Utility of the carbohydrate larval antigen (CarLA®) saliva test to lower the risk of gastrointestinal parasitism in Ontario sheep flocks

绵羊胃肠道寄生虫病是牧场生产的一个重要制约因素，需要采取多方面的方法进行长期可持续控制;其中一种方法是选择能够更好地免疫管理寄生虫感染（即遗传抗性）的绵羊。这种方法的一个潜在工具是使用CarLA唾液测试（AgResearch，新西兰），其测量绵羊产生的抗体到牧场上寄生虫的感染阶段。最近，圭尔夫大学的研究人员对安大略南部的一个羊群进行了研究，发现具有中高CarLA水平的母羊羔羊（MH-CarLA）的寄生虫粪便卵计数（FEC）低于具有低CarLA水平的绵羊。该项目将通过评估CarLA唾液测试在一些鸡群和品种中的实用性来扩展这项工作。通过跟踪两个放牧季节的替代母羊，将确定与CarLA水平较低的母羊相比，MH-CarLA母羊羔羊是否具有较低的寄生虫水平，并且更有可能在第一个放牧季节生下具有较高CarLA水平，更好的生长特性和较低FEC的后代。该项目获得的数据将有助于评估安大略放牧条件下CarLA唾液测试的性能。在额外的工作中，将进行经济分析，以估计与使用该测试来管理加拿大农场的寄生虫相关的经济效益。总的来说，这些发现将有助于将测试从新西兰转移到安大略的诊断实验室，以便有可能向加拿大各地的绵羊生产者提供。这个项目的合作者是加拿大养羊协会、安大略养羊农民和安大略农业、食品和农村事务部。

Gastrointestinal parasitism in sheep is a significant constraint to production on pasture and requires a multi-faceted approach for long-term sustainable control; one such approach is to select sheep that are better able to immunologically manage parasite infection (i.e. genetic resistance). One potential tool for this approach is to use The CarLA Saliva Test (AgResearch, New Zealand), which measures antibodies produced by sheep to the infective stage of parasites on pasture. In recent work carried out by researchers at the University of Guelph on one sheep flock in southern Ontario, ewe lambs with medium-to-high CarLA levels (MH-CarLA) had lower parasite fecal egg counts (FEC) than sheep with low CarLA levels. This project will expand this work by evaluating the utility of The CarLA Saliva Test in a number of flocks and breeds. By following replacement ewes over two grazing seasons, it will determine if MH-CarLA ewe lambs, by comparison to those with lower CarLA levels, have lower parasite levels, and are more likely to give birth to offspring with higher CarLA levels, better growth characteristics and lower FEC in their first grazing season. The data obtained by this project will help evaluate the performance of The CarLA Saliva Test under Ontario grazing conditions. In additional work, economic analyses will be carried out to estimate the economic benefit associated with using the test to manage parasites on Canadian farms. Collectively, the findings will facilitate transfer of the test from New Zealand to a diagnostic laboratory in Ontario so that it can potentially be offered to sheep producers across Canada. Collaborators on this project are the Canadian Sheep Breeders' Association, Ontario Sheep Farmers, and the Ontario Ministry of Agriculture, Food and Rural Affairs.