Can haematological changes constitute a surrogate diagnostic parameter to detect schistosomiasis in migrants and travellers? - A retrospective analysis

Abstract

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.

Keywords: Full blood count; Haematology; Migrants; Returned travellers; S. haematobium; S. mansoni; Schistosomiasis; Travel.

Fig. 1

Haematological parameters of Schistosoma infected returned travellers versus migrants 16+ year-old in relation to CDL-AMC reference values. An independent samples t-test was used to test for differences in means between groups of normally distributed haematological parameters. An independent samples Mann-Whitney U Test was used for not-normally distributed haematological parameters.

Fig. 2

Haematological parameters of returned travellers and migrants 16 years-old infected with urogenital schistosomiasis, intestinal schistosomiasis or mixed in relation to CDL-AMC reference values. The one-way ANOVA was used to test for overall difference between groups; for not-normally distributed haematological parameters the Kruskal-Wallis test was used. In case of significant differences, an independent samples t-test were performed to explore which groups differed and in case of non-normally distributed data, an independent-samples Mann-Whitney U Test.