Canine influenza, also known as the dog flu, was first recognized in racing greyhound kennels in 2004. Though it may have existed unrecognized prior to that time, the virus has since spread to other areas and has now been found in many states in the United States.
What is Canine Influenza?
Canine influenza is a contagious viral disease easily passed from one dog to another through direct contact with infected dogs, aerosolization of viral particles or contact with contaminated fomites (objects such as food dishes, water bowels, hair brushes, clothing or skin of handlers). The virus which causes canine influenza is a type A influenza virus known as H3N8.
The incubation period (time from exposure to appearance of symptoms) is generally 2-5 days and dogs may become infective before they begin to show clinical signs.
Canine influenza is a newly emerging disease . Most dogs will not have been exposed previously and thus will not have any natural immunity to the disease. Therefore, most dogs are likely to become infected if they are exposed to the virus. However, at this point in time, the virus has been recognized mainly in pounds, shelters, veterinary kennels, and other kennel situations. Canine influenza has not been seen commonly in the general canine population to date, but that fact could change drastically over time.
Symptoms of Canine Influenza
Dogs infected with canine influenza typically display respiratory symptoms similar to those seen with the flu in other species. Symptoms seen may include:
- sniffling
- sneezing
- nasal discharge
- coughing
- fever
- lethargy
- depressed appetite
In most cases, symptoms remain mild and may even go unnoticed by the pet owner. Canine influenza can easily be mistaken for kennel cough (infectious canine tracheobronchitis) without more extensive diagnostic testing. Infection usually lasts 2-4 weeks.
Though the majority of canine influenza cases are mild or even asymptomatic, some cases become complicated with pneumonia and may even produce a hemorrhagic, necrotizing form of pneumonia. These dogs usually become critically ill and canine influenza complicated with pneumonia has been known to be fatal.
Though morbidity with canine influenza is very high, mortality is low. Though the infection rate in exposed dogs is high, many exposed dogs will never show symptoms or will show only very mild symptoms. Very few dogs are likely to develop life-threatening disease. The incidence of pneumonia resulting from canine influenza virus infection is estimated at 5-8% of all canine influenza infections.
Diagnosing Dogs with Canine Influenza
Diagnosis of canine influenza can be difficult and is impossible based solely on clinical symptoms because canine influenza so closely resembles other cases of canine kennel cough. Blood testing, in the form of PCR testing or serological testing, is necessary for confirmation of canine influenza and to differentiate the disease from Bordetella, canine parainfluenza virus, canine adenovirus-2 and other causes of canine kennel cough.
Treatment of Dogs with Canine Influenza
Treatment of canine influenza is normally symptomatic in nature. Adequate nutrition and rest are essential to recovery. Dehydration may need to corrected, where present, with fluid therapy. Antibiotics may be necessary to help prevent or to treat secondary bacterial infections which may cause pneumonia.
Tamiflu® is an antiviral medication which has been used in some cases to treat canine influenza infections. However, Tamiflu® must be used early in the course of infection to be effective and its use remains controversial.
Preventing Canine Influenza
Avoiding contact with other dogs which are coughing is important. It should be remembered that canine influenza is more likely to occur in dogs which are placed in kennel situations (pet shops, veterinary hospitals, pounds, shelters, day care programs, boarding kennels) and attention to sanitary measures in these facilities is mandatory to help prevent disease outbreaks.
A new vaccine for canine influenza has recently become available and may be recommended for dogs at risk of exposure to the influenza virus.
Canine influenza is also sometimes commonly called dog flu and is difficult to differentiate from other causes of canine kennel cough. Though usually mild in nature, the canine flu virus can cause serious complications in a small minority of infected dogs. There is no evidence that canine influenza can infect other types of animals or people.
Sources:
Landolt GA, Lunn KF: Canine influenza. Kirk’s Current Veterinary Therapy XIV Elsevier 2008 pp. 1291-4.
Crawford PC, Spindel ME: Canine Influenza Virus. Infectious Diseases of Shelter Animals Blackwell Publishing.
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