Botulism on the Farm
Although instances of botulism affecting humans are rare, it is a common disease of animals and birds. Botulism occurs in animals or birds in some areas of Tasmania.
Botulism is not an infectious disease even though it is caused by bacteria. The bacterium Clostridium botulinum abounds in nature and, under certain conditions, multiplies rapidly producing a deadly toxin in the process - it is said to be the most poisonous known biological substance.
A feature of the toxin is its ability to survive naturally for long periods, sometimes for years. Likewise, spores of the bacterium can survive in the environment for over 30 years.
When the toxin is ingested with food, it produces the symptoms of botulism. However, unless the same food has been shared by another person, or another animal, with the same effect, a diagnosis may be difficult.
The disease cannot be transmitted by contact.
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. It also requires the right environment. In the case of Cl. botulinum types C and D, the ones responsible for botulism in Tasmania, this includes decaying animal or vegetable matter.
Before the use of superphosphate on farms was widespread, and even occasionally today, carcase-initiated botulism resulted from stock chewing old bones while attempting to satisfy their craving for phosphorus.
A common source of vegetable-initiated botulism in livestock is turnips. Calves seem particularly susceptible and sometimes seem to possess an ability to locate the odd dangerous turnip in a whole paddock full of safe ones.
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.
The onset of the disease is rapid and symptoms may pass unnoticed, a dead animal being the first indication of an attack. The initial symptoms in ruminants are slobbering and the inability to swallow. This is followed soon after by ataxia and death.
Treatment of botulism in cattle and sheep, once the disease strikes, is practically impossible. Occasionally, slightly affected animals recover but they usually die from asphyxia after an ascending muscle paralysis, the rate of which is proportional to the quantity of toxin absorbed. Horses are more resistant to the toxin.
Botulism in domestic poultry, especially ducks, is fairly common. There are also many places in yards and duck ponds for the bacteria to multiply. Usually ducks and fowls affected by botulism die quickly. Occasionally there are signs of paralysis beforehand to give a clue. This is very characteristic and has given rise to the name 'Limberneck' for the disease in poultry, because paralysed neck muscles make it impossible for the bird to raise or control its head. Diarrhoea is also a symptom.
Despite the rapid advances of modern science, it is practically certain that botulism will persist. Care is important at all times.
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