Isolation of Neospora caninum from kidney and brain of a bovine foetus and molecular characterization in Brazil.

Bovine neosporosis has become a disease of international concern as it is among the main causes of abortion in cattle. Viable N. caninum has been isolated from brains of fetuses and neonatal calves, and there is no report of isolation of tachyzoites from kidney. Also, detailed information about the genetic diversity of N. caninum is scarce. N. caninum tachyzoites were isolated from the kidney and the brain of an aborted 4-month-old bovine foetus. The parasite was confirmed to be N. caninum by PCR. The tachyzoites of the new isolate, named BNC-PR4, were propagated in Vero cell cultures. Pathogenicity of the parasite was examined in BALB/c mice. Mice inoculated intraperitoneally with BNC-PR4 failed to yield clinical signs of disease and did not induce severe brain lesions, suggesting a bovine isolate with low virulence. The N. caninum-positive DNA sample was further analyzed by multilocus microsatellite (MS) genotyping for MS4, MS5, MS6A, MS6B, MS7, MS8, MS10, MS12, and MS21. Multilocus-microsatellite genotyping revealed a unique genetic profile that differed from previously reported isolates.

Evidence suggesting a point source exposure in an outbreak of bovine abortion due to neosporosis.

A Holstein dairy farm suffered an abortion outbreak due to neosporosis. Abortion losses were > 18%. Cows with the highest Neospora antibody titers were at the greatest risk of aborting. Mummified fetuses were found after the 43rd day of the outbreak. The epidemic curve was suggestive of a point source exposure, which is consistent with the hypothesis that Neospora can be spread by a definitive host.

Bovine fetal neosporosis: a comparison of epizootic and sporadic abortion cases and different age classes with regard to lesion severity and immunohistochemical identification of organisms in brain, heart, and liver.

Eighty bovine fetuses with confirmed neosporosis were used to score lesion severity and presence of parasites in brain, heart, and liver. A comparison was made between epizootic and sporadic abortion cases. The possible influence of fetal age was also investigated. Histologic lesions of multifocal encephalitis, myocarditis, and periportal hepatitis with or without focal hepatocellular necrosis were almost always observed. Neospora caninum tachyzoites were identified immunohistochemically in 85% of the brains, 14% of the hearts, and 26% of the livers. Tissue cysts were observed in 21% of the brains. Significant differences between epizootic and sporadic abortion cases were found only in the liver. Hepatic lesions were more prominent and N. caninum tachyzoites were observed more frequently and in higher numbers in epizootic cases. Examination by immunohistochemistry of the liver in addition to the brain can be highly contributive diagnostically, particularly in epizootic cases. There were no significant age-related differences except for a higher presence of tachyzoites in the hearts of younger fetuses (3-4 months gestational age).

Serological diagnosis of bovine fetal neosporosis.

To evaluate the efficacy of fetal serology in the diagnosis of bovine neosporosis abortion, sera from 48 fetuses with immunohistochemically confirmed neosporosis and 42 fetuses without demonstrable Neospora caninum were examined in the indirect fluorescent antibody test (IFAT). Fetal sera were diluted 2-fold starting at a 1:25 dilution. Antibodies to N. caninum were detected in 31 of 48 (65%) fetuses with confirmed neosporosis; the IFAT antibody titers were 1:25 (5 fetuses), 1:50 (17 fetuses), 1:200 (6 fetuses), and > or = 1:800 (3 fetuses). Neospora caninum antibodies were found in 3 of 42 fetuses without demonstrable protozoa; in all 3 cases, a high titer was found suggesting undiagnosed congenital neosporosis. A recombinant antigen enzyme-linked immunosorbent assay was not useful for the detection of fetal antibodies to N. caninum.