Blackleg disease in cattle

CLOSTRIDIA ARE characteristic spore farming anaerobic bacteria found as saprophytes in soil, helping in decomposition of plant and other organic matter or as commensals in intestine of man and animals. Out of few toxigenic species which cause diseases, Clostridium tetani and Clostridium botulinum are the two universal pathogenic neurotoxin producing clostridia, which cause fatal tetanus and botulism disease in man and animals respectively.

The other major diseases caused by various species of clostridia in man and farm animals are enterotaxaemia, gas gangrene, braxy black disease, bacillary haemoglobinuria, pulpy kidney disease and black quarter (BQ) or blackleg disease. Black quarter or blackleg is an acute disease of well-fed young cattle caused by Clostridium chouvoei. The disease affects normally hind quarters and is characterised by myonecrosis, accumulation of gases with sound, severe toxemia and high mortality.The suffering animal exhibits lameness, painful hot swelling, very high temperature, anorexia, dullness and death. Excessive distension of abdomen, blood stained frothy discharge from the nostril and anus, rancid odour, gas bubbles and blackened musculature are some of the characteristic findings which help in diagnosis of the disease in the field conditions. Effective vaccines are available to protect the animals against the disease.

However during the seventies traditional BQ vaccine was not able to protect the cattle suffering from disesase exhibiting symptoms similar to those of blackleg disease. The disease was common in winter affecting animals of all age groups in contrast to BQ.Investigations led to the isolation of clostridial organisms and most of them were identified as Clostridium perfringens Type - A.

On screening of /environmental samples like soil, mud and water from affected area, Clostridium perfringens were found to be abundant in rich humus soil and ingestion of contaminated feed/fodder was the main source of the organism. After initial extensive studies over a period of 5 years, formalised whole cell vaccine containing local strain of Clostridium perfringens Type-A was prepared. An improved formalised alum percipitated and aluminum hydroxide gel adsorbed vaccine containing two local isolated was standardised to combat the disease. Continuous supply of the vaccine for five years led to complete control of the disease.

But re-emergence of unusual diseases like atypical blackleg in any animal husbandry poses a challenge veterinary practitioners and researchers. Since the organism is widely distributed in the environment and spores produced by the bacterial are capable of withstanding harsh environmental conditions, the total eredication of the disease is not possible. However, concerted emphasis in intensive research directed towards, identification of strains involved, characterisation of toxins at molecular level and finally to develop appropriate vaccine technology for control of the disease will benefit the farmers.

N.D.Verma, Rajeswari Shome & B.R. Shome

ICAR Research Complex for NEH Region

Umrol Road ,Umlam 793 103

Meghalaya

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