# Evidence of Autochthonous Human Strongyloides stercoralis in South Carolina

## TL;DR

This study found evidence of locally transmitted Strongyloides stercoralis infections in South Carolina, highlighting the need for public health interventions.

## Contribution

The study provides the first evidence of autochthonous Strongyloides stercoralis infections in South Carolina in recent years.

## Key findings

- A serosurvey found 5.0% seroprevalence of Strongyloides antibodies among South Carolina residents.
- Geospatial analysis identified hotspots for Strongyloides in northwestern and central South Carolina.
- Autochthonous transmission was confirmed in three seropositive individuals and six confirmed cases in medical records.

## Abstract

Strongyloides stercoralis, a soil-transmitted helminth, was historically known to persist throughout the southeastern United States, but data regarding current prevalence are lacking. This project aimed to evaluate potential seroprevalence and epidemiologic risk factors for Strongyloides infections among South Carolina (SC) residents. First, a cross-sectional serosurvey was conducted on banked serum samples, and seroprevalence status was compared with associated health questionnaires. Seropositive participants were contacted for follow-up confirmation and management. Second, a retrospective chart abstraction was performed within the state’s largest health care system, comparing medical records among patients testing positive for Strongyloides with two matched controls over a 5-year period. From the initial cross-sectional serosurvey, 5.0% (n = 78 of 1,572) of sera tested positive for Strongyloides antibodies. Significant differences in race/ethnicity and education level were noted between positive and negative residents. Geospatial analysis revealed statistical hot spots in northwestern and central SC. Follow-up participation of seropositives was low (n = 14 of 78); however, five of these participants (36%) were positive on confirmation testing. Of these, three had evidence of autochthonous transmission. Conversely, the retrospective chart abstraction revealed 26 patients with confirmed laboratory diagnosis of Strongyloides infection, of which 6 had evidence of autochthonous transmission. We found a small but nonnegligible burden of autochthonous Strongyloides infection among SC residents. Further study is needed to better characterize the clinical burden and epidemiologic risk factors for locally acquired S. stercoralis. This information may provide contemporary data to inform future targeted public health interventions for at-risk populations in the southeastern United States.