Shakya K P, Miller J E, Horohov D W
Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Skip Bertman Drive, Baton Rouge, LA 70803, USA.
Vet Parasitol. 2009 Jul 7;163(1-2):57-66. doi: 10.1016/j.vetpar.2009.03.052. Epub 2009 Apr 5.
Haemonchus contortus is one of the major nematode parasites causing substantial economic losses in small ruminant farming worldwide. Recently, effectiveness of anthelmintic treatment has decreased due to an increasing problem of nematode populations that have developed resistance to anthelmintics. Efforts to develop effective vaccines have had limited success. There are certain breeds of sheep that are relatively resistant to the parasite including Gulf Coast Native (Native) sheep. Understanding the protective nature of the immune response that helps these breeds of sheep control infection could enable the development of vaccines to enhance control programs. This experiment was designed to compare the immunological responses of resistant Native versus susceptible Suffolk sheep in order to identify the mechanisms responsible for this resistance. Immune responses were evaluated in naturally infected Native and Suffolk lambs that grazed pasture contaminated predominantly with H. contortus. Ten lambs of each breed grazed together for 42 days. Fecal, blood and serum samples were collected on 0, 2, 4, 7, 10, 14, 21, 28, 35 and 42 days of exposure. Five lambs of each breed were necropsied on day 35 and five on day 42 for nematode recovery and abomasal tissue sample collection. Throughout the course of infection, Native lambs had significantly lower FEC, significantly lower PCV reduction percent, and significantly higher serum IgE after day 14 and increased expression of IL-4 on day 10 post-exposure compared to Suffolk lambs. At both necropsy time points, Native lambs had significantly greater numbers of mucosal mast cells, eosinophils and globule leukocytes in abomasal mucosa than Suffolk lambs. Results indicated that Native lambs had a more pronounced immune response to infection with H. contortus than Suffolk lambs which may be responsible for the observed resistance to infection.
捻转血矛线虫是导致全球小型反刍动物养殖遭受重大经济损失的主要线虫寄生虫之一。近年来，由于对线虫驱虫药产生抗药性的线虫种群问题日益严重，驱虫治疗的效果有所下降。开发有效疫苗的努力取得的成功有限。某些品种的绵羊对这种寄生虫具有相对抗性，包括墨西哥湾沿岸本地（本地）绵羊。了解有助于这些品种绵羊控制感染的免疫反应的保护性本质，可能有助于开发疫苗以加强防控计划。本实验旨在比较抗性本地绵羊与易感萨福克绵羊的免疫反应，以确定造成这种抗性的机制。在自然感染的本地和萨福克羔羊中评估免疫反应，这些羔羊在主要被捻转血矛线虫污染的牧场上放牧。每个品种的十只羔羊一起放牧42天。在暴露后的第0、2、4、7、10、14、21、28、35和42天采集粪便、血液和血清样本。每个品种的五只羔羊在第35天进行剖检，五只在第42天进行剖检，以回收线虫并采集皱胃组织样本。在整个感染过程中，与萨福克羔羊相比，本地羔羊的粪便虫卵计数显著更低，红细胞压积降低百分比显著更低，在第14天后血清免疫球蛋白E显著更高，并且在暴露后第10天白细胞介素-4的表达增加。在两个剖检时间点，本地羔羊皱胃黏膜中的黏膜肥大细胞、嗜酸性粒细胞和球形白细胞数量均显著多于萨福克羔羊。结果表明，本地羔羊对捻转血矛线虫感染的免疫反应比萨福克羔羊更为明显，这可能是观察到的对感染具有抗性的原因。
