How Canine Influenza Affects Dogs
Unlike disease caused by the human flu virus, canine influenza is not seasonal and can occur in dogs of any age, gender or breed, at any time of the year. There is no natural or vaccine-induced immunity to this recently recognized pathogen. Clinical signs of “dog flu” typically appear suddenly. Most infected dogs have mild symptoms, including a persistent cough that can be moist or dry and usually lasts 2 to 3 weeks despite use of antibiotics and cough suppressants. The cough is accompanied by clear nasal drainage, which often progresses to a thick, greenish discharge. Low-grade fever is common. If the cough is dry and hacking, it may be confused with “kennel cough,” a condition caused by the Bordetella bronchiseptica/Parainfluenza virus that in the early stages is virtually indistinguishable from CIV infection.
Symptoms of Canine Influenza
Unlike disease caused by the human flu virus, canine influenza is not seasonal and can occur in dogs of any age and any breed, during any time of the year. CIV is transmitted by airborne respiratory secretions containing viral particles. It can also be transmitted by contact with contaminated objects or surfaces (food and water bowls, kennels or cages, floors, collars, leashes, hands, clothing, shoes, etc.). Reports suggest that the virus can survive and be infectious on surfaces, clothes and hands for up to 48 hours. Given its mode of transmission, CIV tends to cause disease in dogs that are in close contact with many other dogs, such as in boarding kennels, rescue shelters, humane societies, doggy day-care facilities, at dog shows or in similar group situations.
It normally takes 2 to 4 days for clinical signs to develop once a dog has been exposed to and infected by the canine influenza virus (this is called the “incubation period”). Almost all dogs exposed to CIV become “infected” with the virus, and roughly 60-80% of infected dogs ultimately develop clinical disease. Unfortunately, infected dogs are the most contagious to other dogs during the viral incubation period – even though they have not yet shown any clinical signs of illness. Even the 20-40% of infected dogs who never become ill still shed the virus and can infect other dogs.
Signs of canine influenza range from mild to severe and normally appear suddenly. Most infected dogs have mild clinical signs including a persistent cough that can be moist or dry but lasts 2 to 3 weeks despite use of antibiotics and cough suppressants. The cough is usually first accompanied by a clear nasal discharge, which often progresses to a thick, green-ish mucoid discharge in the presence of a secondary bacterial infection. Low-grade fever is often present. If the cough is dry and hacking, it may be confused with “kennel cough,” which is a condition caused by the Bordetella bronchiseptica/parainfluenza virus and in the early stages is virtually indistinguishable from CIV infection.
In cases of severe canine influenza, dogs may develop a high-grade fever (104-106 degrees F) and pronounced signs of pneumonia, such as increased respiratory rate, effort and wheezing. They also may become lethargic, depressed and anorexic. The fatality rate for canine influenza is low, and very few dogs infected with CIV will die.
If your dog shows signs of coughing, nasal discharge and a moderate fever, contact your veterinarian immediately. Because CIV is so highly contagious, other dogs in the household are at high risk for developing the disease. Until you find out what is causing your dog’s symptoms, keep your dog isolated from other dogs and always wash your hands thoroughly after petting or touching your dog.