Contribution of tick-borne diseases to mortality in juvenile free-living cervids

Introduction and objective: Reports on tick-borne infections in free-living juvenile animals and their impact on survival of cervids in nature are lacking. The aim of the study was to detect and identify the Babesia and Anaplasma phagocytophilum species/ecotypes that may have contributed to the death of juvenile animals from a wildlife rescue centre in spring 2020. Material and methods: PCR amplification and sequencing of two genetic markers (18S rDNA and cox1 for Babesia, 16S rDNA and groEL for A. phagocytophilum) were used for screening eleven samples derived from juvenile animals which died in a rescue centre (seven roe deer Capreolus capreolus, one elk Alces alces, one red squirrel Sciurus vulgaris, one European beaver Castor fiber, one red fox Vulpes vulpes). Phylogenetic analysis of full-length 18S rDNA sequence was performed to enable differentiation between two closely-related species infecting wild ungulates, Babesia capreoli and Babesia divergens (zoonotic). Results: The occurrence of the typical SNPs of B. capreoli at two discriminating positions in the 18S rRNA gene allowed identification of B. capreoli infection in a roe deer calf. In two calves, Anaplasma phagocytophilum ecotype 2 was identified, including the same calf co-infection. No Babesia DNA was amplified in an elk calf treated for babesiosis. Splenomegaly was recorded in roe deer calves with A. phagocytophilum and A. phagocytophilum + B. capreoli infection. Conclusions: The study revealed that tick-borne infections are common among juvenile, free-living cervids and may contribute to their mortality.