EpiCentre, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand.
Prev Vet Med. 2011 Jul 1;100(3-4):221-30. doi: 10.1016/j.prevetmed.2011.03.014. Epub 2011 May 7.
The aim of this study was to identify risk factors for bovine tuberculosis (TB) in a free-roaming, capture-mark-recapture monitored possum Trichosurus vulpecula population in a 22-ha study site at Castlepoint, New Zealand from 1 April 1989 to 31 March 1994. A matched case-control design was used to evaluate the influence of sex, habitat and contact opportunities on TB risk. Cases comprised possums identified as TB-positive throughout the study period. Controls were selected from the group of possums that were captured and showed no clinical signs of TB throughout the study period. Measures derived from a social network analysis of possum capture locations such as degree, clustering coefficient (CC) and betweenness were used to represent potential contact opportunities among possums. Network analysis measures recorded for individual possums in the 12-month period before a diagnosis of TB were evaluated in a conditional logistic regression model. We found no evidence of an association between case status and the total number of possums with which there was potential contact (degree) (P=0.5). The odds of cases being exposed to unit increases in the number of TB-positive contacts was 2.50 (95% CI 1.24-5.05; P<0.01) times that of controls. This effect was conditional on the total number of potential contacts made, with a negative interaction with increasing degree. These findings indicate that potential contact with TB-positive possums increases the odds of disease whereas potential contact with large numbers of possums does not. This suggests that multiple contacts with TB-positive possum(s) are necessary for transmission of TB and this is more likely to occur in networks that are smaller. We challenge the hypothesis that contact with large numbers of individuals increases the probability of becoming TB infected and argue that individual contact behaviour is a determinant of the creation of TB foci within free-living possum populations.
本研究的目的是确定 1989 年 4 月 1 日至 1994 年 3 月 31 日期间在新西兰卡斯尔波因特的一个 22 公顷研究点中，自由放养、捕获-标记-重捕监测的负鼠 Trichosurus vulpecula 种群中发生牛结核病 (TB) 的风险因素。采用匹配病例对照设计来评估性别、栖息地和接触机会对 TB 风险的影响。病例组由整个研究期间被确定为 TB 阳性的负鼠组成。对照组从整个研究期间被捕获且未表现出 TB 临床症状的负鼠中选择。从负鼠捕获地点的社交网络分析中得出的度量，例如度、聚类系数 (CC) 和中间性，用于表示负鼠之间的潜在接触机会。在 TB 诊断前 12 个月内记录的个体负鼠的网络分析度量值，在条件逻辑回归模型中进行了评估。我们没有发现病例状态与潜在接触（度）的负鼠总数之间存在关联的证据（P=0.5）。与对照组相比，病例组接触 TB 阳性接触者数量每增加一个单位的几率为 2.50（95%CI 1.24-5.05；P<0.01）倍。这种效果取决于潜在接触的总数，与度的增加呈负交互作用。这些发现表明，与 TB 阳性负鼠的潜在接触会增加患病的几率，而与大量负鼠的潜在接触则不会。这表明，与 TB 阳性负鼠的多次接触是 TB 传播所必需的，而这种情况更可能发生在较小的网络中。我们挑战了接触大量个体可增加感染 TB 概率的假设，并认为个体接触行为是在自由生活负鼠种群中形成 TB 焦点的决定因素。
