Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis)
Overview
Plain-Language Overview
Strongyloidiasis is an infection caused by a tiny worm called Strongyloides stercoralis that mainly affects the intestines. This parasite can live in the body for many years, often without causing symptoms, but it can sometimes lead to serious problems. The infection primarily affects the gastrointestinal system, causing symptoms like abdominal pain, diarrhea, and weight loss. In severe cases, the parasite can spread throughout the body, leading to a dangerous condition called disseminated strongyloidiasis. This can cause widespread infection and affect multiple organs, which is especially risky for people with weakened immune systems. The infection is usually acquired by walking barefoot on contaminated soil, where the larvae penetrate the skin.
Clinical Definition
Strongyloidiasis is a parasitic infection caused by the nematode Strongyloides stercoralis, characterized by its unique ability to complete its life cycle within the human host through autoinfection. The core pathology involves chronic infection of the small intestine mucosa, leading to symptoms ranging from asymptomatic carriage to severe gastrointestinal manifestations such as diarrhea, malabsorption, and abdominal pain. The infection can become disseminated, especially in immunocompromised patients, resulting in hyperinfection syndrome with widespread larval migration to organs including the lungs, liver, and central nervous system. This disseminated form carries a high mortality risk due to secondary bacterial infections and sepsis. Diagnosis and management are critical due to the parasite’s ability to persist for decades and cause life-threatening complications.
Inciting Event
Skin contact with soil contaminated by infective filariform larvae initiates infection.
Use of corticosteroids or other immunosuppressants triggers hyperinfection in chronic carriers.
HTLV-1 coinfection alters immune regulation, precipitating disseminated strongyloidiasis.
Travel to endemic regions without prophylaxis or screening can lead to new infection.
Latency Period
Chronic infection can persist asymptomatically for decades due to autoinfection.
Symptomatic disease may develop weeks to months after initial exposure in immunocompetent hosts.
Hyperinfection syndrome typically occurs days to weeks after immunosuppression onset.
Disseminated infection can rapidly progress once immune control is lost.
Diagnostic Delay
Nonspecific symptoms and low parasite load cause false-negative stool exams early in disease.
Lack of awareness in non-endemic areas leads to missed diagnosis in immigrants or travelers.
Eosinophilia may be absent in disseminated disease, misleading clinicians.
Misattribution of symptoms to other gastrointestinal or pulmonary diseases delays testing.
Serologic tests may be unavailable or falsely negative in immunocompromised patients.
Clinical Presentation
Signs & Symptoms
Pruritic serpiginous rash (larva currens) often on the trunk or thighs
Gastrointestinal symptoms including abdominal pain, diarrhea, nausea, and vomiting
Chronic cough or wheezing due to pulmonary larval migration
Weight loss and malabsorption in chronic infection
Sepsis-like syndrome with fever and hypotension in disseminated strongyloidiasis
History of Present Illness
Initial symptoms include pruritic rash at larval penetration sites and transient pulmonary symptoms.
Chronic infection presents with intermittent diarrhea, abdominal pain, and weight loss.
Hyperinfection manifests as worsening gastrointestinal symptoms, cough, and fever.
Disseminated disease causes sepsis, meningitis, and multiorgan failure in immunosuppressed hosts.
History often reveals exposure to endemic areas or recent immunosuppressive therapy.
Past Medical History
Prior immunosuppressive treatment such as corticosteroids or chemotherapy.
History of HTLV-1 infection or other immunodeficiency states.
Previous residence or travel in endemic tropical or subtropical regions.
Chronic illnesses like diabetes mellitus or malignancy that impair immunity.
Prior episodes of unexplained eosinophilia or gastrointestinal symptoms.
Family History
No known heritable genetic predisposition to strongyloidiasis.
Family members may share exposure risk if living in endemic areas.
No familial syndromes associated with susceptibility to Strongyloides stercoralis infection.
Physical Exam Findings
Urticarial rash or serpiginous tracks on the skin, especially at sites of larval penetration such as the feet
Tender abdominal examination with possible distension in disseminated infection
Wheezing or crackles on lung auscultation due to larval migration through the lungs
Lymphadenopathy may be present in disseminated strongyloidiasis
Signs of sepsis or shock in severe disseminated cases
Diagnostic Workup
Diagnostic Criteria
Diagnosis of strongyloidiasis is established by identifying larvae in stool samples using concentration techniques or agar plate culture, which is the gold standard. Serologic testing for Strongyloides-specific antibodies can support diagnosis, especially in chronic or low-burden infections. In cases of suspected disseminated infection, larvae may be found in sputum, bronchoalveolar lavage, or other tissue samples. Eosinophilia is a common but nonspecific laboratory finding. Definitive diagnosis requires demonstration of the parasite or its larvae in clinical specimens.
Pathophysiology
Key Mechanisms
Autoinfection cycle of Strongyloides stercoralis allows persistent infection and potential for hyperinfection syndrome.
Larval migration through the lungs and gastrointestinal tract causes tissue damage and inflammation.
Immunosuppression impairs host control, leading to disseminated infection and widespread larval invasion.
Eosinophilic inflammation occurs in response to larval antigens but may be absent in severe immunocompromise.
Bacterial translocation from gut mucosal disruption can cause secondary gram-negative sepsis.
| Involvement | Details |
|---|---|
| Organs | Small intestine is the main organ affected where adult worms embed and cause malabsorption and diarrhea. |
Lungs are involved during the larval migratory phase leading to cough and pneumonitis in hyperinfection. | |
Skin may show larva currens rash due to migrating larvae beneath the epidermis. | |
| Tissues | Intestinal mucosa is the primary site of larval invasion and adult worm colonization causing local inflammation. |
Pulmonary tissue can be involved during larval migration causing respiratory symptoms in disseminated infection. | |
| Cells | Eosinophils play a key role in the immune response by releasing cytotoxic granules that damage Strongyloides larvae. |
Macrophages participate in phagocytosis and antigen presentation during infection. | |
T helper 2 (Th2) cells orchestrate the immune response by producing cytokines that promote eosinophil activation and IgE production. | |
| Chemical Mediators | Interleukin-5 (IL-5) is critical for eosinophil growth and activation in response to Strongyloides infection. |
IgE antibodies mediate parasite recognition and facilitate eosinophil and mast cell responses. | |
Histamine released by mast cells contributes to inflammation and increased intestinal permeability. |
Treatments
Pharmacological Treatments
Ivermectin
- Mechanism:
Binds to glutamate-gated chloride channels in Strongyloides stercoralis, causing paralysis and death of the parasite.
- Side effects:
Dizziness
Nausea
Rash
- Clinical role:
First-line
Albendazole
- Mechanism:
Inhibits microtubule polymerization by binding to beta-tubulin in the parasite, impairing glucose uptake and leading to energy depletion.
- Side effects:
Hepatotoxicity
Leukopenia
Gastrointestinal upset
- Clinical role:
Second-line
Non-pharmacological Treatments
Supportive care including fluid and electrolyte management to address dehydration and electrolyte imbalances.
Avoidance of immunosuppressive therapies when possible to reduce risk of disseminated infection.
Prevention
Pharmacological Prevention
Ivermectin prophylaxis in high-risk immunosuppressed patients
Albendazole as an alternative prophylactic agent in endemic areas
Pre-transplant screening and treatment to prevent hyperinfection in transplant recipients
Empiric anti-helminthic therapy before initiating immunosuppressive therapy in endemic regions
Non-pharmacological Prevention
Avoidance of walking barefoot in endemic areas to prevent skin penetration by larvae
Improved sanitation and sewage disposal to reduce soil contamination
Screening immigrants and travelers from endemic regions before immunosuppression
Use of protective clothing to limit skin exposure in endemic environments
Health education on hygiene practices to reduce transmission risk
Outcome & Complications
Complications
Hyperinfection syndrome with massive larval dissemination
Disseminated strongyloidiasis involving multiple organs including lungs, CNS, and liver
Gram-negative sepsis due to bacterial translocation from gut
Acute respiratory distress syndrome (ARDS) from larval lung migration
Intestinal obstruction or perforation from severe mucosal damage
| Short-term Sequelae | Long-term Sequelae |
|---|---|
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Differential Diagnoses
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) versus Hookworm infection (Ancylostoma duodenale, Necator americanus)
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) | Hookworm infection (Ancylostoma duodenale, Necator americanus) |
|---|---|
Exposure to soil contaminated with human feces in endemic areas, often with poor sanitation | Exposure to contaminated soil in tropical or subtropical regions with barefoot walking |
Autoinfection cycle with larvae penetrating skin and migrating causing disseminated infection | Adult worms attach to intestinal mucosa causing blood loss and iron deficiency anemia |
Eosinophilia with larvae detectable in stool by agar plate culture or Baermann technique | Iron deficiency anemia with eosinophilia but no larvae in stool |
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) versus Strongyloides hyperinfection syndrome
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) | Strongyloides hyperinfection syndrome |
|---|---|
Chronic asymptomatic or mild infection with intermittent symptoms in immunocompetent hosts | Rapid progression with severe respiratory and gastrointestinal symptoms in immunosuppressed patients |
Occurs in immunocompetent or mildly immunocompromised hosts without fulminant dissemination | Occurs mainly in patients with impaired cell-mediated immunity (e.g., corticosteroids, HTLV-1) |
Low larval burden with intermittent stool positivity | High larval burden in sputum and stool with positive culture |
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) versus Giardiasis
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) | Giardiasis |
|---|---|
Nematode causing eosinophilic inflammation and possible disseminated infection | Flagellated protozoan causing malabsorption and watery diarrhea |
Larvae detected in stool by specialized culture or microscopy | Trophozoites or cysts detected in stool by microscopy or antigen testing |
Chronic intermittent symptoms with eosinophilia and possible hyperinfection | Usually acute or subacute diarrhea with steatorrhea, no eosinophilia |
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) versus Disseminated candidiasis
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) | Disseminated candidiasis |
|---|---|
Nematode larvae causing parasitic infection with autoinfection cycle | Yeast and pseudohyphae causing systemic fungal infection in immunocompromised hosts |
Occurs in patients with impaired cell-mediated immunity or corticosteroid use | Occurs mainly in neutropenic or severely immunocompromised patients |
Larvae identified in stool or sputum samples | Positive blood cultures for yeast and fungal elements on biopsy |
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) versus Schistosomiasis
Strongyloidiasis (GI and Disseminated Infections - Strongyloides stercoralis) | Schistosomiasis |
|---|---|
Soil contaminated with human feces containing filariform larvae | Freshwater exposure in endemic areas with cercariae penetration |
Larval migration causing eosinophilic enteritis and possible dissemination | Egg-induced granulomatous inflammation in liver, bladder, or intestines |
Detection of larvae in stool or sputum by specialized culture | Detection of characteristic eggs in stool or urine |