Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia.
College of Veterinary Medicine and Agriculture, Addis Ababa University, Bishoftu, Ethiopia.
BMC Microbiol. 2024 Oct 9;24(1):394. doi: 10.1186/s12866-024-03543-7.
Bovine tuberculosis (bTB) is a chronic disease caused by members of the Mycobacterium tuberculosis complex (MTBC) that ultimately leads to the development of progressive granulomatous lesions. Although the disease is widespread, especially in crossbred cattle in Ethiopia, routine investigations and surveillance are lacking. Thus, the aim of this study was to determine the prevalence, associated risk factors, and species of mycobacteria causing bTB in slaughtered cattle at four slaughterhouses in Central Ethiopia.
Postmortem examination of 7,640 cattle was conducted using a cross-sectional slaughterhouse survey. A total of 388 tuberculous-like lesions (TBLs) were collected from 173 animals and cultured. Six target genes were used to differentiate mycobacterial species using multiplex real-time PCR (mRT-PCR). Multivariate logistic regression analyses and related odds ratios (ORs) were used to gauge the strength of the associations between risk factors, TBL incidence and culture growth.
The prevalence of TBL was 2.3% (95% CI = 2.0-2.6). Logistic regression analysis indicated an increased risk of TBL in crossbred cattle (OR = 11.8, 95% CI: 6.4, 21.2, p < 0.001). Animals slaughtered at Adama (OR = 3.2, 95% CI: 1.2, 7.3, p = 0.009) or Burayu (OR = 5.8, 95% CI: 3.9, 8.9, p < 0.001) had a greater risk of TBL than those slaughtered at Sululta. There were significantly more TBL-positive lesions in the lungs and lymph nodes related to the lung (OR = 7.1; 95% CI: 2.7, 24.5, p < 0.001) and the head lymph node (OR = 5.6; 95% CI: 1.8, 21.7; p = 0.006) compared to gut associated lymph nodes. Among the 173 TBL-positive animals, 36% (95% CI = 28.8, 43.2), and among the 388 TBL-positive tissues, 24.2% (95% CI = 20, 29) were culture and mRT-PCR positive. All the culture-generated isolates were positive for M. bovis in mRT-PCR. Among them, two animals had mixed infections including one zebu cattle tested positive for both M. caprae and M. bovis, and a crossbred cow tested positive for both M. tuberculosis and M. bovis in mRT-PCR. This suggests persistent transmission within the cattle population, posing a substantial public health threat.
This study revealed an eleven-fold greater risk of bTB-related lesions in crossbred cattle compared to local zebu cattle. This finding highlights the necessity for targeted interventions, continuous vigilance, and thorough carcass inspection to mitigate public health risks.
牛结核病（bTB）是由分枝杆菌复合群（MTBC）成员引起的慢性疾病，最终导致进行性肉芽肿病变的发展。尽管该疾病广泛存在，尤其是在埃塞俄比亚的杂交牛中，但常规调查和监测却缺乏。因此，本研究旨在确定在埃塞俄比亚中部的四个屠宰场中屠宰牛中导致 bTB 的分枝杆菌的流行率、相关危险因素和种属。
采用横断面屠宰场调查对 7640 头牛进行了尸检。从 173 头动物中收集了 388 个结核样病变（TBL）并进行培养。使用多重实时 PCR（mRT-PCR）检测 6 个靶基因以区分分枝杆菌种属。使用多变量逻辑回归分析和相关的比值比（OR）来评估危险因素、TBL 发生率和培养物生长之间的关联强度。
TBL 的流行率为 2.3%（95%CI=2.0-2.6）。逻辑回归分析表明，杂交牛的 TBL 风险增加（OR=11.8，95%CI：6.4，21.2，p<0.001）。在阿达玛（OR=3.2，95%CI：1.2，7.3，p=0.009）或伯拉伊（OR=5.8，95%CI：3.9，8.9，p<0.001）屠宰的动物比在苏卢尔塔屠宰的动物更有可能发生 TBL。与肠道相关的淋巴结相比，与肺相关的肺和淋巴结中的 TBL 阳性病变明显更多（OR=7.1；95%CI：2.7，24.5，p<0.001）和头部淋巴结（OR=5.6；95%CI：1.8，21.7；p=0.006）。在 173 头 TBL 阳性动物中，有 36%（95%CI=28.8,43.2），在 388 个 TBL 阳性组织中，有 24.2%（95%CI=20,29）为培养和 mRT-PCR 阳性。所有培养产生的分离株在 mRT-PCR 中均为牛分枝杆菌阳性。其中，有两例动物混合感染，一例瘤牛对牛分枝杆菌和山羊分枝杆菌均呈阳性，一例杂交牛在 mRT-PCR 中对结核分枝杆菌和牛分枝杆菌均呈阳性。这表明在牛群中持续存在传播，对公共卫生构成重大威胁。
与当地瘤牛相比，杂交牛的 bTB 相关病变风险增加了 11 倍。这一发现强调了需要采取有针对性的干预措施、持续监测和彻底的屠体检查，以减轻公共卫生风险。
