Black disease

Black disease (also known as Infectious Necrotic Hepatitis) is a fatal disease primarily affecting sheep and cattle, caused by the bacterium Clostridium novyi Type B. The disease is characterized by sudden death, often with no prior symptoms, and is most common in sheep that are grazing on clover or alfalfa.

Etiology

Black disease is caused by Clostridium novyi Type B, a spore-forming, anaerobic bacterium. The spores of C. novyi can survive in soil for many years, and are ingested by animals while grazing. The spores then migrate to the liver, where they remain dormant until the liver is damaged, often by the common liver fluke Fasciola hepatica. Once the liver is damaged, the spores germinate and produce a potent exotoxin, leading to rapid death.

Clinical Signs

In most cases, the first sign of black disease is sudden death. Occasionally, animals may show signs of acute illness, such as severe depression, loss of appetite, and high fever, shortly before death. On post-mortem examination, the liver is often found to be swollen and dark, hence the name "black disease".

Prevention and Control

Prevention of black disease involves controlling liver fluke infestation and vaccinating at-risk animals with a multivalent clostridial vaccine. Regular deworming of livestock can also help to reduce the risk of liver damage and subsequent C. novyi infection.

Treatment

There is no effective treatment for black disease once clinical signs have developed. Antibiotics can be used to treat animals that are suspected of being infected, but their effectiveness is limited due to the rapid progression of the disease.

See Also

• Clostridium novyi
• Fasciola hepatica
• Clostridial diseases

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