Canine Influenza – The Quick Facts
- Canine influenza, also known as dog flu, is relatively new virus. An epidemic of this infection is currently ongoing in the Southeastern United States
- Clinical signs often mild, and include coughing, nasal and ocular discharge, fever, and reduced energy level
- Approximately 20% of infected patients do develop potentially life-threatening complications like pneumonia, high fevers, and respiratory distress
- Your family veterinarian should evaluate your dog as soon as possible if you observe any respiratory clinical signs
- Non-invasive testing is available to confirm a diagnosis of canine influenza, and treatment is largely supportive in nature
- Most infected dogs will recover within 2-3 weeks
- There is no evidence to support a threat of infection to humans or cats from infected dogs
Canine Influenza – What is it?
To date two strains have been identified: H3N8 and H3N2, the latter being the strain implicated in the most recent outbreak in the Southeast.
Canine influenza virus was initially caused by equine influenza A H3N8 virus, and the first reported infections were documented in racing greyhounds in Florida in 2004. Essentially the virus "jumped ship” from horses and is now considered a dog-specific lineage of H3N8. The newest strain of canine influenza virus, H3N2, was first identified in southern China and the Republic of Korea in 2006, and infectious disease experts thought this strain was isolated only to parts of Asia. No one yet knows exactly how H3N2 came to the United States, but we know both strains of CIV are relatively new. Therefore the vast majority of dogs in the United States has never been exposed to them, and is thus susceptible to infection.
Canine Influenza Virus – How does it spread?
Canine influenza spreads either via respiratory droplets in the air (called aerosolized secretions) or via contaminated objects and people. The virus retains its ability to infect in the environment for several hours:
- Up to 48 hours on surfaces (i.e.: counters, etc.)
- Up to 24 hours on clothing
- Up to 12 hours on hands
Once exposed, dogs could begin to show clinical signs in approximately two to four days. Interestingly dogs are most contagious during this incubation period (the time from exposure to the development of clinical signs); furthermore they can continue to shed the virus for up to 21 days after onset of clinical illness. Approximately 20-25% of dogs exposed to the virus do not develop clinical signs, but still shed the virus, thus posing an infectious threat to other dogs. All dogs are susceptible to infection when first exposed to the virus because dogs don’t have natural immunity to the disease. So an infected dog housed in a boarding facility (or similar environment) could infect a meaningful number of co-kenneled dogs.
Canine Influenza – What are the signs?
Dogs infected with CIV often have clinical signs similar to those caused by canine infectious respiratory disease complex (CIRDC), sometimes also called canine infectious tracheobronchitis and ‘kennel cough.” Dog flu is not a seasonal infection as it is in humans; dogs can become infected any time of year. Common clinical signs of CIV include:
- Coughing (dry or moist)
- Runny nose (nasal discharge can be clear to yellowish-green mucus)
- Eye discharge
- Rapid breathing
- Difficulty breathing
- Decreased (or loss of) appetite
- Decreased energy level
To date it appears the majority of dogs infected with CIV develop mild clinical signs that persist for 2-3 weeks despite treatments like cough suppressants. Affected dogs may have a soft, moist cough or a dry cough. Nasal and/or ocular discharge, sneezing, lethargy and anorexia may also be observed. Many dogs develop a nasal discharge and low-grade fever. Occasionally (~20%) dogs develop life-threatening illness, including pneumonia, high fevers, and respiratory distress.
Canine Influenza – How is it diagnosed?
A veterinarian should evaluate dogs with respiratory clinical signs as soon as possible. The doctor will also perform a complete physical examination to look for clues about your pet’s illness.
The good news is there is a non-invasive blood test that can be performed to confirm canine influenza infection. Currently most reliable method for confirming infection is called serologic testing to identify special proteins called antibodies the body makes to fight the virus. However the body takes approximately one week to make antibodies, and thus one needs to analyze more than one sample of blood to accurately perform serologic testing. To perform serology analysis for canine influenza virus a small sample of blood is collected initially within the first seven days of illness and then again approximately two weeks later. Dog flu is diagnosed when there is a four-fold increase in the quantity of antibodies from the first sample to the second one (called a convalescent sample).
Your pet’s veterinarian may swab the inside of your pet’s nose (called a nasal swab) or the back of his/her throat (called a nasopharyngeal swab) for a non-invasive test called polymerase chain reaction or PCR. This test is commonly done for patients who have been sick for less than four days. If the PCR test is positive, the patient is most likely infected with canine influenza. However false negative results have been documented, and PCR testing is not recommended if a patient has been sick for more than four days.
Canine Influenza– How is it treated?
There are no specific treatments for canine influenza virus infection in dogs, and therapies are largely supportive in nature. Antiviral drugs that are often prescribed for people with the flu have little or no known efficacy or safety in dogs. With appropriate nutrition, oxygen therapy, various respiratory therapies (i.e.: thoracic physiotherapy or nebulization/coupage), maintenance of hydration, and good husbandry interventions, most dogs recover within 2-3 weeks.
As mentioned earlier, some dogs develop serious and potentially life-threatening illness, requiring aggressive critical care. For this reason your veterinarian may recommend referral to veterinary specialty hospital where your pet can receive around-the-clock care from a specialist.
Canine influenza – What is the risk to humans?
Currently there is no evidence canine influenza virus H3N8 or H3N2 can be transmitted from dogs to people. Similarly there is no documentation of human infection with CIV. Thankfully current science tells us canine influenza viruses currently pose a low threat to humans.
Canine Influenza – What can you do to help?
- Avoid high-risk areas: Be cautious of visits to dog parks, dog shows and the groomers where there are bound to be many dogs. If you live in the area of the current H3N2 epidemic, this type of temporary precaution is profoundly important to help curb the spread of infection. Dog parks are a type of environment where canine influenza can be spread easily from dog to dog.
- Clean, clean, and clean: Be sure you thoroughly disinfect your dog’s various items, including beds, harnesses, bowls, and leashes. Of course keeping the general environment to which your pets are exposed is also important. The good news is common disinfectants (i.e.: 10% diluted bleach) kill canine influenza virus, and proper hand washing can help reduce disease transmission.
- Consider vaccination: There is an approved vaccination against canine influenza virus. While vaccination doesn’t prevent disease, it does significantly reduce the severity of clinical signs and the amount of virus shed by infected patients. This specific vaccination is not considered a "core” vaccine, but rather a "lifestyle” one. Therefore not every dog should receive this vaccine, as it’s intended only for those at risk for exposure to canine influenza virus. Talk to your veterinarian to find out if the canine influenza vaccine is right for your dog.
- Get your pet to a vet: As with most diseases, early identification and intervention is important. If you are concerned about your pet’s health for any reason, please seek immediate veterinary medical attention for him/her.