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Farmers Warned to Protect Cattle Against Blackleg

07 September 2012

UK - An increase in the incidence of cattle deaths due to blackleg has been reported in Scotland this year. This may be due to soil disturbances associated with the unusually wet weather and flooding. Although there has been no increase in the number of cases of blackleg confirmed by AFBI’s Veterinary Sciences Division has this year, blackleg is a common disease of cattle and sheep in Northern Ireland and farmers are advised to protect their livestock by the use of vaccination.

Overview

Blackleg is a rapidly fatal clostridial disease affecting the muscles of well-nourished young cattle, particularly beef breeds. The affected muscle is dark red to black and may become dry and spongy (gas-filled). Any muscle may be affected, including the tongue, diaphragm or heart, although it is mostly recognised in the bodymuscles or limbmuscles. The disease is caused by toxins produced by Clostridium chauveoi bacteria.

Signs

Cattle between 6 and 24 months old are particularly susceptible to this disease, but calves as young as 6 weeks and cattle as old as 10-12 years may also be affected. Signs to look out for are non-specific but include general malaise, lameness, going off feed, lying down or difficulty rising, fever and swellings in the muscles which may feel crackly when touched. Not all of these signs may be present in any single animal and often the first sign that something is wrong is when animals are suddenly found dead. Animals that are found dead may bloat from gas more quickly than normal and have widespread subcutaneous emphysema (gas under the skin).

Time of year

Blackleg can occur at any time of year but it is most common in animals at pasture over the summer and autumn. Pasture contaminated with spores of the blackleg organism appears to be a source of organisms. Outbreaks of blackleg have occurred in cattle on farms where there have been recent excavations of soil, which suggests that disturbance of soil may activate latent spores. Alternatively, flooding may disturb large amounts of soil which may explain some of the increase in numbers of cases reported in Scotland this year.

Diagnosis

Your veterinary surgeon may be able to diagnose a field case based on clinical signs, breed, time of year etc. However, the best way to diagnose the condition is by laboratory confirmation of the bacteria in affected muscles. The whole carcass, or samples of affected muscle, should be taken as soon after death as possible and submitted to AFBI’s veterinary laboratories at Stormont or Omagh. The fluorescent antibody test in use at the laboratories for Clostridium chauvoei bacteria is rapid and reliable.

Control

The best control option against the disease is vaccination. There are various vaccines available and cattle should be vaccinated several weeks before the period of major risk and revaccinated on an annual basis (or as specified by the manufacturer). This should be undertaken before turnout in the spring.

Cattle are at major risk of the disease through the grazing period, but cases can also occur in housed cattle. Treatment of clinical cases with antibiotics and symptomatic assistance may be attempted, but it is frequently unsuccessful. Prophylactic treatment with antibiotics for animals thought to be at risk in the face of an outbreak is also a treatment option, although your veterinary surgeon will advise on individual cases.

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