Strongyloidiasis

Essentials of Diagnosis

• Transient pruritic skin rash and lung symptoms

• Anorexia, diarrhea, abdominal discomfort

• Hyperinfection in immunocompromised persons; larvae detected in sputum or other fluids

• Larvae detected in stool

• Eosinophilia

General Considerations

• Infection is caused by Strongyloides stercoralis

• The primary host is humans

• The parasite's life cycle

  • Maintains its life cycle both within humans and in soil

  • Infection occurs when filariform larvae in soil penetrate the skin, enter the bloodstream, and are carried to the lungs and ascend the bronchial tree to the glottis

  • The larvae are then swallowed and carried to the duodenum and upper jejunum, where they mature to the adult stage

• Autoinfection can occur in humans, when some rhabditiform larvae develop into filariform larvae that penetrate the intestinal mucosa or perianal skin, and enter the circulation

• Parasite can cause severe infections in immunocompromised persons due to its ability to replicate in humans

Demographics

• Infects tens of millions of persons in tropical and subtropical regions

• Endemic in some temperate regions of North America, Europe, Japan, and Australia

• A related parasite, Strongyloides fuelleborni, infects humans in parts of Africa and New Guinea

Symptoms and Signs

• Most infected persons are asymptomatic

Acute syndrome

• Pruritic, erythematous, maculopapular rash, usually of the feet

• Pulmonary symptoms (including dry cough, dyspnea, and wheezing)

• Eosinophilia

• Gastrointestinal symptoms

Chronic infection

• Epigastric pain, nausea, diarrhea, and anemia

• Maculopapular or urticarial rashes of the buttocks, perineum, and thighs due to migrating larvae

• Large worm burdens can lead to malabsorption or intestinal obstruction

• Eosinophilia is common but may fluctuate

Hyperinfection syndrome

• Dissemination of large numbers of filariform larvae to lungs, CNS, kidneys, and liver in immunocompromised persons

• Persons at risk include

  • Those receiving corticosteroids and other immunosuppressive medications

  • Those with hematologic malignancies, malnutrition, or alcoholism

  • Those infected with AIDS

• Pulmonary findings

  • Pneumonitis

  • Cough

  • Hemoptysis

  • Respiratory failure

  • Sputum may contain adult worms, larvae, and eggs

• CNS disease

  • Meningitis

  • Brain abscesses

  • Cerebrospinal fluid may contain larvae

• Gastrointestinal symptoms

  • Abdominal pain

  • Nausea, vomiting

  • Diarrhea

  • More severe findings related to intestinal obstruction, perforation, or hemorrhage

  • Bacterial sepsis, probably secondary to intestinal ulcerations

• Various presentations can progress to shock and death

Differential Diagnosis

• Hookworm disease

• Ascariasis

• Giardiasis

• Amebiasis

• Acute eosinophilic pneumonia

• Tropical pulmonary eosinophilia

• Peptic ulcer disease

• Cutaneous larva migrans

Laboratory Tests

Detection of eggs and larva

• Eggs are seldom found in feces

• Diagnosis usually based on identification of rhabditiform larvae in stool or duodenal contents

• Larvae must be distinguished from hookworm larvae, which may hatch after stool collection

• Repeated examinations of stool or examination of duodenal fluid may be required because the sensitivity of individual tests is only about 30%

Serologic and hematologic findings

• Eosinophilia and mild anemia are common

• Enzyme-linked immunosorbent assay (ELISA)

  • Sensitivity and specificity ~90%

  • Cross-reactions with other helminths can occur

Hyperinfection

• Diagnosed by identification of large numbers of larvae in stool, sputum, or other body fluids

• There may be hypoproteinemia, malabsorption, abnormal liver function, and pulmonary infiltrates

• Eosinophilia may be absent

Medications

• Continue treatment until parasite has been fully eradicated

• Ivermectin

  • Treatment of choice

  • 200 mcg/kg orally daily for 1–2 days

  • For hyperinfection, administer daily until clinical syndrome has resolved and larvae have not been identified for at least 2 weeks

• Thiabendazole

  • 25 mg/kg orally twice daily for 3 days

  • Relatively poorly tolerated

• Albendazole

  • 400 mg orally twice daily for 3 days

  • Less effective than ivermectin

Follow-Up

• Follow-up examinations for larvae in stool or sputum are necessary, with repeat dosing if the infection persists

• With continued immunosuppression, eradication may be difficult

• Regular repeated doses of ivermectin may be required

Prognosis

• Mortality rate of hyperinfection syndrome

  • Approaches 100% without treatment

  • About 25% with treatment

When to Refer

• Immunocompromised patients

• Disseminated disease

When to Admit

• Patients with the hyperinfection syndrome

• Severe pulmonary symptoms