Should parasitic disease be investigated in immigrant children with relative eosinophilia from tropical and sub-tropical regions?

Background: Immigrants to Spain are mainly from low- and middle-income countries, and around 20% are children. Absolute eosinophilia is defined as >0.45×109 eosinophilic leucocytes/L of peripheral blood. Absolute eosinophilia in travelers and immigrants from tropical and sub-tropical areas is frequently associated with parasitic diseases. However, the significance of relative eosinophilia in immigrant children, defined as >5% eosinophilic leucocytes in those with <0.45×109 eosinophils/L, is unresolved.Objectives: To describe the importance of relative eosinophilia in a cohort of immigrant children (<18 years) from sub-Saharan Africa, North Africa and Latin America.Methods: 176 immigrant children without absolute eosinophilia were prospectively evaluated.Results: 25 of them (14.2%) had relative eosinophilia. 10 patients with relative eosinophilia had no diagnosis. 15 with relative eosinophilia (60%) were diagnosed with a parasitic disease, 7 (46.7%) of whom had only one parasite, while co-infection accounted for 8 of the 15 cases (53.3%). Of the parasitic infections, the most frequent causes of relative eosinophilia were filariasis spp. (7/15, 46.7%), strongyloides spp. (5/15, 33.3%), schistosoma spp. (4/15, 26.6%) and Ascaris lumbricoides (2/15, 13.3%).Conclusion: The findings suggest that relative eosinophilia is frequently associated with helminthic infection in immigrant children from tropical and sub-tropical areas, so a thorough parasitological study is highly advisable in this group of patients.