Merck Manual

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Professional Version

Cestodes Causing CNS Disease in Animals


Jan Šlapeta

, MVDr, PhD, GradCertEd (Higher Ed), Sydney School of Veterinary Science, The University of Sydney

Reviewed/Revised May 2022 | Modified Nov 2022

Coenurosis in Animals

Taenia multiceps multiceps is an intestinal parasite of canids (especially dogs, foxes, and jackals) and occasionally humans. Intermediate hosts include sheep, goats, deer, antelope, chamois, rabbits, hares, horses, and less commonly cattle; all of which acquire tapeworm eggs while grazing. After ingestion, some oncospheres hatch and reach the brain, developing by endogenous budding into a metacestode (larval) stage known as Coenurus cerebralis. Initial invasion and development of the oncospheres may cause acute suppurative meningoencephalitis. The fully developed coenurus may be 5–6 cm in diameter and cause increased intracranial pressure, producing ataxia, hypermetria, blindness, head deviation, stumbling, and paralysis. This clinical condition is colloquially known as gid, sturdy, or staggers. In sheep, palpation of the skull caudal to the horn buds may reveal rarefaction; surgery to remove the cyst, including its wall, has a fair outcome and is justified in valuable animals. Dogs living with sheep and other production animals should not be fed the brain or spinal cord from infected animals and should be dewormed regularly.

Cysticercosis in Animals

Taenia solium is a tapeworm that may infect humans, affecting the small intestine. Its metacestode (larval) stage, a cysticercus, is a large fluid-filled cavity or vesicle found in the musculature of pigs. This larval stage was once regarded as a separate parasite, and it still retains the scientific name Cysticercus cellulosae. In humans, this larval stage usually develops in subcutaneous sites and musculature but may be found in nervous tissues, eg, the brain and ocular tissues. Infection in humans results from ingestion of tapeworm eggs in contaminated foods or as a result of poor hand hygiene. In the brain, the parasite usually develops in the ventricles. Infection causes pain, epileptiform seizures, locomotor disturbances, paralysis, and possibly death. The larval cysticerci commonly localize on the meninges and in the neuropil. Treatment of cysticercosis in humans is by means of surgical removal of the lesion; however, the prognosis is poor.

Echinococcosis in Animals

Echinococcus granulosus is a tapeworm found in the small intestine of the canid definitive host. Its eggs are ingested by the intermediate hosts, wild and domestic herbivores such as sheep, cattle, and moose. Humans can also serve as intermediate hosts. After hatching in the intestine of the intermediate host, the oncospheres invade the circulatory system and lodge in various organs (the liver and lungs), where they develop into large, thick-walled, unilocular hydatid cysts that bud protoscolices endogenously. Hydatids have been rarely reported in the CNS of domestic animals and are rare in humans, in which they produce symptoms similar to those of a brain tumor.

Foxes are the definitive host for a related species, Echinococcus multilocularis. Microtine rodents (such as voles) are the intermediate hosts. This parasite has been found rarely in the brain of humans post-mortem, in which the invasive, thin-walled multilocular hydatid cysts produce innumerable exogenous daughter cysts that bud protoscolices. Surgical intervention may be successful in removing unilocular hydatid cysts of E granulosus.

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