The tick Rhipicephalus microplus is responsible for the transmission of Anaplasma marginale, which causes hemolytic anemia, abortion, decreased production, and mortality in cattle in Brazil. However, A. marginale can also persist in cattle herds without any clinical signs. This study investigated the relationship between the number of ticks present on each cattle and the circulating number of A. marginale msp1β gene copies in the blood of Brangus and Nellore cattle reared in the Brazilian Cerrado through a year period. Twenty-three animals (11 Brangus and 12 Nellore) were raised for 12 months with ticks counted every 18 days, and blood collected every 36 days. Blood sera was used for total antigen iELISA, genomic DNA was extracted from whole blood by the phenol/chloroform method and then analyzed by PCR to confirm A. marginale presence with the msp5 gene. Positive samples were quantified by qPCR using msp1β gene. Brangus cattle presented 4.5 fold more ticks than Nellore group. Although Brangus cattle carried a higher overall A. marginale msp1β gene presence than Nellore cattle, no relationship of tick count and copy number could be achieved due to high variability in copy number. Moreover, both breeds showed similar weight gain and a similar serological pattern throughout the year. None of the animals showed any clinical signs of anaplasmosis during the experimental period, indicating that a low level of tick infestation may be sufficient to maintain a stable enzootic situation.

中文翻译：

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巴西各种牛品种的微小头hip虫R虫与无性无形体感染之间的相关性。

R Rhipicephalus microplus引起边缘无浆膜的传播，这导致了巴西牛的溶血性贫血，流产，产量下降和死亡率。但是，无缘农杆菌也可以在牛群中持续存在而没有任何临床体征。这项研究调查了每头牛的of虫数量与margin曲霉msp1β循环数量之间的关系。在巴西塞拉多（Cerrado）饲养的Brangus和Nellore牛的血液中的基因复制已有一年的时间。将23只动物（11只Brangus和12只Nellore）饲养12个月，每18天计数一次tick，每36天收集一次血液。用于总抗原iELISA血清中，基因组DNA用酚/氯仿法从全血中提取，然后通过PCR来确认分析A.边缘无存在与MSP5基因。使用msp1β基因通过qPCR对阳性样品进行定量。班格努斯牛的s虫数量比内洛尔牛群高4.5倍。尽管Brangus牛的整体拟南芥msp1β含量较高基因的存在比Nellore牛的要多，由于tick节数的高度变异性，因此无法实现tick计数和copy节数的关系。而且，这两个品种全年都表现出相似的体重增加和相似的血清学模式。在实验期间，没有动物表现出任何临床症状，这表明低水平的tick虫感染可能足以维持稳定的动物疫情。