A new report suggests that horses and other equines can catch, and possibly transmit, the highly infectious avian flu, known as H5N1.
The article was published in Equine Disease Quarterly (EDQ) and made the case by citing findings in donkeys in Egypt in 2009, wild asses in Mongolia in 2020 and Mongolian horses in 2021. In some instances the equines displayed flu-like symptoms, while others were asymptomatic but the H5N1 antibodies found in their blood suggested the animals had been infected at some point.
Specifically, in the Egyptian case, 27 out of 105 donkeys carried the antibodies. In the Mongolian horses, a scant two animals were positive for the viral antibodies out of 2,160 over a period of six months.
This is especially interesting ‒ as well as disturbing ‒ because historically, only one strain of influenza is typically found in horses, that being H3N8. Another subtype, H7N7, is thought to have been eradicated in 1979.
The article in EDQ further suggests that the results of these studies indicates that H5N1 does not transmit well between equines, which is good news for horse owners worldwide. However, there is concern that the common horse flu strain H3N8 could co-infect a horse with H5N1 and develop into a mutant strain at some point.
To try and monitor and prevent horses from contracting bird flu, the University of Kentucky Gluck Equine Research Center has been investigating blood samples from over 1,400 horses across the United States since July 2024 through February 2025. While the research is still ongoing, thus far out of that sample group only one horse showed antibodies from the H5N1 strain.
From this information scientists can glean that risk of the avian flu spilling over into the horse population is currently very low. However, considering an extremely expanded list of host species that can be infected by the avian flu with fatal outcomes, plus the fact that the virus is mutating rapidly, increased surveillance of horses, especially in regions where recent H5N1 outbreaks have infected cattle, is the only way to prevent a potentially deadly outbreak.
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