Williams Andrew R, Ropiak Honorata M, Fryganas Christos, Desrues Olivier, Mueller-Harvey Irene, Thamsborg Stig M
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
Chemistry and Biochemistry Laboratory, School of Agriculture, Policy and Development, University of Reading, Reading, UK.
Parasit Vectors. 2014 Nov 19;7:518. doi: 10.1186/s13071-014-0518-2.
Plant-derived condensed tannins (CT) show promise as a complementary option to treat gastrointestinal helminth infections, thus reducing reliance on synthetic anthelmintic drugs. Most studies on the anthelmintic effects of CT have been conducted on parasites of ruminant livestock. Oesophagostomum dentatum is an economically important parasite of pigs, as well as serving as a useful laboratory model of helminth parasites due to the ability to culture it in vitro for long periods through several life-cycle stages. Here, we investigated the anthelmintic effects of CT on multiple life cycle stages of O. dentatum.
Extracts and purified fractions were prepared from five plants containing CT and analysed by HPLC-MS. Anthelmintic activity was assessed at five different stages of the O. dentatum life cycle; the development of eggs to infective third-stage larvae (L3), the parasitic L3 stage, the moult from L3 to fourth-stage larvae (L4), the L4 stage and the adult stage.
Free-living larvae of O. dentatum were highly susceptible to all five plant extracts. In contrast, only two of the five extracts had activity against L3, as evidenced by migration inhibition assays, whilst three of the five extracts inhibited the moulting of L3 to L4. All five extracts reduced the motility of L4, and the motility of adult worms exposed to a CT-rich extract derived from hazelnut skins was strongly inhibited, with electron microscopy demonstrating direct damage to the worm cuticle and hypodermis. Purified CT fractions retained anthelmintic activity, and depletion of CT from extracts by pre-incubation in polyvinylpolypyrrolidone removed anthelmintic effects, strongly suggesting CT as the active molecules.
These results suggest that CT may have promise as an alternative parasite control option for O. dentatum in pigs, particularly against adult stages. Moreover, our results demonstrate a varied susceptibility of different life-cycle stages of the same parasite to CT, which may offer an insight into the anthelmintic mechanisms of these commonly found plant compounds.
植物源缩合单宁（CT）有望成为治疗胃肠道蠕虫感染的补充选择，从而减少对合成驱虫药物的依赖。大多数关于CT驱虫作用的研究都是针对反刍家畜的寄生虫进行的。齿状食道口线虫是猪的一种重要经济寄生虫，由于能够在体外长时间培养其多个生命周期阶段，它也是一种有用的蠕虫寄生虫实验室模型。在此，我们研究了CT对齿状食道口线虫多个生命周期阶段的驱虫作用。
从五种含CT的植物中制备提取物和纯化组分，并通过高效液相色谱-质谱联用仪进行分析。在齿状食道口线虫生命周期的五个不同阶段评估驱虫活性；即从虫卵发育到感染性第三期幼虫（L3）、寄生性L3期、从L3蜕皮到第四期幼虫（L4）、L4期和成虫期。
齿状食道口线虫的自由生活幼虫对所有五种植物提取物都高度敏感。相比之下，通过迁移抑制试验证明，五种提取物中只有两种对L3有活性，而五种提取物中有三种抑制L3向L4的蜕皮。所有五种提取物都降低了L4的活力，暴露于源自榛子皮的富含CT的提取物中的成虫活力受到强烈抑制，电子显微镜显示虫体角质层和皮下组织受到直接损伤。纯化的CT组分保留了驱虫活性，通过在聚乙烯聚吡咯烷酮中预孵育从提取物中去除CT消除了驱虫作用，有力地表明CT是活性分子。
这些结果表明，CT可能有望成为猪齿状食道口线虫的一种替代寄生虫控制选择，特别是针对成虫阶段。此外，我们的结果表明同一寄生虫的不同生命周期阶段对CT的敏感性各不相同，这可能有助于深入了解这些常见植物化合物的驱虫机制。
