背景:巨大的蛔虫是一种肠道线虫,通过感染全世界的人类和猪而导致蛔虫病。最近的估计表明,蛔虫感染了超过5亿人,慢性感染导致生长和认知能力下降。蛔虫病在世界范围内影响无数猪,并且已知会通过降低肝脏的生长和谴责来降低产量。用于治疗as虫病的主要驱虫药物是苯并咪唑。苯并咪唑与β-微管蛋白相互作用并阻断其功能,在反刍动物线虫的β-微管蛋白中已经描述了几种苯并咪唑抗性相关的突变。最近对蛔虫的研究表明,这些典型的苯并咪唑抗性相关突变可能不存在于蛔虫的β-微管蛋白中,蛔虫或寄生虫,甚至在表型抗性人群中。
方法:为了进一步确定关键β-微管蛋白多态性的推定缺失,我们筛选了两个β-微管蛋白同种型的蛔虫,在成虫中高度表达。使用从世界各地的猪和人类中获得的蛔虫的成虫和卵样本,我们进行了深度扩增子测序,以寻找与蛔虫β-微管蛋白相关的典型抗性突变.随后,我们更详细地检查了这些数据,以研究两种同种型中的蛔虫种群动态和遗传多样性,并测试了基因型是否似乎在人和猪宿主之间存在分布.
结果:在187个分离株中,共发现69种基因型,由8个单倍型的β-微管蛋白同种型A和20个单倍型B组成。在β-微管蛋白同种型A和同种型B的14和37个位置观察到单核苷酸多态性,分别。在人或猪来源的蛔虫分离株中均未发现任何经典苯并咪唑抗性相关突变的证据。有,然而,人和猪来源的蛔虫之间每种同种型的遗传多样性和β-微管蛋白基因型分布的差异。种群分化的统计检验显示猪和人类来源的蠕虫之间存在显着差异(p<0.001);但是,与来自不同宿主的蠕虫相比,来自不同种群的蠕虫之间存在更多的多样性。
结论:我们的工作表明,蛔虫内没有典型的β-微管蛋白突变,但是驱虫抗药性的替代模式可能会出现,需要在监测药物疗效的同时继续进行遗传审查。
BACKGROUND: The giant roundworm Ascaris is an intestinal nematode, causing ascariasis by infecting humans and pigs worldwide. Recent estimates suggest that Ascaris infects over half a billion people, with chronic infections leading to reduced growth and cognitive ability. Ascariasis affects innumerable pigs worldwide and is known to reduce production yields via decreased growth and condemnation of livers. The predominant anthelminthic drugs used to treat ascariasis are the benzimidazoles. Benzimidazoles interact with β-tubulins and block their function, and several benzimidazole resistance-associated mutations have been described in the β-tubulins of ruminant nematodes. Recent research on ascarids has shown that these canonical benzimidazole resistance-associated mutations are likely not present in the β-tubulins of Ascaris, Ascaridia or Parascaris, even in phenotypically resistant populations.
METHODS: To further determine the putative absence of key β-tubulin polymorphisms, we screened two β-tubulin isotypes of Ascaris, highly expressed in adult worms. Using adult and egg samples of Ascaris obtained from pigs and humans worldwide, we performed deep amplicon sequencing to look for canonical resistance-associated mutations in Ascaris β-tubulins. Subsequently, we examined these data in closer detail to study the population dynamics of Ascaris and genetic diversity within the two isotypes and tested whether genotypes appeared to partition across human and pig hosts.
RESULTS: In the 187 isolates, 69 genotypes were found, made up of eight haplotypes of β-tubulin isotype A and 20 haplotypes of isotype B. Single nucleotide polymorphisms were seen at 14 and 37 positions for β-tubulin isotype A and isotype B, respectively. No evidence of any canonical benzimidazole resistance-associated mutations was found in either human- or pig-derived Ascaris isolates. There was, however, a difference in the genetic diversity of each isotype and distribution of β-tubulin genotypes between human- and pig-derived Ascaris. Statistical tests of population differentiation show significant differences (p < 0.001) between pig- and human-derived worms; however, more diversity was seen between worms from different populations than worms from different hosts.
CONCLUSIONS: Our work suggests an absence of canonical β-tubulin mutations within Ascaris, but alternative modes of anthelminthic resistance may emerge necessitating continued genetic scrutiny alongside monitoring of drug efficacy.