Recently I have seen a few cases of “Blackleg” in the area. In spite of the familiarity of this disease to most cattle producers, I continue to see cases every year.
Blackleg is caused by a bacterium called Clostridium chauveoi. This bacterium is a soil borne organism that has the ability to protect itself by producing spores if conditions are not favorable, allowing it to tolerate extreme climate and temperature. These spores are capable of staying viable for decades in soil. When exposed to open wounds or ingested by animals, the spores can develop into infectious bacteria that invade the body and cause disease. Once in the body, C. chauveoi has affinity for muscle tissue, most usually the large muscles of the limbs or back. They can, however, affect any muscle in the body, including the heart. Once the bacteria start to proliferate in muscle tissue, toxins produced by the bacteria are released into the tissue and bloodstream. These powerful toxins destroy tissue, produce gas within the tissue, and lead to shutdown of various body systems. Death can ensue rapidly, often within less than 24 hours of onset of infection. Calves and young stock are more at risk than older cattle, although mature animals that are naïve or under extreme stress can die from blackleg.
There are several other species of Clostridia bacteria that cause disease as well as C. chauveoi. The most common Clostridial diseases other than blackleg that I see in southwest Missouri are malignant edema (Clostridium sordelli), tetanus (Clostridium tetani) and disease caused by various strains of Clostridium perfringens. Malignant edema is often seen in recently fresh cows and is often fatal. It is very similar to blackleg in appearance, but often leads to massive gas production on the back and shoulders of affected cows. Tetanus is most often seen with gangrenous type situations, such as banded calves. This disease is also of importance to horse owners; horses are very susceptible to this particular infection. C. perfringens comes in many types, and generally causes diarrhea in calves, intestinal hemorrhage and diarrhea in cows, and mastitis.
Prevention is the key to controlling blackleg. There are fortunately a number of very good vaccines that provide excellent immunity and protection from blackleg. Over the course of 14 years in practice, my recommendations have changed. I believe I see more cases of clostridial disease than I saw 12 to 14 years ago. I strongly recommend beef calves receive two doses of blackleg vaccine prior to and after weaning. In dairy calves, two doses before six months of age are, I believe, very important. As I diagnose more adult dairy cows with clostridial infections during the post calving period, I feel vaccination at time of dry off is critical. Yearly vaccination of beef cows is recommended. If a case of clostridial disease has been diagnosed on your farm in the last 40 years, it may be wise to be more aggressive about vaccination of calves at younger ages. Discuss a plan of action with your veterinarian. Clostridial vaccines only cost between 25 to 50 cents; in my mind it makes absolutely no sense not to vaccinate.
Successful treatment requires massive, extralabel doses of penicillin. Consult a veterinarian for proper dosage and withdrawal times.
Mike Bloss, DVM, owns Countryside Animal Clinic with his wife, Kirstin Bloss, DVM, in Aurora, Mo.