Animals Get the Flu, Too

As flu season begins and doctors promote flu shots and await patients coming in with the familiar symptoms, veterinarians are anticipating visits from their own patients.

Veterinarian Erin Denney-Jones vaccinates a horse against equine influenza.

(Courtesy American Association of Equine Practitioners)

Although their viruses rarely spread to humans, a variety of animals suffer from their own strains of influenza.

"Several animal species are susceptible to influenza or flu viruses -- birds, ferrets, pigs, marine mammals and horses," said Kathy Connell, a veterinarian with Foxglove Consulting in Olympia, Wash.

Although there have only been a small number of canine cases, dogs were added in the last few years to the list of animals that have contracted influenza.

Bird flu has garnered the most attention in recent years because of its transmission to humans in Asia. While many have feared that avian influenza could become the next pandemic, it has not yet mutated into a form that can spread from human to human.

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However, progress has been slow on creating a vaccine for it. One problem has been that current vaccines are grown in fertilized chicken eggs, and as Columbia University epidemiologist Stephen Morse noted in an interview with ABC News last month, "A virus that is lethal to chickens is very hard to grow in eggs."

But despite the fears, an avian flu pandemic has not arisen, and the virus has been monitored by the World Health Organization for more than a decade.

Horse Trouble

At present, perhaps the most widespread vaccination for flu in animals has been done for horses.

Equine influenza, while it cannot spread to humans, can be devastating to a herd of horses, as almost all horses that are exposed to it become infected. The American Veterinary Medical Association estimates that up to 90 percent of horses in a herd that has not previously been exposed to the virus can die.

Horse flu has been a problem almost everywhere in the world. As of November 2006, the medical association had noted that only Iceland, New Zealand and Australia were "considered to be free of the virus."

But that changed in 2007, when equine influenza hit Australia.