van der Meer, Franciscus JohannesShrestha, Sulav2024-01-242024-01-242024-01-19Shrestha, S. (2024). Exploring the impact of bovine leukemia virus proviral load on production, and its potential use for control (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.https://hdl.handle.net/1880/118048https://doi.org/10.11575/PRISM/42892The main aim of this dissertation was to evaluate the efficacy of a bovine leukemia virus (BLV) control program by selective removal of high proviral load (HPL) BLV-infected subsets. Six chapters are included. 1) To be acquainted with the current understanding on BLV infection, transmission routes, diagnosis, control, and most importantly, BLV proviral load, a literature review was conducted. This review explored the applicability of BLV proviral load in disease diagnosis, BLV transmission risk assessment, and BLV control. 2) We implemented a cross-sectional study to evaluate the impact of BLV proviral load on milk production of dairy cows. Data obtained from nine dairy herds in Alberta, Canada demonstrated a significant reduction in milk, fat, and protein production of HPL cows when compared with the BLV-negative counterparts. 3) The effectiveness of HPL-cow focused BLV control program in reducing BLV prevalence and seroconversions within the herd was evaluated by conducting a 3-year study among ten dairy herds. The BLV prevalence decreased in four herds whereas the BLV incidence was reduced in nine herds, which supported the notion that removal of HPL cows can offer a feasible and economical option for BLV control. 4) A 1.5-year longitudinal study was designed by enrolling subset of cows from BLV-seropositive (further classified into various proviral load categories) and BLV-seronegative group to monitor the dynamics of various parameters such as BLV proviral load, lymphocyte, white blood cell (WBC) count, antibody titer, CD3+, CD4+, CD8+, CD21+, and WC1+ cell proportions. A relatively stable pattern of BLV proviral load, WBC, CD3+, and CD4+ cell proportion was observed, indicating frequent testing might not be required for these parameters in monitoring BLV infection. 5) A cross-sectional study was conducted to investigate the hematological and immunological impact of BLV infection which suggested a simpler categorization of HPL and LPL as an appropriate approach. Additionally, a lower proviral load cut-off was identified as an accurate threshold for identifying HPL cows. 6) Lastly, all the results and findings were thoroughly discussed, and future directions for using HPL-focused strategies as a potential tool for BLV control and management were elaborated.enUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.bovine leukemia virusproviral loadcontrolimpactthresholdVeterinary ScienceVirologydoctoral thesis