Category:Histotoxic Clostridia

• Exotoxins cause local tissue necrosis and systemic effects which can be fatal - toxaemia
• C. chauvei and C. septicum present in muscle as latent spores which can germinate to cause infection
• C. novyi type B and C. haemolyticum have latent spores in the liver
• When inoculated into wounds, cause malignant oedema and gas gangrene
• Endospores persist in the soil
• Most ingested spores excreted in faeces, but some become dormant in tissues
• Tissue injury leads to reduced oxygen tensions allowing germination and replication of bacteria
• Exotoxins cause local necrosis
• Activated spores in the liver and muscles cause endogenous infections including blackleg, infectious necrotic hepatitis and bacillary haemoglobinuria
• Inoculation of wounds causes exogenous infections including malignant oedema and gas gangrene

Clostridium chauvei

Clostridium septicum

• Causes malignant oedema:
  • Infection via wounds
  • Cellutis with minimal gangrene and gas formation
  • Tissue swelling die to oedema; coldness and discoloration of overlying skin
  • Toxaemia with depression; death may be rapis if extensive lesions
• Causes braxy:
  • Abomasitis of sheep
  • Disease occurs during winter
  • Rapidly fatal; anorexia, depression, fever
• Causes gas gangrene and myositis

Clostridium novyi

• Infectious necrotic hepatitis/black disease:
  • Acute disease of sheep, occasionally cattle
  • Hepatic necrosis caused by exotoxins of C. novyi type B in liver damaged by Fasciola hepatica
  • Rapid death
  • Dark discoloration of skin caused by subcutaneous venous congestion
  • Fluorescent antibody test diagnostic
• Causes gas gangrene and myositis.
• May be involved in cutaneous lesions
• Causes big head in rams - oedema of subcutaneous tissues of the head, neck and cranial thorax; necrotising lethal alpha toxin

Clostridium perfringens type A

• Gas gangrene and myositis
  • Extensive bacterial invasion of damaged muscle
  • Gas production causing subcutaneous crepitus
  • Similar manifestations as malignant oedema

Clostridium haemolyticum

• Causes bacillary haemoglobinuria in cattle, occasionally sheep
• Endogenous infection - endospores dormant in liver
• Fluke migration allows germination
• Beta toxin causes intravascular haemolysis and hepatic necrosis
• Haemoglobinuria due to destruction of red blood cells

Clostridium sordelli

• Causes gas gangrene, myositis and abomasitis (lambs)

Treatment of histotoxic infections

• Early penicillin
• Vaccination with bacterin or toxoid at 3 months and booster after 3 weeks, then annually