Molecular survey and genetic diversity of piroplasmids in equids from Midwestern Brazil

Abstract We evaluated the distribution of piroplasmids in equids from the Mato Grosso state in Midwestern Brazil using molecular methods and the interspecific genetic diversity. For this, 1,624 blood samples of equids from 973 farms were examined by PCR, using primer pairs that amplify a fragment of the genes rap-1 and ema-1 of Babesia caballi and Theileria equi, respectively. For molecular characterization and phylogenetic studies, 13 and 60 sequences of the rap-1 and ema-1 genes, respectively, were used to build a dendogram using maximum parsimony. B. caballi and T. equi were detected in 4.11% and 28.16% of the farms, respectively, and molecular prevalence was 2.74% for B. caballi and 25.91% for T. equi. The location of the farms and animals raised in the Pantanal ecoregion influence the probability of equids testing positive for B. caballi and T. equi . Moreover, age and herd purpose were variables significantly associated with T . equi infection. The sequences of B. caballi presented 1.95% intraspecific variability, contrasting with 2.99% in T. equi. Dendrograms for both species demonstrated the presence of subgroups with high values of support of branches. However, it is not possible to associate these groups with geographic origin and/or ecoregion.

摘要 本研究通过分子检测方法结合种间遗传多样性分析，评估了巴西中西部马托格罗索州马属动物体内梨形虫（Piroplasmida）的分布情况。为此，本研究针对来自973个农场的1624份马属动物血液样本开展PCR检测，所用引物对可分别扩增驽巴贝斯虫（Babesia caballi）的rap-1基因与马泰勒虫（Theileria equi）的ema-1基因片段。为开展分子鉴定与系统发育研究，本研究分别利用13条rap-1基因序列与60条ema-1基因序列，采用最大简约法构建系统发育树。本研究分别在4.11%与28.16%的受访农场中检测到驽巴贝斯虫与马泰勒虫，其分子感染率分别为2.74%与25.91%。农场的地理位置以及养殖动物所处的潘塔纳尔（Pantanal）生态区，会影响马属动物对驽巴贝斯虫与马泰勒虫的检测阳性概率。此外，宿主年龄与畜群养殖用途是与马泰勒虫感染显著相关的影响因素。驽巴贝斯虫的序列呈现1.95%的种内变异率，而马泰勒虫的种内变异率则为2.99%。两种虫体的系统发育树均显示存在分支支持度较高的亚组，但无法将这些亚组与地理来源或生态区建立关联。