Strongyloidiasis: Comprehensive Guide To Diagnosis & Treatment

Revised: January 2026

What is strongyloidiasis?

Strongyloidiasis is a human infection caused by the nematode (roundworm) Strongyloides stercoralis. This soil-transmitted helminth is unique due to its ability to complete its entire life cycle within a single host through autoinfection, allowing chronic infections that can persist for decades without symptoms. Transmission primarily occurs when filariform larvae in contaminated soil penetrate intact skin, often affecting bare feet in tropical and subtropical regions.

Globally, an estimated 30–100 million people are infected, predominantly in Southeast Asia, sub-Saharan Africa, Central and South America, and Oceania. In immunocompetent hosts, infections are often asymptomatic or mild, but in those with immunosuppression—such as from corticosteroids, HIV, or malignancies—hyperinfection syndrome or disseminated disease can occur with mortality rates approaching 90%.

Who gets strongyloidiasis?

Individuals at risk include:

• Residents or travelers to endemic tropical and subtropical areas, particularly those walking barefoot on soil contaminated with human faeces.
• Immigrants or refugees from endemic regions.
• Immunocompromised patients, especially those on corticosteroids for conditions like COPD or asthma.
• Veterans or military personnel from endemic areas during World War II or Vietnam.

Chronic carriage is common in up to 75% of cases with mild eosinophilia, and autoinfection enables lifelong persistence without reinfection.

What causes strongyloidiasis?

The causative agent is Strongyloides stercoralis, a small intestinal nematode measuring 2–3 mm in length as an adult female. Key features of its life cycle include:

• Free-living cycle: Rhabditiform larvae in faeces develop into free-living adults in soil, producing filariform larvae that infect humans.
• Parasitic cycle: Filariform larvae penetrate skin, migrate via bloodstream to lungs, ascend trachea, are swallowed, and mature in the small intestine.
• Autoinfection: Rhabditiform larvae in the intestine become filariform, reinfecting the host directly, perpetuating chronic infection.

This autoinfective cycle distinguishes it from other helminths and underlies hyperinfection in immunosuppression.

What are the clinical features of strongyloidiasis?

The clinical spectrum ranges from asymptomatic chronic infection to life-threatening hyperinfection.

Acute strongyloidiasis

Initial skin penetration causes localised pruritic erythematous rash. Larval migration through lungs induces tracheal irritation and dry cough. Gastrointestinal entry leads to abdominal pain, diarrhoea, constipation, or anorexia.

Chronic strongyloidiasis

Often asymptomatic, but symptomatic cases feature:

• Gastrointestinal: Epigastric pain, heartburn, intermittent diarrhoea/constipation, rarely massive haemorrhage or ulcerative colitis-like presentation.
• Cutaneous: Chronic urticaria; larva currens—a pathognomonic fast-moving (up to 10 cm/hour) serpiginous urticarial rash on buttocks, thighs, perineum.
• Other: Mild peripheral eosinophilia (up to 75%), elevated IgE; rare arthritis, malabsorption, nephrotic syndrome.

Hyperinfection syndrome and disseminated strongyloidiasis

Triggered by immunosuppression (e.g., corticosteroids), leading to massive larval proliferation. Mortality nears 90%. Manifestations include:

• Gastrointestinal: Pain, nausea, vomiting, diarrhoea, ileus, obstruction, ulceration, haemorrhage, bacterial sepsis.
• Pulmonary: Cough, dyspnoea, wheezing, pneumonitis, respiratory failure, infiltrates on chest X-ray.
• Neurological: Meningitis, larvae in CSF.
• Systemic: Gram-negative sepsis, SIADH, hypoalbuminemia, absent eosinophilia.
• Cutaneous: Diffuse petechiae, purpura, recurrent larva currens.

Larvae carry gut bacteria, causing secondary infections in lungs, meninges, or bloodstream.

How is strongyloidiasis diagnosed?

Diagnosis is challenging due to intermittent shedding and low sensitivity of single tests. Multiple methods are recommended.

Serology

Most sensitive (85–95%) using ELISA for anti-Strongyloides IgG. Preferred screening in non-endemic areas; cross-reactivity with filariasis possible.

Microscopy

Examine faeces for rhabditiform larvae (safranin stain aids identification). Use concentration techniques (Baermann, formol-ether); repeat 3x due to low yield. Duodenal aspirate or biopsy more sensitive.

Other

• Sputum/blood BAL for larvae in hyperinfection.
• PCR emerging but not routine.
• Eosinophilia supportive but absent in dissemination.

What is the treatment for strongyloidiasis?

Ivermectin is first-line: 200 µg/kg/day orally for 2 days. Repeat if persistent larvae. Alternatives: albendazole 400 mg BID x 7 days (less effective).

• Hyperinfection: Ivermectin 200 µg/kg/day until sputum/faeces negative x 2 weeks; consider subcutaneous if poor absorption.
• Immunosuppression: Reduce steroids cautiously; screen/treat before.
• Follow-up: Serology/microscopy at 3–6 months.

Cure rates >90% with ivermectin in immunocompetent; lower in hyperinfection.

What is the outcome for strongyloidiasis?

Immunocompetent: Excellent with treatment; autoinfection allows recurrence without retreatment in some. Hyperinfection: High mortality if untreated, improved with early ivermectin and immunosuppression reduction. Relapse common; long-term follow-up essential.

How can strongyloidiasis be prevented?

• Wear shoes in endemic areas.
• Sewerage treatment to break transmission.
• Screen/treat immigrants, immunocompromised from endemic areas.
• No vaccine; mass treatment not standard due to autoinfection.

Related topics

• Soil-transmitted helminths
• Larva currens
• Hyperinfection syndrome
• Strongyloides serology

Frequently Asked Questions

What does larva currens look like?

A rapidly advancing (10 cm/hr) itchy, serpiginous urticarial rash on thighs/buttocks due to dermal larval migration.

Is strongyloidiasis contagious?

No direct person-to-person; soil contamination required.

Who should be screened?

Endemic exposure + eosinophilia, immunosuppression, or GI symptoms.

Can strongyloidiasis cause sepsis?

Yes, larvae translocate gut bacteria causing gram-negative bacteraemia in hyperinfection.

Is ivermectin safe in pregnancy?

Avoid in first trimester; data limited.

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Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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