bacterial infection may cause a thick, bloody, nasal discharge. Bacterial species may include Pasteurella multocida and mycoplasma. Some dogs have a dry cough, a symptom often mistaken for Kennel Cough.
After the first week, 10-20% of canines may show symptoms of the severe form: a high-grade fever (104°F to 106°F) and clinical signs of pneumonia. Dogs will show increased respiratory rates and effort. A secondary bacterial infection may cause pneumonia. Greyhounds are the first breed reported to suffer from hemorrhagic pneumonia and acute death. The overall fatality rate is 1-5%.
As yet, no rapid tests for diagnosis exist. Serologic testing may confirm diagnosis. Paired acute and convalescent serum samples would detect recent infection. The first sample should be taken as early as seven days after the first clinical signs appear: antibodies may be detected. The second sample should be taken two to three weeks later. Thoracic radiography may determine consolidation of the lung lobes. Other diagnostic testing options include Flu antigen ELISA kit (Becton-Dickinson Flu-A kit) and PCR that include nasal swabs.
No vaccine exists as a preventative measure. Practising good hygiene can help prevent transmission between infected and uninfected dogs. Clean hands, equipment, clothes, surfaces after exposure to canines with signs of respiratory illness. Canine Influenza persists less than one week locally. Infected dogs should refrain from activities and locations where other dogs may be susceptible, such as in dog shows, kennels, clinics, and shelters. A change of clothes should be in order for any worker in a shelter.
Dogs suffering from Canine Influenza require veterinary medical attention. Providing good animal husbandry and nutrition can result in effective immune response. The veterinarian will ensure treatment that boosts the dog’s immune system to fight the virus. Treatment for the mild form includes a broad spectrum bactericidal antimicrobial. Treating the severe form also requires broad spectrum bactericidal antimicrobial as well as hydration, sometimes with fluids administered intravenously. Infected canines can shed the virus for seven to ten days after initial signs appear.
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Janice Huntingford, DVM, has been in veterinary practice for over 30 years and has founded two veterinary clinics since receiving her Doctor of Veterinary Medicine at the Ontario Veterinary College, University of Guelph. She has studied extensively in both conventional and holistic modalities. Ask Dr. Jan