Botulism is a rapidly fatal motor paralysis caused by ingestion of the toxin produced by Clostridium botulinum types A-G. The spore-forming anaerobic organism proliferates in decomposing animal tissue and sometimes in plant material. Etiology:
Botulism is in most cases an intoxication, not an infection, and results from ingestion of toxin in food. There are seven types of C botulinum, differentiat
ed on the antigenic specificity of the toxins: A, B, C1, D, E, F, and G. Types A, B, and E are most important in people; C1 in most animal species, notably wild ducks, pheasants, chickens, mink, cattle, and horses; and D in cattle. In horses, the most common type in North America and Europe is type B (>85% of USA cases), and in the western USA type A has been reported in only two outbreaks, both in people, known to have been caused by type F. Type G, isolated from soil in Argentina, is not known to have been involved in any outbreak of botulism. The usual source of the toxin is decaying carcasses or vegetable materials such as decaying grass, hay, grain, or spoiled silage. Like tetanus toxin, botulinum toxin is a zinc-binding metalloprotease that cleaves specific proteins in synaptic vesicles. Motor neuron surface receptors vary for the different botulinum toxins, explaining some of the species differences in susceptibility to the different toxins. The exact incidence of botulism in animals is not known, but it is relatively low in cattle and horses, probably more frequent in chickens, and high in wild waterfowl. Probably 10,000–50,000 birds are lost in most years, with losses reaching 1 million or more during the great outbreaks in the western USA. Most affected birds are ducks, although loons, mergansers, geese, and gulls also are susceptible. (Also see Botulism.) Dogs, cats, and pigs are comparatively resistant to all types of botulinum toxin when challenged orally; however, there are recent individual case reports mentioning botulism in dogs. Most botulism in cattle occurs in South Africa and South America, where a combination of extensive agriculture, phosphorus deficiency in soil, and C botulinum type D in animals creates conditions ideal for the disease. The phosphorus-deficient cattle chew any bones with accompanying bits of flesh they find on the range; if these came from an animal carrying type D strains of C botulinum, intoxication is likely to result. Any animal eating such material also ingests spores, which germinate in the intestine and, after death of the host, invade the musculature, which in turn becomes toxic for other cattle. Type C strains also cause botulism in cattle in a similar fashion. This type of botulism in cattle is rare in the USA, although a few cases have been reported from Texas under the name of loin disease, and a few cases have occurred in Montana. Hay or silage contaminated with toxin-containing carcasses of birds or mammals and poultry litter fed to cattle have also been sources of type C or type D toxin for cattle (“forage botulism”). Big bale silage and haylage seem to be a particular risk and result in botulism problems if fermentation fails to produce a low and stable pH (
Botulism is a rare and potentially fatal illness caused by a toxin produced by the bacterium Clostri Toxins of all types have the same pharmacologic action.
