Posted on December 5, 2009 by Scott Weese

H1N1 Influenza And Horses

A colleague mentioned a rumour that is apparently going around some areas about horses getting H1N1 influenza. While we never say never with infectious diseases, there is no evidence that H1N1 can be spread to horses, nor do I have much concern about this. H1N1 can infect different species, including humans, pigs, poultry, cats, ferrets and dogs. That's a pretty impressive range, but it's mostly because the virus is made up of genes from human, swine and avian influenza viruses, and we know that other species like ferrets and cats are prone to occasionally (rarely) catching human or avian influenza. Horses have their own influenza, H3N8 equine influenza A. This virus has been remarkably stable in the horse population in that H3N8 has been the predominant equine influenza strain for a long time. There is little information indicating that horses are susceptible to the variety of seasonal flu viruses that circulate amongst the human population every year, or H5N1 avian influenza. No one has specifically tested H1N1on horses, and equine infections are not theoretically impossible, but it's pretty unlikely that this strain would be a major concern in horses, given what we know right now. Considering the number of people that have been infected with H1N1, horses have certainly been exposed to this virus, but there are no reports of suspected equine infections.

While the risk of horses contracting H1N1 is very low, it can be reduced further with common sense practices to reduce the risk of exposure. If you may have influenza, avoid contact with people and other animals, including pets and horses, and get a flu shot.

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Posted on May 1, 2009 by Scott Weese

Swine Flu: Are Horses At Risk?

I'm sure there are few people that haven't heard about the current worldwide flu epidemic (although you’d pretty much have to have not listened to or watched the news nor read a newspaper nor been on the internet for the last week to have missed it!). It's been called “swine flu” until the last few days, but that terminology is gradually disappearing and being replaced with the virus’s more formal name, H1N1 influenza A. It's been covered extensively in the press and we have numerous posts about it on our sister site, WormsAndGermsBlog.

Influenza is an important disease in horses, so what is the risk to horses from this outbreak?

The real answer is we don't know. However, it's extremely unlikely that it will become a concern in horses. Most flu viruses tend to be host specific, meaning they usually don't infect multiple species. Pigs are a noted exception to this, because they are susceptible to swine, avian and human influenza viruses. This makes pigs a great “mixing pot” for influenza viruses – if a pig is infected by more than one virus at the same time, the viruses can exchange DNA and recombine to form new virus strains with new properties. The virus causing the current epidemic appears to be related to known swine influenza viruses, but also contains genes from avian and human influenza viruses, which may account for why it is able to so readily infect humans.

We don't know what other species this virus may infect, but it's very unlikely that it could infect horses. Horses tend to only be infected by equine influenza viruses. There's no evidence that this virus has any greater chance of jumping to horses than any of the seasonal human influenza viruses, or other influenza viruses. Personally, I'm more concerned about it spreading to cats, since we know that cats are susceptible to different influenza strains such as the H5N1 avian flu virus. While we can’t yet say for sure that horses are completely safe from this infection, I'm not concerned about this flu strain and horses.

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