Glial Changes and Evidence for Apoptosis in the Brain of Cats Infected by Cytauxzoon felis

Ischaemic neuropathological changes associated with Cytauxzoon felis infection in cats have been reported recently. This paper describes the associated glial changes and the evidence for apoptosis in the brain of cats infected naturally by C. felis. Sections of brain from eight affected cats and eight age- and sex-matched control cats were evaluated by immunohistochemistry for expression of glial fibrillary acidic protein, CD18 and cleaved caspase-3. Vascular changes in the leptomeninges and parenchyma, the number of positive astrocytes and phagocytic cells (microglia or macrophages) and the average astrocytic cytoplasmic area and number and length of astrocytic processes were quantified, and a mean value for the grey and white matter in both groups was generated. Astrocytic hyperplasia (astrogliosis) and phagocytic cell hyperplasia were detected in all affected cats. Immunoexpression of cleaved caspase-3 was detected in intravascular and perivascular macrophages in the leptomeninges and, less often, in the grey and white matter in all affected cats. Four cats with encephalomalacia had additional cytoplasmic immunolabelling of phagocytic cells around the necrotic foci and macrophages and cell debris within the areas of necrosis. These results support the role of an extensive reaction of the brain tissue to hypoxia-ischaemia and a potential role of apoptosis in the neuropathogenesis of C. felis infection in cats.