The following was written by Dr. Joe C. Paschal, Livestock Specialist, Texas A&M AgriLife Extension Service
There have been some reports of cattle dying from Blackleg recently. Blackleg is one of a group of usually fatal infections in young calves and lambs caused by bacteria called the Clostridials. These bacteria are coated with a protective shell or spore that protects them and allows them to be potentially infective in the soil and dangerous to livestock for a very long time. Cases are usually seen in pastures with disturbed soils (soil renovations like grubbing or disking, droughts exposing soil, or floods that deposit new soil) and more often in the summer and fall months, seldom in the winter. Usually the younger and growthier animals are affected and usually only a few at a time over several days or a few weeks. But very young (6 week) and very old animals (10-12 years) can be infected and die.
The Blackleg organism is caused by the bacteria Clostridium chauvoei and primarily affects cattle under 2 years of age when it is ingested. Symptoms begin with lameness and depression with a high temperature. As the infection progresses, gas forms and swelling of the legs can be seen and felt as a crackling. Often sudden death occurs with no observed symptoms (the usual case). A post mortem examination will reveal the infected area of black, dead (necrotic) muscles pocked with gas bubbles and smelling like rancid butter. Usually the more active muscles are affected most. Chances for survival are poor unless discovered early. A large dose of antibiotic many save the life of the animal but seldom is the disease is diagnosed early enough to have any effect.
The disease can be effectively and easily prevented by vaccination of all calves at an early age (2-4 months) and boosting the vaccination (as recommended on the label). Almost all clostridial vaccines also contain protection against Malignant Edema (Cl. septicum), Black or Black’s Disease (Cl. novyi), Clostridium sordellii or Bighead, and Enterotoxaemia or Overeating (Cl. perfringens types C&D). Most of these invade the animal’s body through wounds. In addition, some Blackleg vaccines will contain protection against Tetanus (Cl. tetani) or Red Water (Cl. hemolyticum), a disease caused by liver fluke infestation. Many Blackleg or Clostridial vaccines (actually bacterins) are labelled as a 2 cc (ml) subcutaneous (under the skin) injectable product but read the label. Subcutaneous injections should be given in the neck region in front of the shoulder or in the dewlap or in the elbow pocket (the loose skin behind the elbow of the front leg). Blackleg vaccination does have a withdrawal time that must expire before marketing the vaccinated animal.
It is recommended that all cattle (stockers, replacement heifers, mature cows and bulls) be vaccinated annually for Blackleg even though it is primarily a disease of young cattle, it can and has killed mature animals as well.
For more information contact your local County Extension Agent or beef cattle veterinarian.
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Texas A&M AgriLife Extension Service or the Texas A&M AgriLife Research is implied. Extension programs serve people of all ages regardless of socioeconomic level, race, color, religion, disability, or national origin.