Equine Rotavirus is a life threatening disease affecting young horses and one of the most common causes of diarrhea in foals under six months of age.
Rotavirus is extremely contagious and until recently, was caused solely by rotavirus group A viruses. In 2021, however, a novel equine rotavirus B pathogen was detected in farm outbreaks in Kentucky, posing an even bigger challenge for farm owners and veterinarians as there is currently no vaccine against this strain.
How Equine Rotavirus is Contracted
In horses, rotavirus is transmitted through fecal-oral contamination, often occurring when young horses lick surfaces contaminated with infected feces.
A large number of virus particles are shed in fecal matter, but only a small number of particles are needed to infect another horse.
In fact, it’s estimated that one teaspoon of contaminated diarrhea can contain up to half a trillion infectious particles! Researchers also estimate that as few as 100 particles may cause disease in a susceptible foal.
What makes rotavirus so common is that horses of any age can carry the virus without displaying symptoms. Foals can even contract the virus from their mother. Interestingly enough, most adult horses have rotavirus antibodies, indicating a previous exposure or infection.
Newborn foals as young as 24-48 hours are susceptible to contracting rotavirus and are typically more severely affected than older foals. In fact, the majority of rotavirus fatalities occur in foals under three months of age.
However, the severity of disease often depends on the foal’s age, their immune status, as well as the number and virulence of the rotavirus particles they ingest.
Symptoms of Rotavirus in Horses
The main symptoms of foal rotavirus are:
- Watery diarrhea
- Reluctance or failure to nurse (anorexia)
- Abdominal distension due to gut inflammation, and
- Colic due to gut stasis.
The foal can become rapidly dehydrated as they lose fluids and electrolytes through diarrhea and lack of nursing. Electrolyte imbalances that occur as a result can be fatal.
In older foals, aged 75-120 days, diarrhea tends to be the only symptom but it is usually mild and self-limiting, requiring minimal veterinary intervention. Adult horses are not adversely affected by rotavirus.
How Rotavirus Damages the Horse’s Gut
Rotavirus damages villi, the fingerlike projections of epithelial cells in the horse’s small intestine which aid in digestion and absorption of nutrients. This damage reduces the foal’s ability to digest milk and also creates conditions in the gut that allow pathogenic bacteria to flourish, which may lead to other health problems.
Common complications that can occur as a result of rotavirus include gastric reflux, gastric ulcers, pyloric stenosis (swelling of the muscle between the stomach and intestines), duodenal stenosis (narrowing in part of the small intestine), as well as stomach rupture, which is fatal.
Diagnosing Equine Rotavirus
Rotavirus is diagnosed by identifying the virus through enzyme linked immunosorbent assay (ELISA) or reverse transcription polymerase chain reaction (RT-PCR) assays. With that said, once it has been detected on a farm, all foals with symptoms should be treated as if they have the disease.
How to Treat Rotavirus in Foals
The good news is that early detection and treatment of rotavirus can often lead to a quick recovery. However, because the disease is so contagious, preventing spread to other horses on a farm can present quite a challenge.
Primary treatment of rotavirus focuses on supportive care and intravenous fluid therapy to rehydrate the foal. Other treatments may include gastrointestinal protectants and probiotics. Extremely young foals may be placed on prophylactic antibiotics to help prevent bacteria in the gut moving through the compromised gut wall and infecting a joint (septic arthritis).
Fullbucket’s Foal Probiotic Paste can help foals with rotavirus. This highly concentrated formula supports gut and immune health and assists in the digestion and absorption of essential nutrients and provides support for the gastrointestinal mucosa (lining of the stomach and intestines) as well.
Foal Probiotic Paste contains the following proven ingredients:
20 Billion CFU’s of Saccharomyces boulardii, a yeast strain of probiotic that is safe to use during antibiotic therapy
- Probiotics to support a healthy immune system
- L-Glutamine to help maintain a healthy intestinal tract
- Prebiotics to support a healthy microflora, and
- Dried egg product that provides immune support during critical periods of foal development.
Farm Biosecurity During Rotavirus Outbreaks
Biosecurity is of utmost importance once a rotavirus outbreak has been detected on a farm. The virus can survive in the environment, especially on wood or other porous surfaces, for up to nine months.
Therefore, it’s important to disinfect and also protect all horses from contaminated surfaces, supplies such as buckets, shovels, and rakes, as well as contaminated organic materials. Sharing feed and water buckets is not advised. Likewise, because bedding and manure become contaminated with the virus, they should be disposed of in a secure location and never spread on pastures.
To clean contaminated surfaces, scrub with a detergent first and then use a Peroxygen or Phenolic compound or other suitable disinfectant.
According to studies, bleach, chlorhexidine, and quaternary ammonium compounds are not effective disinfectants for equine rotavirus.
Also keep in mind that no disinfectant will work on organic material such as bedding. Removing and safely disposing of organic material can decrease viral load by 90% but it will not eliminate it completely.
For farm personnel, wearing gloves, using disposable footwear and boot baths with an appropriate disinfectant, practicing good hygiene between stalls, and limiting visitors are all important for improving biosecurity. Power washers and leaf blowers should not be used, as they may only serve to spread viral particles.
Sick foals should be separated from other foals on the property and staff handling infected foals should follow strict biosecurity protocols.
Preventing Rotavirus in Horses
Biosecurity measures are the main means of preventing further spread of rotavirus. However other factors such as overcrowding can create an increased risk of outbreaks. For horses on pasture, it is recommended to keep no more than one horse for every two acres of grazing space.
To prevent infection or minimize the risk of an outbreak, pregnant mares should be vaccinated in order to increase foals’ antibodies to the virus. The rotavirus vaccine for horses can be used to prevent Rotavirus Group A in neonatal foals. It should be given to mares as a series of three at months 8, 9, and 10 of gestation during each pregnancy.
Unfortunately, there is currently no vaccine to treat the novel Rotavirus Group B strain.
Studies have shown that vaccination of pregnant mares significantly increases foals’ rotavirus antibody titers with strain A. However, it is critical that newborn foals receive an adequate amount of colostrum in order for these antibodies to be transferred.
If this is a concern, have your veterinarian perform an IgG (immunoglobulin) test to determine if the foal has received adequate antibodies from the mare. If not, foals younger than 24 hours can be given supplementary colostrum and foals older than 24 hours can be given an IV plasma infusion.
Finally, for neonatal foals, administering Fullbucket’s Foal Kick Start Paste during the first 24 hours of life (before moving on to Foal Probiotic Paste) can help to boost their immune system and prevent the contraction of rotavirus.
Foal Kick Start is specifically designed for newborn foals and comes as a highly concentrated paste. It contains immunoglobulins derived from the eggs of hens vaccinated against rotavirus, coronavirus, E. coli, Salmonella and Clostridium, as well as natural Vitamin E and vitamin D3..
Researchers believe as many as 50% of foals become infected with equine rotavirus; fortunately, the mortality rate is low, only around 1%. This is because most owners are proactive, seeking immediate veterinary attention.
If a foal on your farm experiences diarrhea, don’t hesitate to get your veterinarian involved right away and implement biosecurity measures as quickly as possible to prevent an outbreak on your farm. With rotavirus, quick treatment yields much better results than a wait-and-see approach.
Research Update on Equine Rotavirus