Canine influenza is an acute respiratory disease caused by an influenza virus that originated in horses and jumped species to dogs. The virus is highly infectious between dogs but results in a low mortality. In rare cases (less than 1%), complications (such as pneumonia) from canine influenza infection can result in death. Most dog, though, develop either no signs or only mild cough. The best means of diagnosing canine influenza is determining antibody levels in the blood. Treatment is symptomatic (e.g. cough suppressants) and supportive (e.g. antibiotics to prevent secondary infections).
Common name:Canine flu, dog flu
Scientific name: Canine Influenza
SignalmentThere is no breed, age or sex predisposition to canine influenza. All dogs are considered susceptible.
The original reports were of greyhounds at racetracks developing severe respiratory disease. The current actual incidence is not known, but it is thought that the virus is widespread in the canine population.
There is no known geographic predilection for this disease.
Clinical signs (primary most to least frequent, scientific term, synonyms)
Coughing, nasal discharge.
Clinical signs (secondary most to least frequent, scientific term, synonyms)
Fever, difficulty breathing.
Cause (scientific, common term)
Influenza virus, type A.
Organ system affected (most to least affected)
Serology to measure antibody levels during illness and then 3 weeks later, viral isolation from tissues, polymerase chain reaction.
Bordetella bronchiseptica, kennel cough.
Canine influenza is an acute respiratory disease caused by a type A influenza virus that originated in horses and ‚Äújumped species‚Äù to dogs. The virus is highly infectious between dogs but results in a low mortality in the general population. Dogs in stressful situations (racing kennels, animal shelters, etc.) may have a higher incidence and higher rate of complications. In rare cases (less than 1% in the general population, up to 20% of kennel/shelter dogs), complications (such as pneumonia) from canine influenza infection can result in death. Most infected dogs, though, develop either no signs or only mild cough. The cough may be soft and moist or dry and hacking,and may be accompanied by a nasal discharge. Treatment may include cough suppressants as well as antibiotics to prevent secondary bacterial infections. Dogs developing pneumonia will require more intensive treatment. The best means of diagnosing canine influenza is determining antibody levels in the blood at the time of illness and again in 3 weeks to determine a rise in the antibody level, indicating recent exposure to the virus. A DNA test that can detect the virus in swab samples from the nose or pharynx has recently been developed. The prognosis for most dogs exposed to the canine influenza virus is excellent, although those developing complications such as pneumonia have a more guarded prognosis.
Because of the potential severity of any respiratory infection, home care can not be recommended. Dogs that have mild clinical signs may get better with time and supportive care such as cough suppressants. However, these recommendations should be made by the dog's regular veterinarian. Sick dogs should be isolated from other dogs until fully recovered to prevent transmitting the virus to others.
Veterinarians can assess infected dogs and determine the appropriate therapeutic regimen. Cough suppressants are often useful for managing mild cases. Bordetella or other bacterial infections may occur secondarily to viral respiratory infections, making treatment with antibiotics a reasonable precaution.
Veterinarians will perform complete physical exams, including careful listening to the lungs with a stethoscope, evaluating body temperatures, submitting blood tests, and checking for nasal discharges. Radiographs (x-rays) of the lungs may be taken if pneumonia is suspected. Dogs with evidence of pneumonia may be hospitalized and treated with oxygen, intravenous fluids, and antibiotics. A nebulizer (small machine that emits a moist vapor) is often used to deliver medication directed in to respiratory tract. The length of hospitalization can vary from a few days to more than a week, depending on the severity of the pneumonia.
The vast majority of dogs who develop clinical signs of canine influenza virus will recover and have a positive outcome. Less than 1% of dogs in the general population will succumb to the virus and/or complications due to bacterial pneumonia.
Clark, A. Canine influenza virus surfaces. Journal of the American Veterinary Medical Association 2005;227:1377-1378.
Crawford, PC. et al. Transmission of equine influenza virus to dogs. In: Science 2005; 310:482-485.
Newton R, et.al. Canine influenza virus: cross-species transmission from horses. Veterinary Record. 2005; 157:599.
Mike Dugan, DVM
Sharon Gwaltney-Brant, DVM, PhD, DABVT, DABT