Rotaviral diarrhea is caused by a double-stranded RNA, non-enveloped virus of the family Reoviridae, genus Rotavirus.  This virus is one of the most common causes of foal diarrhea in horse breeding centers around the world.  Infectivity and severity of disease generally decline with increasing foal age.  It is not considered to be a cause of diarrhea in horses over the age of six months.

Equine rotavirus is transmitted via the fecal-oral route and damages the small intestinal villi resulting in cellular destruction, maldigestion, malabsorption, and diarrhea.

Vaccination of mares results in a significant increase in foals’ rotavirus antibody titers.


The only available vaccine is conditionally licensed and is indicated for administration to pregnant mares to provide passive transfer of antibodies to foals against equine rotavirus.

Vaccination Schedules:

Pregnant mares (vaccinated or unvaccinated): Administer a 3dose series of intramuscular vaccinations at 8, 9, 10 months of gestation.

  • **It is essential that the newborn foal receives an adequate amount of colostrum and absorbs sufficient anti-rotavirus antibodies from rotavirus-vaccinated mares.

Newborn foals: There are no data to suggest that vaccination of the newborn foal with inactivated rotavirus A vaccine has any benefit for preventing or reducing the severity of infection.

Other adult horses: Vaccination is unnecessary

Reviewed and revised 2019

Resource Type

  • Guideline


  • Vaccinations

Publish Date

April 19, 2024