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Chapter 7

Taeniasis, Cysticercosis, Sparganosis, Other Tapeworm Infections

 

Taeniasis and Cysticercosis

The literature on tapeworms and the larval stage of Taenia solium, the cysticercus, is considerable and venerable. Aristophanes mentions the parasite in one of his plays, written about 400 B. C.; cerebral cysticercosis was discussed by Ramier in 1558. The first radiological report identifying the calcified larval cysts of Taenia solium appeared in the 1890s, but it was another 50 years before an adult Taenia saginata was recognized in a small bowel series.

There are many myths about tapeworms, which is not surprising since they are the longest worms to parasitize man, extending in some patients to a length of 30 feet. Some African tribes believe that it is necessary to have a tapeworm to ensure virility. We have been unable to trace any reports to confirm this; on the contrary, the worms may cause ill health and debility. The remedies and cures that have been devised and offered for elimination of the worm are almost as mythical, yet tapeworms are far from being an endangered species; they live in millions of people all over the world. At some stage in their life cycles, either alive or dead, both T. solium and T. saginata may have clinical significance, and their radiological recognition becomes important to the patients and their physicians.

By far the most important of these tapeworm infections is cysticercosis, caused by the larval stage of T. solium, the pork tapeworm. The larval stage begins after the ingestion of eggs passed in feces by the adult worm. These larvae, or cysticerci, develop in various body tissues with an affinity for muscles and the central nervous system (neurocysticercosis), where the most significant clinical manifestations appear, with no age predilection. T. solium infection is endemic in parts of Asia, India, Africa, Europe, and Latin America. Until recent years, there were only sporadic cases in the United States. However, due to increased immigration from Central America and travel to endemic areas, cysticercosis is on the rise in the United States, especially in California, Arizona, New Mexico, Texas, and Colorado. An understanding of the epidemiology, pathophysiology, and current laboratory and imaging methods, including computed tomography (CT) and magnetic resonance imaging (MRI) is needed to accurately diagnose neurocysticercosis. Imaging manifestations of the different types and stages of neurocysticercosis are reviewed in a separate section below, providing important information for the management of this infection.


Synonyms

Tapeworm: Taenia saginata. Taenia solium. Beefworm. Porkworm. Sp: Taenia saginata/solium. Fr: Taenia inerme/arme. Ger: Taenia saginata/solium.

Cysticercosis: Sp: Cisticercosis. Fr: Cysticercose. Ger: Blasenwurmkrankheit.


Definition

Taeniasis is infection of man by the beef tapeworm, Taenia saginata, or the pork tapeworm, Taenia solium. Other species of tapeworms which infect humans are described at the end of this chapter.

Cysticercosis is infection by the larval stage of the pork tapeworm, T. solium. (There is no acceptable report of infection of man by the larval stage of T. saginata.)


Geographic Distribution

The beef tapeworm, Taenia saginata, is found in Latin America, Africa, Russia, Asia, and throughout the Moslem world. It is said to be "universal" in Ethiopia. It is estimated that about 40 million persons are infected worldwide.

The pork tapeworm, Taenia solium, is a parasite of humans and pigs. It is less common, infecting about 3 million people, and is likely to be rare in Islamic (Moslem) and Jewish communities. It is most common where raw or insufficiently cooked pork is eaten. Infected pigs are common in Central and South America (especially Mexico, Venezuela, and Chile), in Portugal and Eastern Europe, Russia, Manchuria, China, India, Pakistan, Madagascar, and parts of Africa, especially West Africa. It is sometimes thought that the parasite is called "T. solium" because there is usually only one adult worm in a patient, but in fact it is given this name because the rostellum (the hook-bearing part of the scolex) resembles the conventional image of the sun. Although in many patients the adult worm is solitary, as many as 11 worms have been found in one person. In southern Africa, up to 50% of those infected have two worms. Mixed infections with both species of Taenia can occur.

Cysticerci are commonly found in cattle or pigs, but they occur also in cats, rats, monkeys, dogs, giraffes, buffalos, lamas, and some antelopes.
Although of common origin, taeniasis and cysticercosis are clinically and radiologically two quite separate diseases and will be discussed individually.

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