Complejo respiratorio bovino: evidencia de circulación viral múltiple en un establecimiento de cría

Bovine respiratory complex (BRC) is a leading cause of production loss among beef, dairy and feedlot cattle. The infectious agents involved are viruses, bacteria and mycoplasma. Viral agents include Bovine respiratory syncytial virus (BRSV), Bovine parainfluenza-3 virus (BPI3V), Bovine herpesvirus 1 (BHV-1) and Bovine viral diarrhea virus (BVDV). The purpose of this study was to evaluate the circulation of viruses associated with BRC in a beef herd, postweaning, doing a longitudinal assessment of serological tests. Moreover, clinical and hematological findings were described and compared. Thirty two animals between 5 to 7 months old, with no vaccination record, were selected for a daily evaluation of clinical signs consistent with BRC. Blood samples were taken on day 0 (weaning), +14 and +25 (when the study ended). No clinical manifestation of BRC was found and hematological parameters were within the reference range. At the beginning of this study, animals did not show BRSV-specific antibodies (Ab), whereas for the other viral agents the percentage of seropositive animals varied: 53% (BVDV1a), 31% (BPI3V), 25% (BVDV2) and 13% (BHV-1). On day +25, percentages of seropositive animals were 47% (BVDV1a), 50% (BPI3V), 19% (BVDV2), 25% (BHV-1) and 81% (BRSV). Seroconversion percentages for BRSV, BPI3V, BVDV1a and BHV-1 were 34%, 25%, 16% and 13% respectively. Furthermore, 66% of the animals seroconverted to one or more viruses. No seroconversion was observed for BVDV2 and BVDV1b. Thus, there is evidence of circulation and -in some cases- co-infection with BRC-associated viral agents during postweaning. At said production stage, conducting viral follow-up studies to identify and characterize circulating strains is key, particularly in relation to BRSV and PI3, which we have little information about in our country.