Bull K E, Hodgkinson J, Allen K, Poissant J, Peachey L E
Bristol Veterinary School, University of Bristol, Bristol, BS40 5DU, UK.
Department of Infection and Microbiome, Institute of Infection, Veterinary and Ecological Sciences, Leahurst Campus, University of Liverpool, Neston, CH64 7TE, UK.
Int J Parasitol Drugs Drug Resist. 2025 Apr;27:100576. doi: 10.1016/j.ijpddr.2024.100576. Epub 2024 Dec 22.
Cyathostomins are the most abundant equid endoparasites globally. There are approximately fifty cyathostomin species and, whilst they occupy distinct niches within the large intestine, they are generally considered to share similar characteristics in terms of pathogenicity and response to drug treatment. There are three classes of anthelmintic licensed in the UK to treat cyathostomins (benzimidazoles, tetrahydropyrimidines and macrocyclic lactones) and cases of resistance have been documented for all classes. Previously, faecal egg count reduction tests (FECRT) on four UK Thoroughbred studs revealed multidrug resistant cyathostomins on one stud (A), with evidence of resistance to the macrocyclic lactones (MLs) ivermectin (IVM) and moxidectin (MOX), and to pyrantel (PYR). The remaining three studs (B-D) lacked resistance to IVM and MOX but had a shortened egg reappearance period post treatment. To determine whether specific species could be associated with the observed resistance and shortened egg reappearance period, strongyle eggs collected from between six and 15 individual horses per stud were copro-cultured to third larval stage (L3), before and after anthelmintic treatment, over a three-year timeframe (2021-2023). Quantitative DNA metabarcoding of the ITS-2 region was carried out on all samples. On stud A, single but differing species were found to be responsible for ML and pyrantel resistance in yearlings, Cyathostomum catinatum and Cylicocyclus nassatus, respectively. On studs B-D, with shortened egg reappearance periods, species composition remained largely unchanged post treatment. This study is the first to quantitatively profile cyathostomin species composition pre- and post-treatment in a multidrug resistant population in the UK, revealing that resistance in cyathostomins was species specific. This raises the question of whether these species may be responsible for ML and PYR resistance more widely and indicates that anthelmintic resistance in cyathostomins may not be a multi-species phenomenon.
杯冠属线虫是全球最常见的马属动物体内寄生虫。杯冠属线虫约有50个物种，虽然它们在大肠内占据不同的生态位，但一般认为它们在致病性和对药物治疗的反应方面具有相似的特征。英国有三类驱虫药被许可用于治疗杯冠属线虫（苯并咪唑类、四氢嘧啶类和大环内酯类），并且已记录到所有类别的耐药病例。此前，对英国四个纯种马繁育场进行的粪便虫卵计数减少试验（FECRT）显示，其中一个繁育场（A）存在多药耐药的杯冠属线虫，有证据表明其对大环内酯类药物伊维菌素（IVM）和莫西菌素（MOX）以及对噻嘧啶（PYR）耐药。其余三个繁育场（B - D）对IVM和MOX没有耐药性，但治疗后虫卵再现期缩短。为了确定特定物种是否与观察到的耐药性和缩短的虫卵再现期有关，在三年时间（2021 - 2023年）内，在驱虫治疗前后，从每个繁育场6至15匹个体马采集的圆线虫虫卵进行共培养至第三幼虫期（L3）。对所有样本进行ITS - 2区域的定量DNA元条形码分析。在繁育场A，发现分别是杯冠线虫和鼻状环体线虫这两个单一但不同的物种导致一岁马对大环内酯类药物和噻嘧啶耐药。在繁育场B - D，虫卵再现期缩短，治疗后物种组成基本保持不变。本研究首次对英国多药耐药群体中杯冠属线虫物种组成在治疗前后进行了定量分析，揭示杯冠属线虫的耐药性具有物种特异性。这就提出了一个问题，即这些物种是否可能在更广泛范围内导致对大环内酯类药物和噻嘧啶的耐药性，并表明杯冠属线虫的驱虫药耐药性可能不是多物种现象。
