PDF(Pubmed)
Abstract：
BACKGROUND: Visna-maedi is a notifiable disease in Norway, and eliminating the disease is a national goal. The import of sheep into Norway is very limited, and strict regulations apply to the movement of small ruminants between flocks and within defined geographical regions. Several outbreaks have occurred in the last 50 years, and the most recent before 2019 occurred in Trøndelag county in Central Norway in 2002. A national surveillance programme for small ruminant lentivirus infection exists since 2003.
RESULTS: In 2019, the national surveillance programme detected seropositive animals for small ruminant lentivirus in a sheep flock in Trøndelag. Based on the result of polymerase chain reaction analysis and histopathological findings, the Norwegian Food Safety Authority concluded the diagnosis of maedi. Further investigations detected maedi in eight additional sheep flocks in the same county. The flocks were placed under restrictions, and the authorities also imposed restrictions on 82 contact flocks. Sequencing of partial gag genes indicated that the virus in the current outbreak was related to the small ruminant lentivirus detected in the same area between 2002 and 2005.
CONCLUSIONS: The outbreak investigation shows the need for sensitive and specific diagnostic methods, and an improved and more targeted surveillance strategy. It also demonstrates the risk of disease spreading between flocks through animal movements, and highlights the importance of biosecurity and structured livestock trade. In addition to allowing livestock trade only from flocks documented free from maedi, it may be necessary to monitor sheep flocks over many years, when aiming to eliminate maedi from the Norwegian sheep population.
RESULTS: In 2019, the national surveillance programme detected seropositive animals for small ruminant lentivirus in a sheep flock in Trøndelag. Based on the result of polymerase chain reaction analysis and histopathological findings, the Norwegian Food Safety Authority concluded the diagnosis of maedi. Further investigations detected maedi in eight additional sheep flocks in the same county. The flocks were placed under restrictions, and the authorities also imposed restrictions on 82 contact flocks. Sequencing of partial gag genes indicated that the virus in the current outbreak was related to the small ruminant lentivirus detected in the same area between 2002 and 2005.
CONCLUSIONS: The outbreak investigation shows the need for sensitive and specific diagnostic methods, and an improved and more targeted surveillance strategy. It also demonstrates the risk of disease spreading between flocks through animal movements, and highlights the importance of biosecurity and structured livestock trade. In addition to allowing livestock trade only from flocks documented free from maedi, it may be necessary to monitor sheep flocks over many years, when aiming to eliminate maedi from the Norwegian sheep population.
摘要：
背景：Visna-maedi是挪威的一种应报告疾病，消除这种疾病是国家目标。挪威的绵羊进口非常有限，严格的规定适用于小反刍动物在羊群之间和在定义的地理区域内的运动。在过去的50年里发生了几次疫情，2019年之前的最新事件发生在2002年挪威中部的Trøndelag县。自2003年以来，就有一项针对小反刍动物慢病毒感染的国家监测计划。
结果：2019年，国家监测计划在Trøndelag的绵羊群中检测到小反刍动物慢病毒的血清反应阳性。根据聚合酶链反应分析结果和组织病理学结果，挪威食品安全局对maedi的诊断做出了结论。进一步的调查在同一县的另外八只羊群中发现了maedi。羊群受到限制，当局还对82个接触羊群施加了限制。部分gag基因的测序表明，当前爆发的病毒与2002年至2005年在同一地区检测到的小反刍动物慢病毒有关。
结论：疫情调查显示需要敏感和特定的诊断方法，以及改进和更有针对性的监控策略。它还证明了疾病通过动物运动在羊群之间传播的风险，并强调了生物安全和结构化牲畜贸易的重要性。除了只允许从有记录的没有maedi的羊群中进行牲畜贸易之外，可能需要监测羊群多年，旨在消除挪威绵羊种群中的maedi。
结果：2019年，国家监测计划在Trøndelag的绵羊群中检测到小反刍动物慢病毒的血清反应阳性。根据聚合酶链反应分析结果和组织病理学结果，挪威食品安全局对maedi的诊断做出了结论。进一步的调查在同一县的另外八只羊群中发现了maedi。羊群受到限制，当局还对82个接触羊群施加了限制。部分gag基因的测序表明，当前爆发的病毒与2002年至2005年在同一地区检测到的小反刍动物慢病毒有关。
结论：疫情调查显示需要敏感和特定的诊断方法，以及改进和更有针对性的监控策略。它还证明了疾病通过动物运动在羊群之间传播的风险，并强调了生物安全和结构化牲畜贸易的重要性。除了只允许从有记录的没有maedi的羊群中进行牲畜贸易之外，可能需要监测羊群多年，旨在消除挪威绵羊种群中的maedi。
