Tetanus is the result of infection by a bacterial species called clostridial tetani.
These bacteria are commonly present in the feces of animals and in soil contaminated with animal feces. Horses are especially susceptible and should be routinely vaccinated against the disease to prevent infections.
Most cow-calf producers vaccinate their calves with clostridial vaccines at one to three months of age before turning them out to pasture, and calves are usually vaccinated again at weaning.
Clostridial vaccines, which are often referred to as seven-way or eight-way vaccines, provide protection against many clostridial diseases, such as blackleg, but it is important to recognize that they do not always contain tetanus.
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This is probably because tetanus is less common in cattle, but a couple of small outbreaks in the past few weeks have demonstrated the importance of making sure the disease is included in cattle vaccination protocols in certain situations.
The clostridial bacteria that causes tetanus is often introduced through deep puncture wounds. Soil or feces contaminate the wound and the tetanus bacteria may form spores, which lay dormant for a long period of time within an animal’s tissues.
Puncture wounds in horse hoofs are a common source of infection, and tetanus is seen in pigs following castration and in lambs following castration, shearing and tail docking.
Tetanus is much more rare in cattle, and is sometimes reported as occurring after calving or after grazing rough feed that may cause puncture wounds in the mouth.
However, the only cases that we have recognized in recent years have occurred following castration with elastic bands.
The use of elastic bands for castration has been common in young calves for many years. Their use in young calves at less than one to two weeks of age does not seem to be a major risk for tetanus.
However, we have seen an in-creased use of high tension, elastic bands to castrate older cattle during the past 20 years. Devices such as the Callicrate bander and the California bander are designed to be used in heavier calves.
Ideally, we would prefer to castrate cattle at the youngest age possible for welfare reasons, but these devices have been popular for bloodless castration of older animals when necessary. They cut off the blood supply to the scrotum and testicles, and the tetanus bacteria can thrive in this environment.
Tetanus cases are often seen one to two weeks following castration. The bacteria release a potent toxin that affects the nervous system.
Clinical signs begin with muscle stiffness and muscle tremors. As symptoms progress, the animal has difficulty opening its jaw, and in some cases the third eyelid can prolapse and becomes evident over the eye. As the symptoms worsen, animals may have difficulty eating and swallowing.
Eventually the toxins affect more of the musculature, and the animal may adopt a “sawhorse” posture caused by severe muscular contractions. The animal will eventually go down, and the limbs will stick out stiffly behind and the front legs forward. The tail may stick out firmly, almost like a pump handle. Symptoms will often progress over a five to 10 day period.
Treatment can be effective if initiated early, but in many cases, symptoms have progressed to a stage that makes recovery difficult.
Veterinarians have access to tetanus antitoxin for these cases, and large doses of penicillin are used to treat the infection.
This supportive therapy is often necessary for animals that have gone down, but it can be difficult to provide in some circumstances.
In the recent outbreaks of tetanus in cattle that were reported to the Western College of Veterinary Medicine, high tension elastic bands were used to castrate older calves.
Although the calves had received clostridial vaccines, the vaccines used did not include tetanus. In Canada, the only clostridial vaccines that contain tetanus are Covexin plus and Tasvax 8.
Cattle are more resistant to tetanus than most other livestock species, but the use of high tension bands for castration is the one circumstance that can cause tetanus to occur.
Make sure these animals receive a clostridial vaccine that includes clostridium tetani at the time of castration or before castration.
