Table_1_Specific and non-specific effects of Mycobacterium bovis BCG vaccination in dairy calves.XLSX

Bovine tuberculosis (bTB) is a chronic disease mainly caused by Mycobacterium bovis, a zoonotic pathogen with economic significance as it leads to reduced milk and meat production, and high costs for control measures. The Bacillus Calmette-Guérin (BCG) vaccine, primarily used to prevent tuberculosis in humans, has also been studied for controlling bTB. While showing effectiveness in preventing M. bovis infection and disease in cattle, the BCG vaccine can induce non-specific effects on the immune system, enhancing responses to infections caused by unrelated pathogens, and also having non-specific effects on lactation. The aim of this study is to describe both the specific and non-specific effects of BCG vaccination in calves from a commercial dairy herd in central Chile. Diagnosis of M. bovis infection was performed through the IFNγ release assay (IGRA) using ESAT6/CFP-10 and Rv3615c antigens. The records of milk production, somatic cell count (SCC), clinical mastitis (CM) and retained placenta (RP) during the first lactation were compared between vaccinated and non-vaccinated animals. The breed (Holstein Friesian [HF] v/s HF × Swedish Red crossbred [HFSR]) and the season (warm v/s cold) were also analyzed as categorical explanatory variables. Results of IGRA showed significant differences between vaccinated and control groups, indicating a vaccine efficacy of 58.5% at 18 months post vaccination in HFSR crossbred animals. Although milk production did not vary, SCC and CM showed differences between groups, associated to the breed and the season, respectively. When analyzing CM and RP as a whole entity of disease, BCG showed protection in all but the cold season variables. Overall, the BCG vaccine induced protective specific and non-specific effects on health parameters, which may be influenced by the breed of animals and the season. These results provide new features of BCG protection, supporting initiatives for its implementation as a complementary tool in bTB control.

牛结核病（bovine tuberculosis, bTB）是一种主要由牛分枝杆菌（Mycobacterium bovis）引起的慢性传染病，该病原菌为人畜共患病原体，因导致奶肉产量下降、防控成本高昂而具有重要经济意义。卡介苗（Bacillus Calmette-Guérin, BCG）原本主要用于预防人类结核病，目前也被研究用于牛结核病的防控。尽管该疫苗在预防牛感染牛分枝杆菌及相关发病方面已展现出有效性，但卡介苗可诱导免疫系统产生非特异性效应：一方面可增强机体对无关病原体感染的免疫应答，另一方面也会对泌乳功能产生非特异性影响。本研究旨在阐明智利中部某商业奶牛场犊牛接种卡介苗后的特异性与非特异性效应。本研究采用ESAT6/CFP-10与Rv3615c两种抗原，通过γ干扰素释放试验（IFNγ release assay, IGRA）对牛分枝杆菌感染进行诊断，对比了接种组与未接种组奶牛首胎泌乳期的产奶量、体细胞计数（SCC）、临床型乳腺炎（CM）及胎衣不下（RP）相关记录，并将品种（荷斯坦奶牛[HF]与荷斯坦-瑞典红杂交牛[HFSR]）及季节（暖季与冷季）作为分类解释变量纳入分析。γ干扰素释放试验结果显示，接种组与对照组间存在显著差异，在荷斯坦-瑞典红杂交牛群体中，接种后18个月的疫苗保护率达58.5%。尽管两组产奶量未出现明显差异，但体细胞计数与临床型乳腺炎在组间存在显著区别，且分别与品种及季节相关。当将临床型乳腺炎与胎衣不下合并为整体疾病指标进行分析时，除冷季相关组别外，卡介苗在其余所有组别中均展现出保护作用。总体而言，卡介苗可对健康相关参数产生兼具特异性与保护性的非特异性效应，且该效应可能受动物品种与季节的影响。本研究结果揭示了卡介苗保护作用的新特征，为将其作为牛结核病防控的辅助工具提供了科学依据。