School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK.
Veterinary Public Health, Bristol Veterinary School, University of Bristol, Bristol, BS40 5EZ, UK.
Parasit Vectors. 2021 Jun 29;14(1):344. doi: 10.1186/s13071-021-04850-y.
Ovine psoroptic mange (sheep scab) is a highly pathogenic contagious infection caused by the mite Psoroptes ovis. Following 21 years in which scab was eradicated in the UK, it was inadvertently reintroduced in 1972 and, despite the implementation of a range of control methods, its prevalence increased steadily thereafter. Recent reports of resistance to macrocyclic lactone treatments may further exacerbate control problems. A better understanding of the factors that facilitate its transmission are required to allow improved management of this disease. Transmission of infection occurs within and between contiguous sheep farms via infected sheep-to-sheep or sheep-environment contact and through long-distance movements of infected sheep, such as through markets.
A stochastic metapopulation model was used to investigate the impact of different transmission routes on the spatial pattern of outbreaks. A range of model scenarios were considered following the initial infection of a cluster of highly connected contiguous farms.
Scab spreads between clusters of neighbouring contiguous farms after introduction but when long-distance movements are excluded, infection then self-limits spatially at boundaries where farm connectivity is low. Inclusion of long-distance movements is required to generate the national patterns of disease spread observed.
Preventing the movement of scab infested sheep through sales and markets is essential for any national management programme. If effective movement control can be implemented, regional control in geographic areas where farm densities are high would allow more focussed cost-effective scab management.
绵羊痒螨病（绵羊疥癣）是一种由痒螨属（Psoroptes ovis）引起的高致病性传染性感染。在英国经过 21 年的努力消除了这种疾病后，它于 1972 年被无意中重新引入，尽管采取了一系列控制方法，但此后其流行率稳步上升。最近有关对大环内酯类药物治疗产生抗药性的报道可能会进一步加剧控制问题。为了更好地管理这种疾病，需要更好地了解有助于其传播的因素。感染通过受感染的绵羊与绵羊之间或绵羊与环境之间的接触以及受感染绵羊的远距离迁移（例如通过市场）在相邻的绵羊养殖场内和之间传播。
使用随机元种群模型来研究不同传播途径对暴发的空间模式的影响。在最初感染一群高度相连的相邻农场后，考虑了一系列模型方案。
在引入后，痒螨病会在相邻的集群农场之间传播，但如果排除远距离迁移，那么在农场连通性较低的边界处，感染会在空间上自我限制。需要包括远距离迁移才能产生所观察到的全国性疾病传播模式。
防止受感染的绵羊通过销售和市场进行迁移对于任何国家管理计划都是至关重要的。如果可以有效实施迁移控制，则在农场密度较高的地理区域进行区域控制将允许更集中的具有成本效益的痒螨病管理。
