by Alison Bowler

Created on: April 30, 2009   Last Updated: October 15, 2010

There are many different types of intestinal parasitic worms capable of infecting humans. The types of symptoms they produce will differ not only from worm to worm but also from person to person. The lack of symptoms does not mean that you do not have worms, as asymptomatic cases frequently occur with all types of worm infection.

Infections in man occur with cestode worms (also known as flat worms or tapeworms) and by nematode worms (also known as round worms). As the transmission routes for many of these worms are similar, concurrent infection with two or more types of intestinal worm frequently occur.

Dwarf tapeworm.

This is the smallest of the tapeworms to infect man. It is also the most commonly diagnosed. Infection with the dwarf tapeworm, Hymenolepis nana, occurs after the ingestion of tapeworm eggs in contaminated food or water. The adult worms are about 2 inches long.

When symptoms occur, they include loss of appetite, nausea, diarrhea, weakness and abdominal pain. Young children may have headaches and suffer from lack of sleep with this infection. Children will often complain of having an itchy bottom.

Confirmed diagnosis requires the microscopic examination of a fecal sample for tapeworm eggs.

The beef and pork tapeworms

The beef tapeworm, Taenia saginata, and the pork tapeworm, Taenia solium, use man as a host to the adult worm and cattle or pigs as hosts for the juvenile or larval form. Infections with these worms occur after eating undercooked or raw meat from an infected animal. Adult T. solium worms are 3 to 6 feet long while T. saginata adults are 12 to 25 feet long.

The symptoms seen are similar to those seen in infections with H. nana. In addition, patients may show signs of malnutrition owing to malabsorption of food. They may also have an increase in appetite.

The adult worm sheds segments full of eggs. These segments are white and about half an inch long. Tapeworm segments seen in the feces are often the first indication of the presence of a tapeworm in asymptomatic individuals.

Laboratory examination of a fecal sample will show the presence of microscopic eggs.

Occasionally human-to-human infection occurs with the pork tapeworm. A person ingesting eggs from fecal contamination of food or water develops cysticercosis. The larval form of T. solium forms cysts within the tissues of its host. Most infections are asymptomatic. However, cysts within the brain cause neurocysticercosis with symptoms including changed mental status, headache,

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