Imported Eosinophilia in Migrants from Endemic Areas in Spain

Eosinophilia is a valuable biomarker for estimating the likelihood of parasitic infection in immigrants from tropical or subtropical regions. This study aimed to evaluate the frequency and etiology of imported eosinophilia in patients attending the Tropical Medicine Unit (TMU) of Salamanca, Spain, between 2008 and 2023. A total of 773 immigrant patients were assessed: 450 (58.2%) from Africa, 306 (39.6%) from Latin America, and 17 (2.2%) from Asia. Eosinophilia was observed in 338 patients (43.7%), of whom 15 (4.4%) had noninfectious causes. Among the remaining 323 evaluated for infections, 171 (52.9%) presented with relative eosinophilia and 152 (47.1%) presented with absolute eosinophilia. A specific diagnosis was reached in 49.2% of the cases, most commonly filariasis (12.1%), strongyloidiasis (9.9%), and schistosomiasis (4.6%): 58 patients had coinfections. In conclusion, eosinophilia is common among migrants and represents a valuable biomarker for helminthiasis. Despite protocolized evaluation, nearly half of the cases remain undiagnosed. The most frequent etiologies were filariasis, strongyloidiasis, and schistosomiasis, with African patients having the highest probability of diagnosis. Improved diagnostic approaches, including tests for less common parasites, may reduce uncertainty and enhance clinical management.