"Neospora caninum detection in bovine aborted fetuses submitted to the Veterinary Pathology Laboratory (UFMT), Brazil"

Neospora caninum (NC) is a major cause of abortion and neonatal death in cattle worldwide. A prospective, observational diagnostic study was conducted at the Veterinary Laboratory of UFMT to determine the prevalence of this parasite by PCR and immunohistochemistry (IHC) and the associated histopathological lesions in bovine aborted fetuses and placentas. Between 2012 and 2024, 192 bovine abortion cases from mainly dairy and beef farms were investigated. These ranged in estimated fetal age from 3 to 8 months with the majority in the second trimester. All were tested for the presence of N. caninum using a PCR on brain tissue. The 43 (22.4 %) cases which were N. caninum PCR-positive were further examined by IHC and histopathology. Thirty (69) PCR-positive fetuses had histopathological lesions compatible with protozoan infection following ‘blinded’ examination. The most frequent histological lesion was non-suppurative encephalitis, observed in 66.7 % of lesion-positive cases. Of the 11 fetuses that had a liquid consistency in the brain, making it difficult to observe microscopic lesions, 7 (63.7 %) had non-suppurative inflammatory lesions in the skeletal muscle suggesting that skeletal muscle is an excellent auxiliary organ for the diagnosis of Neospora caninum due to its low capacity for autolysis. Immunohistochemistry was positive for Neospora caninum in 10 fetuses (33.33 % - 10/30) with lesions compatible with protozoal infection; this indicates IHC is a relatively insensitive technique.