MALIGNANT EDEMA/GAS GANGRENE

Gas gangrene is due to infection by Clostridium septicum although other clostridia may be involved which includes Clostridium novyi and Clostridium sordelli. The organism is a common habitat of the intestinal tract of herbivores and occurs widely in faeces and soil. In most cases, it enters the body through contaminated wound and consequently produces a severe local reaction resulting in necrosis, edema and gangrene and profound systemic effects due to toxaemia with rapid deterioration and death.
Clinical signs
Incubation period is short. It is just within 1-2 days. There is depression, anorexia, high fever within a short time. Affected animals are completely recumbent. The infection site is swollen, hot and painful in the earlier stages. This rapidly progresses to a stage where swelling persist sometimes with a foul smelling sanguinous or bloody discharge but pain is no longer evident. The swollen area eventually becomes cold, discolored and sometimes emphysematous. Occasionally, a syndrome is encountered where the condition is initially limited to the head especially the intermandibular space. Death occurs within a few days. Commonly, animals are presented at sudden death.
Immunity
It is believed that infected animals are suddenly immuned to infection.
Diagnosis
Swabs may be taken from infected sites immediately after death to establish the identity of the causal organism. As with blackleg, examination of animal which has been dead for more than few hours especially in warm climates is likely to afford little or no information due to invasion of the tissue by clostridia organism.
Prevention and control
Proper management of surgical and accidental wound including administration of antibiotics is often adequate enough to prevent malignant edema. Where the disease is considered to be serious, vaccination is very important. In view of the possibility of mixed infection, it is wise to use polyvalent clostridia vaccine. When faced with outbreak for example after castration of a large number of animals, it is probably wise to carry out a herd vaccination and to administer large doses of long acting penicillin to each animal. Again, animals at risk must be moved to another grazing areas free of the disease.
Treatment
Treatment of individual cases is usually unsuccessful. Wounds should be carefully cleaned and drained adequately. This should be followed by massive doses of procain penicillin both intramuscularly and around infection site together with large frequently repeated doses of soluble penicillin given intravenously.