Babesia bovis and Babesia bigemina are tick-transmitted piroplasms that cause severe damage to the livestock industry in tropical regions of the world. Recent studies demonstrated differences in infection levels of these haemoparasites among bovine breeds and variation between individual cows regarding resistance to these diseases. This study aimed to estimate the repeatability and correlations between B. bovis and B. bigemina using two cattle breeding systems, an individual system (IS) and a collective paddock system (CPS). All animals were Holstein breed, and the levels of B. bovis and B. bigemina in blood samples were estimated by quantitative polymerase chain reaction (qPCR). The estimated correlations for the B. bigemina and B. bovis DNA copy number for IS and CPS were moderate and high, respectively, whereas repeatability estimates for both systems and both Babesia species were moderate. Although we cannot infer that the type of rearing system directly influenced the correlation and repeatability coefficients, it appears that the bovine parasitemia burden may be dependent on (or determine) the parasitemia burden on ticks because the bovines remained in the same place for a longer time in both systems. Thus, the babesiosis infection levels of the ticks may have been uniform, a phenomenon that also ensures greater uniformity in cattle infection. This factor may have favored the occurrence of infected ticks leading to higher repeatability estimates and correlations. Our study confirms high variability in resistance/susceptibility between breeds, and the high correlations found may be linked to this characteristic and the most intensive breeding type of dairy cattle. Besides, under the present study conditions, the estimated correlations suggest that measuring an infection level of one Babesia species can predict the level of infection of the other.

中文翻译：

---

巴贝斯虫属之间的相关性和可重复性。使用两个奶牛繁殖系统的感染水平。

牛巴贝虫和大巴贝虫是tick传播的原质，对世界热带地区的畜牧业造成严重损害。最近的研究表明，在不同牛种之间这些血寄生虫的感染水平存在差异，并且各母牛之间对这些疾病的抵抗力也存在差异。这项研究旨在通过使用两个牛育种系统，一个个体系统（IS）和一个集体围场系统（CPS）来估计牛双歧杆菌和双歧双歧杆菌之间的可重复性和相关性。所有动物均为荷斯坦牛品种，牛双歧杆菌和双歧双歧杆菌的水平通过定量聚合酶链反应（qPCR）估计血液样本中的血红蛋白。IS和CPS的B. bigemina和B. bovis DNA拷贝数的估计相关性分别为中度和高，而两个系统和巴贝斯虫的可重复性估计均种类适中。尽管我们不能推断出饲养系统的类型直接影响相关性和重复性系数，但似乎牛的寄生虫负担可能取决于（或确定）tick的寄生虫负担，因为牛在同一地方待了更长的时间在两个系统中。因此，s的巴贝虫病感染水平可能是一致的，这种现象还确保了牛感染的更大一致性。该因素可能有利于感染s虫的发生，从而导致较高的可重复性估计值和相关性。我们的研究证实了不同品种之间的抗性/敏感性差异很大，并且发现的高度相关性可能与这一特征以及最密集的奶牛育种类型有关。此外，在目前的研究条件下，巴比斯虫物种可以预测另一种的感染水平。