Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2013
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Viral infections are important etiologies in BRD cases. Calves at stocker/feedlot entry usually receive modified live viral (MLV) vaccines containing bovine herpesvirus-1 (BoHV-1), parainfluenza-3 virus (PI3V), bovine viral diarrhea viruses (BVDV), and bovine respiratory syncytial virus (BRSV). In a 2012 study, 516 head arrived over a one week interval from six sale barns in the state by a single buyer. Calves received a five way BRD MLV BoHV-1, PI3V, noncytopathic BVDV1a and 2a, BRSV vaccine at processing. There were 343 calves treated for BRD (66.5%) and 332 head treated in the first 21 days. Of 516 calves, 72 died with 68 respiratory cases (12.2% of 516). There were 15 sentinel calves monitored for viruses with nasal swabs (NS) and serologic testing after arrival. Nasal swabs and respiratory tissue homogenates were inoculated onto MDBK and HRT monolayers. Viruses were confirmed in cultures by PCR for BVDV, PI3V, BRSV, and bovine coronavirus (BoCV). BVDV isolates were subtyped and positives compared to MLV strains. BVDV and BoCV serology was performed using paired samples. There were 12/15 (80%) of sentinels (between days (d) 9-11 after vaccination with MLV NCP BVDV1a in NS. One calf’s NS was positive for PI3Vand BRSV. All sentinels seroconverted to BVDV1a and 7/15 (46.7%) to BoCV. There were 37 tissue sets available for virus isolation from calves dying from d 8 to d 47. Nine calves’ lungs were positive for NCP BVDV1: 7 MLV NCP BVDV1a and 2 BVDV1b. Four calves’ lungs were PI3V positive, one BRSV, and one BoCV. The shipments had one persistently infected BVDV calf. This study found multiple viruses from postweaned calves within 1-2 weeks after MLV vaccination.. MLV vaccine strains should be differentiated from field strains. Viral genome sequences of MLV vaccines should be available permitting PCR and sequencing. In this study NCP MLV BVDV1a vaccine strain was recovered indicating viral shed in nasal swabs and tissues from dying calves.