Strongyloidiasis

Strongyloidiasis is an intestinal nematode infection. Larvae penetrate the skin (dermatitis) and the lungs (pneumonitis) to develop into the adult worm in the intestinal mucosa (abdominal pain). Transmission may occur among institutionalized residents with poor personal hygiene.

CASES/YEAR
50 (US); 100,000,000 (Global)
AGENT TYPE
Helminths
OTHER NAMES
Strongyloides stercoralis; S. fulleborni;
ACUITY
Subacute/Chronic
INCUBATION
2-4 weeks for larvae to appear in feces; [CCDM]
INITIAL SYMPTOMS
Larvae penetrate the skin (dermatitis) and the lungs (pneumonitis) to develop into the adult worm in the intestinal mucosa (abdominal pain). [CCDM, p. 593] "Most infections are asymptomatic." [CDC Travel]
PRECAUTIONS
Standard
COMMENTS
FINDINGS:
In this intestinal nematode infection, eggs hatch in the colon to become larvae that can reinfect the host either internally or externally. Infections persisting for decades have been documented. With acute infection, a pruritic rash may appear at the site of larval penetration. Migration of larvae through the lungs can produce cough, fever, dyspnea, wheezing, hemoptysis, and eosinophilia. Then, patients have diarrhea and abdominal pain. Findings in chronic infection may include: asymptomatic (50%); intermittent eosinophilia (75%); recurrent rashes of the thighs, buttocks, and perineum; a serpiginous rash (larva currens) that migrates up to 10 cm/hour; and GI symptoms with epigastric pain, diarrhea, blood in the stool; and, in heavy infections, bowel obstruction. Respiratory symptoms are uncommon in chronic, uncomplicated infections. Complications of hyperinfection include intestinal obstruction, gastrointestinal bleeding, pulmonary infection, meningitis, brain abscesses, and liver infection. Biopsies of petechial and purpuric linear rashes often reveal larvae. [PPID, 8th Ed, p. 3205] Symptoms of hyperinfection are diarrhea, malabsorption, hepatomegaly, and paralytic ileus. Immunocompromised patients may present with pneumonia and pleural effusions. [Cohen, p. 997,1777] Filariform larvae may be found in pleural fluid. An immune-mediated arthritis has been reported. Leukopenia and thrombocytopenia are associated with disseminated infection and skin purpura (generalized or periumbilical). A polymicrobial sepsis is likely to accompany widespread dissemination of larvae. [Guerrant, p. 948, 808, 810] Recurrent urticaria, often of the buttocks and wrists, is the most common skin finding. With severe infections, eosinophilia is frequently absent. [Harrison ID, p. 1134] Person-to-person transmission is rare. {CDC Travel, p. 345]

EPIDEMIOLOGY:
Transmission may occur among institutionalized residents with poor personal hygiene. Cases reported of Ex-POWs carrying infection for decades; Hyperinfection usually occurs in patient taking corticosteroids or with depressed cell-mediated immunity, e.g. infected with human T-lymphotropic virus 1 (HTLV-1). Hyperinfection is not common in AIDS patients. Dog and cat strains of S. stercoralis occasionally infect humans. Primates are reservoirs for S. fulleborni in Africa. [CCDM, p. 593-5; ID, p. 2362-3; Guerrant, p. 943, 958; Merck Manual, p. 1677-9; PPID, p. 3441; Cecil, p. 2131-2; Harrisons, p. 628]
DIAGNOSTIC
Identify larvae in concentrated stool specimens or by agar plate method; Repeated examinations may be necessary; Serology tests are positive in 80-85% of infected patients. [CCDM] Serologic testing available from CDC (404-718-4745); [CDC Travel]
SCOPE
Endemic in tropical and temperate zones including US and Europe; [PPID, p. 3440]
SIGNS & SYMPTOMS
  • >fatigue, weakness
  • >fever
  • G abdominal pain
  • G blood in stool
  • G constipation
  • G diarrhea
  • G hepatomegaly
  • G nausea, vomiting
  • H eosinophilia
  • H leukopenia
  • H thrombocytopenia
  • R cough
  • R dyspnea
  • R hemoptysis
  • R sputum production
  • R wheezing
  • S papules or plaques
  • S petechiae and ecchymoses
  • S urticaria
  • S skin lesion, linear or serpiginous
  • X lung infiltrates
  • X pleural effusions
  • *ARDS
  • *arthritis
  • *bowel obstruction
  • *brain abscess or lesion
  • *glomerulonephritis
  • *meningitis
  • *pancreatitis
  • *pneumonia
  • *pneumonitis
  • *sepsis
  • *weight loss
ANTIMICROBIC

Yes

VACCINE

No

ENTRY
Ingestion, Skin or Mucous Membranes (Includes Conjunctiva), Sexual Contact
SOURCE
Person-to-Person, Human Fecal-Oral, Fecally Contaminated Soil, Soil or Dust (Ingesting or Inhaling)
RESERVOIR
Cats, Dogs, Monkeys, Human
RISK FACTORS
  • AIDS patients
  • Cancer patients
  • Have dog or cat contact (fecal-oral)
  • Travel to endemic area
  • Walk barefooted in contaminated soil
REFERENCES FOR CASES/YEAR
1. (US) 30-100 million is estimated global prevalence; Most infections in US are immigrants or military veterans who have lived in endemic areas in the tropics and subtropics; [CDC Travel, p. 345-6] 30-100 million worldwide; Most frequently diagnosed in US among SE Asian immigrants, but still endemic in areas of rural Appalachia; [Cecil, p. 2131] Guesstimate: = 50 case/yr;
2. (Global) Global prevalence of 100 million; [Harrison ID, p. 1132t]