Infection with a Hepatozoon sp. closely related to Hepatozoon felis in a wild Pampas gray fox (Lycalopex -Pseudalopex -gymnocercus) co-infected with canine distemper virus.

A species of Hepatozoon closely related to Hepatozoon felis found in the skeletal and cardiac muscle of a wild Pampas gray fox (Lycalopex gymnocercus) is described. The fox was euthanized after showing severe incoordination. On necropsy and histopathology there was bilateral, diffuse, severe, sub-acute, necrotizing bronchointerstitial pneumonia, with intracytoplasmic and intranuclear eosinophilic inclusion bodies. Canine distemper virus was detected by immunohistochemistry in the bronchiolar epithelium, syncytial cells, alveolar macrophages and pneumocytes. The skeletal muscle and myocardium contained multiple round to oval protozoan cysts ranging from 64 μm × 75 μm to 98 μm × 122 μm, with a central eosinophilic meront-like core surrounded by concentric rings of mucinous material resembling Hepatozoon americanum cysts but smaller in size. Macrophages within rare pyogranulomas and monocytes/macrophages in adjacent sinusoidal blood vessels in the skeletal muscle contained intracytoplasmic round protozoa consistent with merozoites or developing gamonts of Hepatozoon. Hepatozoon sp. infection was confirmed by PCR of skeletal muscle and the sequenced 18S rRNA PCR product was found to be 99% identical to H. felis by BLAST analysis and deposited in GenBank as accession number HQ020489. It clustered together in the phylogenetic analysis with published H. felis sequences and separately from H. canis, H. americanum and other Hepatozoon species. However, the close relatedness of the fox Hepatozoon to H. felis does not rule out infection with a different and possibly unknown Hepatozoon species.