Rotavirus is a highly infectious virus which spreads rapidly throughout the population and causes severe diarrhea in foals.
Once ingested, the virus multiplies enormously in the cells of the intestine, destroying large numbers of cells that are responsible for the absorption of fluids and nutrients. The resulting diarrhea contains millions of viral particles which contaminate the foaling box and provide a potent source of infection for the next foal that uses the box.
Foals from 2 days to 6 months may be affected. The first signs include diminished sucking and a foul-smelling diarrhea. This can range from watery to semi-solid and from bright yellow to grey-green in color. Affected foals are dull and depressed but have a normal temperature. Young foals can easily become dehydrated and even more depressed with sunken eyes and a tight skin.
Diagnosis is made by identification of virus in the feces; several test methods are available. Requesting that the laboratory test specifically for rotavirus, collecting feces early in the course of disease, and sampling several foals improve the chances of viral detection. Antibiotics are not used. Treatment is generally supportive and requires plenty of fluids. Absorbent drugs and lactobacillus-rich foods such as natural yogurt, help to ensure a swift return to normal. A vaccine for pregnant mares to induce colostral antibodies directed at reducing the risk of rotavirus infection in their foals is available. The damage done to the intestinal lining is quickly repaired and the diarrhea is normally over in 3 to 4 days.