Outbreaks of blackleg have been reported after earthworks are carried out on Irish farms, Regional Veterinary Laboratories (RVLs) have said.
These earthworks include field drainage work, road construction, and exposure of earth floors during mucking out buildings, which cause exposure to the highly resistant clostridial spores in the soil.
Blackleg is a common disease of cattle worldwide, causing acute muscle damage. It usually results in sudden death or death after a short illness.
The disease is caused by the bacteria Clostridium chauvoei and clostridial spores can enter the body of an animal by ingestion, through skin wounds, or via contaminated needles/injection equipment.
Muscle trauma from bulling events in heifers (involvement of back muscles) and injuries at congested feed barriers (neck) trigger spore activation and lead to disease.
This is according to the Athlone RVL, where the carcase of a one-year-old heifer with a history of sudden death, was examined in April, having been turned out to grass in the preceding fortnight.
This particular caser was highlighted in the RVL’s report published in the Veterinary Ireland Journal.
The right quadriceps muscle of the heifer was dark red in colour, dry, and markedly emphysematous with severe subcutaneous haemorrhages over the right hind quarter.
Impression smears from muscle lesions stained positive in the Clostridium chauvoei fluorescent antibody technique (FAT) test, confirming clostridial myositis caused by C.
chauvoei, or blackleg.
A review of the farm’s clostridial vaccine programme with the herd owner was advised, with recommendations to vaccinate with multivalent clostridial vaccine (containing clostridial toxoids of multiple likely species).
Blackleg cases
Earlier this year, Sligo RVL diagnosed blackleg in a housed, eight-month-old weanling. The animal had been found dead suddenly after presenting with lameness on the evening before.
It had been transported from a different premises in the days prior to death.
On post-mortem examination in February, there was extensive necrotising myositis on the left side of its neck and thorax.
There were concurrent mild acute pneumonia and acute pleuritis. Clostridium chauvoei was detected by fluorescent antibody technique (FAT) in the muscular lesion. Pasteurella multocida was detected in the lung.
The Department of Agriculture, Food and the Marine (DAFM) has said that RVLs have noted a “sharp increase” in the prevalence of blackleg diagnoses in cattle.
These cattle were referred to the RVLs for post-mortem examination.
The department has warned that the RVLs have seen “some quite large” outbreaks in farms around the country with no prior history of the disease.
However, according to the department, prevention is “very straightforward”.
The department said that clostridial vaccines are “extremely effective when used properly” with several brands and suppliers to choose from.
“It is important to follow manufactures’ instructions on the primary course and booster regime, which is simple to implement, but crucial to ensure maximum effectiveness,” the department said.
Farmers are advised to consult their vets for specific advice on diagnosis and prevention of blackleg on their farms.