Investigation of bovine leukemia virus infection in Taiwan

• Main Authors: Chang-Yan Li, 李長晏
• Other Authors: Shih-Te Chuang
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/g6mxa3

碩士 === 國立中興大學 === 獸醫學系暨研究所 === 106 === Bovine leukemia virus (BLV) infection in cattle results in the decrease of milk yield and quality, the loss of carcass value, the compromise of immunity, and the shortening of cow longevity. The purposes of this study were to investigate the seroprevalence of BLV infection, the genotypes of the present BLV in Taiwan, and to offer a clinically useful tool to diagnose BLV infection. Seropositivity was tested by enzyme-linked immunosorbent assay (ELISA) in samples from dairy cattle collected in 16 cities and counties from 2016 to 2017. The animal prevalence and the herd prevalence were found to be 81.8% (540/660) and 99.1% (109/110), respectively. Region-level animal prevalence was found highest in the northern (91.7%), followed by the central (85.2%), the southern (79.2%) and the eastern (72.2%). Complete blood count (CBC) and polymerase chain reaction (PCR) were performed on 152 anticoagulated whole blood samples from healthy dairy cows. A total of 132 (86.8%) cases were found PCR-positive, and white blood cell (WBC) count was found to be the most potential CBC item in predicting BLV infection in the univariate logistic regression model. By the receiver operating characteristic curve analysis, the sensitivity and specificity were examined as 72.0% and 75.0%, respectively, when the cut-off value of WBC was set at 10.215 K/μL. The sensitivity and specificity were revealed as 51.5% and 100.0% when the cut-off value of WBC increased to 12.505 K/μL. A total of 30 amplified env fragments were sequenced. The sequences were phylogenetically analyzed together with 51 sequences representing the 10 known BLV genotypes worldwide previously published. According to the results, the present BLV genotypes in Taiwan were found to be genotype 1 and genotype 3, and genotype 1 was more prevalent (29/30). To control the prevalence of BLV infection, herd managers and veterinarians should control the risk factors and interrupt the routes of transmission of BLV, while the government should execute nation-wide surveillance programs, control policies and strict quarantine to eliminate and prevent further introduction of BLV.