The aims of this study were to describe pathological changes in canine bone marrow associated with natural infections by vector-borne pathogens, as well as to determine the relationships between such changes and abnormalities of the peripheral blood. Cytological disorders and pathological changes of the bone marrow of 25 dogs naturally infected with vector-borne pathogens (Anaplasma platys, Leishmania infantum, Babesia vogeli, and Hepatozoon canis) were evaluated and compared with the corresponding hematological findings. Dysgranulopoiesis and dysmegakaryocytopoiesis were the most frequently observed bone marrow abnormalities in infected dogs. Erythroid suppression and lymphocytic, monocytic and macrophage hyperplasia were also observed. Interestingly, associations between suppression and hyperplasia of specific cell lines in the marrow and corresponding changes in numbers of circulating peripheral blood cells were not observed. We observed vector-borne pathogens: Anaplasma platys 15/25, Babesia vogeli 5/15, Leishmania infantum 1/25, any with Hepatozoon canis, and not determined 4/25, not observed co-infection. The bone marrow cytology allowed a diagnosis in 85% of the cases studied, while 16% was not diagnostic. All the cytological results were confirmed by serology, but a PCR was not performed. Infections with the vector-borne pathogens examined in this study should be considered as differential diagnoses for secondary dysmyelopoiesis in dogs.

Additional studies that further describe and explore mechanisms of bone marrow changes induced by these agents and their relationship with observed changes in peripheral blood cell counts during the course of infection appear warranted.