Background: Neospora caninum is an intracellular protozoan parasite that infects cattle worldwide and is a leading cause of bovine abortion, resulting in significant economic losses. In Iran, initial reports highlighted its role in fetal loss; however, data on long-term trends remain limited. This study aimed to investigate the temporal trend of N. caninum infection in aborted bovine fetuses over the past decade in northeast Iran. Methods: This retrospective study analyzed data from 1009 brain tissue samples of aborted bovine fetuses submitted to the Center of Excellence in Ruminant Abortion and Neonatal Mortality, Ferdowsi University of Mashhad, from 2015 to 2024. DNA was extracted, and a PCR assay targeting the Nc-5 gene (337 bp fragment) was performed. PCR products were visualized by electrophoresis. Statistical analysis included Chi-square tests to compare annual positive rates, with Bonferroni correction for multiple pairwise comparisons. Results: Among 1009 samples, 191 (18.9%) tested positive for N. caninum. Annual prevalence rates ranged from 10.7% to 44.2%, with a significant rise in 2024 (p < 0.05). The overall Chi square test indicated significant differences between years (χ² ≈ 35.5, df=9, p≈0.000047). Pairwise comparisons confirmed 2024 had a significantly higher prevalence than several previous years. Conclusion: The decade-long analysis revealed fluctuating infection rates, with a marked increase in the final year. Factors such as vertical transmission, increased farm size, and exposure to infected dogs may contribute to this trend. Despite nearly two decades since the first report in Iran, neosporosis remains underdiagnosed and unregistered, highlighting the urgent need for systematic surveillance, preventive strategies, and farmer education to reduce its reproductive and economic impact on the cattle industry.

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