Abstract
INTRODUCTION: Neospora caninum is a major infectious cause of bovine abortion, leading to substantial reproductive and economic losses in dairy production systems worldwide. This study aimed to determine the nationwide herd-level prevalence of N. caninum in Türkiye and to identify farm-level risk factors associated with infection. METHODS: Bulk-tank milk samples were collected from 466 dairy farms across 40 provinces representing seven geographical regions of Türkiye between June and November 2023. Antibodies against N. caninum were detected using a commercial competitive ELISA. Farm-level data on management practices, water sources, dog presence and feeding practices, pasture use, and abortion history were obtained through a structured questionnaire. Univariable and multivariable statistical analyses were performed to identify associations with herd-level seropositivity. RESULTS: Overall herd-level seropositivity was 27.47% (128/466; 95% CI: 23.4-31.7%), with significant regional variation (p = 0.03394). The highest prevalence was observed in the Marmara (39.2%) and Southeastern Anatolia (37.5%) regions, while the lowest prevalence occurred in the Mediterranean region (16.7%). Herd seropositivity was strongly associated with reported abortion history, with seropositive herds having markedly higher odds of abortion (OR = 29.4; 95% CI: 16.5-52.9; p < 0.0001). Herds using groundwater had a significantly higher likelihood of seropositivity compared with those using municipal water (p = 0.002), an association that remained significant after multivariable adjustment. Although dogs were present on all farms, feeding practices varied regionally, with most farms providing leftover or raw animal-derived feed, while commercial dog feed use was largely restricted to western Türkiye. DISCUSSION/CONCLUSIONS: This study provides the first nationwide herd-level assessment of N. caninum exposure in Turkish dairy farms using bulk-tank milk ELISA and demonstrates widespread infection associated with key management and environmental risk factors. These findings support the implementation of targeted control strategies focusing on improved biosecurity, water hygiene, and routine herd-level monitoring to reduce vertical transmission and long-term infection pressure.