Background: Earlier studies found characteristic haematological changes in African patients with active schistosomiasis. If consistently present, full blood counts (FBC) may be helpful to diagnose schistosomiasis also in migrants and returning travellers. Methods: A retrospective patient record review was conducted on data from seven European travel clinics, comparing FBC of Schistosoma egg-positive travellers and migrants to reference values. Sub-analyses were performed for children, returned travellers, migrants and different Schistosoma species. Results: Data analysis included 382 subjects (median age 21.0 years [range 2–73]). In returned travellers, decreases in means of haemoglobin particularly in females (β = −0.82 g/dL, p = 0.005), MCV (β = −1.6 fL, p = 0.009), basophils, neutrophils, lymphocytes and monocytes (β = −0.07, p < 0.001; −0.57, p = 0.012; −0.57, p < 0.001 and −0.13 103/μL, p < 0.001, respectively) were observed. As expected, eosinophils were increased (β = +0.45 103/μL, p < 0.001). In migrants, a similar FBC profile was observed, yet thrombocytes and leukocytes were significantly lower in migrants (β = −48 103/μL p < 0.001 and β = −2.35 103/μL, p < 0.001, respectively). Conclusions: Active egg-producing Schistosoma infections are associated with haematological alterations in returned travellers and migrants. However, these differences are discrete and seem to vary among disease stage and Schistosoma species. Therefore, the FBC is unsuitable as a surrogate diagnostic parameter to detect schistosomiasis.
