More Canine Influenza

by Bruce W. Little, DVM

The press continues to report cases of canine influenza (CI) across America. More than 40 states have reported they have diagnosed at least one case of canine influenza since it was first diagnosed in the Chicago area in March 2015. Originally, it was thought the outbreak in the Chicagoland area was the typical canine influenza caused by the H3N8 virus that was first discovered in the United States in 2004 and which had sporadically popped up at various places and intervals since that time, mostly in Greyhound dog racing kennels. However, upon further investigation, the outbreak that infected approximately 1,000 dogs, killing a small number of them, in the Chicago area was a new virus, the H3N2 virus, that had been found only in Asia prior to the Chicago and Upper Midwest outbreak. That was a significant finding because there was an approved vaccine for the H3N8 virus, but no specific vaccine was available for the current strain of canine influenza caused by the H3N2 virus. As is usually the case, this virus more than likely mutated from a similar virus found in some other species of bird or animal in Asia. It has been rumored that the virus was introduced to the United States through rescue dogs that were imported from Asia; however, there is no evidence to confirm those rumors. Canine influenza virus (CIV) does not infect people, although the potential for mutation exists as it does with all viruses. These viruses ARE NOT to be confused with the Zika virus that is being reported in many newspapers and other media outlets and appears to have its epicenter in Brazil. The Zika virus is a mosquito transmitted virus that effects pregnant women causing birth defects in unborn babies, and has not to date been found in species other than humans. Transmission of the Zika virus occurs when an infected person is bitten by a mosquito, and the infected mosquito then bites and infects another susceptible person.

Canine influenza, sometimes called dog flu, is a highly contagious infection caused by the H3N2 and the H3N8 viruses, and the mutated versions appear to infect dogs only at least at this time. Almost all dogs that are exposed to the viruses become infected and thousands of dogs have been infected across the country in the last year. Approximately 80% of those infected will show clinical signs of flu-like illness. Most of these dogs recover in two to three weeks. The other 20% of exposed dogs will not show signs of the disease, but will serve as carriers who transmit the disease to other susceptible dogs. This is why the disease was able to move across much of the area in and around Chicago in a matter of two to three weeks. The signs of illness include symptoms to which people can relate in human influenza infections; such as, a lasting cough, low-grade fever, nasal discharge, loss of appetite and lethargy. About one-fourth of the dogs that show clinical signs after exposure develop more severe illness such as pneumonia and high fever. Less than 10% will develop more complicated symptoms and some may die. If your dog shows signs of illness, especially respiratory illness, you should consult your veterinarian immediately. In order to confirm a diagnosis of canine influenza your veterinarian will send a sample of blood or nasal swab to a laboratory.

Most dogs, regardless of breed or age, are susceptible to canine influenza. With the older version of H3N8 dog flu, it was thought that much like human influenza, the very young, the very old or those dogs that had a pre-existing disease or conditions, such as a compromised immune system were more vulnerable. However, it is generally thought today that dogs of any age or breed are at risk for both strains of canine influenza. In a recent study done by Merck Animal Health Pharmaceutical Company, the ages of dogs that developed the disease most frequently when exposed to the virus were between the ages of 1 through 7 years of age. Dogs that show a high level of social interaction are at more risk than those pets who tend to remain alone and separated from other dog populations. Visits to dog parks, boarding at a doggie daycare facility or kennel, group dog training sessions, grooming parlors, dog show and agility events and dogs that travel with you to various places, both in your home town or state or inter-state travel, places the dog at a greater risk for exposure to canine influenza. It is thought that about 4 in every 5 cases of canine influenza is contracted in boarding kennels and dog daycare facilities. Seasonal events such as holidays and spring break from school when families travel more frequently seem to be conducive to the spread of canine influenza. Those are the times when dogs are left at boarding facilities or placed with dog-sitters who migrate from one dog walking job to another increasing the potential for transmitting this highly contagious disease.

The canine influenza virus travels from infected dogs to uninfected dogs through direct contact, coughing, barking and sneezing, contaminated food and water bowls, contaminated collars and leashes and people moving between infected and susceptible animals. It is imperative that boarding and other temporary housing facilities adhere to a rigid sanitation protocol that includes frequent washing of hands after handling any dog and especially when handling a sick dog. The kennel staff should never share equipment or toys between sick and apparently healthy dogs. If there is an outbreak of canine influenza in the area, this is especially important because as stated above, about 20% of exposed dogs never show signs of the disease; however, they do remain carriers and can transport the disease to vulnerable dogs. Once exposed, the infected dog will usually show signs of the disease within 24 to 48 hours. So, there is a very short time lapse from when a dog is exposed until it shows signs of the disease. There is no seasonal or weather event that may cause an increase in the incidence of canine influenza, except for the fact that people tend to travel more during holiday seasons when dogs are left at boarding facilities or taken to other locations with the family. In the summer months in some parts of the country we create a greater chance for exposure to an infected dog by being outside and in contact with other people and dogs.

Your veterinarian will establish the best course of treatment or treatment options if your dog is diagnosed with canine influenza. As is the case for all viral diseases, treatment is mostly supportive with good care and nutrition that can assist dogs in developing an effective immune response to the disease. The presence of secondary bacterial infection as evidenced by fever, dehydration and nasal discharge may need a course of antibiotics, fluids to correct and maintain hydration and/or anti-inflammatory medications to reduce fever. Your dog should be kept isolated from other dogs in the house and in the neighborhood during the course of the disease.

Preventing your dog from contracting canine influenza is the best scenario possible. Talk to your veterinarian about the risk factors that may affect your dog. Find out if there are widespread cases of canine influenza in the area in which you live or in places that you are contemplating visiting. Make sure boarding kennels, dog day care facilities, groomers and dog-sitters are aware of the potential for your dog regarding canine influenza, and that they take all precautions necessary to keep the disease contained as well as possible. Ask your veterinarian if your dog should be vaccinated against canine influenza as there has been a government approved vaccine against H3N8 influenza since 2009. The vaccine for your dog may not stimulate a total preventative for the disease; however, records show it provides complete immunity to approximately 90% of the dogs who receive it. It also relieves the severity and duration of the illness. The vaccine reduces the period of time that an infected dog may shed the virus in its respiratory secretions, as well as the amount of virus shed, thus making them less contagious to other dogs. There has been no evidence to date that that vaccine will protect your dog against the H3N2 virus.

Recently, vaccines from two different pharmaceutical companies were granted conditional licenses by the U.S. Department of Agriculture (USDA) for H3N2 canine influenza vaccines. These vaccines will be fully licensed by USDA if tests prove they are effective against the respective virus and do not pose any side-effects to vaccinated dogs. Not all dogs may need to be vaccinated. If your dog never goes outside your own home and yard, and if there are no stray dogs or other visiting dogs coming into your home environment, your veterinarian may advise you that your dog does not need the vaccine. Seek out and follow the advice of your veterinary professional and canine influenza can be mitigated or contained altogether. Canine influenza, like human influenza, can make a dog very sick for a period of time. Prevention is always better than treating the disease once it has infected your dog. Your dog deserves the very best of care, and will continue to show its unconditional love regardless.



Bruce W. Little, DVM