Looking at botulism

WHAT IS BOTULISM?

Botulism is a preventable disease, like many other livestock diseases, that should ideally never catch us off-guard. Also known as “lamsiekte”, it is a highly fatal paralytic disease of cattle, sheep, goats, horses, mules, donkeys and, sometimes, pigs. Botulism is caused by animals ingesting a toxin produced by a bacterium called Clostridium botulinum. These bacteria are commonly found in decomposing carcasses and sometimes even plant material. Botulism has also been reported in humans where it is mainly associated with the consumption of improperly preserved food.

WHAT ARE THE SIGNS?

Animals may start with an unsteady gait, lie down and struggle to get up. Muscles associated with voluntary movement, like swallowing and chewing, get progressively paralysed. A loss of tail tone, hard dung and in cattle especially a loss of tongue tone may also be noticed. For example, the tongue may mostly be hanging out or struggle to retract if pulled out of the animal’s mouth. A drooping jaw may also be noticed.

Affected animals may succumb to respiratory and/or cardiac paralysis a few days after the onset of clinical signs. In cases where high amounts of toxin have been consumed animals may be found dead in the morning.

HOW DOES IT AFFECT FARMERS?

Most of the affected animals will die. Animals sick with botulism cannot even be sent for emergency slaughter, as legally only meat from healthy animals may be passed for human consumption. Such animals may even have been through a treatment course when owners try to intervene, in which case drug residues may prohibit inclusion of such carcasses into the food chain. Other costs include attempted treatments as well as preventative measures (vaccinations, supplementary feeding, etc.).

The amount of time spent looking after sick animals is another cost often not taken into account. These hours could otherwise have been invested in healthy animals, with demonstrable returns.

Animals that do not die from botulism are mainly those mildly affected and they can recover with minimal intervention. It will, however, affect their production. It is conceivable that some of the badly affected surviving animals may have an impact on the farming business worse than that of those that die, if one considers cumulative costs of treatment and feeding animals that are not yielding the productivity expected from them. There is a common saying that “dead animals don’t eat, and neither do they have labour and medication costs”.

Other losses include the threat to employment, food security and food safety.

WHEN DOES THE RISK PEAK?

Botulism is common when natural pastures can’t provide animals with the phosphorus they need. As a result, the animals, especially cattle, will develop a tendency to chew bones, and this exposes them to the toxins. Other risk factors that have been identified, include:

■ Vegetable matter, such as decaying grass, hay,

grain or spoiled silage.

■ Small animals dying and decomposing in water tanks and drinking troughs. In the case of high-rise water tanks these carcasses may go unnoticed.

■ Hammermilled rodents in feed. In winter when farmers use supplemenatry feed, small rodents that may have died inside feed bales may be hammermilled and distributed as the feed.

■ Small animals, like tortoises, snakes and lizards, may not be able to escape during veld fires and end up being burnt. Their carcasses may be consumed by cattle.

■ Feeding out chicken litter can pose a botulism risk, especially where broiler litter is used. This litter often contains fragments of decomposing chicken carcasses, which increases the risk of botulism infection.

HOW CAN I PREVENT OR MINIMISE LOSSES?

Treatment: Treatment is often not succesful, apart from the administration of hyperimmune serum aimed at the toxin type involved, unless used in the very early stages of the disease. The

cost of treatment may also be too expensive. Correction of the phosphorus

deficiency: Feeding supplementary phosphorus will eliminate the need to chew bones, but also have an overall productivity benefit for animals, especially young, rapidly growing animals, and pregnant females.

Removal of the source: Carcasses should be safely disposed of to prevent the consumption of bones. Bulk water tanks must be covered, where possible. Should bird carcasses accidentally end up in the water, they must be removed immediately before they decompose, and where feasible the water must be drained and replaced with clean water.

VACCINATION

Vaccination against botulism is critical in cases where exposure is inevitable. It is also advisable for animals that are fed chicken litter to be adequately vaccinated before the chicken litter is fed. A booster dose of the botulism vaccine is extremely important. It is often recommended that animals on chicken litter should be vaccinated on a frequent basis, for example every six months.

It is important to handle vaccines correctly before use. This includes maintaining the cold chain, protection from sunlight and working as hygienically as possible. Inject only on clean, dry skin to minimise the risk of infections that may compromise the animals’ health.

It is generally believed that healthy animals have the greatest chance of benefitting from vaccines. This means paying careful attention to the nutritional state of animals before vaccination. This is especially important when winter arrives.

It is often recommended that nutritional needs of animals be met, including trace mineral supplementation, to give the animals’ immune system the best possible chance of benefitting from vaccines administered.

Speak to your local veterinarian or animal health technician regarding basic vaccination programs that can help make a difference in your operation.

Dr Sello Maboe is the technical and marketing manager at Onderstepoort Biological Products. You are welcom to email him at sello.maboe@ obpvaccines.co.za