Eosinophilia Among Returning Travelers: A Practical Approach Eyal Meltzer, Ruth Percik, Joshuah Shatzkes, Yehezkel Sidi, and Eli Schwartz* Center for Geographic Medicine and Department of Medicine C, Sheba Medical Center, Tel Hashomer, Israel; the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Internal Medicine, Yale-New Haven Hospital, New Haven, Connecticut Abstract. Eosinophilia is not uncommon among returning travelers; however, the optimal diagnostic and therapeutic approach in travelers, as opposed to immigrants and refugees, is not clearly established. This was a retrospective case series. All returning travelers from developing countries presenting at the post-travel clinic with eosinophilia ( 500 cells/mcl) during 1994–2006 were evaluated. Data were compared with other referrals to the post-travel clinic and with a random sample of a pre-travel clinic. Of the 955 returning travelers evaluated during the study period, 82 (8.6%) had eosinophilia, and 44 (4.4%) were diagnosed with schistosomiasis. Another 38 (4.2%) cases presented with non- schistosomal eosinophilia (NSE), among whom a definite parasitologic diagnosis was achieved in only 23.7%. However, an empiric course of albendazole led to a clinical improvement in 90% of NSE cases. Helminthic disease probably accounts for the majority of cases of post-travel eosinophilia. Empiric albendazole therapy should be offered to undi- agnosed NSE patients. INTRODUCTION Eosinophilia (usually defined as absolute eosinophil count  500 cells/L) can arise from an extensive number of medi- cal conditions, including allergic disorders, hematologic, and other neoplastic diseases and infections, particularly helmin- thic. 1 However, the relative importance of these conditions is probably different among travelers returning from developing countries as opposed to other patients. Although eosinophilia is not rare among returning travelers, an optimal diagnostic and therapeutic approach is not clearly established. Previous studies on eosinophilia have often included immigrants, refu- gees, or long-term expatriates and the applicability of their results to travel is unknown. Schistosomiasis is an important cause of eosinophilia among travelers returning from tropical countries. 2–4 Its di- agnosis is straightforward, because the disease is strongly as- sociated with specific activities (i.e., exposure to infected wa- ters), and highly sensitive and specific serologic tests are avail- able. The relative importance of other diagnoses and the best clinical approach to cases of eosinophilia when schistosomia- sis is excluded have not been established. Our aim in this study was to describe our experience with returning travelers presenting with eosinophilia and to highlight the approach to cases of eosinophilia in which schistosomiasis was excluded. MATERIALS AND METHODS Study design. This was a retrospective case series. Travelers (including expatriates) returning from developing countries and presenting to the Center for Geographic Medicine and Tropical Disease at the Sheba Medical Center from January 1994 to June of 2006 were evaluated. Eosinophilia was de- fined as total eosinophil count > 500/L or a percentage of > 6% of total leukocyte count. Immigrants from developing countries were excluded. As a basic evaluation, all patients had a complete blood count and chemistry panel (including liver function tests) performed and submitted at least one stool sample for ova/parasites. Patients with a history of travel to schistosomiasis-endemic areas were tested for Schistosoma ova in the urine as well, and a serologic test for Schistosoma was performed, as described in detail elsewhere. 5 In other cases, serologic tests for several helminthic infections (strongyloidiasis, toxocariasis) were performed according to the physicians’ discretion. These serologic tests, however, are not available in Israel and were performed at the Laboratory for Parasitic Diseases at the Centers of Disease Control (CDC), Atlanta, GA. Other diagnostic procedures, including imaging studies or tissue biopsy, were done according to clini- cal judgment. Throughout the study period, all patients diag- nosed with schistosomiasis were treated with praziquantel 60 mg/kg for 1 day divided into two doses (in cases of acute schistosomiasis, the dose was repeated after 3 months). Other cases with eosinophilia were offered treatment with albenda- zole 400 mg twice a day for 3–5 days. Response to albendazole was evaluated according to symptoms and eosinophil count. The study was approved by the Institutional Review Board at the Sheba Medical Center; a requirement for informed consent was waived. Statistical analysis. Fisher exact test and Student t test were used to analyze categorical and continuous variables, respec- tively. RESULTS During the study period, 995 patients were evaluated at the post-travel clinic, of whom 82 (8.6%) had eosinophilia; 44 (53.7%) patients were diagnosed with schistosomiasis- associated eosinophilia (SAE) and another 38 (46.3%) cases presented with post-travel non-schistosomal eosinophilia (NSE). These represented 4.6% and 4% of all referrals to the post-travel clinic, respectively. Demographic data. Age, travel duration, and male/female ratio were not significantly different between NSE and SAE cases, as detailed in Table 1. Geographical data. SAE cases were almost exclusively ac- quired through travel to Africa (95%), whereas most NSE cases had traveled to Asia (65.7%), with Southeast Asia and the Indian Subcontinent as the dominant regions (Table 1). Clinical data. Twenty-one of 44 (47.7%) SAE cases pre- sented with acute schistosomiasis with fever, rash, and respi- ratory symptoms dominating the clinical picture (Figure 1); * Address correspondence to Eli Schwartz, The Center for Geo- graphic Medicine and Department of Medicine C, The Chaim Sheba Medical Center, Tel Hashomer 52621, Israel. E-mail: elischwa@ post.tau.ac.il Am. J. Trop. Med. Hyg., 78(5), 2008, pp. 702–709 Copyright © 2008 by The American Society of Tropical Medicine and Hygiene 702