Giardiasis and Eosinophilia in Outpatients with Gastrointestinal Symptoms: A Case Series.

Eosinophilia is frequently observed among individuals with soil-transmitted helminth infections, although its connection with Giardia intestinalis is somewhat ambiguous. In this study, 66 outpatients diagnosed with giardiasis were analyzed at Complejo Asistencial Universitario de Salamanca in Spain between 2021 and 2024. Outpatients presented with diarrhea and abdominal pain and were diagnosed via stool microscopy. Eosinophilia, defined as >450 eosinophils/µL, was observed in 45% (30/66) of cases, with a mean eosinophil count of 663 ± 522 cells/µL. After treatment with metronidazole or tinidazole, eosinophil counts significantly decreased to 219 ± 178 cells/µL. These findings suggest an association between Giardia intestinalis infection and eosinophilia, highlighting the importance of including Giardia intestinalis in the differential diagnosis of unexplained eosinophilia in outpatients experiencing gastrointestinal symptoms.