Harmless parasites? Infections with Hemolivia mauritanica (Apicomplexa: Adeleorina: Karyolysidae) and Haemocystidium spp. (Apicomplexa: Haemosporida: Haemoproteidae) have a negligible impact on white cell counts in tortoise hosts

The pathogenicity of haemogregarines and their effects on the health status of ectothermic hosts remain largely unexplored. In this study, we examined the impact of Hemolivia mauritanica (Sergent et Sergent, 1904) infection on the differential leukocyte count (DLC) as a measurable indicator of health in tortoise hosts. A total of 206 blood smears were analysed, including 181 from spur-thighed tortoises (Testudo graeca Linnaeus) and 25 from marginated tortoises (Testudo marginata Schoepff). Light microscopy was used to identify infected individuals, determine DLC, and quantify parasitaemia levels. Overall, H. mauritanica was detected in 125 of 181 (69%) T. graeca samples and 21 of 25 (84%) T. marginata samples. To assess whether infection influenced DLC, we statistically compared leukocyte profiles between infected and uninfected individuals. Additionally, we evaluated the effects of other factors, including host species, parasitaemia intensity, sex, age, and the month and year of blood collection. Wilcoxon rank-sum tests revealed that parasitaemia and age had a statistically significant effect on DLC in T. graeca. Further analysis using linear models showed a significant association between parasitaemia and DLC, specifically affecting azurophils in T. graeca and basophils in T. marginata. Nine T. graeca tortoises positive for H. mauritanica were co-infected with haemosporidian parasites of the genus Haemocystidium Castellani et Willey, 1904, specifically three with Haemocystidium anatolicum (Orkun et Güven, 2013) and six with Haemocystidium caucasicum (Krasilnikov, 1965). Although co-infection itself was not statistically significant, a separate analysis of Haemocystidium parasitaemia revealed a significant effect on lymphocyte DLC. Furthermore, the frequent presence of mitotic and polychromatophilous erythrocytes in H. mauritanica-infected tortoises suggests a potential increase in erythrocyte regeneration.