Strongyloidiasis - Overview

Strongyloidiasis (Latin: strongyloidosis) is a helminthiasis from the group of intestinal nematodoses, caused by Strongiloides stercoralis and occurring with allergic reactions, and later - with dyspeptic disorders. A person becomes infected when larvae penetrate the skin or when they are swallowed with food.

ICD-10 codes

• B78. Strongyloidiasis.
• B78.0. Intestinal strongyloidiasis.
• B78.1. Cutaneous strongyloidiasis.
• B78.7. Disseminated strongyloidiasis.
• B78.0. Strongyloidiasis, unspecified.

Epidemiology of strongyloidiasis

Humans are the main source of environmental contamination. Humans become infected in most cases as a result of active penetration of larvae through the skin upon contact with contaminated soil (percutaneous route). However, other routes of infection are possible: alimentary (when eating vegetables and fruits contaminated with helminth larvae), water (when drinking water from contaminated water sources). Cases of occupational infection have been described due to violation of safety regulations in laboratories during parasitological studies of patients' feces. In strongyloidiasis, intestinal self-infection and sexual transmission (in homosexuals) are also possible.

Infection usually occurs in spring, summer and autumn. Helminthiasis is more often registered in rural areas, since the risk groups for strongyloidiasis include people who come into contact with soil due to their work. In addition, the risk group also includes parasitological laboratory technicians, people in drug addiction departments, psychiatric clinics and boarding schools for the mentally retarded.

Strongyloidiasis is registered everywhere due to intensive importation from endemic territories - countries of the tropical and subtropical zone (between 45° north latitude and 30° south latitude). Sporadic cases are observed in the temperate climate zone. The highest level of infection of the population is in the CIS countries - in Moldova, Ukraine, Azerbaijan, Georgia.

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What causes strongyloidiasis?

Strongyloidiasis is caused by Strongyloides stercoralis (intestinal eel) - a small dioecious nematode, belongs to the type Nemathelminthes, class Nematoda, order Rhabditida, family Strongyloididae. In the development cycle of S. stercoralis, the following stages are distinguished: free-living and parasitic sexually mature individual, egg, rhabditiform larva, filariform larva (invasive stage). Development occurs without an intermediate host.

Mature parasitic females are 2.2 mm long and 0.03-0.04 mm wide and have a colorless thread-like body tapering toward the anterior end and a conical tail. Free-living females are somewhat smaller: 1 mm long and about 0.06 mm wide. Free-living and parasitic males are the same size (0.07 mm long and 0.04-0.05 mm wide).

Pathogenesis of strongyloidiasis

In the early stages, pathological changes in tissues and organs along the migration routes of larvae are caused by sensitization of the body by the products of helminth metabolism and their mechanical impact. Parasitism of females and larvae causes an inflammatory reaction in the gastrointestinal tract. During migration, larvae can enter the liver, lungs, kidneys and other organs and tissues, where granulomas, dystrophic changes and microabscesses develop. In immunodeficiency states caused by long-term use of glucocorticoids or cytostatics, HIV infection, hyperinvasion and disseminated strongyloidiasis occur. S. stercoralis parasitize the host organism for many years. A long-term asymptomatic course of intestinal invasion is possible, which can quickly reactivate when cellular immunity is suppressed.

What are the symptoms of strongyloidiasis?

The incubation period for strongyloidiasis has not been established.

Strongyloidiasis is divided into acute (early migratory) and chronic stages. In most infected individuals, the early migratory stage is asymptomatic . In manifest cases, the symptom complex of acute infectious-allergic disease predominates during this period of strongyloidiasis. In percutaneous infection, erythematous and maculopapular rashes accompanied by itching appear at the site of larval penetration. Patients complain of general weakness, irritability, dizziness and headache.

How is strongyloidiasis diagnosed?

Strongyloidiasis is diagnosed by identifying S. stercoralis larvae in feces or in duodenal contents using special methods (Berman's method, its modifications, etc.). In case of massive invasion, larvae can be detected in a native smear of feces. In case of generalization of the process, helminth larvae can be detected in sputum, in urine.

Additional instrumental studies (X-ray examination of the lungs, ultrasound, EGDS with biopsy of the gastric mucosa and duodenum) are performed according to clinical indications.

How is strongyloidiasis treated?

Strongyloidiasis is treated with antihelminthic drugs. The drugs of choice are albendazole, carbendacim, an alternative drug is mebendazole.

• Albendazole is prescribed in a daily dose of 400-800 mg (for children over 2 years old, 10 mg/kg per day) in 1-2 doses for 3 days, in case of intensive invasion - up to 5 days.
• Carbendacim is recommended orally at a dose of 10 mg/kg per day for 3-5 days.
• Mebendazole is indicated orally after meals at 10 mg/kg per day in 3 doses for 3-5 days.

What is the prognosis for strongyloidiasis?

Strongyloides has a favorable prognosis in uncomplicated cases when etiotropic therapy is administered in the early stages of the disease. In severe cases, especially those occurring against the background of immunodeficiency, the prognosis is serious.