What is strongyloidiasis?

Strongyloidiasis is an intestinal helminth infection caused by Strongyloides stercoralis — unique among parasitic worms in its ability to replicate within the human host (autoinfection), enabling lifelong chronic infection without re-exposure to the parasite in soil. An estimated 600 million people are infected globally, most without symptoms. The critical clinical importance: in immunocompromised individuals, Strongyloides undergoes massive amplification (hyperinfection syndrome) with near-universal fatality if untreated.

How is Strongyloides transmitted?

Infective filariform larvae in soil penetrate intact human skin (primarily feet and lower legs during soil contact — barefoot walking, agriculture, working with soil). From the skin, larvae travel to the lungs (causing transient cough and eosinophilic pneumonitis — Loeffler syndrome), ascend the airways, are swallowed, and mature to adult females in the small intestine. Unlike most other helminths, Strongyloides can also autoinfect the same host — larvae becoming infective while still in the gut, penetrating the gut wall or perianal skin without leaving the host.

Why is hyperinfection so dangerous?

In normal immunity, the autoinfection cycle is kept in check by the immune system — particularly eosinophils and IgE-mediated mechanisms. When immune function is suppressed — particularly by corticosteroids (even short courses, low doses) — the autoinfection cycle accelerates exponentially. Massive numbers of larvae migrate throughout the body, carrying enteric bacteria (Escherichia coli, Klebsiella, Enterococcus) into the bloodstream and CNS — causing Gram-negative sepsis, meningitis and multi-organ failure. Case fatality without prompt ivermectin treatment reaches 50-90%.

Who is at risk of hyperinfection?

Any patient with chronic Strongyloides infection who becomes immunocompromised: corticosteroid users (even relatively short courses — prednisolone ≥20mg/day for ≥4 weeks; sometimes less); organ transplant recipients (especially on tacrolimus/ciclosporin); HTLV-1 infection (profoundly increases risk); lymphoma/leukaemia patients; high-dose chemotherapy recipients. Hyperinfection has occurred from corticosteroids prescribed for asthma, COPD, autoimmune conditions and even from dexamethasone during COVID-19 treatment in unrecognised Strongyloides-infected patients.

How can hyperinfection be prevented?

Pre-immunosuppression screening is the most important preventive strategy: anyone from an endemic area (tropical/subtropical country; parts of Southern/Eastern Europe — Italy, Spain, Romania; US rural Southeast) who is about to receive systemic corticosteroids, transplantation, rituximab, or other significant immunosuppression should be tested with Strongyloides serology (IgG ELISA — most sensitive). If positive, treat with ivermectin (2-day course) before or concurrent with immunosuppression. This simple measure could prevent most hyperinfection deaths globally.

How is strongyloidiasis diagnosed?

Serology: IgG ELISA for Strongyloides (most sensitive — approximately 90%; some cross-reaction with other helminths). Stool examination: direct smear, concentration methods, Baermann funnel technique — less sensitive (multiple stool samples required; larvae not always present). Stool PCR: more sensitive than microscopy. Duodenal aspirate: can find larvae directly. Peripheral eosinophilia: present in most infected patients (but absent in hyperinfection — immune suppression eliminates eosinophilia, a dangerous false reassurance).

How does GMJ News cover strongyloidiasis?

GMJ News covers WHO strongyloidiasis NTD data, hyperinfection cases (particularly in COVID-19 dexamethasone context), pre-immunosuppression screening recommendations, ivermectin treatment evidence and the endemic risk in Eastern Europe. Strongyloidiasis is underrecognised in Georgian clinical practice — patients from rural endemic areas receiving corticosteroids are at risk — relevant to PHIG's infectious disease awareness programme.

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Strongyloidiasis

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

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Strongyloidiasis — caused by the intestinal roundworm Strongyloides stercoralis — is unique among helminth infections in that it can autoinfect the same host indefinitely (autoinfection cycle), causing chronic infection lasting decades; it infects an estimated 600 million people globally with most being asymptomatic or mildly symptomatic (WHO). The critical clinical danger: in immunocompromised patients (corticosteroid users, organ transplant recipients, HTLV-1 infected, lymphoma patients), strongyloidiasis causes hyperinfection syndrome — massive parasite amplification spreading throughout the body, carrying case fatality rates of 50-90% if untreated. Ivermectin is the treatment of choice; pre-immunosuppression screening is an essential preventive strategy.

Key messages

600 million infected — unique autoinfection cycle

Strongyloidiasis infects an estimated 600 million people globally — the only helminth capable of completing its lifecycle inside a single host (autoinfection), enabling chronic infection lasting decades (WHO).

Hyperinfection — 50-90% mortality in immunocompromised

In immunocompromised patients — particularly those receiving corticosteroids — Strongyloides can cause hyperinfection syndrome: massive larval dissemination throughout the body, Gram-negative sepsis and death. Case fatality without treatment is 50-90%.

Pre-immunosuppression screening essential

Every patient about to receive systemic corticosteroids (even short courses), organ transplants, chemotherapy or HTLV-1 infection should be screened for Strongyloides with serology — and treated prophylactically with ivermectin before immunosuppression if positive.

Ivermectin is the treatment of choice

Ivermectin (200 mcg/kg/day for 2 days) is the treatment of choice for strongyloidiasis — achieving cure rates of approximately 95%. In hyperinfection/dissemination: ivermectin continued until larvae are no longer detected; sometimes prolonged. Albendazole is an alternative (less effective).

Often asymptomatic for decades

Most infected people have no or minimal symptoms — mild skin symptoms (larva currens — creeping eruption), intermittent GI discomfort, or peripheral eosinophilia. These are easily overlooked, allowing decades of chronic infection until the patient is immunosuppressed.

Veterans and migrants from endemic areas at risk

People who lived in endemic areas decades ago (tropical/subtropical countries, parts of Southern/Eastern Europe) retain lifelong autoinfection — making strongyloidiasis a consideration in veterans, migrants and refugees from these regions, even years after leaving.

Key statistics

600M

estimated people with strongyloidiasis globally

WHO

50-90%

mortality in untreated hyperinfection

WHO/Clinical

~95%

cure rate with ivermectin

WHO/Cochrane

Decades

chronic infection can persist lifelong (autoinfection)

WHO

2017

year added to WHO NTD list

WHO

Essential

pre-immunosuppression screening for endemic-area exposures

IDSA/WHO

Strongyloidiasis estimated prevalence by region — WHO/GBD

Source: WHO. South/SE Asia and Sub-Saharan Africa carry the majority of the global burden.

Glossary of key terms

Strongyloides stercoralis
WHOA small intestinal nematode (approximately 2mm female) uniquely capable of internal autoinfection — larvae penetrate the gut wall or perianal skin, re-enter the bloodstream and complete their lifecycle within the same host. This allows indefinite infection without re-exposure.

Autoinfection cycle
WHOThe mechanism unique to Strongyloides enabling lifelong infection: rhabditiform larvae in the gut transform to infective filariform larvae → penetrate the intestinal wall or perianal skin → travel via bloodstream to lungs → ascend to airways → swallowed → mature to adult females in the duodenum. In normal hosts, this cycle maintains low-level infection; in immunosuppressed hosts it accelerates catastrophically.

Hyperinfection syndrome
WHO/IDSAMassive amplification of the autoinfection cycle in immunocompromised patients — particularly those on corticosteroids. Huge numbers of larvae disseminate throughout the body (liver, lungs, heart, brain). Larvae carry gut bacteria (Gram-negative bacilli) into the bloodstream → septicaemia, meningitis. Case fatality without treatment: 50-90%.

Larva currens
WHO/DermatologyA characteristic cutaneous manifestation of strongyloidiasis — a rapidly migrating, serpiginous (snake-like), urticarial skin rash caused by filariform larvae migrating rapidly through the skin (up to 5-15cm/hour). Appears on the thighs, buttocks and perianal area. Pathognomonic when present.

Ivermectin for strongyloidiasis
WHO EMLThe drug of choice for strongyloidiasis — 200 mcg/kg/day for 2 days, achieving approximately 95% cure rates. Albendazole (400mg twice daily for 7 days) is an alternative but less effective (approximately 60%). In hyperinfection/dissemination: continued until no larvae detected; sometimes daily until cure confirmed by serial stool examinations or serology.

Eosinophilia
WHO/LaboratoryElevated eosinophils in the peripheral blood — a characteristic finding of strongyloidiasis (and other tissue-invasive helminths). May be the only laboratory abnormality in asymptomatic chronic infection. Persistent unexplained eosinophilia in anyone from an endemic area should prompt strongyloidiasis serology.

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Strongyloidiasis

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