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Clostridia are a group of bacteria that are commonly found in soil and in the digestive tracts of animals. They can produce toxins that cause a variety of diseases in farmed animals, and which can lead to sudden death in many cases. The bacteria can survive as spores in the environment for a long time and therefore preventing exposure is usually not feasible, and treatment of affected animals is typically unsuccessful. However, vaccines are available which provide protection against the toxins.

Clostridial vaccines generally require a primary course of 2 doses followed by an annual booster. For breeding females this booster should be in late pregnancy to provide protection for their offspring. Lambs and suckler calves will then need vaccination when the colostral protection runs out after 12 weeks.

Black Leg

Clostridial spores are ingested and travel from the gut to the muscle through the blood. Subsequent damage to the muscle (for example following trauma or excess exercise) can lead to toxin production. In sheep there is often a history of wounds, for example following shearing or tail docking. The toxins damage the muscle and spread in the blood leading to fever, inappetence and rapid death. Affected muscles are often massively swollen and may feel crackly when touched. Cases are commonly seen soon after turnout to new pasture and animals in good condition may be more likely to be affected.


The bacteria causing tetanus usually to enter the body through contaminated wounds, such as following tail docking, dehorning or castration. They then produce a toxin which attacks the nervous system, leading to rigid paralysis. Clinical signs include a raised tail, extended neck, lock jaw, difficulty walking, and bloat followed by death.


Botulism is caused by direct ingestion of clostridial toxins which are usually associated with bird carcasses or poultry manure in feed. The toxins affect the nervous system leading to weakness which may progress to recumbency and death. In some cases, affected animals may recover, however often euthanasia on welfare grounds is required. Protection against botulism is not provided by multivalent clostridial vaccines and therefore a separate vaccine is needed for high-risk farms.

Pulpy kidney

Pulpy Kidney disease is frequently reported to be in the top 3 causes of lamb death. Lambs are found dead with no clinical signs. Vaccination of dams with a booster in late pregnancy provides protection for young lambs, and older lambs can also be vaccinated to provide ongoing protection.

Lamb dysentery

Lamb dysentery is another common cause of sudden death in lambs that can be prevented through vaccination with clostridial vaccines.

Black disease

In late summer/early autumn migration of immature fluke through the livers of sheep and cattle can trigger clostridial toxin production and lead to sudden death. Prevention relies upon clostridial vaccination and appropriate fluke control.

Other clostridial diseases such as big head in rams and other enterotoxaemias cause disease in a similar way to those mentioned above. Since all these diseases will often cause sudden death as the first clinical sign, and the bacteria are common in soil, vaccination is the only way to prevent losses. If one cow is saved every 16 years in a 100-cow herd the vaccine will have paid for itself!