|CALERO-BERNAL, RAFAEL - Orise Fellow|
|VERMA, SHIV - Orise Fellow|
|MOWERY, J - Desiderio Finamore Veterinary Research Institute (FEPAGRO)|
Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2016
Publication Date: 6/15/2016
Citation: Dubey, J.P., Calero-Bernal, R., Verma, S.K., Mowery, J. 2016. Pathology, immunohistochemistry, and ultrastructural findings associated with neurological sarcocystosis in cattle. Veterinary Parasitology. 223:147–152.
Interpretive Summary: Toxoplasmosis, caused by the single-celled parasite, Toxoplasma gondii, continues to be a public health problem. Its diagnosis from its relatives in the genera, Sarcocystis and Neospora is often difficult because of morphological similarities and cross reacting antibodies among these parasites. The authors report severe neurological disease in a cattle simulating toxoplasmosis. Detailed morphological and immunohistochemistry examinations revealed that the parasite involved was unlike Toxoplasma and Neospora. The findings described should help in differential diagnosis of parasites related to Toxoplasma. These results will be of interest to parasitologists and biologists.
Technical Abstract: The case of neurological sarcocystosis in a nine months old bull calf that died in 1982 was restudied. The bull was suspected to have rabies. Therefore, only brain was examined histologically. Thirty four years later, we restudied sections from paraffin-embedded blocks of brain. Numerous schizonts and merozoites were found associated with extensive but focal necrosis and severe meningoencephalitis. Developing stages of schizonts as well as free merozoites were indentified. The schizonts were primarily in perivascular areas. Ultrastructurally, schizonts were seen both in capillaries and in extravascular space. Merozoites were often concentrated in adventitial layers of capillaries. Schizonts divided by endopolygeny, where the nucleus became multi-lobed, and at the terminal stage nuclear lobes were incorporated into budding merozoites. Individual merozoites were seen in neurons, astrocytes, oligodendrocytes, leukocytes, and vascular endothelial cells. Occasionally merozoites were present in the nucleus of mononuclear cells. Individual merozoites were ovoid, 3-5 x 2-3 µm in size, and contained a prominent nucleus, numerous micronemes, a conoid, but no rhoptries. Schizonts and merozoites did not react to polyclonal rabbit Neospora caninum, Toxoplasma gondii, and Sarcocystis neurona antibodies but did react to Sarcocystis cruzi antibodies. Attempts to characterize DNA extracted from paraffin-embedded tissue failed. Because of morphological characteristics and the type of lesions, the parasite was likely due to an unidentified Sarcocystis species, different from Sarcocystis cruzi.