It’s flu season, and most people are doing what they can to avoid catching this year’s viruses. As most of us remember, swine flu was the big bug of 2009 — not just for humans, but for companion animals as well. Currently named North American Influenza, it’s scientifically known as Porcine Influenza A Virus subtype H1N1. Most of us know it simply as H1N1.

H1N1 was first isolated from swine in 1930 and had been previously detected in birds and humans. As swine serve as hosts for multiple subtypes of influenza virus, they’re a veritable melting pot of infectious respiratory diseases. It’s because the epithelial cells lining their respiratory tracts have receptors for both avian (bird) and mammalian (person, swine, dog, cat) influenza viruses. The 2009 H1N1 strain originated in Canadian pigs; people were infected through direct contact with ocular (eye) or respiratory secretions from swine.

A look at zoonoses

I have a keen interest in diseases that pass between animals and people. These are known as zoonotic diseases, or zoonoses. Prevalent public health concerns are for animal-to-human zoonoses, such as rabies, tapeworm and toxoplasmosis, rather than diseases that move from humans to animals.

In 2009, feeling that someone needed to explore H1N1’s potential to transfer from people to animals, I wrote an article entitled Swine Flu — Could H1N1 Infect Your Canine? To my surprise, the veterinary virologists I consulted expressed a lack of concern about possible transmission of H1N1 to animals. At the time, no positive cases of H1N1 had been confirmed in companion animals, but considering the close personal space people share with their dogs and cats, I concluded that a human-to-animal zoonosis seemed inevitable.

According to the American Veterinary Medical Association, the first confirmed cases of H1N1 infection in companion animals in the US occurred in one cat and two ferrets near the end of 2009. The cat and one of the ferrets recovered. Shortly after that, several dogs tested positive and reportedly survived the infection. The presence of H1N1 in these animals was verified via Idexx Laboratories’ Canine and Feline Upper Respiratory Disease (URD) RealPCR Panel, which evaluates ocular and oral secretions for a variety of bacterial and viral organisms.

A greater number of dogs, cats and other companion animals may have become sick or even died of H1N1 infection than have been reported. I speculate that thousands of animals were likely never tested for the H1N1 virus, due to lack of awareness of the test or the cost prohibitive nature of laboratory testing.

There are no reports of H1N1 spreading from one companion animal to another (e.g. dog to dog). Also, no humans were reported to have been infected by their dogs or cats. However, I feel this could happen if the necessary biological and environmental situations are met.

Symptoms and treatment

A variety of illnesses can cause clinical signs of respiratory disease in animals. Some are infectious (viral, bacterial, fungal, etc) and others non-infectious (allergies, irritants, etc). Signs include coughing, sneezing, wheezing, gasping for air, nasal and ocular discharge, light pink to purple gums, and lethargy. Respiratory tract afflictions can also cause decreased appetite, vomiting and diarrhea. It would be realistic to suspect H1N1 infection if the animal was exposed to a human with flu-like symptoms, regardless of the person’s official diagnosis of H1N1.

Appropriate treatment for H1N1 can be administered based on test results and suspicion of disease. In veterinary clinical practice, however, respiratory infections are commonly treated with antibiotics and supportive care (fluids, etc) without achieving an official diagnosis.
H1N1 is shed for only a short time post infection, so false negatives can occur even when an animal is sick.

What the future may hold

In August 2010, the World Health Organization declared the H1N1 pandemic officially over. It’s still a life threatening epidemic in certain countries, such as India, and it continued to infect companion animals and wildlife in the US into early 2011.

Although the number of American H1N1 infections is no longer on the rise, we may face a potentially more virulent form of this virus in the future. In June 2010, researchers at the University of Hong Kong and Shantou University Medical College discovered a hybrid virus containing genetic material from 2009 H1N1 and other avian and swine viruses. This hybrid virus was found among pig herds in China. Until this discovery, H1N1 was not proven to re-assort with viruses from other species besides swine. The hybrid has generated concern that additional 2009 H1N1 multi-species viral combinations may emerge in the future. The pandemic of 2009 may be just the beginning of a series of organisms that could potentially affect humans, companion animals and wildlife.

Protecting yourself and your animal

Do your part in keeping communicable diseases from infecting you and your animal companions.
• Practice good sanitary habits by washing your hands with soap and warm water after touching an animal (or another person).
• Avoid contact with other people and animals when you’re sick.
• Strive for an optimal state of health through a nutritious diet, regular exercise, and minimizing or preventing states of chronic inflammation (obesity, arthritis, etc). Do the same for your dog or cat.

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