Barroso Arévalo, SandraRe, Michela TatianaAyanz, José María San MiguelVal, Eugenia PeraltaAlvarado-Piqueras, AlbertoFernández-Valeriano, RocíoBlanco Murcia, Francisco Javier2025-08-042025-08-042025Barroso-Arévalo S, Re M, Ayanz JMSM, Val EP, Alvarado-Piqueras A, Fernández-Valeriano R and Blanco-Murcia J (2025) Prevalence of bacteria involved in bovine respiratory disease in dairy heifers in Spain: influence of environmental factors. Front. Vet. Sci. 12:1605045. doi: 10.3389/fvets.2025.160504510.3389/fvets.2025.1605045https://hdl.handle.net/20.500.14352/123003Contribución de autores: SB-A: Conceptualization, Data curation, Methodology, Writing – original draft, Writing – review & editing. MR: Conceptualization, Data curation, Investigation, Supervision, Writing – review & editing, Methodology, Validation. JA: Formal analysis, Funding acquisition, Methodology, Supervision, Validation, Writing – review & editing. EV: Data curation, Formal analysis, Funding acquisition, Methodology, Validation, Writing – review & editing. AA-P: Data curation, Formal analysis, Methodology, Writing – review & editing. RF-V: Data curation, Formal analysis, Methodology, Writing – review & editing. JB-M: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Supervision, Validation, Writing – original draft, Writing – review & editing.Introduction: Bovine Respiratory Disease (BRD) is a multifactorial condition and a major health and economic concern in dairy production. Methods: This study aimed to determine the prevalence of five key bacterial pathogens—Mannheimia haemolytica, Pasteurella multocida, Trueperella pyogenes, Mycoplasma bovis, and Histophilus somni—in Spanish dairy heifers and to evaluate the influence of seasonality, geographical location, farm size, and antibiotic use. In 2017, samples (deep nasopharyngeal swabs, transtracheal aspirates, and blood) were collected from 855 heifers (<12 months old) in 50 farms across Spain. Bacterial isolation and serological testing (ELISA) were performed. Results: Mycoplasma spp. showed the highest overall prevalence (26.7% at the individual level by culture; 75.7% of cultured farms), with PCR confirming M. bovis in 89% of Mycoplasma-positive farms. Serology revealed 16.3% individual-level positivity for M. bovis and 63% farm-level positivity. T. pyogenes was also notable, detected in 6.0% of animals (45% of farms). Lower isolation rates were observed for M. haemolytica (2.5%) and P. multocida (3.5%), while H. somni was not detected. Larger farm size, winter season, and certain regions were significantly associated with higher prevalence of M. bovis and T. pyogenes. Discussion: These findings underscore the need for improved management practices—such as better ventilation, reduced stocking density, and targeted vaccination—to mitigate BRD risk in high-prevalence settings.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/journal article2297-1769https://doi.org/10.3389/fvets.2025.160504540661169open access636.2.09Bovine respiratory diseaseBacterial prevalenceDairy heifersMycoplasma bovisTrueperella pyogenesRisk factorCattle disease managementVeterinaria3109 Ciencias Veterinarias3205.08 Enfermedades Pulmonares