Hookworm infection (ancylostomiasis) is an infection of the intestines that can cause an itchy rash, respiratory and gastrointestinal problems, and eventually chronic blood loss and iron deficiency anemia.
About 1.3 billion people are infected with hookworms, which are intestinal roundworms. The infection is most common in tropical areas where sanitation is poor. Hookworms thrive in warm, moist places. Two species of hookworm cause infection in people: Ancylostoma duodenale and Necator americanus. Both species are present in tropical areas of Africa, Asia, India, and China. Ancylostoma duodenale is present in the Middle East, North Africa, southern Europe, and Japan. Necator americanus is present in Central and South America. It once was common in the southern part of the United States but is now rare there.
Eggs are passed in stool and hatch in the soil after they incubate for 1 to 2 days. Larvae emerge and live in the soil. When fully developed, the larvae can penetrate the skin. A person can become infected by walking barefoot or sitting in contaminated soil. Once larvae enter the body, they move through the lymphatic vessels and the bloodstream to the lungs. The larvae pass into the air spaces of the lungs and move up the respiratory tract. They are coughed up into the throat and swallowed. About a week after penetrating the skin, they reach the intestine. Once inside the intestine, the larvae develop into adults. They attach themselves by their mouth to the lining of the upper small intestine, where they suck blood and produce substances that keep blood from clotting.
Symptoms and Diagnosis
Many people with hookworm infection do not have symptoms. However at the start of infection, an itchy, red, raised rash (ground itch) may develop where the larvae penetrate the skin. The movement of the larvae through the lungs can cause fever, coughing, and wheezing. When adult worms first attach in the intestine, they can cause pain in the upper abdomen, loss of appetite, diarrhea, and weight loss. Over time, anemia develops as blood is lost and people become iron deficient. Children with severe anemia may not grow normally. Severe anemia may also cause heart failure and widespread tissue swelling.
The diagnosis is made by identifying hookworm eggs in a sample of stool. Stool should be examined within several hours after defecation. Blood tests for anemia and nutritional deficiencies, particularly iron, are also done.
A doctor prescribes albendazole, mebendazole, or pyrantel pamoate, taken by mouth. Because of possible adverse effects to the fetus, these drugs cannot be taken by pregnant women. Iron supplements are given to people with anemia.
Last full review/revision March 2007 by Richard D. Pearson, MD