Blackleg; cause, symptom, treatment and prevention in cattle, Adama (2026)

septicum, C. sordelli, and C. novyi.[4][5] C. chauvoei is Gram-positive, rod-shaped, anaerobic, and motile, and can produce environmentally persistent spores when conditions are not ideal for growth. These spores can remain in the soil for years in an inactive state, and return to their infectious form when consumed by grazing livestock. Contaminated pasture is a predominant source of these organi

sms, which are also found naturally in the intestines of animals.[6] Cases can occur over many years in areas where soil or manure is contaminated with the bacteria, and it is exceedingly difficult to remove the spores from the environment. chauvoei can produce a large amount of gas as a metabolic byproduct when growing and reproducing, hence the alternate name gas gangrene, present in humans.[7] This gas builds up in infected tissue, usually large muscles, and causes the tissue to make a crackling or popping sound when pressed. Large gas-filled blisters can also form, which can be extremely painful as they build up in the tissues.[citation needed]
Clinical presentations
When infection begins, the animal may develop a fever, and the affected limb can feel hot to the touch. The limb usually swells significantly, and the animal can develop lameness on the affected leg. Crepitation (the sensation of air under the skin) can be noticed in many infections, as the area seems to crackle under pressure.[8]
Once clinical signs develop, the animal may only live a short while, sometimes as few as 12 hours. Occasionally, cattle succumb to the disease without showing any symptoms, and only a necropsy reveals the cause. During a necropsy, a diagnosis is usually made very quickly, as the affected muscle is usually mottled with black patches, which are dead tissue, killed by the toxins the bacteria release when they infect live tissue. If viewed under a microscope, small rod-like bacteria can be seen to confirm the diagnosis.[citation needed]
Vaccination and prevention
The use of a seven-way clostridial vaccination is the most common and cost effective preventative measure taken against blackleg,[5] but its efficacy is disputed.[2] Burning the upper layer of soil to eradicate left-over spores is the best way to stop the spread of blackleg from diseased cattle. Diseased cattle should be isolated. Treatment is generally unrewarding due to the rapid progression of the disease, but penicillin is the drug of choice for treatment. Treatment is only effective in the early stages and as a control measure.[citation needed]

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Importance of Vaccination
As previously stated, blackleg has an extremely high mortality rate, near 100%. Vaccination is needed for prevention, and many multivalent clostridial bacterin 7-way vaccines are available on the commercial market for livestock producers. Vaccines are very effective and inexpensive.

It is a very inexpensive insurance policy to protect animals with vaccination. Most blackleg products will cost producers approximately $1.20 to $1.60 per head, plus the cost of labor, depending on the product used.

Blackleg vaccines protect against several clostridial diseases, including Cl. Chauvoei (blackleg), Cl. Novyi (black disease), Cl. Septicum (malignant edema), Cl. Sordelli (gas gangrene), and Cl. perfringens types C and D (various types of enterotoxemia).

An 8-way vaccine contains an additional agent, Cl. Haemolyticum, which causes redwater disease in cattle, but it is not prevalent in West Virginia.

Clostridial vaccines are usually labeled as toxoids or bacterintoxoids, because the antibodies produced by the vaccine actually neutralize the deadly toxin produced by the growing bacteria, rather than the bacteria alone.

When using 7-way blackleg vaccines, they require a two-shot series administered three to four weeks apart. For example, for cattle, give the first vaccination at 60 to 90 days of age or when the calves are first processed. Then, administer a 7-way booster dose in four weeks or at weaning. Animals must be vaccinated annually.

One product, Alpha-7 (Boehringer Ingelheim), only requires one dose, but calves vaccinated under three months of age must be vaccinated again at weaning or at four to six months of age to be protected.

Many producers ask if adult cattle need a blackleg vaccine. Incidents of blackleg are rare in cattle over two years of age, but it can happen. Annual vaccination of adult cows will boost their immune response, plus they will produce antibodies in colostrum milk to provide stronger protection for calves.

Good quality colostrum from the dam will protect the calf from disease for up to three to four months of age until vaccination is effective. Work with your local veterinarian for recommendations and individual farm consultations as part of a good working veterinary client patient

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Symptoms
Unfortunately, the most common first sign of blackleg is for producers to find a dead animal. This disease can kill within 12 hours of infection and usually does so in 48 hours. Contact your veterinarian immediately.

There are several signs and symptoms an infected animal will exhibit, including lameness, loss of appetite, depression, rapid breathing, fever and swelling. Sometimes the animal will appear lame on the affected leg before any other sign is noticed.

The swollen muscle starts out hot and painful, but it quickly becomes cold and insensitive as the muscle dies. Swelling with air pockets or gas under the skin is the classic telltale symptom of this disease.

Cl. chauvoei are anaerobic, which means they only multiply in the absence of oxygen. This bacterium attacks the muscular skeletal system of the animal. As the bacterium multiplies in the animal's muscle tissue, toxins, called toxin A, and gas are released, causing damage to the muscle and swelling as gas accumulates under the skin.

The swelling is characteristically in the hip, back, neck, chest and shoulder. It should feel hot to the touch and will present as being very painful to the animal. The gas, which builds up under the skin, makes a crackling or rattling sound known as crepitation when the skin is pushed down over the affected area.

Deceased animals need to be dealt with immediately. Pick animals up and carry them out of the pasture as opposed to dragging them out on a chain. The entire carcass is a breeding ground and major shedding source for the Clostridium chauvoei bacteria and becomes your herd's number one risk factor.

The carcass should be burned completely or covered with quick lime and buried deeply, where predators, scavengers and normal rainfall cannot reintroduce the carcass and its spores to your herd.

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The Disease Process
Blackleg is not contagious. The source for transmission is the clostridia bacterium spores waiting in the soil for the opportunity to come in contact with an open wound or to be ingested by a grazing animal. Ingested bacteria will invade the body via small puncture wounds in the animal's digestive tract. Animals also can eat feed with contaminated with spores.
As previously stated, blackleg usually attacks livestock younger than two years of age. The soilborne blackleg organism enters the animal through ingestion of contaminated forage. Following ingestion, the organism may live in the gastrointestinal tract, spleen and liver without causing any problem.
It is not entirely understood what causes the bacteria to proliferate, but one theory is muscle bruising associated with handling and shipping may be a major cause. Once the spores begin to germinate, bacteria grow and produce a deadly toxin and excrete gasses.
The disease affects both skeletal muscle and cardiac (heart) muscle and is frequently found in both the leg and the heart. Of the skeletal muscles, the thigh (hindquarters) is most commonly affected.
If sheep or cattle have ever grazed the land you are currently pasturing, it is most likely you have the Clostridium chauvoei spores. This is why vaccination is so important for prevention.
Certain environmental conditions may cause the disease to become active in a pasture field. Fresh disturbances of the soil, such as tilling and erosion from heavy rains, can increase your herd's risk of an outbreak. Additionally, flooding may force the spores up out of saturated soil and provide a greater opportunity for animal contact.
It is not uncommon for prime blackleg conditions to affect an area for a period of 10 days, leading to continually finding sick and/or dead animals over a two-week time period.

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Cause of Blackleg
Most cases of blackleg are caused by the anaerobic, spore forming bacteria, Clostridium chauvoei. Very few cases are caused by Clostridium septicum. Blackleg gets its name because it typically infects the rear leg muscle, causing it to turn a darkened or black color.
There are more than 60 types of Clostridium bacteria. Clostridial organisms are anaerobes, which means they like to live and grow where there is no oxygen. There are several diseases in cattle caused by different Clostridial species. Some examples are malignant edema (Cl. Septicum), black disease or infectious hepatitis (Cl. novyi), and several types of enterotoxemia (Cl. perfringens types C and D).
Clostridium bacteria have developed the ability to survive extreme environmental conditions by developing into highly resistant spores. As spores, the bacterium can live in soil for many years, waiting for its opportunity to strike and infect a host.

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Blackleg is a preventable, soilborne disease of both cattle and sheep that producers need to be concerned about. It is caused by an anaerobic, soilborne bacterium (Clostridium chauvoei) and is almost always lethal. Animals are usually found deceased and exhibit swelling under the skin which “crackles” when pushing down on it.
Blackleg vaccines, usually 7- and 8-way products, are widely available and are very effective at preventing livestock from contracting this deadly disease.

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