Botulism is a rapidly fatal motor paralysis. It is caused by ingestion of toxin of Clostridium botulinum in food. Many species of domesticated, wild animals and birds suffer from this disease. The disease arises from ingestion of preformed toxin present in food and not from the establishment of an infection.The causative organism is Cl. botulinum which proliferates only in decaying animal or plant material under favourable conditions. The organisms are extremely resistant and survive for long periods. The toxin also remains for long period. On the basis of toxins strains of Cl. botulinum are identified as belonging to types A, B, C, D, E, or F. T he usual habitat of organisms is soil and alimentary tract of herbivores. Contamination of soil and water occurs from faeces and decomposing carcass. The toxins of Cl. botulinum are neurotoxins which produce functional paralysis and the animal dies of respiratory paralysis.
Transmission: Decomposing animal carcasses are the commonest source of toxin.Proliferation of organism also occurs in decaying vegetable matter.
Symptoms: In cattle and horses signs usually appear 3-7 days after the animals gain access to toxic material. Peracute cases die without prior signs of illness. The characteristic clinical picture is one of progressive muscular paralysis affecting the muscles of limbs, jaw and throat. Affected animals lie in sternal recumbence with head on the ground or turned into the flank. The tongue gets paralysed and hangs from the mouth. The animal is unable to chew or swallow and saliva drools. Paralysis of chest muscles results in abdominal type respiration.Sheep do not show typical flaccid paralysis. There is stiffness in walking,incoordination and some excitability in initial stages. In the terminal stages there is abdominal respiration, limb paralysis and death. Among poultry, the ingestion of fatal doses of toxin gives rise to the disease known as duck sickness or limberneck inchicken. Limberneck derives its name from paralysis of neck muscles because of birds eating the larvae of blowflies that have fed upon contaminated carcasses. The main symptoms in poultry are paralysis of the wing, legs, neck and protrusion of nictitating membrane, Birds become comatose.
Lesions: There are no specific lesions. Endocardial and subepicardial haemorrhages, and congestion of intestines are present. Perivasicular haemorrhages in the brain may be present.
Diagnosis: The disease can be diagnosed by detecting toxin in the suspected food stuff, intestinal contents or serum of affected animals.
Prophylaxis: The immunization of animals is not widely practised. In certain places where special risks exist, the animals are given 2 injections of toxoid at an interval of several weeks. Specific or polyvalent antitoxic serum may be used in very early cases. In range animals correction of dietary deficiency by feeding protein and phosphorus may be undertaken. Hygienic disposal of carcasses is advisable.