Williams J C, Knox J W, Loyacano A F
Department of Veterinary Science, LSU Agricultural Center, Baton Rouge 70803.
Vet Parasitol. 1993 Feb;46(1-4):313-24. doi: 10.1016/0304-4017(93)90069-y.
Epidemiologic events in the life cycle of Ostertagia ostertagi are best known in the weaner-yearling phase of cattle development throughout the concentrated cattle-rising areas of the world. Animal and pasture management demands placed on this age class are greater than for suckling calves and adult stock in either beef or dairy breeds. This fact alone would likely account for a higher prevalence of clinical and subclinical disease in weaner-yearlings. Additionally, the developing immune response provides relatively early protection against intestinal genera such as Cooperia and Oesophagostomum, but is delayed against Ostertagia ostertagi and Trichostrongylus axei. Both Type I and Type II disease may occur within the weaner-yearling stage. Factors affecting population changes of Ostertagia ostertagi have been described as extrinsic, i.e. weather-climate and grazing management, and intrinsic or host factors, i.e. age, sex, immune status, heredity and reproductive state. Immune status, particularly in weaner-yearlings, may be of primary importance, as affected by host and extrinsic factors. With slow development of protective immunity against Ostertagia ostertagi in calves, the possible role of immunity in both induction of inhibition and larval maturation, the potential immunopathologic involvement in pathogenesis of Type II disease, hypersensitivity to larval intake in resistant adult cows, and the reported delay of a protective response following anthelmintic prophylaxis in younger cattle, the immune response may have profound influence on epidemiologic variation through age classes. Although continual epidemiological observations from birth to early adulthood in the same cattle have not been undertaken, some notable studies in the UK, the Netherlands, and Denmark have closely examined epidemiological events through first and second grazing seasons.
在世界上集中养牛地区，奥斯特他线虫的生命周期中的流行病学事件在断奶犊牛到一岁龄牛阶段最为人所知。这个年龄段的动物和牧场管理要求比肉牛或奶牛品种的哺乳犊牛和成年牛更高。仅这一事实就可能导致断奶一岁龄牛临床和亚临床疾病的患病率更高。此外，正在发育的免疫反应能相对较早地提供针对如古柏线虫和食道口线虫等肠道属的保护，但对奥斯特他线虫和牛毛圆线虫的保护则会延迟。I型和II型疾病都可能发生在断奶一岁龄牛阶段。影响奥斯特他线虫种群变化的因素被描述为外在因素，即天气气候和放牧管理，以及内在或宿主因素，即年龄、性别、免疫状态、遗传和生殖状态。免疫状态，特别是在断奶一岁龄牛中，可能至关重要，因为它受宿主和外在因素影响。由于犊牛对奥斯特他线虫的保护性免疫发展缓慢，免疫在抑制诱导和幼虫成熟中的可能作用，II型疾病发病机制中潜在的免疫病理参与，抗性成年母牛对幼虫摄入的超敏反应，以及在较年轻的牛中驱虫预防后保护反应的延迟报道，免疫反应可能通过不同年龄组对流行病学变化产生深远影响。尽管尚未对同一批牛从出生到成年早期进行持续的流行病学观察，但英国、荷兰和丹麦的一些显著研究已经仔细研究了第一个和第二个放牧季节的流行病学事件。
