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While most animals can contract tetanus, or lockjaw as it is commonly known, the disease is especially prevalent in castrated lambs or lambs whose tails have been docked using a rubber ring or elastrator. It is less common in cattle, but cases do crop up from time to time, especially after surgical procedures such as dehorning, castration or hoof trimming.
Dr Bertus Nel, a veterinarian from Calvinia, says the spores of the bacterium Clostridium tetani are ubiquitous in soil, on rusted nails and on the pins of old ear tags that lay around the crush, manure and even the intestinal tract of healthy animals. These spores are resistant to drought and can survive in the soil for years. The spores gain access to the animal’s body through wounds or broken skin. It forms the toxin tetanospasmin in the wound, which affects the motor neurons in the nervous system. This is what leads to the characteristic paralysis and nervous symptoms observed in animals.
“It thrives in deep wounds, in places with tissue necrosis and where little oxygen is present. The bacterium is anaerobic, which means it multiplies in the absence of oxygen. Once the spores germinate the bacteria starts multiplying rapidly, producing a toxin that affects the animal’s nervous system,” he explains.
Dr Nel is not in favour of castration using rubber rings nor tail-docking involving the use of rubber rings, as it creates the ideal conditions in which tetanus can gain a foothold. He believes there are better ways of docking lambs’ tails.
Signs of disease
The first signs of disease, he says, are usually visible seven to ten days after the animal has sustained a wound or the elastrator has been attached. Some of the first signs include slight stiffness and the white membrane of the eye that protrudes over the eyeball. The animal has a stiff gait and when it lies down on its side, it cannot get up again.
“The toxin affects the motor neurons in the animal’s nervous system and causes the muscles to contract and spasm, which leads to rigidity. The muscles of the mouth contract, causing the jaws to clamp shut – hence the name, lockjaw,” he explains.
These symptoms typically mean the animal cannot move, feed or drink. In most cases the animal succumbs after a few days, usually due to suffocation and starvation.
The best way of preventing tetanus is through immunisation. Once the first signs of disease are visible, treatment involving antibiotics is almost always ineffective. In fact, says Dr Nel, there is no real treatment for an animal that already has tetanus.
“The only treatment for animals exhibiting signs of tetanus is anti-serum which, for all practical reasons, is unavailable. Therefore, producers should do everything in their power to prevent their animals from ending up with tetanus,” he says.
Tetanus is not contagious, but under favourable conditions several animals in the herd or flock can contract it at the same time.
According to him there are various top-quality vaccines available in the market for the prevention of tetanus. It is quite easy to prevent the disease, he says. “Vaccines against tetanus are very effective and various commercial combinations are available. Most multi-clostridial vaccines also provide protection against tetanus. Read the vaccine label to check for the presence of Cl. tetani on the bacteria list.”
To afford protection to lambs until they are branded, it is best to make sure ewes are vaccinated annually before the lambing season arrives. The ewe’s colostrum will protect the lamb until it reaches tail-docking age or needs to be castrated. If the lambs are to be marked at the age of six weeks and older, they must have been vaccinated at least two weeks before being branded.
Dr Nel advises producers not to castrate lambs or dock their tails using rubber rings. Methods involving a gas-operated docking iron, burdizzo or open castration will reduce the risk of tetanus. – Koos du Pisanie, Stockfarm
For more information, contact Dr Bertus Nel on 027 341 2770.