The Hopkirk Research Institute, AgResearch, Private Bag 11008, Palmerston North 4442, New Zealand.
Vet Parasitol. 2012 May 4;186(1-2):109-17. doi: 10.1016/j.vetpar.2011.11.051. Epub 2011 Nov 20.
Infection with gastrointestinal nematodes (GIN) is a major constraint on the productivity of grazing livestock. The development of selection methods to quickly and accurately identify animals capable of developing an effective natural immunity to infection would contribute to the development of sustainable worm control programs. A carbohydrate larval surface antigen (CarLA), present on the infective-stage larvae (L3) of all trichostrongylid nematodes, is a target antigen for host antibody (Ab). The levels of various Ab isotypes in serum and/or saliva of field-grazed lambs were assessed by ELISA, and Ab titres compared with parasite faecal egg counts (FECs) and a range of animal productivity parameters. Levels of anti-CarLA IgA in saliva proved to be the most heritable (h(2)=0.3), and had the closest genetic correlation with FEC (r=-0.5). Those animals identified as having 'high levels' of anti-CarLA IgA typically have 20-30% lower FEC than animals with low or undetectable titres. Furthermore, animals with 'high levels' of anti-CarLA IgA tend to have improved growth rates post-weaning, and have no tendency for increased breech-soiling. The assay performed well regardless of parasite genera present on pasture. The saliva assay has a number of key practical advantages over the use of FEC for selection purposes: animals can be identified without a requirement to withhold anthelmintic treatment; sampling is rapid and easy and there is a significantly reduced barrier to adoption within the farming community. Measurement of anti-CarLA IgA in saliva by ELISA offers a practical, rapid and easy method of selecting for natural immunity to GIN in sheep.
胃肠道线虫（GIN）感染是放牧牲畜生产力的主要制约因素。开发能够快速准确识别具有有效天然抗感染能力的动物的选择方法，将有助于开发可持续的驱虫计划。碳水化合物幼虫表面抗原（CarLA）存在于所有三刺线虫的感染阶段幼虫（L3）上，是宿主抗体（Ab）的靶抗原。通过 ELISA 评估了田间放牧羔羊血清和/或唾液中各种 Ab 同种型的水平，并将 Ab 效价与寄生虫粪便卵计数（FEC）和一系列动物生产参数进行了比较。唾液中抗 CarLA IgA 的水平被证明是最具遗传性的（h(2)=0.3），并且与 FEC 具有最接近的遗传相关性（r=-0.5）。那些被认为具有“高水平”抗 CarLA IgA 的动物通常比低或无法检测到效价的动物的 FEC 低 20-30%。此外，具有“高水平”抗 CarLA IgA 的动物在断奶后往往具有更好的生长速度，并且没有增加臀部污染的趋势。无论牧场上存在哪种寄生虫属，该检测都能很好地发挥作用。与使用 FEC 进行选择相比，唾液检测具有许多关键的实际优势：无需停止驱虫处理即可识别动物；采样快速、简便，并且在农民社区中采用的障碍大大降低。通过 ELISA 测量唾液中的抗 CarLA IgA 为选择绵羊对 GIN 的天然免疫力提供了一种实用、快速和简便的方法。
