Rotavirus a very common viral agent and although it can be isolated from most foals it may not necessarily indicate disease.

The role of the virus is not clear but it is thought that the disease occurs when there is the concurrent presence of other pathogens e.g. ascarids, salmonella, cryptosporidium.

Foals are most susceptible to viral diarrhoea during the neonatal period as they are immunologically naive. The disease is usually reported in foals less than 6 months of age and most often in the 1 - 3 month age bracket. The disease presents itself as lethargy, anorexia, often normal temperature, abdominal distension and diarrhoea.

The incubation period is 1 - 2 days, and infected foals shed the virus for 10 days. Carrier animals can shed the virus asymptomatically for up to 12 months.

Treatment consists of electrolyte and nutritional support given intravenously or by nasogastric intubation.

Prevention is centred on good hygiene and reducing the population density of foals by decreasing numbers in close contact. Infected foals should be separated from healthy ones, cleaning their stables with separate and disinfected tools and properly disposing of the manure. The use of disinfectants would be recommended, especially the phenolic disinfectants such as Environ. Bleach is ineffective against rotavirus.

A vaccine is available (Duvaxyn R) which contains an inactivated oil adjuvanted equine rotavirus H2 strain which is administered to pregnant mares. This vaccine is administered intramuscularly during the 8th, 9th and 10th month of pregnancy.

Vaccination is recommended to increase the rotavirus antibody level in the mare’s colostrum and is strongly advised in situations where there is a high foal population and frequent movement of animals on and off public studs.