Disease Du Jour: Rotavirus B in Foals

foal newborn mare stall
Rotavirus B is a watery diarrhea most often seen in foals from two 2 to four days of age. iStock

Discovering the new Rotavirus B in foals started with industry conversations, said Emma Adam, DVM, PhD, DACVIM, DACVS. Adam is an assistant professor at the University of Kentucky’s Gluck Equine Research Center. She called the discovery of the new Rotavirus B in foals a “massive team effort.” But she said the discovery all started with some phone calls.

“About the end of January until the middle of February [2021], I was chatting with local vets and farm managers and there was a fair bit of neonatal diarrhea [in young foals],” Adam recalled. “Usually you don’t see 2- to 4-day-old foals with diarrhea. There was a pattern. The first few foals born on a farm would be fine, then there would be a succession of foals with watery diarrhea at two to three days of age. Then every foal from then on had it!”

She said the veterinarians and farm managers were “on it,” so there were no foal deaths. “Then we realized it was happening on multiple farms,” Adam said.

Building on Rotavirus A

It was interesting that Adam was living in a farm house on the Dr. Walter Zent farm in Kentucky during this podcast interview. That gave her even more of a connection with the history of Rotavirus in Kentucky. That was the same farm house where at one time Dr. Roberta Dwyer lived. Dwyer worked at the University of Kentucky prior to her retirement. When she was based in the Gluck Center, she had investigated Rotavirus A. Dwyer was key in developing biosecurity measures and pushing for the identification of that diarrheal virus in foals.

Because of that work, farm managers and veterinarians “cranked down” on biosecurity during the 2021 outbreak of young foal diarrhea, said Adam. “This is a very contagious organism, and it requires a lot of protective gear,” she added.

Changed in management were made while the virus was being identified. Farms began foaling outside and not touching the mare or foal any more than was necessary.

“They still cared for and monitored the foal, put in a microchip so they could take temperatures without touching the foal, and put in biosecurity measures,” said Adam. She noted those measures significantly reduced illness in the young foals.

Rotavirus B

Part of the team that played a critical role in identifying the new pathogen causing the diarrhea in very young foals were Feng Li and his wife, Dan Lang. They joined the Gluck Center in in 2020. Feng Li was been named the William Robert Mills Chair in Equine Infectious Disease and Dan Wang joined the department as a virologist. 

“I would get samples and give them to Drs. Li and Lang,” said Adam. “They did metagenomic sequencing, and 12 days later, the genome was mapped!”

Because the genome has been identified, Rotavirus B has been added to foal diarrhea pathogen testing panels and many laboratories. “We can help set labs up for Rotavirus A and B testing,” said Adam.

Rotavirus B has been documented in many places where there is a large population of foals. This includes California, New York, New Jersey, Florida Pennsylvania and Maryland. “And we suspect Louisiana and Texas,” said Adam.

She warned that when collecting samples for testing, make sure the samples remain chilled before and during shipment to the lab or the test could result in a false negative.

Editor’s Note: Hear many more facts about the identification of Rotavirus B and tips on managing foaling mares on this podcast.

About Dr. Adam

Emma Adam, DVM, PhD, DACVIM, DACVS, is an assistant professor at the University of Kentucky’s Gluck Equine Research Center. Her career focuses on the health and well-being of the equine athlete. She has worked in four countries on three continents. Dr. Adam received her veterinary degree from the Royal Veterinary College, University of London, after which she gained equine internal medicine specialty training at Texas A&M University and equine surgery specialty training at the University of Pennsylvania’s New Bolton Center. She did her PhD research in regenerative medicine as it relates to articular cartilage using RNA-sequencing at the Gluck Center. Her primary role now is in collaborative research.

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