The nematodes Ancylostoma duodenale (Old World hookworm) and Necator americanus (New World hookworm).
Ancylostoma ceylanicum, hookworm of dogs, causes a similar disease and is in some areas common also in humans.
Distribution
The most common helminthiasis throughout tropical and subtropical regions and also endemic in Southern Europe.
A. duodenale: Mediterranean countries, Iran, India, Pakistan, the Far East
N. americanus: North and South Americas, Middle America, Indonesia, Pacific islands, parts of India
A. ceylanicum: India, Southeast Asia, tropical Australia, Pacific Melanesian islands
Over 500 million people are estimated to be infected.
Transmission
Adult worms live in the small intestine. The eggs land in the soil through faeces. There, larvae hatch out and can penetrate through intact human skin, most commonly into the feet. The consumption of vegetable matter may also allow the larvae to penetrate the buccal mucous membranes.
The larvae that have entered the body are transported in blood through the heart into the lungs. They exit the circulation and penetrate into the pulmonary alveoli about 8-21 days after the infection and climb along the airways to pharynx, and they are finally swallowed. They develop in the small bowel into adult worms that attach to the intestinal wall and cause mucosal bleeding. In an untreated person the worms die within 1-2 years.
A. duodenale can enter the body also through oral route.
Signs and symptoms
Usually asymptomatic. Local irritation, termed ground itch, and rash may occur at the site of the skin invasion. Minor cough or laryngeal irritation, and more rarely asthmatic symptoms, lung infiltrates and eosinophilia may occur during the lung migration phase.
When the worms migrate into the small intestine, symptoms resembling those of a duodenal ulcer may develop, i.e. burning upper abdominal pain or intermittent diarrhoea or vomiting and nausea. The principal complication resulting from hookworm infection is anaemia.
Diagnosis, treatment and prevention
Identification of eggs in a faecal sample. Eggs are found in the faeces only weeks after the infection (N. americanus 8 weeks, A. duodenale 38 weeks)
Notice! The currently available test for detecting nucleic acids of parasites is not suitable for diagnostics of helminthiases, since it covers only some protozoa.
Mebendazole is used for treatment; the dose for adults and children over two years of age is 100 mg twice daily for 3 days.
Mebendazole may only be available under special license in some countries.
Albendazole 400 mg once daily for 3 days taken on an empty stomach can be used as an alternative (the dose is 200 mg once daily for 3 days for children under the age of 2 years). Albendazole is somewhat more effective than mebendazole.
Albendazole may require a special licence in some countries.
Mebendazole or albendazole should not be used during pregnancy, or at least during the first trimester, even though teratogenicity has not been established. They may be used whilst breast feeding.
To ensure a parasitologic cure, the stool examination should be repeated after 3 weeks.
Drug therapy is effective. Reinfection is common in endemic regions.
The cornerstones of prevention are good toilet hygiene, use of footwear, clean drinking water and food, as well as treating infected individuals.