Botulism is a neuromuscular disease of great importance to cattle worldwide. It is caused by neurotoxins produced by seven different strains of a spore-producing anaerobic bacteria called Clostridium botulinum. The two strains that affect cattle are types C and D. Botulinum toxin is a protein that C. botulinum secretes, which causes muscle paralysis by blocking the presynaptic release of the neurotransmitter acetylcholine.
C. botulinum is of the Clostridium genus, which are the same organisms responsible for tetanus, enterotoxaemia (pulpy kidney), black leg, black disease, and malignant odema (gas gangrene). It is a spore forming bacterium that thrives in decaying animal or plant material, able to rapidly produce its highly lethal toxin into the surrounding environment.
Cattle are one of the most susceptible animals to the toxic compounds produced by C. botulinum. The botulinum toxin can be absorbed through wounds infected with the bacteria or from the gastrointestinal tract after ingestion of feed contaminated with the bacteria or preformed toxin. Ingestion of spores that develop into bacteria and colonize the gut can also cause the production and absorption of the toxin. Hay can also be contaminated with the bacteria during the raking and baling process.
The botulism bacteria grows on food sources which are above a pH of 4.5 and that are in an anaerobic (non-oxygen) environment. Cattle are one of the most susceptible species.
Clinical signs of infection usually occur between 3 to seven days following ingestion of the toxin.