Transmission, Symptoms, and Treatment of Canine Influenza

Canine flu is a viral infectious respiratory disease that can affect our dogs. It's caused by the Influenza type A virus and presents with a clinical picture similar to what appears in humans.

It affects many animal species, and given its outstanding ability to mutate, high environmental resistance, and high transmission rate, it's worth knowing its symptoms and what treatment it requires.

Origin of the Influenza Type A Virus

Over the past 400 years, influenza epidemics have been reported in many countries. Epidemics since the 16th century in England and the 18th century in the USA are recognized as influenza. The 1918 influenza pandemic was the largest in recent history, causing 20 million deaths worldwide.

Every type of influenza A affecting mammals comes from birds. Two subtypes of the Influenza A virus are known, but the most pathogenic is H3N8. In both cases, the microorganism jumps between species, is transmitted to dogs, and spreads between them.

The official start of canine influenza was the identification of an influenza virus in cases of respiratory disease in greyhounds in the racing industry in the United States in March 2004.

How Is Canine Influenza Transmitted?

Transmission between individuals occurs via the respiratory route through the release of particles when breathing, coughing, sneezing, or through contact with contaminated surfaces containing respiratory secretions. The influenza virus has high environmental resistance in conditions of low temperature and high humidity. The incubation period in dogs is one to three days.

Canine flu can't be transmitted from dogs to humans (it's not considered a zoonosis), just as we can't give our dog a human flu. So, if our dog is infected, it can only infect other dogs. However, there's evidence of canine influenza in humans against equine strains.

Symptoms of the Influenza Virus in Dogs

Dogs affected by the Influenza virus will show one or several of the symptoms described below, with their severity varying depending on our dog's immune system, age, as well as the viral load they've acquired, etc.

The real challenge with this disease is that its symptoms are very similar to other diseases, meaning they're quite nonspecific.

• Lethargy.
• Anorexia
• Nasal and eye discharge
• Sneezing.
• Listlessness.
• Fever (in few dogs, and mild).
• Pneumonia from secondary bacterial infection.
• Coughing (can last three weeks).

Not every dog shows signs, and those that do may not show all of the ones described.

How to Diagnose Canine Flu?

This condition can't be diagnosed based solely on clinical signs, since these are shared with other canine respiratory diseases, as mentioned above.

To properly confirm Influenza type A infection, specific tests need to be used. Tests are available at labs that can identify virus strains through PCR, which are sensitive to any H subtype.

Treatment for Canine Influenza

We can act against canine flu once the animal shows the disease, or try to develop preventive measures aimed, above all, at preventing transmission.

Treatment will be symptomatic, aimed at relieving symptoms once the condition shows up. So, depending on the symptoms, drugs such as mucolytics will be used to ease congestion and help eliminate the virus, along with anti-inflammatories and antibiotic therapy if considered necessary to treat or prevent secondary bacterial infections.

Barring later complications, the dog usually makes a full recovery within a period ranging from 1 to 3 weeks, depending on many of the factors mentioned above.

How to Prevent Influenza?

Vaccination is the usual method of prevention. In this case, it's not useful for preventing infection — its effect is limited to reducing how long the disease lasts and the severity of symptoms.

Proper nutrition strengthens the immune system. We should also follow cleaning and disinfection protocols to reduce the risk of viral transmission through contact. The virus is easily eliminated with common alcohol-based disinfectants.

Normally, based on veterinary clinical experience, this type of respiratory condition is more common during the autumn months, so we should be especially careful around other dogs.

Bibliography Research from: Dr. Hideyo Noguchi, Universidad Autónoma de Yucatán, Mérida, Yucatán, México. Edward J. Dubovi, PhD.