Video Documents Rapid Spread of Equine Influenza

In August 2007, 13 horses arrived in Melbourne, Australia, from Japan. Unbeknownst at the time, eight of those horses were infected with the equine influenza virus. Within two months, those eight infected horses would initiate the spread of the disease to 76,000 horses on 10,000 properties. Previously equine influenza-free, Australia was facing an epidemic.

How did it happen? A new online video, "Birth of an Outbreak," provides the details.

"Our goal is to help educate horse owners about the threats and consequences of equine diseases," says April Knudson, DVM, equine specialist for Merial's Large Animal Veterinary Services. "An eye-opening event like the one that occurred in Australia helps people understand how quickly and easily equine influenza can spread--and how important it is to vaccinate their horses."

The video uses maps to demonstrate the influenza outbreak, beginning with the arrival of the 13 horses from Japan. Ultimately, the virus continued to spread, resulting in the widespread outbreak. The video is designed to help horse owners understand how just a handful of infected horses can rapidly lead to an outbreak, and how important it is to use a fast-acting vaccine like the European recombinant vaccine used to help make Australia equine influenza-free once again.

"Equine influenza spreads easily," says Knudson. "A coughing horse may spread infected droplets as far as 50 yards. Combine that with the fact that a single horse infected with influenza can infect up to ten others, and it's easy to see how the virus can become a problem very quickly. Almost all unvaccinated horses exposed to equine influenza become infected, and unprotected foals may develop fatal viral pneumonia."

Besides explaining the outbreak in easy-to-follow terms and graphics, the video also offers insights about vaccinations and tips to help keep horses protected.

To access the equine influenza video, go to, click on the "Downloads" section and then select "Videos."

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