Botulism can be transmitted through the ingestion of infected feed or through the deposition of botulism spores into a deep wound. When the rout of transmission is through ingestion, the condition is commonly called “forage botulism”, while transmission through a wound is commonly called “wound botulism”. In foals botulism presents an especially serious condition that is called “ ”.
Predisposition includes horses that eat haylage or silage. Foals are most susceptible.
The clinical presentation of the disease includes symmetric, motor neuron paralysis that starts in the hind quarters and progressively moves cranially to affect the forelimb, neck and head. Other symptoms include myasthnea, dysphagia, inability to eat or drink, inability to lift the head, tail or eyelids, ileus, recumbency and sudden death due to asphyxiation. Botulism is diagnosed through the isolation of spores in feces, serology and through the necropsy of a infected by blood transfusion from the animal being treated. Treatment of botulism poisoning is difficult and . If the disease is caught before paralysis sets in it is possible to administer botulism antitoxin, however the cost is prohibitive for most horse owners. Antibiotics can be given both systemically and locally in the case of wound botulism if it is caught early on. Supportive care including IV fluids, catheters, slings, and artificial airways should be provided if necessary. Prognosis for individuals infected with botulism is poor to grave and there is almost total in recumbent individuals. Care should be taken when feeding horses silage, haylage, round bales wrapped in plastic or tightly packed round bales as the anaerobic environment provided in these types of forage is ideal for the replication of botulism bacteria.
Equine Protozoal Myeloencephalitis (EPM)
Equine Protozoal Myeloencephalitis (EPM) is caused by
, a
sporocyte forming protozoan.
The
is thought to be the definitive host for S. neurona , though other omnivores
such as raccoons and skunks may also be a reservoir of disease.
Horses are infected with EPM through the ingestion of feed or water infected by sporocytes of S. neurona . Feed becomes infected when opossums defecate on or near forage or water sources. The horse then ingests this feed or water introducing the sporocytes into the digestive tract where they mature into . The protozoa then move through the intestinal wall into the blood stream, where they travel to the CNS. Once inside the CNS the protozoa form in the tissue of the spinal cord, where they go through a phase of dormancy. These cysts cause an inflammatory reaction in the spinal cord and cause of the surrounding nerve tissue and blood vessels. Ischemia, inflammation and compression all impair the function of the motor neurons found within the spinal cord. The motor neurons of the limb are
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