Animals – Clostridial diseases

Clostridial diseases, such as tetanus and blackleg, are caused by bacteria that live in the environment and sometimes inside animals. They produce the most potent toxins known to occur in nature. When conditions are right for the bacteria to multiply inside an animal, tiny, tiny, tiny traces of the toxin already present – not causing problems – rise to the point where they overwhelm the animal.                                                                                                  

The best known clostridial disease is tetanus. Horses and humans are the most sensitive to this, but stock are not that far behind. The bacterium that causes tetanus (Cl. Tetani) loves necrotic tissue, which is dead tissue in a living individual. The classic risk factor is sustaining a deep puncture wound or creating docking wounds in lambs or castration wounds in young rams and bulls, but sometimes no obvious wound is ever found. Skeletal muscle becomes more and more tense and the sufferers become stiffer and stiffer. A loud noise or a slap on the back will show an overreaction spasm. Look for the third eyelids to shoot across the eyes. Dogs are much less sensitive. On the rare occasions they get tetanus, the onset is over weeks, not days. If your dog starts looking like it has had face-lift surgery that has gone too far and it starts falling over, then it could be tetanus. Dogs often survive where horses and stock are euthanised.

The next  best known clostridial disease in New Zealand is pulpy kidney. The name comes from a post mortem change that is seen in sheep only. Cl. perfringens type D lives in the gut of stock, loving it when the animal is eating lush pasture. The biggest, fastest-growing individuals are the ones most likely to succumb. They go from healthy to dead in a few hours. I have seen this mostly in lambs in the nice, spring weather. This disease is sometimes simply called “enterotoxaemia”. It is a worry in sheep, goats and alpacas. It can kill cattle but is not so commonly diagnosed in them.

For New Zealand cattle, maybe the biggest clostridial worry is blackleg. Cl. chauvoei loves bruised muscle tissue and affected animals are often seen a few days after yarding.

Again, it is often the biggest animals that are most affected. They progress from healthy to dead so quickly that they are mostly found dead. If you find an infected animal that is still alive, you may feel gas under the skin over a well-muscled area. Blackleg can occur in sheep and, although less common than in cattle, it is likely to affect more than just a few individual sheep if it does strike.

It is not easy to identify clostridial bugs and their toxins using laboratory tests. Diagnoses are usually made on histories, post mortem and sometimes clinical symptoms, but even then the picture is not always clear. The ‘8in1’ and ‘10in1’ vaccines to combat clostridial diseases are restricted veterinary medicines only available through your vet. Head there for advice on these diseases and their prevention.                                          

David Haugh, Wellsford Vet Clinic
www.vetsonline.co.nz/wellsfordvet