Acute fulminant sarcocystosis in a captive-born rhesus macaque

A captive-born juvenile female rhesus macaque (Macaca mulatta) was acquired from a commercial breeder and placed in quarantine. Within 8 days of arriv al, the animal became anorexic, inactive, and dehydrated. Subsequently, gen eralized edema and facial ecchymoses developed, and despite supportive ther apy, the animal became moribund and was euthanatized. Macroscopic examinati on showed diffuse stippling and streaking of the myocardium. Histopathologi c examination revealed multifocal to coalescing myocardial edema, necrosis, lymphohistiocytic inflammation, and generalized endothelial infection with Sarcocystis sp. Immature and mature schizonts within endothelial cells wer e most prevalent in the heart. Fewer schizonts were present in the vasculat ure of other tissues, including skeletal muscle, smooth muscle, adipose tis sue, brain, and retina. Mature tissue cysts within muscle fibers were not f ound in the myocardium but were occasionally seen in skeletal muscle. Analy sis of polymerase-chain-reaction-amplified 18s ribosomal RNA gene sequences revealed 96% identity to published sequences of S. hirsuta. S. hominis, an d S. fusiformis and 95% identity to S. cruzi and S. tenella. However, seque nces did not show complete identity with any organism in the GenBank databa se. Sequence homology suggests that this is a newly described Sarcocystis s p. Results of antibody tests for simian retrovirus, simian T-lymphotropic v irus 1, and simian immunodeficiency virus were negative, suggesting that vi ral immunosuppression was unlikely to have augmented the pathogenicity of s arcosporidial infection. Clinical and histopathologic findings in this case of fulminant sarcosporidiosis are similar to those described in Dalmeny di sease in cattle, which is associated with ingestion of massive numbers of i nfective Sarcocystis oocysts.