What is the epidemiology of strongyloidiasis (infection with Strongyloides stercoralis) in the United States (USA)?

Epidemiology of Strongyloidiasis in the United States

Strongyloidiasis affects approximately 613.9 million people globally, with a reported seroprevalence of 4% in the United States, primarily occurring in immigrant populations. 1

Geographic Distribution

• Strongyloides stercoralis is widely distributed throughout tropical and subtropical regions, with small foci in temperate regions including the United States 2
• In the United States, strongyloidiasis is predominantly found in the southeastern states, particularly in the Appalachian region 3
• The infection is becoming increasingly important in the United States, especially among immunocompromised immigrant populations 4
• Endemic pockets exist in the southeastern United States and Puerto Rico, where infection rates may exceed 6% of the population 5

At-Risk Populations

• Immigrants from endemic areas represent the highest risk group for strongyloidiasis in the United States 1, 6
• Immunocompromised individuals are particularly vulnerable to developing severe clinical syndromes associated with strongyloidiasis, such as hyperinfection syndrome (HS) or disseminated disease 4
• Specific risk factors for severe disease include:
  • Corticosteroid therapy 7, 1
  • Human T-lymphotropic virus type 1 (HTLV-1) infection 3, 1
  • Hypogammaglobulinemia 1
  • Alcoholism and malnutrition 1
  • Organ transplant recipients 4
  • HIV infection, though cases can occur even with relatively preserved CD4 counts 6

Clinical Presentation

• Most infections are asymptomatic or present with mild symptoms 3, 1
• Common clinical manifestations include:
  • Larva currens - an itchy, linear, urticarial rash that typically moves rapidly around the trunk, upper legs, and buttocks 7
  • Non-specific gastrointestinal symptoms including diarrhea and abdominal bloating 2
  • Loeffler's syndrome (transient respiratory symptoms with eosinophilia) 2
• Severe manifestations in immunocompromised hosts:
  • Hyperinfection syndrome - unchecked replication in individuals with defective immune function 2
  • Disseminated disease - with reported mortality rates of up to 87.1% 1

Diagnostic Considerations

• Diagnosis is challenging due to the often low parasite burden and intermittent larval shedding 3
• Methods include:
  • Concentrated stool microscopy (often requiring multiple samples) 3
  • Serologic testing, though highly sensitive screening tests are still not widely available in major tertiary medical centers 4
• Peripheral eosinophilia is a common finding and should raise suspicion in at-risk individuals 6

Public Health Implications

• Screening is recommended for:
  • Patients likely to require prolonged corticosteroid therapy 2, 7
  • Organ transplant donors and recipients 4
  • Individuals from endemic areas who will be receiving immunosuppressive therapy 7
• Household members of patients with strongyloidiasis acquired in non-endemic areas should be screened for tapeworm carriage as a public health measure 2

Prevention

• Primary prevention in endemic areas involves wearing shoes to avoid contact with infected soil 3
• For high-risk individuals from endemic areas who require immunosuppression, empiric treatment may be considered even without confirmed diagnosis 7

Strongyloidiasis remains an underdiagnosed and potentially fatal infection in the United States, particularly among immigrants and immunocompromised individuals. Clinicians should maintain a high index of suspicion in patients with compatible symptoms, especially those with risk factors or eosinophilia, regardless of recent travel history 6.