Enterotoxemia in sheep can be fatal. It results from the sudden release of toxins by the bacteria Clostridium perfringens type D in the digestive tract of sheep. Enterotoxemia affects sheep of all ages, but it is most common in lambs under 6 weeks of age that are nursing heavy-milking ewes, and in weaned lambs on lush pasture or in feedlots. Creep-fed lambs and sheep being fitted for show are often affected. Frequently, the most vigorous lambs in the flock are lost. In unvaccinated feedlot lambs, approximately 1 percent of the lambs can be expected to die from this disease, with an average of about 2 to 3 percent. In severe outbreaks, losses may range from 10 to 40 percent.
The bacteria that cause the disease normally are present in the intestine of most sheep. Under circumstances generally brought about by heavy feeding, the Clostridium perfringens type D bacteria grow rapidly and produce a powerful poison (toxin) that is absorbed through the intestine wall. Death typically occurs within only a few hours, often before the owner observes any sick animals.
Conditions that can bring about enterotoxemia include changing feed suddenly, feeding excessively high energy diets, feeding irregularly, increasing the grain content of the ration too rapidly, not providing enough space at the feed-bunk, and feeding lambs of different sizes together. Heavy internal parasite burden also can cause this condition.
Occasionally, animals may be observed sick for a few hours before they die. Affected lambs frequently exhibit nervous symptoms, their heads are drawn back, and they exhibit convulsive grinding movements of the teeth, congestion of mucous membrane of the eye, and frothing at the mouth. In addition, diarrhea may be present shortly before death.
There is no satisfactory treatment for this affliction, but there are some preventive measures. Prior to placing lambs in a feedlot, vaccinate them with a Clostridium perfringens type D bacteria or toxoid. Allow at least 10 days after vaccination for immunity to develop. Under certain conditions, a booster shot is required two to four weeks later. Fast-gaining lambs grazing pasture or on creep feed may require a vaccination at 6 to 8 weeks of age. If they continue on high-grain rations, revaccinate them after weaning. Losses may be prevented in young lambs up to 6 weeks old by vaccinating the ewe during pregnancy. Ewes that have not been vaccinated previously should be vaccinated twice, two to four weeks apart, with the second vaccination administered two to four weeks before lambing. An annual booster two to four weeks before lambing is advisable.