背景:在有地方病的地区,回收的牛是携带者,离开新生小牛和引入种群作为最易感的群体,在蜱虫感染寄生虫传播后发展为临床疾病。
方法:为了获得有关由毒性ikeda和几糖基因型以及T.orientalis的“良性”buffeli基因型引起的感染和发展的动力学和影响的信息,这项研究对来自多里戈3个农场的134头小牛进行了采样,澳大利亚,具有多种寄生虫基因型的区域。此外,30个引入的牛肉断奶者在到达后放血并称重6个月。
结果:在这两个队列中,在3-4周内,>95%的组中,通过PCR可检测到定向T的ikeda和几丁糖(基因型1和2)的寄生虫血症,在出生或出生后5-7周左右产生最大的基因拷贝,在下降之前。相比之下,定向水痘的寄生虫(基因型3),缓慢增加,大约80%的人群在4个月后通过PCR检测呈阳性。buffeli基因型的寄生虫不超过40,000个基因拷贝/ul,与牛进入携带者状态后的“第一波寄生虫血症”后ikeda和几糖基因型所表现出的相似。在30个引进的断奶者中,早期感染伊克达T.orientalis和几丁糖也导致压缩细胞体积(PCV)显着减少,体重增加估计减少了20Kg;后者在引入后6个月仍未恢复。
结论:该结果支持先前在其他流血病流行区的发现,并暗示毒力基因型改善早期高水平的寄生虫病可以减少Theleriosis对生产的最初影响,一旦动物进入携带者状态,这似乎受到的影响要小得多。
BACKGROUND: In regions with endemic Theileria orientalis, recovered cattle are carriers, leaving newborn calves and introduced stock as the most susceptible groups to develop clinical disease after tick infestation with parasite transmission.
METHODS: To gain information on the kinetics of infection and development and effects of theileriosis caused by virulent ikeda and chitose genotypes and the \"benign\" buffeli genotype of T.orientalis, this
study sampled a total of 134 calves from 3 farms in Dorrigo, Australia, a region with multiple genotypes of the parasite. In addition, 30 introduced beef weaners were bled and weighed for 6 months after arrival.
RESULTS: In both cohorts, parasitaemia with the ikeda and chitose (genotypes 1 & 2) of T.orientalis was detectable by PCR within 3-4 weeks in >95 % of the groups, with maximal gene copies generated around 5-7 weeks after birth or introduction, before declining. In contrast, parasitaemias of T.orientalis buffeli (genotype 3), increased slowly, with around 80 % of the population testing positive by PCR after 4 months. The parasitaemias of the buffeli genotype did not exceed 40,000 gene copies /ul and were similar to those exhibited by ikeda and chitose genotypes following the \"first wave of parasitaemia\" as cattle entered the carrier state. In the 30 introduced weaners, the early infection with T.orientalis ikeda and chitose also caused significant reductions in packed cell volume (PCV) and incurred an estimated 20Kg loss in weight gain; the latter had not been recovered by 6 months after introduction.
CONCLUSIONS: The results support previous findings in other endemic regions of theileriosis, and imply that amelioration of the early high levels of parasitosis by the virulent genotypes could reduce the initial impact of theileriosis on production, which appears much less affected once animals enter the carrier state.