hookworm

hookworm

 [hook´werm]

a parasitic roundworm, found mostly in the southeastern United States, that enters the human body through the skin and migrates to the intestines, where it attaches itself to the intestinal wall and sucks blood for nourishment. The hookworm most common in the United States and Central America is Necator americanus, which literally means “American killer.” It is about 1 cm (half an inch) long, with sharp hooklike teeth and a muscular gullet used in sucking blood. The female, slightly larger than the male, can lay more than 10,000 eggs a day, any one of which can hatch into a larva and invade the human body. Another common hookworm is Ancylostoma duodenale.

Life cycle of a hookworm. From Mahon and Manuselis, 2000.

hookworm disease necatoriasis, ancylostomiasis, or infection with some other type of hookworm. Once fairly common, it is now largely confined to rural or poor areas where modern sanitation is lacking.

Larval hookworms enter the body by burrowing through the skin, usually that of the sole of the foot. The first sign of the disease may appear on the skin as small eruptions that develop into pus-filled blisters; this condition is sometimes called “ground itch.” The hookworms then enter blood vessels and are carried by the blood into the lungs. After they leave the lungs, they propel themselves up the trachea, are swallowed and washed through the stomach, and end up in the intestines. Here, if left alone, they will establish a parasitic relationship, using their host's body as a source of nourishment.

By the time they reach the intestines, about 6 weeks after they entered the body as larvae, the worms are full-grown adults. Each worm now attaches itself by hooked teeth to the intestinal wall, where it sucks its host's blood by contraction and expansion of its gullet. If large numbers of worms are present, they can cause considerable loss of blood and severe anemia. The symptoms include pallor and loss of energy; the appetite may increase. The thousands of eggs laid every day by each female worm pass out of the body in the stool, in which they can easily be seen. If the stool is not properly disposed of, the larvae that hatch from the eggs may infect other persons.

Treatment and Prevention. A nutritious, high-protein diet supplemented by iron is given to relieve anemia and improve health. Drug treatment is with pyrantel pamoate or mebendazole. When left untreated, hookworms can cause not only anemia but also bronchial inflammation and occasionally stunting of growth, mental retardation, and even death. Hookworm infection can be prevented by installation of sanitary toilets or, if that is not possible, by disposal of human feces in deep holes so that the soil with which the human foot comes in contact is not contaminated. Shoes should be worn outdoors to protect the feet from infection.

hook·worm

(huk'wŏrm),

Common name for bloodsucking nematodes of the family Ancyclostomatidae, chiefly members of the genera Ancylostoma (the Old World hookworm), Necator, and Uncinaria, and including the species A. caninum (dog hookworm) and N. americanus (New World hookworm).

hookworm

(ho͝ok′wûrm′)

n.

Any of numerous small parasitic nematode worms of the family Ancylostomatidae having hooklike mouthparts with which they fasten to the intestinal walls and suck the blood of humans and other animals.

hookworm

Parasitology A hematophagous nematode of family Ancylostomatidiae–eg, Old World hookworm–Ancylostoma duodenale and New World hookworm–Necator americanus that sensitizes the penetration site–eg, skin, causing 'ground itch', or lungs–eg, Loeffler syndrome as the worms wiggle through, causing eosinophilia and, due to bloodsucking, anemia Lab Rhabditidiform larvae may be confused with Strongyloides stercoralis; eggs may be confused with Trichostrongylus and Meloidogyne spp. See Ancylostoma duodenale, Necator americanus.

hook·worm

(huk'wŏrm)

Common name for bloodsucking nematodes, chiefly members of the genera Ancylostoma (Old World hookworm), Necator, and Uncinaria, and including the species A. caninum (dog hookworm) and N. americanus (New World hookworm).

hookworm

OLD WORLD HOOKWORM: The anterior end of an adult worm

A parasitic nematode belonging to the superfamily Strongyloidea, esp. Ancylostoma duodenale and Necator americanus. See: illustration

Hookworm Disease

Hookworm eggs deposited on the soil in feces mature into larvae capable of penetrating the skin, esp. the bare skin of the foot. An allergic or inflamed rash may develop at the entry site. The larvae pass from the skin into the venous circulation and travel to the alveolar capillaries of the lungs, up the bronchi and trachea and into the gastrointestinal tract. There they mature, attach to the mucous membrane of the intestine, and begin feeding on host blood. The adults secrete an anticoagulant, which promotes additional bleeding. Eventually, the host develops iron-deficiency anemia. Patients sometimes report nausea, colicky abdominal pain, bloating, and pica. Affected children may suffer growth retardation. The adult worms produce eggs that are excreted in the feces, perpetuating the cycle of infection. The detection of these eggs in the stool provides the basis for diagnosis of the disease.

Treatment

Mebendazole and pyrantel pamoate are used to eradicate the infection. Iron supplements are needed to treat the anemia.

hookworm

a NEMATODE parasite of man that gives rise to anaemia and mental and physical retardation. see ANCYLOSTOMIASIS.

Hookworm

Parasitic intestinal infestation caused by any of several parasitic nematode worms of the family Ancylostomatidae. These worms have strong buccal hooks that attach to the host's intestinal lining.

Mentioned in: Antihelminthic Drugs