McRae Kathryn M, Good Barbara, Hanrahan James P, Glynn Assumpta, O'Connell Mary J, Keane Orla M
Vet Parasitol. 2014 Dec 15;206(3-4):200-7. doi: 10.1016/j.vetpar.2014.10.023.
The objective of this study was to identify Scottish Blackface lambs that were at the extremes of the spectrum of resistance to gastrointestinal nematodes and characterise their response to an experimental nematode challenge. Lambs (n = 90) were monitored for faecal egg count (FEC) (2 samples from each of 2 independent natural infections). The most resistant (n = 10) and susceptible (n = 10) individuals were selected and challenged with 30,000 Teladorsagia circumcincta larvae (L3) at 9 months of age. Response to infection was monitored by measuring FEC, plasma pepsinogen, serum antibodies against nematode larval antigens and haematology profile, until necropsy at 71 days post infection. Worm burden, worm fecundity and the level of anti-nematode antibodies in abomasal mucosa were determined at necropsy. FEC was consistently higher in susceptible animals (P < 0.05), validating the selection method. Worm fecundity was significantly reduced in resistant animals (P = 0.03). There was also a significant correlation (r = 0.88; P < 0.001) between the number of adult worms and FEC at slaughter. There was no effect of phenotype (resistance/susceptibility) on plasma pepsinogen or on haematology profile. Phenotype had a significant effect on the level of anti-nematode IgA antibodies in serum (P < 0.01), reflecting a higher peak in resistant animals at day 7 post infection. It is concluded that significant variation in the response to gastrointestinal nematode challenge exists within the Scottish Blackface population with resistant animals displaying significantly lower FEC, lower worm fecundity and higher concentration of anti-nematode IgA antibodies in serum.
本研究的目的是识别对胃肠道线虫抵抗力处于极端水平的苏格兰黑脸羔羊，并描述它们对实验性线虫攻击的反应。对90只羔羊进行粪便虫卵计数（FEC）监测（来自2次独立自然感染，每次采集2份样本）。挑选出最具抗性（n = 10）和最易感（n = 10）的个体，在9月龄时用30000条环纹奥斯特线虫幼虫（L3）进行攻击。通过测量FEC、血浆胃蛋白酶原、抗线虫幼虫抗原的血清抗体和血液学指标来监测感染反应，直至感染后71天进行尸检。尸检时测定皱胃黏膜中的虫负荷、虫繁殖力和抗线虫抗体水平。易感动物的FEC始终较高（P < 0.05），验证了选择方法的有效性。抗性动物的虫繁殖力显著降低（P = 0.03）。屠宰时成虫数量与FEC之间也存在显著相关性（r = 0.88；P < 0.）。表型（抗性/易感性）对血浆胃蛋白酶原或血液学指标没有影响。表型对血清中抗线虫IgA抗体水平有显著影响（P < 0.01），反映出抗性动物在感染后第7天的峰值更高。结论是，苏格兰黑脸羊群体对胃肠道线虫攻击的反应存在显著差异，抗性动物的FEC显著较低，虫繁殖力较低，血清中抗线虫IgA抗体浓度较高。
