Dr Eddie Snyman is a retired veterinarian from Middelburg in the Eastern Cape. He has many years of experience in treating and preventing diseases caused by the Clostridium group of bacteria. Diseases caused by the Clostridium group of bacteria is known as clostridial diseases.
“These bacteria are found throughout nature, with some commonly found in the intestinal tract of animals and humans, where they live as harmless saprophytes.”
Most textbooks group and discuss clostridial infections under the following headings:
- The neurotoxin-producing group of Clostridium sp.
- The malignant oedema/gas gangrene group of Clostridium sp.
- The Clostridium perfringens group.
Tetanus (lockjaw) and botulism are the most significant infections in the neurotoxin-producing group. “Deep penetration wounds in unvaccinated horses and lambs that have been castrated or docked using the rubber band method, or sustained a skin lesion while an ear tag was attached, are very susceptible to tetanus,” says Dr Snyman.
He also refers to Clostridium botulinum, which causes botulism, found in decomposed carcasses – here the neurotoxin accumulates in the bones. “Cattle with a phosphate deficiency chew and swallow the dry bones strewn in the veld. Farm animals can also ingest finely ground feed or chicken manure contaminated with dead rodents or chickens, and absorb the toxin into their bloodstream. When circulated to the brain it can lead to paralysis of voluntary muscles.”
Malignant oedema group
This group contains Clostridium chauvoei, which causes blackquarter in cattle and sheep.
Malignant oedema – a watery accumulation under the skin with a sharp, foul odour – is caused by Clostridium septicum, Clostridium oedematiens and Clostridium sordellii. Dr Snyman specifically refers to swollen head in sheep rams as a form of malignant oedema. “These bacteria can also infect the reproductive system of recently-lambed ewes, leading to deaths due to uterine gas gangrene.”
Clostridium perfringens group
According to Dr Snyman, the C. perfringens organisms are found in soil as well as in the intestinal tract of healthy animals and humans. “Diseases present when the organisms proliferate rapidly in the intestinal tract and toxins are circulated throughout the body.”
C. perfringens organisms are divided into five types, each with the ability to produce several lethal primary and secondary toxins:
- Type A: Redgut in sheep and enterotoxaemia in calves and foals.
- Type B: Lamb dysentery in lambs and bloody enteritis in sheep.
- Type C: Necrotic enteritis in lambs, calves, piglets and humans.
- Type D: Pulpy kidney.
- Type E: Enterotoxaemia in calves.
Methods of diagnosis
In cases of tetanus, there are no obvious post-mortem lesions and checks for deep penetration wounds should be conducted instead. In lambs, the withered scrotum or tip of the tail must be examined to establish whether a rubber band is still stuck to it.
In the case of cattle with botulism, the tail and tongue, among others, must be checked for paralysis. Blood serum, manure and feed can be analysed. During post-mortem examinations, samples can be taken of the rumen, small intestine and colon, as well as the feed, for further testing.
Where blackquarter and malignant oedema are concerned, at least six imprint smears should be made on clean microscope slides. The imprints must be made across a section of the affected muscle group, or wound, as well as on the surface of the liver next to the diaphragm. These imprints are sent to the laboratory, where the fluorescent antibody test is used to identify the causative organism.
With enterotoxaemia, organs must be placed on ice and sent to the laboratory as soon as possible to isolate and typify the cause.
Dr Snyman reiterates that some of the Clostridium bacteria, such as C. septicum and C. sordellii, are key necrotic bacteria. “Similarly, other normally occurring commensal organisms in the intestinal tract, such as Bacillus bacteria, can grow much quicker when samples are transferred to slides in the laboratory, which can severely impede or prevent the growth of pathogenic organisms.”
Clostridial diseases can be successfully controlled through regular vaccination, some of which have been registered for use in farm animals. “Some of the agents contain only one antigen, for example the vaccine for pulpy kidney, or two antigens, such as for botulism or blackquarter, while multiclostridial vaccines, which contain up to ten antigens, are currently being marketed.”
He suggests giving consideration to additional management practices. “Consider, for example, small stock that graze cultivated pastures or feedlot animals that have been adapted too quickly. Providing good quality hay can help limit the sudden multiplication of Clostridium bacteria. It also helps reduce mortalities until a follow-up vaccination provides sufficient immunity.” – Carin Venter, Stockfarm
For more information, send an email to Dr Eddie Snyman at firstname.lastname@example.org.