Efficacy of Oral Administration of Sodium Iodide to Prevent Bovine Respiratory Disease Complex.

BACKGROUND: The prevention of bovine respiratory disease complex (BRD) in beef cattle is important to maintaining health and productivity of calves in feeding operations. OBJECTIVE: Determine whether BRD bacterial and viral pathogens are susceptible to the lactoperoxidase/hydrogen peroxide/iodide (LPO/H2 O2 /I- ) system in vitro and to determine whether the oral administration of sodium iodide (NaI) could achieve sufficient concentrations of iodine (I) in the respiratory secretions of weaned beef calves to inactivate these pathogens in vivo. ANIMALS: Sixteen weaned, apparently healthy, commercial beef calves from the University of Missouri, College of Veterinary Medicine teaching herd. METHODS: In vitro viral and bacterial assays were performed to determine susceptibility to the LPO/H2 O2 /I- system at varying concentrations of NaI. Sixteen randomly selected, healthy crossbred beef weanlings were administered 70 mg/kg NaI, or water, orally in a blinded, placebo-controlled trial. Blood and nasal secretions were collected for 72 hours and analyzed for I- concentration. RESULTS: Bovine herpesvirus-1, parainfluenza-3, Mannheimia haemolytica and Bibersteinia trehalosi were all inactivated or inhibited in vitro by the LPO/H2 O2 /I- reaction. Oral administration of NaI caused a marked increase in nasal fluid I concentration with a Cmax  = 181 (1,420 µM I), T12 , a sufficient concentration to inactivate these pathogens in vitro. CONCLUSIONS AND CLINICAL IMPORTANCE: In vitro, the LPO/H2 O2 /I- system inactivates and inhibits common pathogens associated with BRD. The administration of oral NaI significantly increases the I concentration of nasal fluid indicating that this system might be useful in preventing bovine respiratory infections.

Generation of calves persistently infected with HoBi-like pestivirus and comparison of methods for detection of these persistent infections.

The identification and elimination of persistently infected (PI) cattle are the most effective measures for controlling bovine pestiviruses, including bovine viral diarrhea virus (BVDV) and the emerging HoBi-like viruses. Here, colostrum-deprived calves persistently infected with HoBi-like pestivirus (HoBi-like PI calves) were generated and sampled (serum, buffy coat, and ear notches) on the day of birth (DOB) and weekly for 5 consecutive weeks. The samples were subjected to diagnostic tests for BVDV--two reverse transcriptase PCR (RT-PCR) assays, two commercial real-time RT quantitative PCR (RT-qPCR), two antigen capture enzyme-linked immunosorbent assays (ACE), and immunohistochemistry (IHC)--and to HoBi-like virus-specific RT-PCR and RT-qPCR assays. The rate of false negatives varied among the calves. The HoBi-like virus-specific RT-PCR detected HoBi-like virus in 83%, 75%, and 87% of the serum, buffy coat, and ear notch samples, respectively, while the HoBi-like RT-qPCR detected the virus in 83%, 96%, and 62%, respectively. In comparison, the BVDV RT-PCR test had a higher rate of false negatives in all tissue types, especially for the ear notch samples (missing detection in at least 68% of the samples). The commercial BVDV RT-qPCRs and IHC detected 100% of the ear notch samples as positive. While ACE based on the BVDV glycoprotein E(rns) detected infection in at least 87% of ear notches, no infections were detected using NS3-based ACE. The BVDV RT-qPCR, ACE, and IHC yielded higher levels of detection than the HoBi-like virus-specific assays, although the lack of differentiation between BVDV and HoBi-like viruses would make these tests of limited use for the control and/or surveillance of persistent HoBi-like virus infection. An improvement in HoBi-like virus tests is required before a reliable HoBi-like PI surveillance program can be designed.