We inject our most of our cattle and sheep at least annually for clostridial diseases. We can use 5 in 1, 6 in 1 or Covexin, but often it is unclear where these diseases come from and why we need to vaccinate annually to maintain immunity. In this series of articles, we will go over the individual diseases in the vaccines and explain why we need to protect stock against them.

Clostridial diseases are a constant threat to livestock in most parts of the world. This group of bacterium is highly resistant and can survive in soil for many years. They grow in soil, water, or composting plant and animal material, and they play an important role in putrefaction (rotting). Some Clostridial bacteria are present in the normal healthy gut, but if an animal dies from some other cause, the clostridial bugs are first to invade the carcass and start the decomposing process. This means diagnosing clostridial disease as a cause of death can be challenging.

Clostridial diseases are not contagious, and they are often present in or on the animal or the environment, but require some predisposing factor to allow infection to take hold e.g. muscle bruising for Blackleg. Some of the diseases also appear to occur more frequently in well fed animals in good condition e.g. Enterotoxaemia, and Blackleg. Fortunately, vaccines are highly effective and when used as recommended, total prevention is usually achieved.

Blackleg

Blackleg causes acute, infectious, gangrenous muscle inflammation caused by activation of Clostridium Chauvoei spores. It is thought that the bacteria are eaten and then pass through the wall of the intestine and become widely distributed throughout the body. Theses spores are harmless until the animal damages the muscle tissue with a wound, bruising or even excessive exercise. The activated bacteria multiply and rapidly damage further muscle, resulting in a severe toxaemia and death. Most cases occur in late Spring and Autumn and classically affect well fed individuals. There seems to be an increased incidence where the ground has been disturbed by excavation, drainage or flooding and most commonly affects animals between six months and two years.

Animals are usually found dead with a swelling of one or more legs, although any muscles can be affected. The carcass very rapidly bloats, and the affected muscles are black, spongy with foam and gas. Occasionally animals are found alive but are depressed with high fever, lameness and muscle swelling. Prevention is by vaccination.