Epidemiological Research Team, National Institute of Animal Health, 3-1-5, Kannondai, Tsukuba-shi, Ibaraki, Japan.
BMC Vet Res. 2010 Jan 7;6:1. doi: 10.1186/1746-6148-6-1.
Although several attempts have been made to control enzootic bovine leukosis (EBL) at the local level, a nationwide control program has not been implemented in Japan, except for passive surveillance. Effective control of EBL requires that the transmission routes of bovine leukemia virus (BLV) infection should be identified and intercepted based on scientific evidence. In this cross-sectional study, we examined the risk factors associated with within-herd transmission of BLV on infected dairy farms in Japan. Blood samples taken from 30 randomly selected adult cows at each of 139 dairy farms were tested by enzyme-linked immunosorbent assay (ELISA). Information on herd management was collected using a structured questionnaire.
Infected farms were defined as those with more than one ELISA-positive animal and accounted for 110 (79.1%) of the 139 farms in the study. Completed questionnaires obtained from 90 of these 110 farms were used for statistical analysis. Seroprevalence, which was defined as the proportions of animals that tested positive out of all animals tested on the farm, was 17.1%, 48.1%, and 68.5% for the 25th, 50th, and 75th percentiles, respectively. A mixed logistic regression analysis implicated a loose housing system, dehorning, and a large number of horseflies in summer as risk factors (coefficient = 0.71, 1.11, and 0.82; p = 0.03, < 0.01, and 0.01, respectively) and feeding of colostrum to newborn calves from their dams as a protective factor (coefficient = -1.11, p = 0.03) against within-farm transmission of BLV on infected farms.
Control of EBL in infected dairy farms in Japan will be improved by focusing particularly on these risk and protective factors.
尽管已经有几次尝试在局部范围内控制地方性牛白血病（EBL），但除了被动监测外，日本并没有在全国范围内实施控制计划。有效控制 EBL 需要根据科学证据确定和拦截牛白血病病毒（BLV）感染的传播途径。在这项横断面研究中，我们研究了日本感染奶牛场 BLV 场内传播的相关风险因素。从 139 个奶牛场的 30 头随机成年奶牛中采集血液样本，通过酶联免疫吸附试验（ELISA）进行检测。使用结构化问卷收集有关牧场管理的信息。
感染场定义为有超过一个 ELISA 阳性动物的场，研究中 139 个场中有 110 个（79.1%）属于感染场。从这 110 个场中的 90 个获得了完整的调查问卷，用于统计分析。血清阳性率（定义为所有农场检测动物中阳性动物的比例）分别为第 25、50 和 75 百分位数的 17.1%、48.1%和 68.5%。混合逻辑回归分析表明，宽松的饲养系统、去角和夏季大量的马蝇是风险因素（系数分别为 0.71、1.11 和 0.82；p 值分别为 0.03、<0.01 和 0.01），而给新生小牛喂初乳是一个保护因素（系数为-1.11，p=0.03），可以防止感染场 BLV 的场内传播。
特别关注这些风险和保护因素，将有助于改善日本感染奶牛场的 EBL 控制。
