Claerebout E, Hilderson H, Meeus P, De Marez T, Behnke J, Huntley J, Vercruysse J
University of Gent, Faculty of Veterinary Medicine, Department of Parasitology, Merelbeke, Belgium.
Vet Parasitol. 1996 Nov 15;66(3-4):225-39. doi: 10.1016/s0304-4017(96)01012-6.
The relative contribution of the third (L3), fourth (L4) and adult stages of Ostertagia ostertagi to the development of immunity was assessed in calves which were either continuously infected during 21 weeks or subjected to infections truncated by anthelmintic treatment at the L3 or L4 stage. A fourth group remained uninfected (control group). Faecal samples and blood samples were collected weekly for faecal egg counts and determination of pepsinogen and antibody levels. Only the continuously infected animals showed positive egg counts, which fell towards the end of the primary infection period. Pepsinogen and antibody levels remained high in the continuously infected group until the end of the primary infection period. At that time, they were significantly higher compared to the control calves, with intermediate values in the truncated infection groups. After the 21 weeks primary infection period all animals were dewormed. To evaluate the protection provided by the different immunisation protocols, all animals were challenged 1 week later with 156000 Ostertagia L3, spread over 12 consecutive days. The marked reduction in egg counts following challenge infection indicated a certain degree of immunity in the continuously infected calves, which was confirmed at necropsy by the reduced worm burdens, the high percentage of inhibited early L4 larvae, the reduced size of the adult worms and the higher numbers of mucosal mast cells in this group. Numbers of globule leucocytes and eosinophils were not significantly different from the control group. Infections truncated by anthelmintic treatment elicited poor development of immunity as shown by the egg output after the challenge infection and the percentages of arrested larvae and the lengths of adult worms which were intermediate to those of the continuously infected calves and control animals.
在犊牛中评估了奥斯特他线虫第三期（L3）、第四期（L4）和成虫期对免疫发育的相对贡献，这些犊牛要么在21周内持续感染，要么在L3或L4期接受驱虫治疗而截断感染。第四组未感染（对照组）。每周收集粪便样本和血液样本，用于粪便虫卵计数以及胃蛋白酶原和抗体水平的测定。只有持续感染的动物粪便虫卵计数呈阳性，且在初次感染期结束时下降。持续感染组的胃蛋白酶原和抗体水平在初次感染期结束前一直很高。此时，与对照犊牛相比，它们显著更高，截断感染组的值处于中间水平。在21周的初次感染期后，所有动物都进行了驱虫。为了评估不同免疫方案提供的保护作用，1周后所有动物用156000条奥斯特他线虫L3进行攻击，连续12天投喂。攻击感染后虫卵计数显著减少，表明持续感染的犊牛有一定程度的免疫力，尸检时该组虫负荷减少、早期L4幼虫抑制百分比高、成虫尺寸减小以及黏膜肥大细胞数量增加证实了这一点。该组的球形白细胞和嗜酸性粒细胞数量与对照组无显著差异。如攻击感染后的虫卵排出量以及停滞幼虫的百分比和成虫长度所示，驱虫治疗截断的感染引发的免疫发育较差，这些指标介于持续感染的犊牛和对照动物之间。
