Zika Virus: Are Horses at Risk?

It’s possible that horses could be exposed if they live in areas where infected Aedes egyptii or Aedes albopictus (pictured above) mosquitoes are present.

Photo: James Gathany/Centers for Disease Control

Q. I've heard a lot about Zika virus in the news. Does Zika virus affect horses? If so, what are the signs of disease?

A. There’s currently no evidence that Zika virus can infect horses. Zika—which is a mosquito-borne virus related to West Nile virus and dengue fever— has only been found in nature in humans and nonhuman primates.

It’s possible that horses could be exposed if they live in areas where infected Aedes egyptii or Aedes albopictus mosquitoes are present; however, exposure doesn’t necessarily mean disease. For example, a horse could be exposed to a person with chickenpox but wouldn’t get sick because the chickenpox virus is unable to infect horses. As far as we know, Zika virus is the same, but this hasn’t received any research of which I’m aware.

While we can’t yet say there’s no risk, it’s reasonable to assume that the likelihood of Zika virus infecting horses and causing serious disease is low. Now that Zika virus has emerged in areas where horses are common, there researchers will hopefully study whether this virus can infect horses.

In the unlikely event that Zika virus does cause disease in horses it would probably mainly cause mild disease, with fever and other general signs that go away on their own. The main concern in people is a link to birth defects (specifically microcephaly, or the abnormal smallness of the head with incomplete brain development), something that still needs to be proven. There’s no indication that Zika-associated birth defects occur in species other than humans.

Editor’s note: To read more about Zika virus in species other than humans and horses, please visit Weese’s post “Zika Virus and Animals” on his University of Guelph blog, Worms and Germs: Promoting Safe Pet Ownership.

About the Author

J. Scott Weese, DVM, DVSc, Dipl. ACVIM

J. Scott Weese, DVM, DVSc, Dipl. ACVIM, is an associate professor in the Department of Pathobiology at the University of Guelph's Ontario Veterinary College in Canada.

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