An Update on Rotavirus in Foals

Rotaviral diarrhea is a life-­threatening disease and the most common cause of foal diarrhea. It also causes serious diarrhea in other animals and can be deadly in infants and children worldwide.

The rotavirus family of viruses is large and categorized into Groups A-D and F-J based on genome sequence. They tend to infect in a species-specific fashion. Until recently, researchers considered Group A rotaviruses to be the only ones responsible for equine infections, though they can also infect other animals. The other groups were known to infect humans and animals besides horses. Rotaviruses are considered zoonotic (can pass between animals and humans). It’s important to consider any animal with diarrhea a zoonotic risk.


Rotaviruses cause infection via the fecal-oral route, with disease occurring about 12 to 24 hours after ingestion. Diarrheic animals can shed up to 100 billion virus particles per gram of diarrhea, and only small numbers of particles are required to cause disease. The virus can persist in the environment for up to nine months and can easily transfer between animals via equipment, tools, and contaminated hands. As such, outbreaks can develop quickly after the first case of diarrhea on a farm. Recovering foals can shed the virus in their feces for about three days after their diarrhea

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