Bit & Bridle

Equine Rotavirus

Other Names

  • Equine Group A Rotavirus (RVA)
  • Equine Rotavirus A
  • Foal diarrhoea virus

What is Equine Rotavirus?

Equine rotavirus is one of the most common causes of infectious diarrhoea in foals under six months of age. It is a highly contagious, non-enveloped double-stranded RNA virus that specifically targets and destroys the enterocytes — the absorptive cells lining the small intestine. This damage impairs the gut’s ability to absorb fluids and nutrients, resulting in osmotic diarrhoea that can rapidly lead to dehydration and electrolyte imbalances in very young foals.

While healthy foals over a few weeks old generally recover without specific treatment, neonates (foals in the first week of life) and immunocompromised foals can deteriorate rapidly. On breeding premises, rotavirus spreads easily between susceptible foals and can cause significant losses during the foaling season. The virus is environmentally stable and survives for months on surfaces, equipment, and bedding, making hygiene and biosecurity critical on busy stud farms.

Causes

Equine rotavirus is spread via the faecal-oral route:

  • Direct contact: Infected foals shed enormous quantities of virus in their faeces. Contact with infected faeces on bedding, clothing, boots, grooming equipment, or hands can transfer virus to susceptible foals.
  • Shared equipment: Buckets, headcollars, and grooming tools used across multiple foals can serve as fomites
  • Environmental contamination: The virus is highly stable in the environment, surviving for months in cool, moist conditions
  • Carrier mares: Adult horses may shed low levels of virus without showing clinical signs and can expose susceptible foals

The incubation period is typically 12-24 hours after exposure. Peak viral shedding coincides with clinical illness but can continue for several days after signs resolve.

Symptoms and Signs

Rotavirus diarrhoea in foals typically presents as:

  • Profuse, watery diarrhoea — often yellowish or greyish in colour
  • Onset typically between one and four weeks of age (most commonly 5-14 days)
  • Lethargy and reduced interest in nursing
  • Mild to moderate fever (38.5–39.5°C)
  • Signs of dehydration: sunken eyes, tacky gums, skin tenting
  • Abdominal discomfort and straining
  • Scalding and skin irritation around the hindquarters and perineum

In mild cases, diarrhoea resolves within three to five days. In neonates or foals with additional complications (failure of passive transfer, concurrent infection), the condition can be life-threatening within 24 hours.

Diagnosis

Diagnosis is confirmed by identifying the virus in faecal samples:

  • ELISA antigen test: Rapid stall-side ELISA kits are available for rotavirus antigen detection in faeces. Sensitivity is highest during peak shedding.
  • PCR testing: More sensitive than ELISA and can detect lower levels of viral shedding; useful for confirming negative ELISA results in suspected cases
  • Electron microscopy: The classic “wheel-like” (rota = wheel in Latin) appearance of rotavirus particles can be seen under electron microscopy, though this is rarely used in routine practice
  • Blood tests: Packed cell volume (PCV), total protein, and electrolyte analysis assess the degree of dehydration and guide fluid therapy
  • IgG levels: Checking immunoglobulin G levels in young foals helps assess the adequacy of passive transfer from colostrum, as failure of passive transfer significantly worsens prognosis

Treatment

There is no specific antiviral treatment for equine rotavirus. Management is supportive:

  • Oral electrolytes: For mildly affected foals that are still nursing and alert, oral electrolyte replacement between feeding can be sufficient
  • Intravenous fluids: Required for foals that are significantly dehydrated, weak, or unable to nurse. Correction of fluid and electrolyte deficits is the priority.
  • Nutritional support: Maintaining milk intake is important. In severe cases, temporary partial withholding of milk may reduce osmotic diarrhoea but must be balanced against energy needs. Foal milk replacer or frequent small amounts of mare’s milk via tube feeding may be used.
  • Di-tri-octahedral smectite (Biosponge/BioSponge): An intestinal adsorbent that binds toxins and helps slow diarrhoea
  • Probiotics: Some practitioners use probiotic pastes to help restore normal gut flora
  • Antibiotics: Not indicated for uncomplicated viral diarrhoea but may be used if bacterial secondary infection or failure of passive transfer is present
  • Barrier protection: Applying petroleum jelly or zinc oxide cream around the perineum prevents skin scalding from acidic diarrhoea
  • Isolation: Affected foals should be isolated immediately to prevent spread to other foals on the premises

Prevention

  • Vaccination of mares: A killed rotavirus vaccine (Equine Rotavirus Vaccine) is licensed in the UK and is given to mares in late pregnancy (at 8, 9, and 10 months of gestation). This boosts rotavirus antibody levels in colostrum, providing passive protection to the foal via nursing. This is the single most effective preventive measure on busy stud farms.
  • Colostrum management: Ensure all foals receive adequate high-quality colostrum within the first two hours of life. Check IgG levels at 12-24 hours of age on breeding premises.
  • Strict hygiene: Boot-dipping stations, individual equipment for each foal, and prompt disposal of infected bedding
  • Isolation protocols: New arrivals should be isolated, and affected foals separated immediately
  • Environmental disinfection: Rotavirus is resistant to many common disinfectants. Products effective against non-enveloped viruses should be used — check with your vet for appropriate agents.

Prognosis

The prognosis for healthy foals over two weeks of age is good with appropriate supportive care. Most recover within three to five days. The prognosis is significantly more guarded for:

  • Neonates under one week old
  • Foals with failure of passive transfer
  • Foals with concurrent infections
  • Foals in poor body condition or on poor nutritional planes

On stud farms with good vaccination programmes and biosecurity protocols, the impact of rotavirus outbreaks can be greatly reduced. For guidance on disease management on breeding premises, consult the British Equine Veterinary Association (BEVA).

When to Call the Vet

  • A foal under four weeks old develops diarrhoea — do not wait to see if it resolves
  • The foal appears weak, depressed, or stops nursing
  • Diarrhoea has been present for more than 24 hours in any young foal
  • Multiple foals on the property develop diarrhoea in a short period — suspect an outbreak and implement biosecurity immediately
  • The foal’s gums appear tacky or pale, or the skin tent test is positive — these indicate significant dehydration

Frequently Asked Questions

Can adult horses get equine rotavirus?

Adult horses can be infected with rotavirus and may shed the virus without showing clinical signs. This is why adult horses — including mares — can be a source of infection for susceptible foals. Clinical disease in adults is very rare due to acquired immunity, but adults should still be included in hygiene protocols on affected premises.

Can humans catch equine rotavirus?

Equine rotavirus (Group A, equine genotype) is considered to have a very low zoonotic risk to immunocompetent adults. However, as a precaution, particularly when handling infected foals’ faeces, basic hygiene measures (gloves, handwashing) are always sensible. Immunocompromised individuals should take additional care.

How do I disinfect a stable after a rotavirus case?

Remove all bedding and organic material before disinfecting — organic matter inactivates many disinfectants. Use a product proven to be effective against non-enveloped viruses, such as those containing citric acid or bleach-based formulations at appropriate dilutions. Allow adequate contact time and ensure good ventilation during drying. Empty and rest the stable where possible before introducing a new foal.

Is the rotavirus vaccine given every year?

Yes. The mare vaccination protocol requires boosters in each subsequent pregnancy to maintain high antibody levels in colostrum. Mares are typically vaccinated at 8, 9, and 10 months of gestation in each breeding year. Speak to your vet about integrating this into your stud farm health programme.