Ancylostoma duodenale is a species of the worm genus Ancylostoma. It is a parasitic nematode worm and commonly known as Old World hookworm. It lives in the small intestine of hosts such as humans, cats and dogs, where it is able to mate and mature. Ancylostoma duodenale and Necator americanus are the two human hookworms that are normally discussed together as the cause of hookworm infection. They are dioecious. Ancylostoma duodenale is abundant throughout the world, including in the following areas: southern Europe, north Africa, India, China, southeast Asia, some areas in the United States, the Caribbean, and South America.
Ancylostoma duodenale is small cylindrical worm, greyish-white in color. It has two ventral plates on the anterior margin of the buccal capsule. Each of them has two large teeth that are fused at their bases. A pair of small teeth can be found in the depths of the buccal capsule. Males are 8 mm to 11 mm long with a copulatory bursa at the posterior end. Females are 10 mm to 13 mm long, with the vulva located at the posterior end; females can lay 10,000 to 30,000 eggs per day. The average lifespan of Ancylostoma duodenale is one year.
When a filariform larva (infective stage) penetrates the intact skin, the larva enters the blood circulation. It is then carried to the lungs, coughed up, and swallowed back into the small intestine. The larva later matures into an adult in the small intestine and female worms can lay 25,000 eggs per day. The eggs are released into the feces and reside on soil. Embryonated eggs on soil will hatch into juvenile 1 stage (rhabditiform or noninfective stage) and mature into filariform larvae. The filariform larvae can then penetrate another exposed skin and begin a new cycle of infection.
Ancylostoma duodenale is prevalent in southern Europe, northern Africa, India, China, and southeast Asia, small areas of United States, the Caribbean islands, and South America. This hookworm is well known in mines because of the consistency in temperature and humidity that provide an ideal habitat for egg and juvenile development. It is estimated 1 billion people are infected with hookworms. Transmission of Ancylostoma duodenale is by contact of skin with soil contaminated with larvae.
Light infection causes abdominal pain, loss of appetite and geophagy. Heavy infection causes severe protein deficiency or iron deficiency anemia. Protein deficiency may lead to dry skin, edema and potbelly, while iron deficiency anemia might result in mental dullness and heart failure.
The eggs of Ancylostoma duodenale and Necator americanus cannot be distinguished. Larvae cannot be found in stool specimen unless they are left at ambient temperature for a day or more.
Education, improved sanitation and controlled disposal of human feces are important. Wearing shoes in endemic areas can reduce the prevalence of infection as well.
Ancylostoma duodenale can be treated with albendazole, mebendazole and benzimidazoles. Pyrantel pamoate is an alternative. In severe cases of anemia, blood transfusion may be necessary.
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- Ancylostoma duodenale image library at DPD