Department of Animal Virology, Research and Diagnosis, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Organization (AREEO), Karaj, Iran.
Iran Veterinary Organization, Tehran, Iran.
Prev Vet Med. 2020 Jun;179:104994. doi: 10.1016/j.prevetmed.2020.104994. Epub 2020 Apr 30.
Bluetongue virus (BTV) remains as an economically major concern in the world. Seroprevalence and potential risk factors of BTV were assessed in a cross-sectional study at both the herd and animal levels in Iran. A total of 73 Epidemiologic Units (E.Unit), defined as a herd, flock or village including animals with equal chance of exposure to infectious agents, were randomly selected. Serum samples from all animals (n = 34,575) within the E.Units were collected and tested for BTV sero-group antibodies by using commercially competitive ELISA test. Using cluster analysis, 90.41 % (95 %, CI: 80.85 %-95.47 %) of the E.Units and 56.13 % (95 % CI: 55.61 %-56.66 %) of the tested animals were detected seropositive against BTV. A seroprevalence rate of 57.59 % (95 % CI: 48.01 %-66.63 %), 65.65 % (95 % CI: 59.10 %-73.74 %) and 27.63 % (95 % CI: 14.40 %-46.43 %) was estimated for sheep, goats and cattle, respectively. At E.Unit (herd) level, density was identified as a great risk factor for the infection (r = 0.891; P = 0.000), and particularly density of cattle significantly correlated with BTV infection within the E.Units (r = 0.247; P = 0.019). Using multilevel logistic regression, adjusted odds ratios (ORs) were estimated at individual level. A significantly less risk of BTV infection was evaluated for cattle than for sheep (OR = 0.42, 95 % CI: 0.38-0.47, P < 0.001), while no significant difference was observed between sheep and goat (OR = 1.03, 95 % CI: 0.97-1.10, P = 0.345). Animals over 2 years and between 6 months and 2 years expressed 2.22 (OR = 2.22, 95 % CI: 1.96-2.52, P < 0.001) and 2.18 (OR = 2.18, 95 % CI: 1.92-2.49, P < 0.001) times higher chance for the infection than animals under 6 months. Males were at significantly less risk of the infection than females (OR=0.68, 95 % CI: 0.63-0.74, P < 0.001). Animals kept in industrial farming systems displayed 0.46 (OR=0.46, 95 % CI: 032-0.66, P < 0.001) times less chance than animals kept in traditional farming system for BTV, while animals lived in semi-industrial farming system were found to be at 2.97 (OR=2.97, 95 % CI: 2.41-3.66, P < 0.001) times higher chance for BTV than animals lived in traditional farming system. Furthermore, seropositive animals exhibited a high amount of antibodies against BTV (s) suggesting that viral exposure may have frequently occurred during their lifetimes. This large - scale study yielded information on epidemiology of BTV in Iran that is prerequisite for further research, and also for evaluation of any cost-benefit control measure to be established in an enzootic zone of the virus.
蓝舌病病毒（BTV）仍然是世界范围内一个具有重大经济意义的关注点。本研究在伊朗采用横断面研究，在畜群和动物两个层面上评估了 BTV 的血清流行率和潜在风险因素。共随机选择了 73 个流行病学单位（E.Unit），定义为一个畜群、一群或村庄，其中的动物有同等机会接触到传染性病原体。从 E.Unit 内的所有动物（n = 34575）中采集血清样本，并使用商业竞争性 ELISA 检测试剂盒检测 BTV 血清群抗体。通过聚类分析，90.41%（95%CI：80.85%-95.47%）的 E.Unit 和 56.13%（95%CI：55.61%-56.66%）的检测动物对 BTV 呈血清阳性。绵羊、山羊和牛的血清流行率分别估计为 57.59%（95%CI：48.01%-66.63%）、65.65%（95%CI：59.10%-73.74%）和 27.63%（95%CI：14.40%-46.43%）。在 E.Unit（畜群）层面上，密度被确定为感染的一个重要危险因素（r = 0.891；P = 0.000），特别是牛的密度与 E.Unit 内的 BTV 感染显著相关（r = 0.247；P = 0.019）。使用多水平逻辑回归，在个体层面上估计了调整后的优势比（OR）。与绵羊相比，牛感染 BTV 的风险显著降低（OR = 0.42，95%CI：0.38-0.47，P < 0.001），而绵羊和山羊之间没有显著差异（OR = 1.03，95%CI：0.97-1.10，P = 0.345）。2 岁以上和 6 个月至 2 岁之间的动物感染的几率比 6 个月以下的动物高 2.22 倍（OR = 2.22，95%CI：1.96-2.52，P < 0.001）和 2.18 倍（OR = 2.18，95%CI：1.92-2.49，P < 0.001）。雄性比雌性感染的风险显著降低（OR = 0.68，95%CI：0.63-0.74，P < 0.001）。与传统养殖系统相比，在工业养殖系统中饲养的动物感染 BTV 的几率降低了 0.46 倍（OR = 0.46，95%CI：032-0.66，P < 0.001），而在半工业养殖系统中饲养的动物感染 BTV 的几率则增加了 2.97 倍（OR = 2.97，95%CI：2.41-3.66，P < 0.001）。此外，血清阳性动物对 BTV（s）的抗体含量很高，这表明在其一生中，病毒暴露可能经常发生。这项大规模研究提供了伊朗 BTV 流行病学的信息，这是进一步研究的前提，也是评估在病毒地方性流行区建立任何成本效益控制措施的必要条件。
