The objective of this study was to evaluate the reduction in nematode faecal egg count (FEC) in Pelibuey lambs segregated as resistant (RES), susceptible (SUS) and intermediate (INT) to gastrointestinal nematodes. Twenty-nine weaned Pelibuey lambs, aged five months old, free of nematode infection, were used. Nine lambs were RES, six were SUS and 14 were INT lambs. The study consisted of two phases: in Phase 1 the lambs were infected experimentally with Haemonchus contortus. In Phase 2, the lambs were naturally infected by grazing. Faecal and blood samples were taken every week. The packed cell volume and total protein were quantified. The FEC value (FECmax) per lamb was recorded together with a natural reduction in FEC in the two phases. The data were analysed with a model of measures repeated over time. During Phase 1, the RES lambs showed the lowest FEC (1061 ± 1053) compared to the other groups (INT: 2385 ± 1794 eggs per gram of faeces (EPG); and SUS: 3958 ± 3037 EPG). However, in Phase 2 no significant differences (p > 0.05) were observed between the groups of lambs (RES: 275 ± 498 EPG; SUS: 504 ± 1036 EPG; and INT: 603 ± 1061 EPG). At the end of Phase 1, the FEC of RES lambs was naturally reduced by 75.5% in respect to FECmax (p < 0.05), and at the end of Phase 2 the reduction in FEC was 90% in respect to FECmax (p > 0.05); the same behaviour was observed in RES and SUS lambs. It is concluded that the artificial infection in the lambs induced a more rapid immune response in RES than SUS lambs, and all lambs developed high acquired resistance by continuous infection.

中文翻译：

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人工捻转血矛线虫感染作为诱导 Pelibuey 羔羊对自然感染的保护性免疫反应的策略

本研究的目的是评估 Pelibuey 羔羊中线虫粪便卵数 (FEC) 的减少，这些羔羊被隔离为对胃肠道线虫具有抗性 (RES)、易感 (SUS) 和中间 (INT) 线虫。使用了 29 只断奶的 Pelibuey 羔羊，年龄为 5 个月大，没有线虫感染。九只羔羊是RES，六只是SUS，14只是INT羔羊。该研究包括两个阶段：在第 1 阶段，羔羊被实验性感染扭曲血矛线虫. 在第 2 阶段，羔羊因放牧而自然感染。每周采集粪便和血液样本。对堆积的细胞体积和总蛋白质进行定量。记录每只羔羊的 FEC 值 (FECmax) 以及两个阶段中 FEC 的自然降低。使用随时间重复的测量模型分析数据。在第 1 阶段，与其他组相比，RES 羔羊的 FEC 最低（1061 ± 1053）（INT：每克粪便 2385 ± 1794 个鸡蛋（EPG）；SUS：3958 ± 3037 EPG）。然而，在第 2 阶段没有显着差异（p> 0.05）在羔羊组之间观察到（RES：275 ± 498 EPG；SUS：504 ± 1036 EPG；和 INT：603 ± 1061 EPG）。在第 1 阶段结束时，RES 羔羊的 FEC 相对于 FECmax 自然降低了 75.5%（p< 0.05)，在第 2 阶段结束时，FEC 相对于 FECmax 降低了 90% (p> 0.05); 在 RES 和 SUS 羔羊中观察到相同的行为。可以得出结论，羔羊的人工感染在RES中诱导的免疫反应比SUS羔羊更快，并且所有羔羊都通过持续感染产生了高度的获得性抗性。