Acute Hepatic Sarcocystosis in a Chinchilla

Formalin-fixed sections of heart, liver, lung, kidney, spleen, and intestine from a 7-month-old female pet chinchilla were submitted for histologic examination to the Athens Diagnostic Laboratory, University of Georgia. The animal had been purchased at 4 months of age and was 1 of a litter of 2; its littermate had died within hours of birth from an unknown cause. At the time of death, the subject of this report was housed with 6 related chinchillas in a single large cage and was fed chinchilla and guinea pig feeds, dried and fresh vegetables, rose hips, alfalfa, and raisins. No abnormalities were seen in any of the animals until the chinchilla of this report was found dead, after last being observed as normal less than 2 hours previously. Paraffin-embedded sections of tissues were cut at 3 μm and stained with hematoxylin and eosin (HE) or periodic acidSchiff (PAS). Paraffin-embedded sections were dewaxed and reacted with antisera to Toxoplasma gondii, Neospora caninum, and Sarcocystis cruzi by an avidin-biotin complex (ABC) immunohistochemical staining procedure. Microscopically, the liver was characterized by marked disruption of architecture by numerous randomly distributed coalescing areas of inflammation and necrosis (Figs. 1, 2). Inflammatory infiltrates consisted primarily of neutrophils and macrophages. Sinusoids throughout the liver were filled with large blast-type cells interpreted as representing immature blood cells (extramedullary hematopoiesis). Various stages of protozoa were scattered within the areas of necrosis and inflammation (Figs. 3-8). The lung was congested and atelectatic. Septa were thickened by fibrin and increased numbers of mixed inflammatory cells. Alveoli contained macrophages and proteinic fluid. No parasites were evident, and no bacteria or fungi were detected with Brown and Brenn, Giemsa, and Gomori’s methenamine silver stains. Blood vessels in all tissues contained large numbers of immature white blood cells, but no inflammation or evidence of parasites was seen in any other tissues. Protozoa1 schizonts in the liver divided by endopolygeny, a process in which the parasite nucleus becomes multilobed before formation of numerous merozoites (Figs. 4-8). The earliest schizont (9 x 7 μm) contained 1 nucleus with a prominent nucleolus (Fig. 3). The nucleus then enlarged and became multilobed (Figs. 4, 5). Schizonts varied in shape and the number of nuclei. Merozoites budded peripherally, often forming a rosette around a central residual body (Fig. 7). The residual body was eosinophilic, diffuse, and up to 7 μm in diameter. Schizonts with merozoites were up to 25 x