Helminth infections in Northern California refugees are declining

Background: Each year, the United States (U.S.) welcomes between 50-70,000 refugees, many from countries with a high prevalence of intestinal parasites. Consequently, the CDC promulgated recommendations for presumptive pre-departure treatment of refugees. Objective: To compare the prevalence of intestinal helminths and protozoa among refugees at the Santa Clara County, California, Refugee and Tuberculosis Clinic from 2008-2010 with the prevalence reported in a prior survey from 2001-2004. Methods: Refugees living in the U.S. for less than two years and between the ages of 18 and 55 provided three stool specimens on different days. Parasite infection was determined by presence of ova or parasites in at least 1/3 stools. Results: In the 2008-2010 cohort, of 231 participants, 97.5% had been U.S. residents for less than one year. We found stool parasites in 12.6%, similar to the prior survey (16.4%, p=0.2). The most common infections were Entamoeba histolytica (3.9%), Giardia lamblia (3.9%), and Strongyloides stercolaris (0.9%). Protozoa were more common among refugees from South Asia (OR: 3.1 [1.4-6.6]) and Africa (OR: 2.6 [1.03-6.5]) than among those from the Middle East. Helminths were mainly identified in immigrants from South Asia (6/7 cases). Although the rates of protozoa infection were similar in the two cohorts(10.8%, 2008-2010 vs. 8.6%, 2001-2004, p=0.2), the rate of helminth infection was significantly lower in recent years (1.7% vs 7.9%, p<0.001). Conclusion: Helminth infections are uncommon in recent immigrants. Pre-departure treatment programs may have contributed to this finding, but further studies are needed to specifically address program penetrance and efficacy.