Botulism is a disease caused by the toxin produced by the bacteria Clostridium botulinum. Although instances of botulism affecting humans are rare, the C. botulinum spores are common in the soil, rivers, and sea water sediment, and in the gut of many healthy animals.
Under specific conditions, the C. botulinum spores will grow and rapidly multiply, producing a deadly toxin in the process. This toxin is believed to be the most poisonous natural toxin known to humans. It is this toxin which leads to signs of disease and eventually death in people, birds, and other animals. Once produced, the toxin is able to persist for months in the environment. Likewise, spores of the bacterium can survive in the environment for over 30 years waiting for the right conditions to grow and multiply.
The disease cannot be transmitted by contact. When the toxin is ingested it produces the symptoms of botulism, or occasionally ingested spores may grow in the gut of an animal and produce the toxin internally. The onset of the disease is often rapid, and symptoms may pass unnoticed. The toxin binds to the nerve endings and leads to paralysis of muscles. Animals affected by botulism may die suddenly or develop a slowly progressive paralysis and die within days. The initial symptoms in ruminants are slobbering and the inability to swallow. This is followed soon after by weak and wobbly movements, collapse and eventually death.
Treatment of botulism in cattle and sheep is practically impossible. Occasionally, slightly affected animals recover but most animals that are showing signs of muscle paralysis die from asphyxiation (suffocation). The severity of the disease and the time taken until death, is directly proportional to the amount of toxin absorbed.
The botulinum organisms belong to the same family of bacteria as those responsible for tetanus, gangrene, enterotoxaemia, black disease, and blackleg. Like all clostridial organisms, Cl. botulinum needs anaerobic (airless) conditions in which to reproduce and is sensitive to pH, light, and temperature. Cl. botulinum types C and D, the ones responsible for botulism in Tasmania, may grow in decaying animal or vegetable matter. Cattle can be affected from chewing on old bones, a sign of phosphorus deficiency. A common source of vegetable-initiated botulism in livestock is turnips. Calves seem particularly susceptible, whereas horses are more resistant to the toxin than other species.
Botulism in domestic poultry, especially ducks, is common, as there are many places in yards and duck ponds for the bacteria to multiply. Duck and fowls affected by botulism usually die quickly. If clinical signs are observed, “Limberneck”, the inability to raise or control the head, is a classic sign to look for. Diarrhoea may also be symptom.
Laboratory diagnosis of botulism is challenging and therefore clinical signs and history are important indicators. Tests can potentially find the toxin in gut contents, blood of affected animals and feedstuffs. Cattle that survive may also have antibodies to the toxin. Outbreaks of botulism are difficult to predict but, if a property has a history of botulism, it could pay to discuss the merits of vaccination with your veterinarian. Other prevention measures include ensuring pests are prevented from dying in stored feed and water sources, along with ensuring cattle have adequate phosphorous in their diet. It is important to remember that it is illegal in Australia to feed poultry litter or animal matter to cattle. It is also illegal to use poultry litter as fertilizer, unless it has been ploughed into the soil or given time to break down before animals are allowed to graze.
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