Norwegian Veterinary Institute, Ullevålsveien 68, 0454, Oslo, Norway.
TINE SA, Postboks 7, 0901, Oslo, Norway.
Acta Vet Scand. 2020 Nov 23;62(1):64. doi: 10.1186/s13028-020-00561-z.
Outbreaks of infectious arthritis in young lambs associated with Streptococcus dysgalactiae subspecies dysgalactiae (SDSD) lead to reduced animal welfare, increased use of antibiotics and economic losses for sheep farmers. Understanding risk factors is essential when developing strategies to prevent such outbreaks. This questionnaire-based cross-sectional study classified sheep flocks of respondents as cases or controls. Flock-level risk factors for outbreaks of infectious arthritis were assessed using a multivariable logistic regression model.
Eighty-four of 1498 respondents (5.6%) experienced an outbreak of infectious arthritis in their flock in 2018, the year of study. Factors associated with a higher risk of outbreak were larger flock size (OR 1.3, 95% CI 1.1-1.4, per 100 lambs), plastic mesh flooring in the lambing pen (OR 3.0, 95% CI 1.7-5.3) and a lambing percentage greater than 200 (OR 2.0, 95% CI 1.1-3.5). Flocks where farmers observed infections around the ear tags of lambs also had an increased risk of outbreak (OR 2.6, 95% CI 1.6-4.3).
The risk factors identified in this study are characteristic of modern and intensively managed sheep farms in Norway. A distinguishing feature of Norwegian sheep farming is winter housing and indoor lambing. One might expect that this in itself is a risk factor because of high stocking densities during lambing. However, outbreaks of infectious arthritis in young lambs are reported by the industry to be a more recent phenomenon. The current study indicates that intensification of indoor management systems with larger flocks and higher production per ewe may predispose to outbreaks. The results provide a basis for further studies on transmission dynamics of SDSD in sheep flocks with indoor lambing.
由兽疫链球菌兽疫亚种（SDSD）引起的幼羊传染性关节炎疫情会导致动物福利下降、抗生素使用增加以及绵羊养殖户经济损失。在制定预防此类疫情爆发的策略时，了解风险因素至关重要。本基于问卷调查的横断面研究将绵羊养殖户分为病例组和对照组。使用多变量逻辑回归模型评估绵羊群的传染病关节炎爆发的畜群级风险因素。
在研究年 2018 年，1498 名受访者中有 84 名（5.6%）经历了其羊群的传染病关节炎爆发。与爆发风险较高相关的因素包括：较大的羊群规模（每增加 100 只羔羊，比值比 1.3，95%置信区间 1.1-1.4）、产羔栏中使用塑料网地板（比值比 3.0，95%置信区间 1.7-5.3）和产羔率大于 200（比值比 2.0，95%置信区间 1.1-3.5）。农民观察到羔羊耳标周围有感染的羊群，其爆发风险也会增加（比值比 2.6，95%置信区间 1.6-4.3）。
本研究确定的风险因素是挪威现代集约化管理绵羊养殖场的特征。挪威绵羊养殖的一个显著特点是冬季舍饲和室内产羔。人们可能认为，由于产羔期间的高存栏密度，这种方式本身就是一个风险因素。然而，行业报告称，幼羊传染性关节炎的爆发是最近才出现的现象。本研究表明，随着较大羊群和每只母羊更高的生产水平，室内管理系统的集约化可能会导致疫情爆发。研究结果为进一步研究室内产羔绵羊群中 SDSD 的传播动态提供了基础。
