Ancylostomiasis

Ancylostomiasis
ICD-10	B76.0
ICD-9	126.9
eMedicine	ped/96
MeSH	D000724

Ancylostomiasis (also anchylostomiasis or ankylostomiasis) is a hookworm disease caused by infection with Ancylostoma hookworms. The name is derived from Greek ancylos αγκυλος "crooked, bent" and stoma στομα "mouth."

Ancylostomiasis is also known as miner's anaemia, tunnel disease, brickmaker's anaemia and Egyptian chlorosis. Helminthiasis may also refer to ancylostomiasis, but this term also refers to all other parasitic worm diseases as well. In the United Kingdom, if acquired in the context of working in a mine, the condition is eligible for Industrial Injuries Disability Benefit. It is a prescribed disease (B4) under the relevant legislation.§

Ancylostomiasis is caused when hookworms, present in large numbers, produce an iron deficiency anemia by sucking blood from the host's intestinal walls.

Signs and symptoms

In children (or adults) who walk barefoot, the hookworm can penetrate the sole of the foot and cause a lesion. The larva will then begin to mature while it moves towards the intestines. As in dogs, the hookworm will attach to the intestinal wall. Humans who have become infected will show symptoms of intestinal bleeding, abdominal pains, anemia, severe diarrhea and malnutrition.

As mentioned earlier larval migrans or as it is also known, creeping eruption, is also a very uncomfortable symptom of this disease, and can also be caused by invasion of hookworms from other animals such as cats and dogs. Because they are in an abnormal host they do not mature to adults but instead migrate through the skin until killed by the host's inflammatory response. This causes local intense itching. Topical treatment with thiabendazole ointment is very effective in controlling this condition.

Causes

The infection is usually contracted by persons walking barefoot over contaminated soil. In penetrating the skin, the larvae may cause an allergic reaction. It is from the itchy patch at the site of entry that the early infection gets its nickname "ground itch". Once larvae have broken through the skin, they enter the bloodstream and are carried to the lungs (unlike ascarids, however, hookworms do not usually cause pneumonia). The larvae migrate from the lungs up the windpipe to be swallowed and carried back down to the intestine. If humans come into contact with larvae of the dog hookworm or the cat hookworm, or of certain other hookworms that do not infect humans, the larvae may penetrate the skin. Sometimes, the larvae are unable to complete their migratory cycle in humans. Instead, the larvae migrate just below the skin producing snake-like markings. This is referred to as a creeping eruption or cutaneous larva migrans.

Diagnosis

They commonly infect the skin, eyes, and viscera in humans.

• Ancylostoma brasiliensis causes cutaneous larva migrans.

• Toxocara causes visceral larva migrans.

Prevention

Control of this parasite should be directed against reducing the level of environmental contamination. Treatment of heavily infected individuals is one way to reduce the source of contamination (one study has estimated that 60% of the total worm burden resides in less than 10% of the population). Other obvious methods are to improve access to sanitation, e.g. toilets, but also convincing people to maintaining them in a clean, functional state, thereby making them conducive to use.

Epidemiology

Hookworms still account for high proportion of debilitating disease in the tropics and 50-60,000 deaths per year can be attributed to this disease.

Treatment

The drug of choice for the treatment of hookworm disease is mebendazole which is effective against both species, and in addition, will remove the intestinal worm Ascaris also, if present. The drug is very efficient, requiring only a single dose and is inexpensive, the perfect drug. However, treatment requires more than giving the anthelmintic, the patient should also receive dietary supplements to improve their general level of health, in particular iron supplementation is very important. Iron is an important constituent of a multitude of enzyme systems involved in energy metabolism, DNA synthesis and drug detoxification.

An infection of N. americanus parasites can be treated by using benzimidazoles, albendazole, and mebendazole. A blood transfusion may be necessary in severe cases of anemia. Light infections are usually left untreated in areas where reinfection is common. Iron supplements and a diet high in protein will speed the recovery process. In a case study involving 56-60 men with Trichuris trichiura and/or N. americanus infections, both albendazole and mebendazole were 90% effective in curing T. trichiura. However, albendazole had a 95% cure rate for N. americanus, while mebendazole only had a 21% cure rate. This suggests albendazole is most effective for treating both T. trichiura and N. americanus.

Gallery

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  Unstained micrograph of the Ancylostoma duodenale hookworm's mouth parts; Mag. 125X. From Public Health Image Library (PHIL).

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  This enlargement shows hookworms, Ancylostoma caninum attached to the intestinal mucosa. From Public Health Image Library (PHIL).

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  Micrograph depicting the tail tip of a Strongyloides filariform infective stage larvae on the left, and a hookworm on the right. From Public Health Image Library (PHIL).

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  This micrograph depicts a hookworm (Lt), and a Strongyloides (Rt) filariform infective stage larvae. From Public Health Image Library (PHIL).

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  This child with hookworm shows visible signs of edema, and was diagnosed with anemia as well. From Public Health Image Library (PHIL).

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  The human hookworms include two nematode (roundworm) species, Ancylostoma duodenale and Necator americanus. From Public Health Image Library (PHIL).

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  Diagram depicting the various stages in the life cycle of the Strongyloides stercoralis nematode. From Public Health Image Library (PHIL).