Background: Neospora caninum is an obligate intracellular protozoan that is well established as a causative agent of abortion in dairy cattle worldwide. Objectives: The objective of this study was to detect N. caninum infection in the brains of aborted bovine fetuses and its association with abortion in dairy cattle in the Khorasan Razavi Province, Iran. Methods: From 2022 to 2024, 105 aborted bovine fetuses were collected from dairy cattle in Khorasan Razavi province. Brain samples of aborted fetuses were tested using nested PCR and histopathological examination. In addition, blood samples were collected from dairy cattle that had aborted PCR-positive fetuses and were analyzed using ELISA. Results and Conclusions: In the present study, N. caninum infection was detected in 24.76% (26 out of 105) of aborted bovine fetuses by nested PCR analysis. The brain tissues of 20 bovine-aborted fetuses were only suitable for histopathological examination. Lesions of the central nervous system were severe hypremia, perivascular cuffing, astrogliosis, mild encephalitis, and focal necrosis. One fetus exhibited a 40-μm N. caninum cyst within the brain tissue. IgG antibodies against N. caninum were identified in all dairy cattle that aborted infected fetuses through ELISA testing. Molecular, histopathological and serological findings strongly suggest that N. caninum plays a significant role in bovine abortion in dairy cattle in Khorasan Razvi Province, northeast Iran.

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