What is canine influenza?
Canine influenza virus (CIV) is primarily the result of two influenza strains: H3N8, which originated in horses, and H3N2, which originated in birds. Although these viruses previously infected other species, both have adapted to infect and spread among dogs.
CIV has been detected in most American states. Fortunately, CIV kills very few healthy individuals and has a mortality rate between 1% and 5%, with most deaths in dogs that have other severe illnesses.
There are approved CIV vaccines in the United States and Canada. Vaccination against canine flu should be considered for dogs that travel or show, and those that have frequent contact with other dogs (e.g., dogs that are boarded or go to dog parks).
What are the clinical signs of CIV?
The signs of canine influenza are like the human flu:
- Cough
- Runny nose
- Fever
- Reduced appetite
- Lethargy (decreased energy)
The most common sign is a cough that lasts 10 to 21 days and does not respond to antibiotic or cough suppressant therapy. This cough may be productive (moist) or non-productive (dry). Most dogs infected with canine influenza develop only mild clinical signs. However, dogs infected with the H3N2 strain may be more likely to develop severe clinical signs.
The signs of canine influenza are similar to those caused by other respiratory infections, including kennel cough and other diseases in the canine infectious respiratory disease (CIRD) complex. Because these conditions can be difficult to distinguish, any dog showing signs of respiratory illness should be examined by a veterinarian.
Although most infected dogs will only develop a mild form of canine influenza and will recover without complications, some dogs (approximately 10% to 20%) may develop severe pneumonia that can be life-threatening.
How is canine influenza spread?
CIV is spread through:
- Respiratory secretions (e.g., sneezing, coughing, nasal discharge)
- Contaminated objects such as kennel walls and floors, food and water bowls, collars and leashes
- Clothing and skin of people who encounter infected dogs
CIV can survive on skin and hands for 12 hours, on clothing for 24 hours, and surfaces for up to 48 hours. Infections may occur year-round. It takes about two to five days (incubation period) for clinical signs to develop after contact with the virus. Infected dogs are most contagious during this incubation period, making rapid transmission likely. Infected dogs continue to spread the virus for up to 28 days.
All dogs are susceptible to infection with CIV, as they have little or no naturally acquired immunity. If your dog is exposed to the virus, they will likely become infected and develop clinical signs. Approximately 20% to 25% of infected dogs may have a subclinical infection, which means they show no signs of illness but remain contagious and can spread the virus.
How is canine influenza diagnosed?
Canine influenza cannot be diagnosed on clinical signs or symptoms alone due to its similarities to other respiratory infections. If a veterinarian sees a dog within the first few days of clinical signs beginning, they can send a nasal swab for a polymerase chain reaction (PCR) test to a veterinary laboratory. If the PCR test is positive, the dog most likely has CIV.
After 10 days of illness, PCR results are less likely to be accurate because there may be false-negative results. At this stage, your veterinarian will perform blood testing for CIV antibodies. This type of testing, called serology, involves comparing antibody levels two to three weeks apart. If antibody levels rise significantly over this period, it indicates active CIV infection. Your veterinarian may also wish to run other tests, such as blood work and radiographs (X-rays), to assess the severity of the infection.
Any dog suspected of having CIV should be tested to determine whether the disease is spreading in your area. If there are confirmed CIV cases in your area, consult your veterinarian and consider vaccinating your dog.
Should my dog be vaccinated against CIV?
The decision to use any vaccine is based on each dog’s risk and lifestyle. Indoor dogs with little exposure to other dogs are at less risk than dogs that travel, are kenneled, or encounter other dogs frequently.
If you live in an area where outbreaks occur, you should consider vaccinating your dog against CIV. Cases have been identified in most U.S. states, the District of Columbia, and some provinces in Canada. There have been no reported issues with the CIV vaccination to date.
It is important to note that the CIV vaccine cannot completely prevent the disease. It may, however, reduce the severity and duration of clinical signs associated with infection, which is especially important in at-risk dogs and helps reduce the spread of outbreaks. Talk to your veterinarian about whether your dog should be vaccinated against CIV.
What is the treatment for CIV?
As with nearly all viral infections, CIV treatment is largely supportive, which means it aims to relieve symptoms. You can help your dog mount an adequate immune response by ensuring good nutrition and care while they are sick.
- Keep your pet in a warm, dry area away from other dogs
- Feed your pet a high-quality diet
- Ensure they are well hydrated
Dogs affected with a mild form of canine influenza often develop a secondary, bacterial upper respiratory infection. These dogs typically have a thick green mucous discharge from their nose and benefit from broad-spectrum antibiotic therapy. Dogs that develop pneumonia may require hospitalization, intravenous fluids, and medications, including potent broad-spectrum antibiotics.
Most dogs fully recover from canine influenza within two to three weeks. Dogs exposed to the virus should be isolated for four weeks to prevent further spread, even if they do not develop any respiratory signs. It is essential to consult with your veterinarian to determine the best course of treatment.
How can I care for my dog with canine influenza?
Your veterinarian will recommend specific treatment based on your dog’s physical examination and respiratory signs. Almost all dogs exposed to CIV will become infected, so it’s important to keep an infected dog away from other dogs in any environment, including the groomer, dog parks, walks, and kennels. Thoroughly clean clothing, equipment, floors, and hands with soap and water after contact with any dog with signs of respiratory illness.
Can people or other pets get the flu from a dog with canine influenza?
CIV poses no threat to humans and is closely monitored by the Centers for Disease Control and Prevention (CDC), Health Canada, and their partners. If your dog contracts CIV, you can care for them without worrying about acquiring the infection yourself.
Cats can contract canine influenza virus from dogs and other forms of influenza from humans, so their contact should be restricted as much as possible with any animal suspected to have flu. Cats rarely spread the virus to other animals, but it is best to keep them inside to prevent spreading the flu to other animals.
