Lawrence K E, Gibson M, Hickson R E, Gedye K, Hoogenboom A, Fermin L, Draganova I, Pomroy W E
School of Veterinary Science, Massey University, Palmerston North, New Zealand.
School of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
Vet Parasitol Reg Stud Reports. 2018 Dec;14:85-93. doi: 10.1016/j.vprsr.2018.09.004. Epub 2018 Sep 15.
Since 2012, New Zealand has suffered from an epidemic of infectious bovine anaemia associated with T. orientalis (Ikeda), an obligate intracellular protozoan parasite of cattle. Despite widespread agreement that T. orientalis (Ikeda) infection has impacted beef and dairy farming in New Zealand there is very little quantitative data to support this conclusion. A randomised controlled experimental study of the effect of T. orientalis (Ikeda) infection on the live weight, haematocrit (HCT), temperature and activity of 2-year-old Friesian bulls was conducted at a Massey University Research farm, Palmerston North. Ten out of seventeen 2-year-old Friesian bulls were injected intravenously with 30 mL whole blood from 2 clinical cases of Theileria-associated bovine anaemia and then followed over a period of 20 weeks. The bulls were blood sampled, had rectal temperature recorded and weighed 3 times weekly for 13 weeks and then once weekly thereafter until the end of the trial. Infection intensity was monitored using qPCR. All 10 inoculated bulls were successfully infected with T. orientalis (Ikeda). The results showed that the live weight response to infection was varied and the bulls could be divided into two groups based on this response. Four infected bulls showed a significant weight reduction of 41.5 kg (p < 0.0001), a financial loss of around NZ$112 per bull, compared with the other 6 bulls in the infected group, which were not different to the 7 uninfected controls. The live weight of the 4 poor growing bulls was significantly lower than the other 6 infected bulls from Day 71 post infection (p < 0.05). All ten infected bulls showed a similar decrease in HCT, with the lowest HCT reached around Day 60 to 80 post-infection, however the four infected bulls that grew poorly did have a significantly elevated HCT for the first 1 to 3 weeks post infection (p < 0.05). The 4 infected bulls which grew poorly also had a significantly higher infection intensity than the other infected bulls from Day 27 to Day 60 post-infection (p < 0.05). There was no pyrexia recorded in the infected group or control groups, instead there was a tendency for the infected group to have a lower rectal temperature from Day 5 to 70 post infection. The infected bulls walked on average 239 steps per day less than the control bulls, although this difference was not significant (p = 0.35). Overall the study clearly showed, by controlling infection date and infectious dose, that a proportion of cattle infected with T. orientalis (Ikeda) have significantly decreased live weight gains.
自2012年以来，新西兰遭受了与东方泰勒虫（池田株）相关的传染性牛贫血疫情，东方泰勒虫（池田株）是牛的一种专性细胞内原生动物寄生虫。尽管人们普遍认为东方泰勒虫（池田株）感染对新西兰的肉牛和奶牛养殖产生了影响，但几乎没有定量数据支持这一结论。在梅西大学位于北帕默斯顿的研究农场，对东方泰勒虫（池田株）感染对2岁弗里生公牛的体重、血细胞比容（HCT）、体温和活动的影响进行了一项随机对照实验研究。17头2岁的弗里生公牛中有10头静脉注射了来自2例泰勒虫相关牛贫血临床病例的30毫升全血，然后在20周内进行跟踪观察。每周对公牛进行3次血样采集、记录直肠温度并称重，持续13周，之后每周一次，直至试验结束。使用qPCR监测感染强度。所有10头接种的公牛均成功感染了东方泰勒虫（池田株）。结果表明，感染后体重反应各不相同，根据这一反应，公牛可分为两组。与感染组中的其他6头公牛相比，4头感染公牛体重显著减轻41.5千克（p<0.0001），每头公牛造成约112新西兰元的经济损失，而这6头公牛与7头未感染的对照公牛没有差异。从感染后第71天起，4头生长不良的公牛的体重显著低于其他6头感染公牛（p<0.05）。所有10头感染公牛的血细胞比容均有类似下降，最低血细胞比容在感染后第60至80天左右达到，然而，4头生长不良的感染公牛在感染后的前1至3周血细胞比容显著升高（p<0.05）。从感染后第27天至第60天，4头生长不良的感染公牛的感染强度也显著高于其他感染公牛（p<0.05）。感染组和对照组均未记录到发热情况，相反，从感染后第5天至第70天，感染组有直肠温度较低的趋势。感染公牛每天平均比对照公牛少走239步，尽管这一差异不显著（p=0.35）。总体而言，该研究通过控制感染日期和感染剂量清楚地表明，一部分感染东方泰勒虫（池田株）的牛体重增加显著减少。
