Canine Influenza (Dog Flu)
By: Dr. Cindy Krane and Dr. Anthony Krawitz (Calusa Veterinary Center)
In late May 2017 an outbreak of the Canine Influenza Virus (CIV) N3H2 started at a dog show in Georgia and spread to Deland, Florida, just north of Orlando, worrying owners sick. The virus is highly contagious.
There are currently two known strains of the Canine Influenza Viruses (CIV), H3N8 and H3N2. Both of which infect dogs in the United States. Cats can become infected as well, but people are not susceptible to the canine strains of Influenza.
The origins of the H3N8 strain are still not fully known. The virus is thought to have mutated from horses in 2004, appearing on greyhound tracks in Florida. Within a year, the virus had spread to more than 30 states. It now continues to emerge in pockets throughout the United States, making it a scary and sporadic epidemic.
In the spring of 2015, the H3N2 strain was found in Chicago. It is almost identical to an Asian strain of the influenza virus (H3N2) that was first noted in Asia between 2006-2007. There are theories that this strain arose from an avian virus in one of several large bird markets, then mutated to affect dogs. Another theory holds that the H3N2 strain may be porcine in origin. It likely entered the United States via an infected dog or cat, perhaps one rescued from a Korean meat market. Since the first infected animal entered the states, around 1500 dogs across the Mid- West have become infected, and many have died. This is the same strain traveling through Georgia and Florida at this time.
These viruses are highly contagious and spread easily from dog to dog in social settings. Dogs in shelters, boarding kennels, doggie day cares, dog parks, rescue groups, pet stores, dog shows, and race tracks are at the highest risk of contracting the virus. Anywhere there are large groups of dogs in close quarters is somewhere highly susceptible to attracting and spreading the disease. All ages and breeds of dog are susceptible to the virus. There is little natural or vaccine induced immunity for the non-seasonal nor regional CIV. Dogs that become exposed will quickly become infected.
Transmission can occur in one of three ways. Virus particles can be aerosolized from respiratory secretions (coughing/sneezing) of infected dogs. It is important to note that infected dogs can spread the disease this way 2-4 days before the onset of clinical signs. That means that a dog may appear and feel perfectly healthy and at the same time pass on the disease. It can travel 20 feet or more from a single cough or sneeze. The virus can also be spread from fomites (objects / material like food and water bowls, collars and leashes, toys, bedding, that carry infections). Additionally, people moving amongst infected and healthy animals can transmit the virus for up to 12 hours on their hands and up to 24 hours on their clothing. It is import to note that while people can be vectors of these viruses they are NOT susceptible to infection. There is zero evidence that people can become infected/ill with CIV. There is evidence that cats can become infected/ill from CIV. The virus gets into the nasal passages and replicates there. It causes rhinitis, tracheitis, and bronchitis (inflammation of the nose, trachea and bronchial tree respectively). In severe cases it causes pneumonia. It then kills the cells that line and protect the respiratory tract allowing for secondary bacterial organisms to invade and add to the dogs’ morbidity. The morbidity rate (illness) is around 80%, with a mortality rate (death) as high as 10%.
Clinically, CIV looks and acts exactly like any other pathogen causing CIRDC (canine infectious respiratory disease complex). CIRDC may be associated with one or more bacteria and viruses that layman refer to as “kennel cough”. CIRCD causative organisms including Bordetella, Parainfluenza, Influenza, Mycoplasma, Pasteurella amongst others. Clinical signs caused by CIRDC mimic each other and include fever, nasal discharge, coughing, sneezing, and malaise. Severity of illness due to CIV ranges from mild sniffles and lethargy to life threatening pneumonia. It can last 2 or more weeks.
Confirming the diagnosis of CIV is difficult, as it must be done early in the disease process. The virus can be isolated using PCR technology from respiratory secretions by nasal/throat swabs within the first four days of illness. Alternatively paired serologic blood samples can be taken within one week of infection and with a follow-up sample 10-14 days later if the antibody titer increases dramatically between the 2 samples. Samples should be submitted to a reference lab well versed in identifying the viruses.
Treatment, as for most viruses, is supportive and symptomatic. Affected dogs should be treated with IV fluids if dehydrated, antibiotics if secondary bacterial infections are present, anti-inflammatory for fever and inflammation, cough suppressants, nutrition and immune support. Anti-viral human medications like Tamiful are not currently recommended as there are no good controlled studies documenting their efficacy to warrant their extra label use and expense. Treatment should extend for 2- 3 weeks; at least twice as long for typical cases of CIRDC. Many dogs will be treated on an outpatient basis at home. As they remain contagious for up to 4 weeks they must be isolated from all other dogs. Unfortunately, some of the dogs infected will develop more severe disease like pneumonia and will require aggressive therapy and hospitalization.
The incubation period (the time from exposure to showing symptoms) is usually around 2-5 days. Prevention of CIV is centered around isolating ill from healthy dogs for 3-4 weeks and isolating exposed dogs from healthy ones for 1-2 weeks. Good hygiene like employee hand washing and disinfecting fomites is essential. The viruses are liable (do not live long in the environment) and can be killed with bleach and other disinfection solutions. Use alcohol based hand sanitizer after petting other dogs.
Multivalent vaccines effective against both H3N2 & H3N8 stains are available, safe and efficacious. They are not considered “core” vaccines, they are considered “lifestyle vaccines”. If your dog lives a “social” lifestyle participating in group events or housed in communal facilities your veterinarian may recommend a series of CIV vaccinations. Patients currently receiving the Bordetella bronchiseptica “kennel cough” vaccine should have a risk benefit assessment for the CIV vaccine. Both infectious diseases target the same group of dogs and carry the same risk factors, mainly close contact with other dogs. Dogs that stay home or walk around the block are at lower risk.
Just like with the human flu shot, the vaccine will not prevent infection 100% of the time. It will make infection less likely and if infection is to occur the illness is expected to be milder and for a short period of time.
The initial vaccination series requires 2 doses, 2-3 weeks apart. At Calusa Veterinary Center, the fee is $71 for the initial exam and risk assessment, and $49.00 per vaccination. Annual revaccination should be considered.
If your dog has been exposed (think dog shows, groomers, doggie day cares, dog training, boarding, local dog parks, dog shows, sporting events, greeting other dogs on walks, veterinary offices) or is showing any signs of respiratory disease, please call your vet immediately. Do not arrive at the hospital nor enter the hospital without calling first. To limit the spread of disease and chances of an outbreak do not come into the hospital. Rather call us from your car when you arrive and we will either examine your dog outside or in our isolation ward.
We are advising that all dogs boarding or being groomed at our facility be vaccinated for CIV for their protection and for the protection of others. Make sure to schedule your dog’s vaccinations beforehand so the two vaccines can be given two weeks apart prior to your dog’s boarding reservation or grooming appointment.
As always, if you have any concerns at all about your pet’s health, or if your pet is showing signs of CIV infection, please call our hospital at 561-999-3000. To prevent the spread of illness and chances of an outbreak, please do not arrive at our facility without calling us first.
We hope this information will help you protect your pets against CIV, as well as prevent the spread of CIV to other pets in our community. Please contact us if you have any questions at all.