Domestic Refugee Health Screening Guidance
Intestinal Parasite Screening

Strongyloides parasites, other soil-transmitted helminths, and Schistosoma species are some of the most common infections among refugees. Strongyloides and Schistosoma, in particular, can persist for long periods of time in the body of a host, without new environmental exposure. Although frequently asymptomatic or subclinical, some infections may cause significant morbidity and mortality.

Epidemiological studies of the prevalence of Strongyloides among Eastern European refugees are limited. The most common way of becoming infected with Strongyloides is by contacting soil that is contaminated with Strongyloides larvae. Most infections are acquired through environmental exposure. Although the typical duration of infection is unknown, chronic, potentially life-long, infection can occur. The most common clinical presentation in refugees is an elevated eosinophil count, although lack of eosinophilia does not exclude infection. Common clinical symptoms in refugees include abdominal complaints, nausea, diarrhea, constipation, dry cough, and skin manifestations (e.g., larva currens).

Soil-transmitted helminth infections, including Ancylostoma duodenale and Necator americanus (hookworm), Ascaris lumbricoides (ascariasis), and Trichuris trichiura (whipworm) are often found in areas with warm and moist climates where sanitation and hygiene are poor, including in temperate zones during warmer months. Ascaris and Trichuris infections occur through indirect exposure. Hookworm infections require direct contact of skin with contaminated soil, and penetration of the larval worm through skin. Infections are most frequently asymptomatic or subclinical. However, ascariasis, when symptomatic, may be associated with abdominal pain, cough (Löffler syndrome), and if high-burden, intestinal obstruction, appendicitis, or cholecystitis. Trichuriasis (whipworm infection) may cause bloody stools, anemia, and rarely, rectal prolapse. Hookworm may cause anemia, which is of particular concern in young children and pregnant women.

All sub-Saharan African countries (except Lesotho) are considered endemic for schistosomiasis. Infection requires direct skin contact with Schistosoma-contaminated fresh water; larval parasites enter by penetrating the skin. Young infants without direct skin exposure to contaminated fresh water are at low risk of infection. However, babies bathed in basins with contaminated fresh water are at risk of infection. Infections are frequently asymptomatic or subclinical; however, infections may persist for more than 50 years, causing ongoing damage. The most common sign of infection is asymptomatic eosinophilia; however, severe manifestations of chronic Schistosoma infection include bowel wall pathology, liver cirrhosis, portal hypertension, dysuria, hematuria, urinary tract obstruction, renal failure, and bladder cancer.

Starting in 1999, CDC initiated presumptive albendazole pre-departure treatment to refugees just prior to U.S. departure. Currently, refugees from Asia, Africa, the Middle East, North Africa, and Latin America all receive pre-departure albendazole unless there are contraindications. In 2005, CDC initiated pre-departure presumptive ivermectin treatment for Strongyloides for refugees departing from those same regions. Presumptive praziquantel treatment for schistosomiasis was initiated in 2010 for refugees departing from sub-Saharan African. At this time, refugees departing from Eastern Europe do not receive presumptive treatment for intestinal parasites.

Though many of the parasitic infections that refugees are recommended to be screened for are not endemic to Minnesota, Giardia is found worldwide, including in every region of the United States. From 2009 to 2018 there were 6,556 cases of giardiasis reported in Minnesota, with recent immigrants and refugees accounting for 8% of cases.

Many refugees arriving to the United States are treated presumptively for intestinal parasites prior to U.S. arrival. This treatment includes albendazole, ivermectin, and/or praziquantel, depending on the individual’s region of origin. During 2009-2019, 67% of refugee arrivals who received a refugee health assessment were treated presumptively for intestinal parasites overseas. The proportion being treated presumptively overseas has increased in recent years, with 53% of those arriving as primary refugees having received presumptive treatment in 2011 compared to 82% in 2019.

Among those not treated presumptively overseas, CDC recommends screening for intestinal parasites or post-arrival presumptive treatment. Among those who did not receive overseas presumptive treatment during this time period, 91% were screened for intestinal parasites using serology and/or ova and parasite stool exam. Fourteen percent of refugee arrivals tested positive for ≥1 pathogenic parasite; the most common parasite identified was Giardia lamblia.

Prevalence of Intestinal Parasites among Primary Refugees to Minnesota, 2011-2019

*Based on MDH's world regions
**Refugee Health Assessment (RHA): health screening done in U.S., usually within 90 days of U.S. arrival
*** Received presumptive, pre-departure anti-helminthic overseas (albendazole, ivermectin, and/or praziquantel); % among those who received RHA
**** Screened for intestinal parasites using serology and/or ova and parasite stool exam; % among those who received RHA and were not presumptively treated overseas
† % among those screened for intestinal parasites who were not treated presumptively overseas