Serological evidence of exposure to Besnoitia besnoiti, Neospora caninum, and Toxoplasma gondii in dairy cows from Costa Rica.

Apicomplexan parasites affecting cattle compromise health and welfare, and some have zoonotic potential. This descriptive cross-sectional study assessed the serological evidence of exposure to Besnoitia besnoiti, Neospora caninum, and Toxoplasma gondii and described co-seropositivity patterns in dairy cows from the Huetar Norte Region of Costa Rica. Blood samples were collected from 600 cows on 40 specialized dairy or dual-purpose farms and tested using indirect immunoassays (IDVET, Montpellier, France). All sera were analyzed for B. besnoiti, and a structured subset of 327 sera, selected according to B. besnoiti serostatus, was evaluated for antibodies against N. caninum and T. gondii to describe co-seropositivity patterns. Seropositivity to B. besnoiti was 27.3% (164/600) in cows and 85.0% (34/40) in farms. In the subset, the proportion of seropositive animals was 29.4% for T. gondii (96/327) and 16.2% for N. caninum (53/327). At the farm level, based on the structured subset, 70.0% (28/40) of farms had at least one seropositive animal for T. gondii and 67.5% (27/40) for N. caninum. Co-seropositivity within the subset occurred for T. gondii/B. besnoiti in 41 cows (12.5%), N. caninum/B. besnoiti in 17 (5.2%), and T. gondii/N. caninum in 13 (3.9%); seven cows (2.1%) were seropositive to all three agents. These findings indicate frequent exposure to these apicomplexans in Huetar Norte herds, supporting strengthened biosecurity and preventive measures on farms, particularly for toxoplasmosis from a One Health perspective. Because T. gondii and N. caninum were assessed in a structured subset, these results should be interpreted as subset-level proportions and co-seropositivity patterns rather than population-level prevalence estimates for the full 600-cow sample.