CANINE INFLUENZA – A Summary of What We Know Now

Canine Influenza (CIV) is caused by the Influenza A virus.  The first stain H3N8 was discovered in Florida in 2004.  According to Dr. Kevin Snekvik at WSU/CVM-WADDL, the Influenza A H3N8 virus specific to dogs originated in horses and evolved over the last 40 years before jumping species. The virus continued to mutate till it was able to transmit between dogs.  By 2004 H3N8 had mutated to a dog specific virus. A second Influenza A strain H3N2 was discovered in Chicago in 2015. This strain is closely related to the Asian strain of Influenza which has been in wide circulation in the Chinese and South Korean dog populations since at least 2006. The H3N2 strain was thought to come in from Korea to Chicago’s O’Hare International airport in 2015.  

Unlike the Human Influenza Virus, CIV occurs year round.  There is no evidence of cross infection between dogs and people.  CIV is not related to Avian Influenza virus.  There does appear to be cross infection between dogs and cats. 

 

EPIDEMIOLOGY

CIV infection resembles Canine Infectious Bronchitis (Kennel Cough).  CIV is highly contagious since most dogs have never seen the virus.  CIV is easily spread between dogs through contact; nasal secretions via barking, sneezing or coughing; contaminated objects such as, kennel surfaces, food & water bowls, collars & leashes; and by people moving between infected and non-infected dogs.  High risk areas for spread of the CIV are areas where dogs congregate, such as, doggie day care & boarding kennels; grooming facilities; dog parks; dog shows & sporting events; and public common areas. 

 

CLINICAL SIGNS

Clinical signs may be mild or sever.  Clinical signs may include: a new and/or persistent cough lasting several days; thick nasal & eye discharge; sneezing; reduced appetite; fever-often 104-105; and increase respiratory rate.  Some dogs may not show any signs of illness, but can shed the virus to other dogs for up to 3 weeks.  Most dogs recover within 2-3 weeks, but secondary bacterial infections can lead to a more sever illness like pneumonia.

 

DIAGNOSIS

CIV can be diagnosed by testing a nasal or throat swab (PCR Testing) if diagnosed within 3 days of illness. The most accurate test requires a blood test taken during the first week and again 2 weeks later (paired serology tests on acute and convalescent samples).

Dogs are most contagious during the first 2-4 day incubation period of the CIV.  These infected dogs are shedding the CIV in their nasal secretions for up to 3 days but are not showing clinical signs.   80-90 % of all the dogs exposed to these infected dogs will become infected (morbidity rate) and develop flu symptoms.  The mortality rate is less than 10%-usually causing death in immune-compromised or geriatric dogs.

 

TREATMENT

Treatment is largely supportive care and treatment of any secondary bacterial infection.

 

 

PREVENTION

Isolating all sick dogs, dogs exposed to an infected dog and those dogs showing respiratory signs, can reduce the spread of CIV.  The CIV does not survive in the environment beyond 48 hours and is inactivated or killed by commonly used disinfectants.  Good hygiene (hand washing) and sanitation (through cleaning of feeding & watering bowls and kennels) will reduce the spread of CIV.

Keeping your dog updated with their Core vaccinations, including Bordetella (Kennel Cough) is extremely important.

There is a vaccine against the first strain of H3N8 CIV.  The vaccine may not completely prevent infection (no vaccine is 100% protective!), but it appears to reduce the severity, duration of illness, length of time an infected dog sheds the virus in its secretion, and amount of virus being shed.

It is not known whether the H3N8 vaccine provides protection against the new 2015 strain H3N2.  The USDA has given a conditional licensing to Zoetis and Merck for a H3N2 CIV vaccine. 

The AVMA’s current recommendation for vaccination against CIV is- as follows: “CIV vaccination is a Lifestyle Vaccination recommended for dogs at risk of exposure due to their increased exposure to other dogs-such as boarding, attending social events with dogs present, and visiting dog parks”

 

CIV-THE SEATTLE STORY

In December 2015, a boarding kennel in Kent had a respiratory illness outbreak.  Initially, it was thought these dogs had kennel cough.  So far, testing has confirmed 4 of these dogs had CIV H3N2 infections.  There have been no other confirmed cases of CIV in Washington.  At this time, CIV cases have been confirmed in Illinois, Wisconsin, Indiana, Michigan, Minnesota, California, New York, New Jersey, Ohio, Iowa, Georgia, and Alabama and now Washington.  The list of states is growing.

For further updates, consult the AVMA website under Pet Owner’s Guide for Canine Influenza or the WSVMA website.  If you are concerned about your dog’s exposure risk, contact your veterinarian to discuss vaccination status and possible risk factors.  If your dog has signs of respiratory disease, isolate your dogs and contact your veterinarian.

Stay tuned!

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