Strongyloidiasis

How is it transmitted?

Contamination occurs through direct skin contact with soil contaminated by parasite larvae. The thread-like larvae actively penetrate intact skin, most often on bare feet. Transmission via the digestive tract (ingestion of contaminated water or food) is also possible but less frequent. There is no direct person-to-person transmission.

What are the at-risk areas?

Strongyloidiasis is endemic in tropical and subtropical regions, but cases are regularly diagnosed in Quebec, mainly in people who have traveled to or immigrated from at-risk areas. The populations most affected are:

• People who have lived in or traveled to Sub-Saharan Africa, Southeast Asia, Central or South America, or certain regions of the Caribbean
• Immigrants and refugees from endemic areas, sometimes infected for many years without knowing it
• War veterans who have stayed in humid tropical areas
• People living in precarious sanitary conditions with frequent exposure to contaminated soil
• Agricultural workers in regular contact with potentially contaminated soils

What are the symptoms?

The clinical presentation varies considerably depending on the immune status of the infected person. Three clinical forms are distinguished:

Larva currens: characteristic sign

Larva currens is a pathognomonic skin manifestation of chronic strongyloidiasis. It presents as a rapidly progressing, erythematous, and pruritic serpiginous (snake-like) track on the skin, primarily on the buttocks, perineum, and lower extremities. This track spontaneously resolves within a few hours to days, then reappears during new episodes of auto-infection. Its presence in a patient who has traveled to a tropical area is highly suggestive of the diagnosis.

Who is particularly at risk of severe illness?

Hyperinfection and dissemination occur almost exclusively in people with weakened immune systems. High-risk situations include:

• Long-term corticosteroid treatment, even at moderate doses
• HTLV-1 virus infection, which specifically impairs anti-parasitic immunity
• Solid organ or bone marrow transplantation with immunosuppression
• HIV infection with advanced immunodeficiency
• Malignant hematological diseases treated with chemotherapy
• Immunosuppressive biologic treatments (anti-TNF and related)

How is it diagnosed?

The diagnosis of strongyloidiasis is often delayed due to its non-specific clinical presentation. Several complementary examinations are used, with varying sensitivities:

• Blood count: hyper-eosinophilia (increase in eosinophils) frequent but inconsistent, often the first clue pointing towards the diagnosis
• Stool parasitological examination: detection of larvae in stool, but limited sensitivity due to intermittent shedding; multiple samples on different days increase sensitivity
• Anti-Strongyloides serology: most sensitive test for screening, recommended in at-risk individuals even if asymptomatic
• Stool PCR: increasingly available technique, high sensitivity and specificity
• Duodenal aspiration or Bermann capsule: reserved for cases difficult to confirm by standard methods

What treatments are available?

Effective antiparasitic treatments exist and can eliminate the infection in the vast majority of cases. The choice of treatment, its duration, and post-treatment follow-up are determined by the doctor based on the clinical presentation and the patient's immune status. Parasitological monitoring after treatment is recommended to confirm recovery, especially in immunocompromised individuals. Disseminated forms require specialized medical care.

How to prevent infection?

• Wear closed-toe shoes in risk areas, especially in humid and tropical environments.
• Avoid bare skin contact with the ground in endemic areas.
• Follow food hygiene measures when traveling to tropical areas
• Consult a doctor for screening upon returning from a prolonged stay in an endemic area, even in the absence of symptoms.
• Report any history of tropical travel to your doctor before starting immunosuppressive treatment.

Where to consult in Quebec?

Clinique Omicron offers medical consultations and health check-ups at its service points in Quebec. If you have traveled to a tropical or subtropical area and are experiencing digestive or skin symptoms, or unexplained eosinophilia, our healthcare professionals can initiate the appropriate diagnostic work-up and refer you to specialized resources if necessary.

The content of this page is provided for informational purposes only and is not intended to replace the advice of a qualified healthcare professional. Consult a physician for any symptoms, questions or decisions you may have regarding your health.