School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, England, United Kingdom.
Vet Parasitol. 2012 Sep 30;189(1):8-14. doi: 10.1016/j.vetpar.2012.03.028. Epub 2012 Mar 28.
The free-living stages of gastrointestinal nematode parasites of sheep are strongly affected by climate. Thus, extreme heat and cold are detrimental to development and survival, while, within tolerable limits, increasing temperatures generally accelerate development but increase mortality. Moisture is needed for development and translation of larvae from faeces to pasture, and so rainfall is a limiting factor for transmission. Together, these factors underpin seasonal patterns of infection in sheep, as well as geographic variation in the epidemiology and relative importance of different species within Europe. Local knowledge and experience enable treatment to be targeted appropriately to prevent dangerous levels of infection. This traditional know-how can be supplemented by predictive epidemiological models, built on thorough understanding of the influence of climate on larval availability. However, management also has a dominant role in determining patterns of infection, and is itself influenced by climate. Current geographic variation in nematode epidemiology across Europe, and knowledge of systems from outside Europe, can provide only limited perspectives on the likely effects of climate change on disease in future. This is because disease arises from complex interaction between host and parasite factors, and the implementation of optimal control strategies to meet new challenges will be slowed by the inertia of current systems. Approaches to nematode control must therefore take account not only of parasite biology, but also the forces that shape sheep farming systems and management decisions.
羊的自由生活阶段的胃肠道线虫寄生虫强烈受到气候的影响。因此，极端的高温和低温对其发育和生存都是不利的，而在可承受的范围内，温度升高通常会加速其发育，但会增加死亡率。幼虫从粪便到牧场的发育和转化需要水分，因此降雨是传播的限制因素。这些因素共同构成了羊季节性感染模式以及欧洲内部不同物种的流行病学和相对重要性的地理差异。当地的知识和经验使治疗能够针对预防危险的感染水平。这种传统的专门技术可以通过预测性的流行病学模型来补充，这些模型建立在对气候对幼虫供应的影响的透彻理解之上。然而，管理在确定感染模式方面也起着主导作用，而且本身也受到气候的影响。目前欧洲各地的线虫流行病学的地域差异，以及对欧洲以外系统的了解，只能提供关于气候变化对未来疾病可能产生的影响的有限视角。这是因为疾病是由宿主和寄生虫因素之间的复杂相互作用引起的，而实施最佳控制策略以应对新挑战将因现有系统的惯性而受到阻碍。因此，线虫控制方法不仅必须考虑寄生虫生物学，还必须考虑塑造绵羊养殖系统和管理决策的力量。
