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Aina Meducci 2012


The following blog posts is not genuinely from my research but through readings and citation from trusted website. I do not own any of the copyright and therefore you may use it at your own risk


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Blackleg disease

I came across this disease when I read my old bacteriology notes.


Blackleg disease

Blackleg is a highly fatal disease of young cattle caused by the spore forming, rod shaped, gas producing bacteria Clostridium chauvoei. The spores of the organism can live in the soil for many years. The bacteria enters the calf by ingestion and then gains entrance to the body through small punctures in the mucous membrane of the digestive tract. Cattle that are on a high plane of nutrition, rapidly gaining weight and between 6 months and 2 years of age are most susceptible to the disease. The disease is not transmitted directly from sick animals to healthy animals by mere contact.

The name ‘blackleg’ derives from the fact that the site of infection is often a leg muscle, and that the affected muscle is dark in colour.

Extensive necrosis of the leg musculature with a blackish-red discoloration with a "bubbly" appearance


C chauvoei is found naturally in the intestinal tract of animals. It probably can remain viable in the soil for many years, although it does not actively grow there. Contaminated pasture appears to be a source of organisms. Outbreaks of blackleg have occurred in cattle on farms in which recent excavations have occurred, which suggests that disturbance of soil may activate latent spores. The organisms probably are ingested, pass through the wall of the GI tract, and after gaining access to the bloodstream, are deposited in muscle and other tissues.

The spore or dormant form of the cell exists under conditions where the vegetative state cannot. When the vegetative cells grow in high numbers, the bacteria produce toxins.Under ideal conditions, the bacteria form spores which allow the bacteria to survive in dormant state until exposed to conditions that can support their growth.

C. chauvoei
The bacteria is a Gram-positive (blue), anaerobic rod-shaped bacillus

How does the bacteria affect the animal?

Bacterial spores are eaten in contaminated feed or soil. The spores then enter the bloodstream and lodge in various organs and tissues, including muscles. Here they lie dormant until stimulated to multiply, possibly by some slight injury to the animal. The injury reduces blood flow to the area, thereby reducing the supply of oxygen to the tissues. In the absence of oxygen, the spores germinate and multiply. As they grow, the bacteria produce toxins which destroy surrounding tissues(that's why the muscle become black in color). The toxins are absorbed into the animal’s bloodstream which makes the animal acutely sick and causes rapid death.

Symptoms of disease

The first sign observed is usually lameness, loss of appetite, rapid breathing and the animal is usually depressed and has a high fever. Characteristic swellings (edema) develop in the hip, shoulder, chest, back, neck or elsewhere. First the swelling is small, hot and painful. As the disease progresses, the swelling enlarges and becomes spongy and gaseous. If you press the swelling, gas can be felt under the skin.

The rapid accumulation of gas under the skin and in the body cavity gives the carcass a bloated appearance, with the limbs spread apart and pointing upwards. There may be a frothy, blood-stained discharge from the mouth, nostrils and anus.

If the skin over the affected area is removed, excess bubbly bloodstained fluid can be seen, and the muscle immediately below will be dark in colour. However, when the affected muscle is inside the carcass, such as when the heart muscle is affected, no external evidence of the disease is found.

discoloration of skeletal muscle

The animal usually dies in 12 to 48 hours. In most cases the animal is found dead without being previously observed sick. The speed with which blackleg kills usually makes individual treatment useless.


The speed with which blackleg kills usually makes individual treatment useless. In some cases, however, animals treated early with penicillin (antibiotic) may survive, although they often suffer permanent deformity due to partial or complete destruction of muscles.


The only effective means of controlling blackleg is by vaccination. Several makes of multivalent vaccine (‘5 in 1’ or ‘7 in 1’) are available commercially and care should be taken to follow the manufacturer’s instructions. The most commonly used clostridial vaccination in cattle is the 7-way type which protects against Clostridium chauveoi (blackleg), Clostridium septicum and Clostridium sordelli(malignant edema), Clostridium novyi (black disease), and three types of Clostridium perfringens (enterotoxemia).

  • Calves should receive two doses of blackleg vaccine. Two vaccinations 1 month apart are essential to provide the best protection.
  • A booster vaccination 12 months later should provide lifelong immunity to blackleg.
  • It is desirable to give the initial two doses of vaccine before young cattle reach their most susceptible age of six months.
  • To await the occurrence of blackleg before vaccinating is unwise, as vaccines take 10–14 days before they begin to provide immunity.

7 ways types of blackleg vaccination


Carcasses of animals known to have died from blackleg should not be opened. Opening the carcass can liberate bacteria which will form spores that will contaminate the ground and subsequently infect other cattle. Also, do not drag carcasses along the ground. If possible, burn or deeply bury the carcasses where they lie.

Sources: Cattle Diseases:Blackleg cattletoday.info, The Merck veterinary manual, blackleg in cattle, thedairysite.com


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