High Prevalence of Parasitic Infections Among Recent Immigrants in Chicago

Background. Parasitic infections are likely under-recognized among immigrant populations in the United States (US). We conducted a cross-sectional study to evaluate the frequency of such infections among recent immigrants in Chicago and to identify predictive factors for parasitic infections. Methodology and principal findings 133 recent immigrants were enrolled, filling out a standardized questionnaire regarding medical history and exposures and providing blood and stool samples for evaluation. Fifteen of 125 subjects (12%) who provided a blood or stool sample for testing were found to have evidence of current or prior infection with a pathogenic parasite, of which Toxocara spp. (8 subjects, 6.4%) and Strongyloides stercoralis (5 subjects, 4%) were most commonly identified. Parasitic infection was more likely among subjects who had immigrated within the previous 2 years and those with a self-reported history of ever having seen worms in the stool. Infected individuals were likely to have multiple nonspecific physical complaints; however, classic symptoms of parasitic infections (skin rashes, diarrhea, etc.) were not increased among infected individuals. The most useful surrogate markers identified for parasitic infections were an elevated Immunoglobulin E level (seen in 7/15 subjects with parasitic infections, 46.7% and 22/110 uninfected individuals, 20%, p=0.04) and the presence of Blastocystis hominis cysts on Ova & Parasite exam (detected in 5/13 subjects with parasitic infections who provided a stool sample, 38.5% and 5/98 uninfected subjects, 5.1%, p=0.002). In contrast, the Absolute Eosinophil Count (typically thought of as an indicator of parasites) was not found to be a good screening test for parasitic infections in this study. Conclusions Our study found that parasitic infections are common in recent US immigrants, which highlights an important health disparity among a vulnerable population. Further, we found that classically used symptoms and laboratory tests had a low predictive value for parasitic infections in this population. AUTHOR SUMMARY – Parasitic infections, though rare in the United States (US), are common in many areas of the world including the regions of origin of many US immigrants. However, the prevalence rates and health impacts of these infections in immigrant populations are undefined. We conducted a study to identify the frequency of parasitic infections among healthy immigrants in one community, recruiting 133 immigrants from 28 countries. Subjects completed a standardized questionnaire regarding symptoms and infection risk-factors and provided blood and stool samples for testing. Twelve percent of subjects in our study had evidence of current or previous pathogenic parasitic infections. Symptoms and risk factors classically thought to be associated with parasitic infection (allergic symptoms, elevated blood eosinophil counts, etc.) were common among enrolled subjects, but did not differ significantly between those with and without evidence for infection. Overall, our results suggest that many immigrants, even those who are asymptomatic, may have undiagnosed parasitic infections. These results highlight an important health disparity among a vulnerable underserved population in the US. As most of these infections are easily treatable, more research should be done to further characterize the optimal testing strategies for recent immigrants.