School of Veterinary and Biomedical Sciences, Murdoch University, Western Australia, Australia.
Vet Parasitol. 2009 Oct 28;165(1-2):66-73. doi: 10.1016/j.vetpar.2009.07.018. Epub 2009 Jul 19.
Nine flocks of sheep with a high prevalence (>30%) of diarrhoea and severe breech faecal soiling were investigated over a three-year period to examine the causes of diarrhoea in sheep with low mean faecal worm egg counts (WEC). All nine flocks were located in the southwest of Western Australia in areas with a winter rainfall pattern (Mediterranean climate). There was no difference (p=0.304) in WEC of diarrhoeic sheep (loose faeces and severe breech faecal soiling) and "normal sheep" (pelleted faeces and mild or no breech faecal soiling). Teladorsagia (Ostertagia) circumcincta and Trichostrongylus spp. were the nematodes most commonly identified by total worm counts and differentiation of larvae recovered from faeces and pasture. Larval stages of strongyle worms accounted for the largest proportion of total worm counts in both diarrhoeic and normal sheep. Adult worm burdens were small in most sheep. Diarrhoeic sheep had higher numbers of fourth stage larvae than normal sheep (p=0.046). There was no histopathological evidence of bacterial or viral causes of diarrhoea in any of the flocks or bacteriological evidence of bacterial infections associated with diarrhoea. Two flocks had marginal selenium glutathione peroxidase (selenium) levels. One flock was diagnosed with helminthosis based on rising WEC and high total worm counts. Larval hypersensitivity diarrhoea, nutritional factors or a combination of these two factors were the most likely causes of diarrhoea in the other eight flocks based on exclusion of other known causes of diarrhoea. Treatment with moxidectin and an ivermectin controlled-release capsule did not change faecal moisture content of treated sheep compared to untreated sheep three to five weeks after treatment. The findings suggest that the immune response to strongyle larvae may explain some cases of low WEC diarrhoea observed during winter-spring in immunocompetent mature sheep grazing in Mediterranean environments.
三年期间，对 9 群高腹泻发病率（>30%）和严重臀部粪便污染的绵羊进行了调查，以检查低平均粪便虫卵计数（WEC）绵羊腹泻的原因。所有 9 群绵羊均位于西澳大利亚西南部，冬季降雨模式（地中海气候）。腹泻绵羊（稀便和严重臀部粪便污染）和“正常绵羊”（颗粒状粪便和轻度或无臀部粪便污染）的 WEC 无差异（p=0.304）。通过总蠕虫计数和从粪便和牧场中分离出的幼虫的分化，最常鉴定出 Teladorsagia (Ostertagia) circumcincta 和 Trichostrongylus spp. 线虫。在腹泻和正常绵羊中，强虫幼虫阶段占总蠕虫计数的最大比例。大多数绵羊的成虫负荷较小。腹泻绵羊的第四期幼虫数量高于正常绵羊（p=0.046）。在任何一个羊群中都没有细菌性或病毒性腹泻的组织病理学证据，也没有与腹泻相关的细菌性感染的细菌学证据。有 2 个羊群的硒谷胱甘肽过氧化物酶（硒）水平偏低。根据 WEC 上升和高总蠕虫计数，有 1 个羊群被诊断为寄生虫病。根据排除其他已知腹泻原因，另外 8 个羊群最有可能是由于幼虫过敏腹泻、营养因素或这两种因素的组合导致腹泻。莫昔克丁和伊维菌素控释胶囊治疗与未治疗的绵羊相比，在治疗后 3 至 5 周内，粪便水分含量没有变化。研究结果表明，对强虫幼虫的免疫反应可能解释了在免疫功能正常的成熟绵羊在地中海环境中放牧的冬季-春季期间观察到的一些低 WEC 腹泻病例。
