Kumari Ansu, Agnihotri Divya, Nehra Anil Kumar, Moudgil Aman Dev, Singh Yudhbir, Maurya Prem Sagar, Pateer Devendra Prasad, Garg Rajat
Department of Veterinary Medicine, Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, Haryana, 125004, India.
Department of Veterinary Medicine, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Rampura Phul, Punjab, 151103, India.
BMC Vet Res. 2025 Jul 26;21(1):492. doi: 10.1186/s12917-025-04947-x.
Babesia gibsoni is a tick-borne intraerythrocytic protozoan parasite causing piroplasmosis in dogs globally. A significant knowledge gap exists regarding the genetic characterization of B. gibsoni using the mitochondrial cytochrome c oxidase subunit I (COXI) gene. To address this, the current study aimed to investigate the genetic diversity and population genetics of B. gibsoni based on COXI gene sequences (≥ 649 bp) in the GenBank.
Phylogenetic analysis revealed that all B. gibsoni isolates clustered into a single large monophyletic clade based on nucleotide and amino acid sequences, exhibiting high sequence similarity ranging from 98.2-100% at the nucleotide level and 99.1-100% at the amino acid level. Sequence alignment of the COXI gene identified 17 variable sites, including 13 synonymous (T66A, T162C, C177T, T240C, A423G, C426T, G474A, T477C, G486A, T489C, T516C, A531G, and T609A), and four non-synonymous (G138A, C191T, C194T, and G316A) mutations that resulted in amino acid substitutions at four places (M46I, T64I, S65F and V106I). A median-joining haplotype network constructed from the sequences revealed 10 distinct haplotypes, with six of them comprising multiple sequences (2-5 sequences each). No haplotype was shared between any two countries. The Indian population exhibited the highest nucleotide and haplotype diversities, while the Japanese population showed the lowest. Global dataset demonstrated low nucleotide (0.00767 ± 0.00076) and high haplotype (0.911 ± 0.040) diversities. Significant genetic differentiation was observed between Indian and Japanese populations (F = 0.51910; P < 0.05), with moderate gene flow (Nm = 0.46321) between them. Analysis of molecular variance (AMOVA) revealed that over half of the genetic variation occurred between populations (52.23%), rather than within them (47.77%). Neutrality tests and mismatch distributions suggested that B. gibsoni populations have maintained a constant size. Analysis of the secondary structure of the COXI protein revealed a composition of nine alpha helices, with no beta sheets present. It contained three extracellular domains, five transmembrane domains, and three cytoplasmic domains. Notably, the structure lacked disulfide bonds and signal peptides but featured one N-glycosylation site at position 197. No O-glycosylation sites were detected.
This study presents the first comprehensive genetic and population-level characterization of B. gibsoni using mitochondrial COXI gene analysis. The findings offer a valuable reference for developing more effective control strategies against canine babesiosis caused by B. gibsoni.
吉氏巴贝斯虫是一种蜱传播的红细胞内原生动物寄生虫，在全球范围内导致犬梨形虫病。关于使用线粒体细胞色素c氧化酶亚基I（COXI）基因对吉氏巴贝斯虫进行遗传特征分析，存在重大知识空白。为解决这一问题，本研究旨在基于GenBank中COXI基因序列（≥649 bp）研究吉氏巴贝斯虫的遗传多样性和群体遗传学。
系统发育分析表明，所有吉氏巴贝斯虫分离株基于核苷酸和氨基酸序列聚类成一个单一的大单系分支，在核苷酸水平上序列相似性高达98.2 - 100%，在氨基酸水平上为99.1 - 100%。COXI基因的序列比对鉴定出17个可变位点，包括13个同义突变（T66A、T162C、C177T、T240C、A423G、C426T、G474A、T477C、G486A、T489C、T516C、A531G和T609A），以及4个非同义突变（G138A、C191T、C194T和G316A），这些突变导致4个位点的氨基酸替换（M46I、T64I、S65F和V106I）。根据这些序列构建的中位数连接单倍型网络显示有10个不同的单倍型，其中6个包含多个序列（每个2 - 5个序列）。任意两个国家之间均未共享单倍型。印度群体表现出最高的核苷酸和单倍型多样性，而日本群体最低。全球数据集显示核苷酸多样性低（0.00767 ± 0.00076），单倍型多样性高（0.911 ± 0.040）。观察到印度和日本群体之间存在显著的遗传分化（F = 0.51910；P < 0.05），它们之间有适度的基因流（Nm = 0.46321）。分子方差分析（AMOVA）表明，超过一半的遗传变异发生在群体之间（52.23%），而非群体内部（47.77%）。中性检验和错配分布表明吉氏巴贝斯虫群体保持了恒定的大小。对COXI蛋白二级结构的分析揭示其由9个α螺旋组成，不存在β折叠。它包含3个细胞外结构域、5个跨膜结构域和3个细胞质结构域。值得注意的是，该结构缺乏二硫键和信号肽，但在第197位有1个N - 糖基化位点。未检测到O - 糖基化位点。
本研究首次使用线粒体COXI基因分析对吉氏巴贝斯虫进行了全面的遗传和群体水平特征描述。这些发现为制定更有效的针对吉氏巴贝斯虫引起的犬巴贝斯虫病的控制策略提供了有价值的参考。
