目的 了解青海部分地区马属动物蜱媒梨形虫感染情况及其遗传进化特征，为该地区马梨形虫病的防控提供科学依据。 方法 2023年3月—2024年7月在青海省海东、西宁、海西和海北4市（州）采集散养马属动物血液样品，提取基因组DNA，巢式PCR扩增18S rRNA基因。通过NCBI BLAST程序对获得的序列进行同源性比对与分析，并利用DNASP v.6软件进行单倍型分析，PopArt构建单倍型网络图。GenBank中选取马泰勒虫基因型A~E和驽巴贝虫基因型A~C作为参考序列，通过MEGA 6.0最大似然法构建系统进化树。 结果 176份散养马属动物血样中马梨形虫感染率为47.73%（84/176），其中马泰勒虫和驽巴贝虫感染率分别为47.16%（83/176）和0.57%（1/176）。83条马泰勒虫序列共有16个单倍型，单倍型多样性为0.450，核苷酸多样性为0.026 43。马泰勒虫单倍型以H1为主（占73.49%，61/83），其次为H5单倍型（占9.64%，8/83），其余14个单倍型（H2~H4、H6~H16）均各占1.20%（1/83）。单倍型H5、H8~H14、H16与GenBank中马泰勒虫基因型A（JX177672、MT463613）在系统进化树上聚为一支，其余的7个单倍型与GenBank中马泰勒虫基因型B（EU642507、AB515310）聚为一支；驽巴贝虫序列与GenBank中驽巴贝虫基因型A（EU642512、KJ787774、AY309995、AB734392、MH651219、MH651220、JX049130）聚为一支。 结论 青海省部分地区马属动物梨形虫感染率较高，感染虫种为马泰勒虫和驽巴贝虫，流行基因型为马泰勒虫基因型A、B以及驽巴贝虫基因型A，其中马泰勒虫基因型B为优势流行基因型。

Objective To investigate the prevalence of tick-borne piroplasm infections and the genetic evolutionary characteristics in equines in selected areas of Qinghai Province, so as to provide insights into management of equine piroplasmosis in Qinghai Province. Methods The blood samples were collected from free range equines in four cities (prefectures) of Haidong, Xining, Haixi and Haibei in Qinghai Province from March 2023 to July 2024. Genomic DNA was extracted from blood samples and the 18S rRNA gene was amplified using nested PCR assay. The obtained gene sequence was subjected to homology alignment and analysis using the NCBI BLAST program. Haplotype analysis was performed using the software DNASP 6, and a haplotype network diagram was plotted using PopArt. The sequences of Theileria equi genotypes A to E and Babesia caballi genotypes A to C were selected from GenBank as reference sequences, and a phylogenetic tree was built using the maximum likelihood estimation with the software MEGA 6.0. Results The prevalence of piroplasm infections infection was 47.73% (84/176) in 176 blood samples from free-ranging equines, and the prevalence rates of T. equi and B. caballi infections were 47.16% (83/176) and 0.57% (1/176), respectively. A total of 16 haplotypes were identified in the 83 sequences of T. equi, with a haplotype diversity of 0.450 and a nucleotide diversity of 0.026 43, and H1 was the dominant haplotype of T. equi (73.49%, 61/83), followed by H5 haplotype (9.64%, 8/83), and the remaining 14 haplotypes (H2 to H4, H6 to H16) each accounted for 1.20% (1/83). Phylogenetic analysis showed that the gene sequences of T. equi haplotypes H5, H8 to H14, H16 were clustered together with T. equi genotype A (GenBank accession numbers: JX177672 and MT463613) in GenBank into the same clade, and the remaining 7 haplotypes were clustered together with T. equi genotype B (GenBank accession numbers: EU642507 and AB515310) into the same clade, while the gene sequences of B. caballi and B. caballi genotype A (GenBank accession numbers: EU642512, KJ787774, AY309995, AB734392, MH651219, MH651220 and JX049130) in GenBank were clustered into the same clade. Conclusion T. equi and B. caballi are piroplasm species infecting equines in selected areas of Qinghai Province, with a high prevalence rate of infections. The prevalent genotypes are T. equi genotypes A and B and B. caballi genotype A, with T. equi genotype B as the dominant genotype.