Ankylostomidosis: ankylostomiasis, necatoriasis: causes, symptoms, diagnosis, treatment

Ancylostomiasis is a geohelminthiasis. Adult helminths parasitize in the duodenum and jejunum of humans.

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The development cycle of ancylostomiasis

Humans become infected with ancylostomiasis and necatoriasis when invasive (filariform) larvae penetrate the skin, for example when walking barefoot. Infection with ancylostomiasis can occur when swallowing hookworm larvae found in water or on vegetables and fruits.

When the larvae penetrate the skin, their further development occurs with migration. The larvae migrate through the venous system to the right ventricle of the heart, then to the lungs, enter the alveolar cavity, move into the pharynx, oral cavity and are swallowed a second time. The larvae pass through the esophagus into the stomach and then end up in the small intestine. Five to six weeks after the larvae penetrate the skin, migrate and molt twice, they become sexually mature helminths. After this period, eggs can be found in the feces.

In northern areas of ankylostomiasis with a pronounced change of seasons, there are strains of ankylostoma whose larvae may not develop for 8 months. Then they continue and complete their development. Due to this, the eggs are released into the external environment at the time most favorable for their development.

When hookworm larvae enter through the mouth, migration does not occur. The larvae immediately end up in the intestines.

The lifespan of hookworms is 7-8 years, and that of necators is up to 15 years.

Epidemiology of ancylostomiasis, hookworm, necatoriasis

About 25% of the world's population is infected with ancylostomiasis. This disease is most often found in areas with poor sanitation. Ancylostomiasis is a disease common on all continents within 45° N and 30° S. About 900 million people in the world are affected by ancylostomiasis, and about 450 million new cases of the disease are registered annually. Most often, these diseases are found in tropical and subtropical countries. Ancylostomiasis foci are found in South and Central America, Africa, Hindustan, Indochina and on the islands of the Malay Archipelago. Ancylostomiasis is found in the Caucasus, Turkmenistan, and Kyrgyzstan. Necatoriasis is registered on the Black Sea coast of the Krasnodar Territory, on the border with Abkhazia. Mixed foci of necatoriasis and ancylostomiasis are known in Western Georgia and Azerbaijan.

The source of infection is an infected person releasing eggs into the external environment.

The female hookworm releases 10-25 thousand eggs per day, and the hookworm releases 5-10 thousand. The eggs enter the soil with feces. The development of larvae occurs at a temperature of 14 to 40 °C. For the development of hookworm larvae, 85-100% humidity is needed, and for the hookworm - 70-80%. The larvae require access to free oxygen; at 0 °C, they can remain viable for no more than a week. Under favorable conditions, rhabditiform larvae develop in the eggs after 1-2 days. They have two bulbi in the esophagus. These larvae are non-invasive. 7-10 days after molting, the larvae become filariform. They have a cylindrical esophagus. After the second molt, the filariform larvae become invasive. The larvae can freely move in the soil vertically and horizontally.

The main factor of pathogen transmission is soil contaminated with eggs and larvae of helminths. Human infection occurs most often as a result of penetration of filariform larvae through the skin (percutaneously) when walking barefoot. Transplacental and transmammary routes of infection are also possible. Sometimes infection occurs orally when eating the meat of rabbits, lambs, calves, pigs, as well as vegetables, fruits and water contaminated with invasive helminth larvae.

Epidemic foci of ancylostomiasis are formed in humid tropics, and necatoriasis - in countries with a subtropical climate of the humid type. Intensive foci of ancylostomiasis can be formed in mines, where in conditions of high humidity and high temperatures, larvae are able to develop quickly.

What causes hookworm disease?

Ancylostomiasis includes two helminthiases: ancylostomiasis, caused by the hookworm of the duodenum - Ancylostoma duodenale, and necatoriasis, caused by the hookworm - Necator amencanus.

These helminths are similar in morphology, development cycles and effects on the body. The body of nematodes is pinkish-yellowish in color, small in size. The female hookworm of the duodenum is 10-13 mm long, and the male is 8-10 mm. The length of the female hookworm is 9-10 mm, and the male is 5-8 mm. The anterior end of the body of the hookworm is bent to the ventral side, and in the hookworm - to the dorsal side. The head end has a mouth capsule, with the help of which the helminths attach to the wall of the small intestine. The capsule of the hookworm has four ventral and two dorsal cutting teeth, and in the hookworm - two cutting plates.

Males have a bell-shaped enlargement of the cuticle (genital bursa) at the tail end. In hookworm, it is larger and wider than in hookworm.

The eggs of hookworms and hookworms are indistinguishable in structure. They are oval in shape, covered with a smooth, thin, colorless membrane, and measure 66 x 38 µm. Freshly hatched eggs contain 4-8 blastomeres.

Pathogenesis of ancylostomiasis, ankylostomiasis, necatoriasis

The pathogenesis of ankylostomiasis is different in the early and chronic stages. In the early stage, the larvae migrate through the organs and tissues of the host, cause allergic reactions, and have a sensitizing effect on the body. Along the migration path of the larvae, as in ascariasis, the respiratory tract tissues are injured, eosinophilic infiltrates are formed, and hemorrhages occur. The duration of the early stage is 1-2 weeks. The intestinal (chronic) stage begins after the completion of migration and penetration of the larvae into the duodenum. With the help of cuticular teeth, the larvae attach to the mucous membrane, injure blood vessels, secrete anticoagulants and cause severe bleeding. Ankylostomes are hematophages: per day, one hookworm consumes 0.16-0.34 ml of blood, and a hookworm - 0.03-0.05 ml. Ulcers form at the sites of attachment of ankylostomids. Intensive invasion by helminths contributes to the development of hypochromic anemia.

Symptoms of hookworm, hookworm, necatoriasis

There are three clinical phases of ancylostomiasis.

The first phase is associated with the penetration of larvae through the skin. This phase is accompanied by the development of dermatitis (papulo-vesicular rash). Neutrophilic infiltration of connective tissue with the presence of lymphoid and epithelioid cells and fibroblasts is noted in the skin. The rash disappears after 10-12 days. With repeated infections, urticaria and local edema develop.

In the second (migration) phase of the disease, cough, hoarseness, shortness of breath, and fever sometimes appear. The number of eosinophils in sputum and blood increases, focal pneumonia, bronchitis, tracheitis, and laryngitis occur.

The third, intestinal phase is long-term and chronic. The first symptoms of ankylostomiasis are gastrointestinal tract dysfunctions that appear 30-60 days after infection. Symptoms of ankylostomiasis depend on the number of parasites. The mild form is almost asymptomatic.

Unpleasant sensations in the epigastric region are possible. By the end of the 12th month, duodenitis develops with nausea, loss of appetite and abdominal pain.

The severe form leads to significant blood loss and is accompanied by chronic iron deficiency anemia, shortness of breath, lethargy, developmental delay, edema, diarrhea with blood and mucus in the feces, loss of albumin, leading to myocardial damage and cardiac dysfunction.

In black patients, skin depigmentation occurs due to iron deficiency and hypoalbuminemia.

In case of ankylostomia invasion, the invasion develops faster and reaches a higher degree than in case of necator invasion.

Complications of hookworm infection

Ancylostomiasis may be complicated by decompensated anemia.

Diagnosis of hookworm

Differential diagnostics of ancylostomiasis is carried out with other intestinal helminthiases, and in the case of anemia development - with anemias of other etiologies.

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Laboratory diagnostics of ancylostomiasis

The diagnosis of "ancylostomiasis" is made when eggs are found in feces or duodenal contents. When examining feces, flotation methods are used (according to Fulleborn - after 15-20 minutes, according to Kalantaryan - after 10-15 minutes). Diagnosis of ancylostomiasis is carried out by a special method of Harada and Mori - culturing larvae in a test tube on filter paper. Epidemiological and clinical data are taken into account when making a diagnosis.

Treatment of ancylostomiasis, hookworm, necatoriasis

Treatment of ankylostomiasis involves the use of the following drugs:

• albendazole (nemozole) - adults and children over 2 years old 400 mg once;
• mebendazole (vermox, antiox) - adults and children over 2 years old 100 mg twice a day for 3 days (600 mg per course);
• carbendacim (medamin) - for adults and children at a rate of 10 mg/kg/day in three doses for 3 days;
• pyrantel (helmintox) - 10 mg/kg (maximum 750 mg for adults and children over 12 years old) per day once for 3 days in a row.

If anemia develops, iron and folic acid preparations are prescribed. To monitor the effectiveness of treatment, 3 fecal studies are carried out one month after deworming with an interval of 30 days.

How to prevent hookworm, ancylostomiasis, necatoriasis?

Hookworm infections can be prevented by identifying and treating patients, sanitary and hygienic measures aimed at protecting the environment from faecal contamination, disposal of waste, wearing shoes in disease hotspots, observing personal hygiene rules, and washing vegetables and fruits before eating.