Black quarter (BQ) is an acute infectious disease of ruminants caused by Clostridium chauvoei. BQ is also known by several other names as quarter ill, quarter evil, black leg, symptomatic anthrax, or emphysematous gangrene. It is an endemic disease in both developed and developing countries. BQ is characterized by swollen, hot, and painful wounds mostly in the hind limb. The disease is infectious, causing severe toxicity, inflammation of the cardiac and skeletal muscle, and high mortality. The disease is predominantly found in cattle but has also been found to cause disease in other animals. In the cattle and sheep, BQ is fatal, but outbreaks also reported in horse, pig, deer, and ostrich. In cattle, BQ is generally infecting young calves between the age of 6 months and two years.

Clostridium chauvoei

is a gram-positive, spore-forming, rod-shaped, and toxin-producing anaerobic bacteria. The bacterial spores are highly resistant to adverse environmental conditions and can withstand up to 120°C for 10 min. The bacterium is destroyed by formalin (3% for 15 min) and 2% mercury dichloride. The spores can survive in the soil for many years and grow best in media with alkaline pH. BQ generally occurs in the summer season. The excavation of soil can lead to exposure and activation of dormant spores, which can cause outbreaks. The disease is mostly found to occur in areas having a history of flooding. It is found to infect several animals in a short time. The route of infection of BQ in cattle is by ingestion of soil-borne spores in the intestinal mucosa. The disease develops when the spores reach a suitable cardiac or skeletal muscle and germinate after localized trauma or anoxia. The toxin released by the bacteria causes necrotizing myositis and systemic toxaemia. BQ is preliminarily diagnosed in the animal by the clinical symptoms and typical crepitating swelling within the muscles. Post-mortem symptoms of BQ in the affected area are discoloured, dark, rancid, and swollen muscle. The affected part also has excess fluid and gas bubbles. The body cavities are also filled with excess fluid, and rapid decomposition of tissues is also seen. There is usually a significant amount of fluid accumulation around the heart with vast amount of fibrin in the case of cardiac myositis. For the confirmation of BQ diagnosis, quick post-mortem examination, and lab analysis of the samples is required. BQ typically kills animals quickly, so the individual treatment is useless. However, animals that are given antibiotics earlier may survive, but they may have permanent deformity due to the destruction of muscles. The option to prevent losses due to BQ disease is to adopt a good immunization program.

Cause

A bacterial disease caused by Clostridium chauvoei

Host Species

Cattle and Sheep

• The disease is spread by ingestion of contaminated feed, fodder and from wound.
• Animals acquire infection through the alimentary mucosa after ingestion of contaminated feed or associated with erupting teeth.
• The soil and pasture contaminated with infected feces or carcasses of animals died from the disease are also the source of infection.
• Sheep gets infection from wound on the body.
• Infection of skin wounds after shearing and docking and removal of the navel at birth may cause the development of local lesions.
• After lambing, the infections of the vulva and vagina of the ewe cause serious outbreaks and the disease has occurred in groups of young ewes and rams up to a year.
• Disease may occur as a result of infection of skin wounds caused by fighting.
• Sometimes, outbreaks have also occurred in sheep after vaccination against enterotoxemia specially the formalinized vaccine causes sufficient tissue damage to permit latent spores of the organism to proliferate.

Cattle

• Animals become very depressed, complete anorectic and there will be stasis of ruminal contractions, a high temperature (41°C, 106°F) and pulse rate (100-120/min).
• Rise of temperature of fever may not present in all cases.
• The animal shows severe lameness and pronounced swelling of the upper part of the affected leg before death.
• Initially, there will be swelling of skin with hot and painful in touch followed by cold and painless, and edema and emphysema can be felt. Thereafter the skin is discolored and soon becomes dry and cracked.
• Although, in most of the cases the lesions are usually restricted to the upper part of one limb, however, the lesions may be present in on the base of the tongue, the heart muscle, the diaphragm and psoas muscles, the brisket, and the udder occasionally.
• The condition develops rapidly and the animal dies quietly 12-36 hours after the appearance of signs.
• Many animals die without showing any sign.

Sheep

• The infected sheep show high fever, anorexia, and depression, and death occurs very quickly.
• There will be stiff gait and the sheep becomes unable to move or walk properly because of severe lameness in one limb or, more commonly, in several limbs.
• Subcutaneous edema and gaseous crepitation cannot be felt before death.
• The skin may be discolored but necrosis and gangrene do not occur.
• The local lesions are seen extensively on the skin, vulva, or vagina when the infection occur from the wound of these organs.
• The swelling of head and bleeding from the nose are also seen.
• Sheep with cardiac myositis associated with C. chauvoei are usually found dead suddenly.

Management

Therapeutic management is as follows: Non-steroidal anti-inflammatory drugs (NSAID) to alleviate fever and pain

• Large doses (40000 IU/kg BW) should be administered, commencing with crystalline penicillin intravenously and followed by longer-acting preparations.
• Surgical debridement of the lesion, including fasciotomy, is indicated if the animal is not moribund.
• Black leg antiserum, helpful in very large doses are available.
• Dressing of wounds with 0.01 to 0.02% potassium permanganate solution three to four times/day followed by topical spray preparations
• Administration of multivitamins preparations to accelerate the healing process of epithelial cells

Preventive measures

• In enzootic area, annual vaccination of all cattle between 3 and 6 months with two vaccinations given 4 weeks apart followed by an annual booster vaccination is recommended.
• This should be done just prior to the anticipated danger period, before monsoon and summer.
• In an outbreak, all unaffected cattle should be vaccinated immediately and injected with penicillin at a dose of 10000 IU/ kg BW intramuscularly.
• Movement of the cattle is to be restricted from the affected pasture.
• In enzootic area, the ewes should be vaccinated twice, the last vaccination is given about 1 month before lambing.
• The vaccination before lambing will protect lambs against umbilical infection at birth or infection of the tail wound at docking in young age.
• If an outbreak is suspected of ewes at lambing time, prophylactic injections of penicillin will prevent the disease

Control

Regular vaccination is the only effective way to control the disease

Type of vaccines

Inactivated vaccine (Aluminum hydroxide gel or oil adjuvant)

Combined vaccine is also available

Vaccination schedule

First vaccination is done at 5-6 months of age followed by booster after 6 months and to be repeated annually interval

Dose

2/3 or 4/5 mL S/C or I/M route or according to manufacturer's instructions:

Note: Deworming is must at least 15 days before vaccination

Source/manufacturer of vaccine in India

• Bio Vet. Pvt. Ltd., Karnataka
• Indian Immunologicals, Hyderabad
• Brilliant Bio Pharma Ltd., Hyderabad
• Biomet. Pvt. Ltd., Ghaziabad (UP)
• State Veterinary Vaccine Institutes e.g. Institute of Veterinary Biologicals, Pune, Thiruvananthapuram