Hussain Tanveer, Periasamy Kathiravan, Nadeem Asif, Babar Masroor Ellahi, Pichler Rudolf, Diallo Adama
Vet Parasitol. 2014 Dec 15;206(3-4):188-99. doi: 10.1016/j.vetpar.2014.10.026.
Haemonchus species are major gastro-intestinal parasites affecting ruminants across the world. The present study aimed to assess the sympatric species distribution, genetic diversity, population structure and frequency of β-tubulin isotype 1 alleles associated with benzimidazole resistance. Internal transcribed spacer 2 (ITS2) sequences revealed three sympatric species of Haemonchus, H. contortus, H. placei and H. longistipes with 12 distinct genotypes circulating among ruminant hosts in Pakistan. High genetic variability was observed in Pakistani Haemonchus isolates at nicotine amide dehydrogenase subunit 4 (ND4) and cytochrome oxidase subunit 1 (COI) gene loci. Intra-population diversity parameters were higher in H. contortus isolates than H. placei. Phylogenetic analysis of ND4 and COI sequences did not reveal clustering of haplotypes originating from a particular host indicating high rate of gene flow among Haemonchus parasites infecting sheep, goat and cattle in Pakistan. ND4 and COI haplotypes from Pakistan were compared to sequences of Haemonchus isolates from 11 countries to elucidate the population structure. Multidimensional scaling (MDS) plot of pairwise FST derived from 531 ND4 haplotypes revealed clustering together of H. contortus from Pakistan, China, Malaysia and Italy while the isolates from Yemen and United States were found to be genetically distinct. With respect to H. placei, isolates from Pakistan were found to be genetically differentiated from isolates of other countries. The tests for selective neutrality revealed negative D statistics and did not reveal significant deviations in Pakistani Haemonchus populations while significant deviation (P < 0.05) was observed in Brazilian and Chinese H. contortus populations. Median Joining (MJ) network of ND4 haplotypes revealed Yemenese H. contortus being closer to H. placei cluster. β-tubulin isotype 1 genotyping revealed 7.86% frequency of Y allele associated with benzimidazole resistance at F200Y locus in Pakistani Haemonchus isolates.
血矛线虫属是影响全球反刍动物的主要胃肠道寄生虫。本研究旨在评估同域分布物种、遗传多样性、种群结构以及与苯并咪唑抗性相关的β-微管蛋白同工型1等位基因的频率。内部转录间隔区2（ITS2）序列显示血矛线虫有三个同域分布物种，即捻转血矛线虫、柏氏血矛线虫和长柄血矛线虫，在巴基斯坦的反刍动物宿主中有12种不同的基因型在传播。在巴基斯坦血矛线虫分离株的烟酰胺脱氢酶亚基4（ND4）和细胞色素氧化酶亚基1（COI）基因位点观察到高遗传变异性。捻转血矛线虫分离株的种群内多样性参数高于柏氏血矛线虫。对ND4和COI序列的系统发育分析未显示来自特定宿主的单倍型聚类，表明在感染巴基斯坦绵羊、山羊和牛的血矛线虫寄生虫中基因流率很高。将来自巴基斯坦的ND4和COI单倍型与来自11个国家的血矛线虫分离株序列进行比较，以阐明种群结构。由531个ND4单倍型得出的成对FST的多维标度（MDS）图显示，来自巴基斯坦、中国、马来西亚和意大利的捻转血矛线虫聚集在一起，而来自也门和美国的分离株在遗传上是不同的。关于柏氏血矛线虫，发现来自巴基斯坦的分离株与其他国家的分离株在遗传上有差异。选择中性检验显示D统计量为负，且未显示巴基斯坦血矛线虫种群有显著偏差，而在巴西和中国的捻转血矛线虫种群中观察到显著偏差（P < 0.05）。ND4单倍型的中位数连接（MJ）网络显示也门捻转血矛线虫更接近柏氏血矛线虫聚类。β-微管蛋白同工型1基因分型显示，在巴基斯坦血矛线虫分离株的F200Y位点，与苯并咪唑抗性相关的Y等位基因频率为7.86%。
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