Key Facts About Symptoms Risks Vaccines and Protection
Blackleg is a rapidly fatal disease in cattle, most common in calves aged 6 to 12 months. It is caused by the bacterium Clostridium chauvoei. Many affected calves are found dead without showing signs of illness.
The disease often occurs in well‑conditioned calves. As the bacteria grow, they produce toxins that destroy muscle tissue, especially in the hindquarters and heart, leading to death. There is no effective treatment, but vaccination with a 7‑way clostridial bacterin‑toxoid offers strong protection.
Cattle become infected by ingesting spores found in soil or water. These spores can enter the bloodstream and settle in muscle tissue, where they may lie inactive for months or years. When muscle oxygen levels drop due to injury or bruising, the spores activate, multiply, and release deadly toxins.
Most calves die within 12–24 hours of symptoms beginning, so early warning signs are often missed. Possible signs include fever, loss of appetite, swelling of muscles, lameness, and depression. Swollen muscles may have a “bubble wrap” feel due to gas buildup, creating a crackling sound when pressed.
Spores persist for many years in soil and are extremely resistant to environmental conditions. They can survive over a decade and grow only when oxygen levels are low. The toxin they produce leads to muscle death, giving the affected tissue a dark red or black appearance and a rancid odor.
Blackleg is most common in pastured calves but can affect housed cattle if feed is contaminated with soil. Cases have occurred in cattle of all ages, especially when adults were not properly vaccinated.
Vaccination is nearly 100% effective when given according to label directions. Calves should not be vaccinated at birth, as newborns cannot produce a strong immune response. Most vaccines require two doses followed by annual boosters. Adult cows should also receive yearly vaccines to maintain immunity and improve protection passed through colostrum.
Some vaccines include protection against multiple clostridial diseases. Producers should ensure “Clostridium chauvoei” is listed on the vaccine label.
Blackleg is fatal and unpredictable, making vaccination essential for protecting cattle herds.
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