Adams D B, Lynch J J, Anderson B H, Fell L R, Hinch G N, Munro R K
CSIRO Division of Animal Health, Pastoral Research Laboratory, Armidale, New South Wales.
Aust Vet J. 1990 Dec;67(12):443-5. doi: 10.1111/j.1751-0813.1990.tb03056.x.
Three-year-old, non-lactating and non-pregnant Merino ewes, raised on pasture under a program of strategic treatment with anthelmintic and found to be extremely resistant to "trickle" infection with Haemonchus contortus, were given single-dose infections with either H. contortus or Trichostrongylus colubriformis or both species together. The purpose was to ascertain the intensity of protective immunity against the 2 parasites in sheep with immunity acquired from a presumably slight exposure to infection. To provide a criterion, some infected ewes were immunosuppressed with corticosteroid, dexamethasone. Untreated ewes were extremely resistant to challenge infection with either 15,000 or 150,000 H. contortus or 15,000 T. colubriformis. Surprisingly, when mixed infection was given, egg counts for H. contortus were significantly elevated compared with infection by that species alone. Antibody to antigens from infective larval and adult H. contortus was measured in serum by enzyme-linked-immunosorbent assay (ELISA) during the course of infection. Serum titres against larval antigens were significantly depressed when infections with either H. contortus or T. colubriformis were permitted by immunosuppression with dexamethasone, whereas those against adult antigen were depressed when infection with T. colubriformis was permitted.
三岁、非泌乳且未怀孕的美利奴母羊，在接受驱虫药战略治疗方案的牧场饲养，被发现对捻转血矛线虫的“微量”感染具有极强抗性，分别给予单剂量的捻转血矛线虫感染、蛇形毛圆线虫感染或两种线虫的混合感染。目的是确定从可能轻微感染中获得免疫力的绵羊对这两种寄生虫的保护性免疫强度。为提供一个标准，一些感染的母羊用皮质类固醇地塞米松进行免疫抑制。未治疗的母羊对15,000条或150,000条捻转血矛线虫或15,000条蛇形毛圆线虫的攻击感染具有极强抗性。令人惊讶的是，当给予混合感染时，与单独感染该物种相比，捻转血矛线虫的虫卵计数显著升高。在感染过程中，通过酶联免疫吸附测定（ELISA）测量血清中针对感染性幼虫和成年捻转血矛线虫抗原的抗体。当用地塞米松免疫抑制允许感染捻转血矛线虫或蛇形毛圆线虫时，针对幼虫抗原的血清滴度显著降低，而当允许感染蛇形毛圆线虫时，针对成年抗原的血清滴度降低。
