Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 21 3 2026 09 02 381 386 Mona Hamedi Department of Veterinary Pathobiology Sciences, Science and Research Campus SR.C., Islamic Azad University, Tehran, Iran Hanieh Rezaei Department of Veterinary Medicine, Science and Research Campus SR.C., Islamic Azad University, Tehran, Iran Delnavaz Nazari Department of Veterinary Medicine, Science and Research Campus SR.C., Islamic Azad University, Tehran, Iran Fatemeh Zahra Roostaei Department of Veterinary Medicine, Science and Research Campus SR.C., Islamic Azad University, Tehran, Iran Kiana Beirami Department of Veterinary Medicine, Science and Research Campus SR.C., Islamic Azad University, Tehran, Iran 2024 12 13 2026 09 02 Background: Neospora caaninum, a cyst-producing parasite is identified as main causes of reproductive failure in cattle worldwide. Neosporosis results in increased rates of abortion and reduced milk production, leading to financial losses. This study aimed to identify Neospora caninum infection in aborted cattle and their fetuses, at a dairy cattle farm, focusing on the involvement of stray dogs in spreading the agent within the herd. Methods:Twenty-one cattle showed abortion at 2, 4, 5, and 7 months of pregnancy, while stray dogs had free access to various sections of the farm. Serum samples were collected from each of the aborted dams. Seven aborted fetuses, along with two placentas, were also transported to the laboratory in frozen ice packs for testing for N. caninum. The fetal and placenta samples underwent examination through molecular and histopathological assessments. Results: Anti-Neospora antibodies were detected in sera of 7 out of 21 cattle corresponding to a seroprevalence rate of 33.3%. Three out of seven aborted fetuses tested positive using real-time PCR. No evidence of N. caninum was found in one of the placental samples. Histopathological results were consistent with the results of serological and molecular tests. Conclusion: The findings of the current research demonstrate that N. caninum significantly influences the occurrence of abortions in dairy cattle. Although transmission of infection from an infected dam to a fetus is the most prominent route of the disease transmission, the proximity of stray dogs to cattle herds plays a key role in increasing number of infected cases. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/4479 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/4479/1513