Blackleg is an acute, highly fatal disease of young cattle. It is caused by the spore forming, rod-shaped, gas-producing bacteria Clostridium chauvoei. The disease is infectious and may cause severe inflammation of the muscle, toxicity, and a high rate of mortality (death). This disease is common throughout the world. Cattle aged 3-24 months on a high plain of nutrition are most commonly affected with a sporadic occurrence, but all ages are susceptible.
The spores of the organism can live in the soil for many years. The bacteria mostly occur on permanent pastures and disease is most often documented in the summer and autumn months. The bacteria enter the calf by ingestion and then gains entrance to the body through the mucous membranes and lining of the digestive tract. Blackleg develops when the spores locate in normal muscle and then proliferate after localized trauma. The toxins from the spores are then released resulting in local muscle death.
The most common first clinical sign is a single animal or group of animals found dead without premonitory signs. Animals may be severely ill with obvious subcutaneous (under the skin) swellings. Other clinical signs include lameness, loss of appetite, rapid breathing, and the animal is usually depressed and has a high fever. The characteristic subcutaneous swellings develop in the hip, shoulder, chest, back, neck or elsewhere. If you press the swelling, gas can be felt under the skin. The animal usually dies in 12 to 48 hours. The mortality rate in untreated and unvaccinated animals can reach 10-25% of the herd.
Diagnosis is generally made through history and clinical signs. Post mortem is often required to help rule out other possible diagnoses. During post mortem, gas and a gelatinous discharge are apparent in the subcutaneous tissue. The deeper muscles appear dark red to almost black. Incision into these muscles will reveal a rancid odor. There is generally a large amount of blood tinged fluid in the body cavities with fibrin (a protein fluid clot involved in inflammation).
Treatment of Blackleg is very difficult and only pursued if found early. Penicillin is the treatment of choice in high volumes. All animals will also be vaccinated in the face of an outbreak.
Prevention is key and highly effective! A vaccine is readily available and very cost effective! Our recommended Blackleg vaccine protocol is to vaccinate calves at:
- Branding time or on their way out to pasture—spring time as calves
- Weaning time or in the fall as calves and
- As yearlings prior to the breeding season or prior to being turned out on grass to background.
Once this protocol has been followed, we are recommending vaccinating cows every 3-5 years, depending on your pastures level of risk. Our vaccine, Fermicon 7/Somnugen, contains Clostridium chauvoei (blackleg), Cl. speticum, Cl. sordelli, (malignant edema) Cl. nvyi (black disease), and Cl. perfringens type C and D (enterotoxemia). It also contains Haemophilus somnus (ITEME).
If you have any questions regarding the above information or any questions/concerns in general, please contact Twin Valley VHS at 745-6642.
Dr. Justin Noble DVM
Twin Valley Veterinary Health Services