Seroprevalence of viral pathogens associated with bovine respiratory disease complex and biosecurity-related risk factors in cattle farms in Türkiye.

Bovine respiratory disease complex (BRDC) is one of the main causes of illness and financial losses in cattle farming around the world. The aim of this cross-sectional study was to estimate the seroprevalence of viral pathogens associated with the bovine respiratory disease complex (BRDC) and to identify farm- and animal-level risk factors, including biosecurity practices and indirect contacts, in cattle farms in Konya and Adana provinces of Türkiye. However, the role of farm-level biosecurity practices and indirect contacts in shaping these infection patterns remains unclear, including in Türkiye where data on farm-level biosecurity practices and indirect contacts are limited. This cross-sectional study involved collecting blood and nasal swab samples from 274 cattle on 16 farms in the provinces of Konya and Adana between March 2023 and April 2024. Blood serum samples were tested using indirect ELISA to determine the presence of antibodies against Bovine respiratory syncytial virus (BRSV), Bovine parainfluenza virus-3 (BPIV-3), and Bovine viral diarrhea virus (BVDV). Nasal swabs were analyzed using one-step multiplex real-time RT-PCR to detect the presence of viral nucleic acids. Information about biosecurity at the farm level was collected using a questionnaire and field observations. Potential risk factors were evaluated using logistic regression and generalized estimating equations (GEE). At the farm level, the number of seropositive animals varied from 0% to 50%, while at the animal level, the overall seropositivity rate was 21% (57 out of 274). The test showed that 2.19% (6/274) of the samples had BVDV RNA, but none had BRSV or BPIV-3. In the multivariable analyses, increasing age (odds ratio [OR] = 7.05; 95% confidence interval [CI]: 3.21–15.48; p < 0.001) and farm visitors (OR = 11.74; 95% CI: 4.86–28.5; p < 0.001) were found to be the most significant risk factors. The size of the farm was almost statistically significant. The study showed substantial heterogeneity between farms in seropositivity for viral BRDC pathogens, and highlighted the role of indirect contacts and biosecurity-related factors in shaping these patterns. Visitors and shared transport vehicles were identified as the main determinants of transmission. Main strategies to reduce risk include providing protective clothing, minimizing unnecessary animal movements, and strengthening vehicle disinfection protocols. The findings highlight the importance of raising biosecurity awareness among farmers and veterinarians. Due to budgetary and logistical constraints, this exploratory study was conducted in a relatively small number of herds from only two provinces.