Special Veterinary Pathology

GAS GANGRENE

Synonym: Malignant oedema

Definition

• Acute toxaemic wound infection of man and domestic animals caused by Clostridium sp. characterized by soft swelling at the site of infection which pits on pressure

Etiology

• Clostiridium septicum

Transmission

• Infection is usually soil borne
• Wound infection

Pathogenesis

• Organism enter heavy muscles where exudation and blood clots favours growth
• Anaerobes produced powerful exotoxin (alpha, beta, gamma and delta toxins, of which alpha toxin is the most dangerous) inhibit neutrophils, injure the capillary endothelium causing oedema and necrosis of muscles
• If travels through blood and produce lesions in various organs
• All clostridium organisms produce gas except Cl. novyi – No gas production

Clinical signs

• High fever, depression and anorexia
• Following injury rapidly spreading oedematous swelling at the site of infection which is soft, hot and painful initially, cold and less sensitive later
• Infection after parturition causes swelling of the vulva
• infection after castration causes swelling of the abdomen under the skin
• Skin over the lesion is gangrenous
• Death occurs due to toxaemia within 24 to 48 hrs after the onset of symptoms

Gross lesions

• Involved tissues are oedematous and usually haemorrhagic and they contain gas bubbles
• Septicaemia often occurs with haemorrhages distributed throughout the body
• Lungs are congested and oedematous
• Serous, blood tinged effusion from the peritoneum may also be present

Miroscopical lesions

• Malignant oedema usually affects in older animals while B.Q affects younger ones
• C.septicum can be easily demonstrated in tissue sections

Diagnosis 

• Symptoms and lesions
• Inoculation in guinea pigs
• The disease must be differentiated from black quarter by the absence of typical muscle involvement and the presence of wounds