One farmer in Co. Kilkenny recently lost a high quantity of his stock overnight due to suspected blackleg infections, but what is it? Can it be treated? How does one best prevent it?
What is it -
Blackleg is an infectious bacterial disease which is caused by a gram-positive bacteria species called Clostridium Chauvoei.
A fatal disease, it is found in all types of livestock from cattle to sheep and goats, while some cases have even been identified in farmed deer. In general, Blackleg mainly affects animals aged from 6-months to two years old. Some cases can occur as young as two months old, while animals who have a high daily feed intake are usually more susceptible. It can affect sheep at any age.
Blackleg can, unfortunately, occur at any time of the year, though most cases occur during the warmer summer months. The nature of the blackleg disease means that treatment is extremely difficult, while the effectiveness of vaccines has been disputed.
Caused by the Clostridium bacterium, spores created by these bacteria can remain in the soil in an inactive state for years, before making a return once conditions return to optimum levels. It can prove an extremely difficult task to rid pastures of the Blackleg causing bacteria.
Once infected, the first sign is usually the development of a fever in an animal. Following this, the affected leg will begin to feel hot to touch and will begin to swell slightly. This will lead to the animal becoming lame and struggling to walk on it. In some cases, air pockets (crepitation) can be identified under the skin at the site of infection. This skin will later turn dry and leathery to feel.
Other signs of blackleg infection include a loss of appetite, depression and sudden death. Usually, the animal will only survive for a short period after the first signs of the disease are noticed, with many dying within 12 hours.
Often some stock do not showcase any of the main signs or symptoms. In such circumstances, infections can only be identified through the inspection of the animal’s carcass. Should infection be present, black patches will be found on and around the affected area.
Prevention and Treatment -
Due to the rapid nature of the disease, treatment of blackleg is rarely an option for farmers. Penicillin is used to treat animals when the disease is identified early, though should only be used as a method of control. One way to prevent spreading is to burn the upper layer of the soil where an infected animal was kept.
Vaccination is the best form of prevention, though its effectiveness is often disputed. The most common vaccination used is a seven-way clostridial vaccination. For calves under 6months old and sheep previously unvaccinated, two vaccinations four weeks apart should be administered. This should be followed by a booster dose 12months later.
Annual boosters should be carried out about a month before calving or lambing to allow for passive immunity is transferred from dam to offspring. Young sheep should always be vaccinated before being put onto pasture.
Note - Infected animal carcasses should always be disposed of correctly to prevent further spreading.