The symptoms of an infection vary based on the type of infections. The smaller roundworms can be asymptomatic, but they can often cause abdominal pain, fatigue due to iron deficiency, anemia and diarrhea. Strongyloides can penetrate the intestinal wall which allows intestinal bacteria to enter the blood stream which can cause severe systemic infection. Pinworms can cause itching around the rectal area. If the worm becomes large, intestinal obstruction may occur.
Amazingly, the large tapeworms often are asymptomatic. They can live for months in the intestine without the host's knowledge of a problem. When symptoms occur, it is usually weight loss and nutritional deficiencies.
The tapeworms that we hear about belong to the Taenia species. Taenia solium is found in pig meat and Taenia saginata is found in cattle. The organism is made of rectangular segments that form a chain. The organism attaches itself to the intestinal wall and each segment is capable of absorbing nutrients and reproducing. An infected individual may pass these segments in the stool. Each segment is about the size of half of a postage stamp. As the organism grows, it can reach 7 meters in length. The Taenia solium eggs can enter the body and form cysts in various places of the body, a condition known as cysticercosis.
The diagnosis of intestinal worms is made primarily by inspection of the stool. Often the eggs or the segments of the tape worm can be seen in the stool. The small worms known as pinworms can be seen by direct visualization. Treatment usually consists of oral medications such as mebendazole or niclosamide. The parasites are quite sensitive to these medications and treatment is usually straightforward. The best method to protect oneself from infection is to cook meat to recommended temperatures. Try to avoid ingesting soil that may have been contaminated by human or animal feces.
Likelihood of Infection
Fortunately, intestinal parasites and worms are uncommon in the United States. For those who travel to exotic locations or spend long periods of time in the wilderness, however, extra precautions such cooking food well, ensuring that water is fit to drink and cleaning well are prudent strategies to avoid infection.
A huge "thank you!" to Peter C. Smith, M.D. Board Certified Internal Medicine, Big Thompson Medical Group, Loveland, Colorado for addressing the makes-your-skin-crawl issue of intestinal parasites.