Every Season is Canine Influenza Season

Have you ever heard your dog cough and decided to wait to call the vet and see how it worked out? Coughing is a tricky thing. We don’t go to the doctor every time we have a cough. Sometimes it is the common cold virus or allergy and we have to let it work its way through our system. Why should we bring our dogs in for a cough?

A cough can be something serious such as an indication of end-stage heart disease, heartworm infection, parasitic worm or fluke migration through the lungs, fungal infections, bronchitis, pneumonia, asthma, foreign body, malformation of the trachea, and primary or metastatic cancer in the lungs or thyroid gland. If a cough persists for more than 1-2 days you should definitely be calling your veterinarian.

A kennel cough is a constellation of signs caused by multiple bacteria and viruses. It usually involves a harsh cough with a gag at the end that sounds like the pet will vomit. The cough can last for 1 week to 2 months and keep you up all night with your dog but it will not be lethal in 99.99% of the cases. Frequently the cough happens when the pet is excited, or at night. Viruses such as parainfluenza virus or adenovirus can cause a kennel cough. The bacteria Bordetella bronchiseptica can co-infect and cause a cough.

Canine influenza virus infection (CIV) also causes a cough. This Type A flu virus is named after the unique amino acid composition of glycoproteins hemagglutinin (H) and neuraminidase (N) on its surface H3N8. The virus was first discovered in 2004 in dogs. Previously the virus was an equine (horse) virus. It is a very rare event in evolution when the entire genome of a virus jumps species. It happened when retrovirus jumped from African chimpanzees to humans and we discovered HIV. This time the virus jumped from horses to dogs. Having observed my dogs and many others in the horse barn devouring horse droppings like fine delicacies I am not too shocked by this occurrence. Dogs ingesting horsemeat could have caused the jump as well. The newly adapted virus is made up of 8 strands of single strand RNA surrounded by a glycoprotein capsid. It acts by destroying the cells that are the lining of the lungs or epithelial cells.

The first outbreaks around the country were in greyhound racetracks around the country in 2004. In 2005 a Massachusetts kennel had an outbreak and greyhounds were severely ill. The virus was likely spread when dogs were transported to different racetracks for competition.

A large outbreak of canine flu in Chicago last year was discovered to be the H3N2 strain, a whole new CIV that spreads like wildfire in closely quartered dogs. Last year a vaccine was developed for this new strain of flu. In the interest of not over-vaccinating dogs, veterinarians advocated for a combination vaccine. It is now available in a double (bivalent) flu vaccine with the H3N8 strain.

Unlike human flu, the symptoms are not seasonal. The outbreaks occur year-round for dogs. 80% of dogs exhibit a mild form of canine influenza with symptoms very similar to a kennel cough although many times the cough is a softer moist sounding cough. The cough persists for 10-21 days in spite of antibiotic and cough suppressant administration. Recent research has found that severe illness and death were much more likely when the dog was co-infected with CIV and common Streptococcus bacteria. The death rate of dogs showing symptoms is between 1-5%.

The most problematic characteristic of CIV is that it sheds on the pet before the symptoms appear. So for 4 to 10 days before any signs appear the dog can be spreading the virus to other dogs. Also, 20% of the infected dogs show no illness and just spread the virus. What a fantastic way to propagate the virus! And what mayhem it can cause when it is in a boarding, daycare breeding kennel or shelter.

At a large grooming facility or pet store, the virus can be spread by a healthy looking dog that leaves the virus on a surface via a cough or licking. It remains viable on surfaces for 48 hours clothes for 24 hours and on hands for 12 hours. The owner will never know where the dog got the virus if it was at a groomer or pet store. If canine influenza hits a facility where dogs spend their days and/or nights it will cause the facility to have to shut down and lose a huge amount of business. This has happened at facilities near us such as in New York.

Once the virus was isolated in the lab the race was on to make a vaccine to prevent CIV. Within the past 6 years, the vaccine has become available. It was hard to justify the vaccine when there was just one localized outbreak yearly in Massachusetts over the past 3 years. One of the reasons the canine flu is not diagnosed more often is that the testing is expensive and veterinarians and their owners tend to treat the kennel cough symptoms and do not test for CIV.

How do we prevent the infection? The virus can be removed from the skin by hand washing. All surfaces dogs come in touch with must be cleaned with quaternary ammonium compounds (eg, benzalkonium chloride) and 5% bleach solutions after each and every dog contact. Keep your dog away from dogs that are coughing. Consider having your dog vaccinated with the CIV vaccine if your dog goes to the Dog Park, groomer, pet store, and boarding or daycare facility. Your boarding facility may require it. The CIV series consists of one vaccine and a booster 2 weeks later. Many of these facilities that are on top of their dog health news are now requiring this vaccine before the dog can enter the facility. The CIV is a lifestyle vaccine so you and your veterinarian can make the decision together about administering the vaccine.

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Salem, MA 01970
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