Malignant oedema is a clostridial disease that more commonly affects sheep but also goats and cattle.
Contamination of wounds by the bacteria leads to inflammation and severe toxaemia (blood poisoning).
Malignant oedema results from infection of wounds with certain clostridial organisms (Cl.chauvoei, Cl.novyi or Cl.septicum), which cause local swelling and discolouration. General toxaemia (blood poisoning) and death of the animal occurs within days.
Susceptible wounds may occur during routine operations like shearing, mulesing, and marking. Infection is not uncommon if these operations are carried out under dirty, unhygienic conditions. The genital tract may become infected following prolonged or assisted lambing, kidding or calving.
Swelled head is a similar condition seen in rams. This occurs in young animals due to fighting, with the bacteria entering wounds on the head, resulting in the typical “swelled head” appearance.