In recent news, there have been reports of a canine influenza outbreak in the Chicago area. Canine influenza virus (CIV), or “dog flu”, is a viral respiratory tract disease that is included in the “kennel cough” syndrome. In previous years, the causative agent of canine influenza was identified as the H3N8 influenza virus. However, recent reports indicate that the ongoing influenza outbreak in the Chicago area is actually due to a different subtype, H3N2. This is the first identification of the H3N2 subtype outside of Asia. Influenza viruses, by nature, easily mutate (or change) in ways that allow them to persist and cause disease. At this time there are no reports of canine influenza causing illness in humans. Currently, almost all dogs are susceptible to infection, especially dogs that are housed in high-density dog populations such as kennels, shelters, rescue groups, dog shows, and racing facilities.
The influenza virus is efficiently spread between dogs by respiratory secretions, objects carrying the virus (i.e. chew toys, bedding) and direct transmission. The virus is easily killed with bleach but can persist in the environment for approximately one week. Because CIV is a relatively new virus, most dogs have not been exposed, rendering dogs of any age, breed, and vaccine status susceptible to infection.
Clinical signs range from mild to severe and generally occur one week after exposure. Dogs shed the virus nasally for approximately 2-10 days becoming infected. Mild clinical signs include a soft, moist cough. Approximately 10% of dogs can develop a severe form of illness that includes high fever (104-106°F), lethargy, and bronchopneumonia. If CIV is quickly diagnosed and treated, and if dogs are affected with the mild form of the disease, the fatality rate is low. However, if severe disease ensues, the fatality rate can be as high as 5-8%.
Diagnosis of CIV includes physical examination, blood tests, virus isolation, chest radiographs, and appropriate clinical signs. Unfortunately, there is no specific antiviral medication available (human Tamiflu is not recommended). Treatment of mild cases may require only isolating the dog and providing supportive care (good nutrition, rest, prevention of dehydration and secondary infections). Severe cases require hospitalization with intravenous antibiotics and fluids as well as good nutrition.
Prevention of CIV requires reducing the spread of the virus between dogs. A vaccine against the old strain of the CIV virus (H3N8 subtype) is available. However, at this time it is not known if the currently available vaccine will provide any cross-immunity or protection to dogs exposed to the newly identified H3N2 subtype. There are currently no reports of CIV in New Mexico; thus, the risk of canine influenza to dogs in this area is very low and most clinics do not stock the vaccine. We still recommend vaccinating dogs against the more common causes of kennel cough, including Bordatella bronchiseptica, canine parainfluenza (a different virus), and canine adenovirus-2 at least two weeks prior to boarding. This vaccine is an intranasal vaccine and lasts for approximately six months.
If you have any further questions, please contact one of the doctors at Gruda Veterinary Hospital.