Cytological and histopathological bone marrow findings in dogs with natural <i>Babesia rossi</i> infection

An inappropriate regenerative response to anaemia has been reported in <i>B. rossi</i>-associated canine babesiosis. We investigated the impact of canine babesiosis on the bone marrow by evaluating the cytological and histopathological changes. Bone marrow smears and histopathology specimens were obtained post-mortem (within 24 hours of death) from six <i>Babesia rossi</i>-infected dogs and five healthy control dogs. Findings were interpreted together with the circulating haemogram, a Perls' Prussian blue special stain for iron and immunohistochemical markers CD3, CD20, MUM-1, MAC387 and CD204. Infected dogs had an inflammatory leukogram, inappropriately regenerative anaemia, hypercellular bone marrow due to erythroid hyperplasia, dyserythropoietic changes within the metarubricyte population, a myeloid hyperplasia with a left shift, a significant increase in the number of CD204-positive resident macrophages, a left shift within the megakaryocyte population and a significantly increased iron content. Whether iron-restricted erythropoiesis plays a role in the anaemia of canine babesiosis could not be established in this study. Our findings concur with what has been recorded in the bone marrow of humans with falciparum malaria and confirm that dyserythropoiesis is partially responsible for the inappropriate erythroid response in canine babesiosis.