Treatment of Parasitic Diseases

Pre-Arrival in the U.S.
In 2010 CDC initiated presumptive pre-departure treatment with praziquantel for refugees from sub-Saharan Africa, an area highly endemic for schistosomiasis. Strongyloidiasis infection is common in refugees from Asia, Africa and the Middle East.  In 2012 CDC ramped up programs to presumptively treat refugees for Stronglyoides. Increasingly, refugees are receiving presumptive treatment for Stronglyoides before resettling in the U.S.  Information on current pre-departure regimens being received by specific refugee populations is available from the CDC.

CDC also maintains an updated list of presumptive treatments and vaccines for each refugee population.

Post-Arrival in the U.S.
Refugees should receive screening and/or presumptive treatment for soil-transmitted helminths, schistosomiasis and strongyloidiasis post-arrival according to the pre-departure treatment they received. CDC provides guidance for management of parasitic diseases in refugees. 

No anti-parasitic is completely effective and any refugee with signs or symptoms of infection after arrival should undergo further evaluation.  In addition, a thorough physical and laboratory examination may find indications of parasitic infections not fully addressed by pre-departure treatment. Examples include physical findings of ectoparasites (i.e. scabies) or other invasive parasites (e.g. onchocerciasis), ongoing eosinophilia due to other less frequently encountered parasites (e.g. tapeworms) or hematuria (e.g. Schistosoma hematobium).

The protozoal infections Giardia and Entameba histolytica are commonly encountered in refugees when routine stool ova and parasite (O&P) testing is performed.  Giardia is also known as Giardia intestinalis, Giardia lamblia and Giardia dudenalis.  Common symptoms of Giardia disease include diarrhea, greasy/floating stools, nausea, vomiting, gas, bloating, and cramping.  Please bear in mind that a majority of Giardia infections in refugees are asymptomatic. Infection is associated with failure to thrive in children, although a definitive causative effect has not been established [1].

There is no agreed upon clinical or treatment approach for those asymptomatically infected with Giardia, and routine screening to detect Giardia is not recommended.  However, when clinical disease is suspected based on clinical signs and symptoms, testing should be performed.  Also, because of the linguistic and cultural challenges inherent in working with diverse refugee populations, clinicians may be uncertain about the presence of symptoms in some populations. In the context of the relatively high prevalence of giardiasis seen historically in refugee populations, clinicians should consider screening either individuals or populations. Testing may be performed by stool O&P examination, although stool antigen detection testing is easier to perform and has comparable sensitivity.  Giardia may also be incidentally detected when testing for other parasitic infections.  When Giardia is detected, even in persons who do not have symptoms, most experts would treat.

In approximately 2% of refugees who have routine stool O&P testing, cysts of Entameba histolytica or E. histolytica/dispar complex are reported [2].  Cysts of E. histolytica are indistinguishable from more common non-pathogenic amoeba infections such as E. dispar and E. moshkovskii [3].  Treatment of luminal E. histolytica is expensive and carries a risk of adverse drug effects.  Therefore, it is recommended that confirmation testing with E. histolytica stool antigen testing be performed prior to treatment when E. histolytica cysts are reported.  In most immunocompetent individuals, asymptomatic infection with Giardia and E. histolytica spontaneously resolves within several months [4, 5].

Due to the number, variety and complicated lifecycles of parasites, clinicians may find parasitic infections to be the most challenging and fascinating conditions they encounter while caring for refugees.

Contributed by William Stauffer M.D., M.S.P.H., University of Minnesota


1. United States Environmental Protection Agency.  Giardia: Risk for infants and children. EPA-823-R-99-011.  Available at:  Last Accessed, Sept 15, 2012.
2. Swanson SJ, Phares CR, Mamo B, et al. Albendazole therapy and enteric parasites in United States-bound refugees. N Engl J Med 2012;366;1498-507.
3. Blessman J, Buss H, Phuong A, et al.  Real-time PCR for detection and differentiation of Entamoeba histolytica and Entomoeba dispar in fecal samples.  J Clin Microbiol 2002;40:4413-17.
4. Rendtorff RC. The experimental transmission of human intestinal protozoan parasites.  II.  Giardia lamblia cysts given in capsules.  Am J Hyg 1954;59:209-220.
5. Hague R, Ali IM, Petri WA.  Prevalence and immune response to Entamoeba histolytica infection in preschool children in Bangladesh.  Am J Trop Med Hyg 1999;60:1031-34