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Nematodes Symptoms

Nematodes are various types of roundworms--parasites that mature and live in the intestines. The eggs and larvae are often expelled in the stool and live in the soil. You can become infected by eating contaminated food or touching the mouth with contaminated hands. Some nematodes can penetrate the skin, especially if you walk barefoot in contaminated soil. The most common symptoms are gastrointestinal, but nematodes may also cause allergic reactions, lung and heart symptoms.

  1. Roundworm (Ascaris lumbricoides)

    • Roundworms can be 15 to 35 cm long. Most infections occur from contaminated food or hands. The eggs hatch and enter the circulatory system from the small intestines and travel to the lungs and other organs. Roundworms migrate up the throat, and you swallow them, returning them to the small intestines. You may develop a cough (sometimes coughing up large worms) shortness of breath and abdominal discomfort. Sometimes large clumps of worms cause intestinal blockage, with abdominal pain and distention following.

    Cod or Herring Worms (Anisakis simplex)

    • Cod or herring worms are small worms ingested in raw or pickled seafood. Larvae attach to the mucosal lining of the stomach. About 12 hours after eating seafood (sushi, sashimi, ceviche), you may develop abdominal pain and symptoms similar to food poisoning. Usually the worms are eliminated from the system in about three weeks, but some people develop chronic infections with gastric lesions causing severe pain, requiring surgical removal of the nematodes.

    Pinworms (Enterobius vermicularis)

    • Pinworms (Enterobius vermicularis) are 5 to 10 mm long. After you ingest the eggs, the pinworms feed on the mucosal lining in the cecum (near the rectum). The female lays eggs outside the anus in the perineal area, causing itching. When you scratch, you contaminate your fingers, which can transmit the eggs to your mouth. You might have mild symptoms, such as nausea, abdominal discomfort, anal itching and restlessness. Females can get a urinary infection from worms migrating into the bladder. Worms can also migrate up the vagina and into the peritoneal cavity.

    Hookworms (Ancylostoma duodenale and Nectar americanus)

    • Hookworms (Ancylostoma duodenale and Nectar americanus) are 7-12 mm long. They live in the small intestines and lay eggs that are expelled in the stool. Larvae develop in contaminated soil and can be swallowed inside contaminated food or they can even penetrate the skin. The larvae enter the circulatory system and go to the heart and lungs, from which they are coughed up and then swallowed, going to the small intestines, where they live on blood. You might have itching where the larvae entered or develop a rash. You might also have heartburn, shortness of breath, enlarged heart and pulse irregularities. Over time, you will develop symptoms of malnutrition from loss of protein and iron or anemia from blood loss. Children may even experience retarded growth.

    Threadworms (Strongyloides stercolis)

    • Threadworms are about 2 mm long and live in the mucosal lining of the small intestines. The larvae burrows into the skin on contact, entering the circulatory system, which carries them to the lungs, from which the worms are coughed up and swallowed. Most infections are asymptomatic, but you might develop an itching rash about the buttocks and waist, a cough or vague abdominal discomfort and diarrhea.

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