Blackleg

From Cow
Myonecrosis in a steer which died from C. chauvoei infection

Blackleg (clostridial myositis; gas gangrene) is a relatively sporadic bacterial disease of cattle worldwide caused by Clostridium chauvoei.

The Clostridial organisms are commensal intestinal-dwelling bacteria which localise in wounds, bruises or in muscle after heavy exercise, and release toxins and neuraminidase which cause extensive myonecrosis[1].

Clinical signs

Affected cattle of all ages show signs of acute fever,emphysematous swelling, usually in the heavy muscles[2] and sudden death.

In less severely affected cattle, fever, lameness and depression are common. Crepitant swellings can be palpated in the affected area, usually the hindlegs or back. As the disease progresses, subcutaneous gangrene occurs with resultant toxemia. Lesions can also be observed in internal organs such as the heart and diaphragm.

Outbreaks have been reported primarily in summer months or after recent heavy rains[3], but also in housed cattle with heavily soiled bedding[4].

Diagnosis

Diagnosis is based on presenting clinical signs and postmortem findings on those cattle found dead or euthanized.

Definitive diagnosis requires laboratory isolation of C. chauvoei from muscle samples and PCR assays[5].

Treatment

Severely affected cattle rarely respond to treatment but broad-spectrum antimicrobial therapy may assist recovery, including large doses of penicillins.

Multivalent vaccines are available to prevent outbreaks and should be given to at risk cattle and all weanling calves[6].

References

  1. Useh NM et al (2003) Pathogenesis and pathology of blackleg in ruminants: the role of toxins and neuraminidase. A short review. Vet Q 25(4):155-159
  2. Merck Vet Manual
  3. Useh NM et al (2006) Relationship between outbreaks of blackleg in cattle and annual rainfall in Zaria, Nigeria. Vet Rec 158(3):100-101
  4. Groseth PK et al (2011) Large outbreak of blackleg in housed cattle. Vet Rec 169(13):339
  5. Kuhnert P et al' (1997) Identification of Clostridium chauvoei in cultures and clinical material from blackleg using PCR. Vet Microbiol 57(2-3):291-298
  6. Ontiveros Corpus Mde L et al (2008) Prevention of Blackleg by an immunogen of Clostridium chauvoei. Ann N Y Acad Sci 1149:303-305