Seropositivity and Risk Factors for Toxoplasma gondii and Neospora caninum in Intensive Dairy Cattle from Different Farms in Central Chile

Toxoplasma gondii and Neospora caninum are apicomplexan parasites infecting cattle, with implications for public health and livestock productivity, respectively. Since effective vaccines against these parasites are not currently available, identifying epidemiological factors associated with infection is important for improving control strategies. This study aimed to estimate the seroprevalence of both parasites and to identify factors associated with seropositivity in intensive dairy cattle in central Chile. A cross-sectional study was conducted using serum samples from 567 cattle, analyzed by ELISA. Epidemiological data were collected through semi-structured surveys, and associations with seropositivity were evaluated using multivariable logistic regression models, including mixed-effects models to account for farm-level clustering. Seroprevalence was 7.6% for T. gondii and 22.4% for N. caninum. For T. gondii, factors associated with seropositivity included older age categories (OR = 7.09; 11.25) and the presence of dogs in pens (OR = 6.07). For N. caninum, straw bedding use (OR = 5.13) and cat presence (OR = 6.32) were associated with higher odds of seropositivity. An additional association with lower N. caninum seropositivity was observed for BCG vaccination (OR = 0.24). These findings provide updated epidemiological data for dairy cattle in Chile. The association observed with BCG vaccination should be interpreted cautiously, as the study design does not permit causal inference.