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Worms and Helminths

Intestinal helminth infestations most commonly affect travelers, migrant laborers, refugees, children of foreign adoptions, and the homeless. These parasitic infections are associated with day care centers and overseas travel.

Clinical evaluation

Intestinal helminth infections are usually asymptomatic, but serious infections may cause symptoms ranging from abdominal discomfort to severe pain. Anorexia nausea, diarrhea, pruritus, rectal prolapse, bowel obstruction, and death may occur. Hives and eosinophilia may develop.

Enterobiasis

The pinworm (Enterobius vermicularis) is the most common helminth. Pinworms present as anal pruritus in irritable children. The disorder tends to occur in temperate climates. Many patients are asymptomatic. Heavier infections may cause insomnia, restlessness, vulvovaginitis, loss of appetite, and intractable anal itching.

Pinworms are about 10 mm in length. The female worm has a pin-shaped tail. At night, worms migrate through the anus, then deposit their eggs and die on the perianal skin.

Pinworms are best diagnosed by examining the perianal skin. The stool is usually negative for ova and worms. To obtain the eggs, a tongue blade covered with clear tape is placed sticky-side down.

The elongate, colorless eggs measure 50 to 60 Fm and are flattened on one side. Worms may also be visualized if the anus is examined late at night.

Treatment

Mebendazole ( Vermox), one 100-mg tablet orally, is safe and effective. A second dose is given 10 days later.

Infested clothing and bedding are washed and fingernails should be kept trimmed, and the perianal area kept clean. Dogs and cats.

Ascariasis

Roundworms ( Ascaris lumbricoides) measure up to 18 inches in length. The infection is fairly common in the rural southeastern United States and is frequent among immigrants.

Ascaris eggs reach the soil in feces, and they may persist in the soil for more than a decade until they are accidentally consumed. In the gut, worms may cause intestinal obstruction.

Treatment

Mebendazole ( Vermox), 100 mg bid.

Trichuriasis

Whipworm ( Trichuris trichiura) infestation is less common than Ascaris infestation.

Treatment of trichuriasis is the same as for ascariasis.

Less common parasites

Hookworms

Hookworms develop in the soil from eggs in feces. The larvae are capable of penetrating the bare feet.

Strongyloidiasis

Filariform larvae are capable of penetrating intact skin, persisting for 40 years or more in the small intestine. It can also be spread in feces or as a sexually transmitted disease.

Tapeworms

Beef tapeworm is transmitted by inadequately cooked beef, reaching up to 10 to 15 feet in length in the gut. Diagnosis is made by passage of ribbon-like tapeworm segments from the rectum.

Pork tapeworm is far more dangerous than T. saginata since its eggs can cause cysticercosis, the invasion of human tissue by developing larval forms. In severe cases, the larvae may invade.

Dwarf tapeworm is the most common tapeworm in the U.S. This tapeworm is 1 inch in length. Ingestion of food contaminated with mouse droppings may spread the infection. H. nana infection.

Fish tapeworm is occasionally transmitted by undercooked fish.

Treatment of all tapeworms consists of praziquantel ( Biltricide) or niclosamide ( Niclocide).