Infections with Taenia species tapeworms are a significant risk to humans. They are typically associated with ingestion of undercooked beef and pork. The most important human pathogen is Taenia saginata, the beef tapeworm, and Taenia solium, the pork tapeworm. Dogs can occasionally act as intermediate hosts, and therefore do not develop infection or shed eggs. A variety of Taenia species can be found in dogs, of which T. multiceps is of greatest relevance in humans.
Taenia multiceps is a tapeworm, which inhabits the small intestine of dogs and other canids (foxes, wolves, and jackals), making these definitive hosts a widespread infection reservoir. The coenurus (larva of T. multiceps) parasitizes the central nervous system (CNS) of sheep, occasionally goats, deer, antelopes, chamois, rabbits, hares and horses, and less commonly, cattle. It frequently causes the death of infected animals, and can lead to huge economic losses of sheep/goats. The parasite can also cause zoonotic infections in humans, leading to serious pathological conditions in humans, which occur more commonly than previously assumed.1
The segments (proglottids) of T. multiceps are discharged from infected dogs and are ingested by intermediate hosts, including humans, especially in rural grazing areas where people raise sheep or other ungulates, and keep guard dogs in close proximity) through contaminated food or water. The proglottids then penetrate the intestinal mucosa and blood vessels. After reaching the brain through the bloodstream, they will take 2–3 months to grow into a coenurus causing increased intracranial pressure. This will lead to the onset of clinical signs, such as ataxia, hypermetria, blindness, head deviation, headache, stumbling and paralysis. After some weeks animals die from starvation.
Taenia crassiceps tapeworms are intestinal parasites of carnivores (final hosts), mostly foxes and dogs, in North America, Europe, and Russia. Rodents are natural intermediate hosts that harbor the cyst-like larvae (metacestodes, cysticerci) in their body cavities or under skin, where the larvae spread by budding. Prevalence among foxes in Germany and Lithuania is high, 24% and 26.4%, respectively. Although humans rarely serve as intermediate hosts, an increasing number of zoonotic infections have emerged in recent years.2 Human ocular infection by Taenia crassiceps occurs when individuals accidentally ingest eggs in contaminated food or water, causing severe anterior uveitis, orbital cystic tumor-like masses, and lesions. The onset of inflammation results in a red and painful eye, followed by development of glaucoma, retinal fibrosis, and ultimately blindness as the final result of the infection. Surgical removal of accessible cysts is the only choice to cure the infection 3
Can Helminths Cause Epilepsy?
Only a few helminths cause CNS symptoms, some cause seizures, but few are associated with epilepsy. Neurocysticercosis (parasitic disease of the nervous system caused by T. solium (pork tapeworm), is the best known, since it appears to be an important cause of epilepsy in South and Central America, where it is estimated to account for 30% of seizures in some areas. In neurocysticercosis the parasite appears to pass through four phases in the brain. The initial vesicular phase is characterised by larva inside translucent liquid-filled cystic structures surrounded by a thin membrane. The larva can remain viable for months to years, and do not appear to elicit an immune reaction in the brain, nor appear to cause of symptoms. The cyst degenerates, passing through a transitional stage in which edema occurs around the cyst. These stages may be associated with clinical manifestations, such as seizures, but in many people this stage is asymptomatic. Thereafter the cyst dies, either disappearing or becoming an inactive calcified nodule. These calcified lesions appear to be inert, yet if occur in certain parts of the brain in a susceptible individual may produce seizures.4
- Detailed Transcriptome Description of the Neglected Cestode Taenia multiceps
- Cerebellar Cysticercosis Caused by Larval Taenia crassiceps Tapeworm in Immunocompetent Woman, Germany
- Zoonotic helminths affecting the human eye
- Do Helminths cause Epilepsy?