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Author: Daniel Jun Yi Wong, Medical Student, University of Melbourne, Australia, 2013.
Taeniasis is an infection caused by a particular tapeworm called Taenia. There are 32 recognised species of Taenia, but only 3 appear to affect humans, these include Taenia saginata, T. solium, and T. asiatica.
Taeniasis occurs when an individual eats contaminated, undercooked or raw meat, usually beef, where cattle are infected with T. saginata, or pork, where pigs are infected with T. solium and T. asiatica.
Most individuals with taeniasis do not show any signs or symptoms of tapeworm infection. However, some people may have gastrointestinal symptoms such as abdominal pain, weight loss, poor appetite, and upset stomach. Sometimes, individuals with taeniasis can see tapeworm segments (called proglottids) being passed through the anus and in the stool.
Taeniasis can lead to urticaria, an itchy rash of weals and hives.
Humans with taeniasis pass eggs or proglottids in the stool which can contaminate pastures. Cattle or pigs become infected with these eggs or proglottids when ingesting contaminated vegetation. The tapeworm eggs hatch and migrate to the muscles of infected pigs or cattle. They develop into larvae called cysticerci. Humans then become infected by eating raw or undercooked beef or pork containing these cysticerci. The larvae attach to the intestinal wall and develop into mature tapeworms, which then produce on average 50,000 eggs per day.
Tapeworm infection is maintained by poor food preparation practices, as well as the continuous infection of pigs and cattle by feeding on vegetation contaminated by tapeworm eggs.
Cysticercosis is a condition where tapeworm larvae move outside of the intestine and infect other organs and tissues such as the brain, eye, or heart. It is caused by ingestion of T. solium eggs from contaminated pork. Subcutaneous nodules affect about half of the patients with cysticercosis.
Involvement of the brain can cause seizures and other central nervous system problems and occurs in about 60-90% of cases. This condition is called neurocysticercosis.
Taeniasis is diagnosed by finding taenia eggs when examining the stool under the microscope. Taenia eggs can be detected 2 to 3 months following infection. The proglottids can also be seen and may indicate a species-specific diagnosis.
Biopsy of a subcutaneous nodule or radiological imaging may detect the cysts of cysticercosis.
Taeniasis is treated with praziquantel. The dose may vary depending on the particular type of tapeworm infection. This drug works by affecting the parasite's structure and leads to paralysis of the tapeworm so that the human body can clear the infection. If praziquantel is not available, niclosamide is a suitable alternative.
Cysticercosis may be treated with antihelminthics such as praziquantel and albendazole. Treatment can result in inflammatory reactions so requires caution and consideration of the use of systemic corticosteroids and anticonvulsants.
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