de Albuquerque Ana Cláudia Alexandre, Bassetto Cesar Cristiano, de Almeida Fabiana Alves, Amarante Alessandro F T
Universidade Estadual Paulista (UNESP), Faculdade de Medicina Veterinária e Zootecnia, CEP 18618-681, Botucatu, SP, Brazil.
Universidade Estadual Paulista (UNESP), Instituto de Biociências, CEP 18618-681, Botucatu, SP, Brazil.
Vet Parasitol. 2017 Nov 15;246:112-117. doi: 10.1016/j.vetpar.2017.09.010. Epub 2017 Sep 18.
This study examined the development of resistance to anthelmintics in Haemonchus contortus in lambs under suppressive or selective treatment regimens that included monepantel. Twenty Ile de France and 20 Santa Ines lambs were allocated to two anthelmintic treatment regimens, based on body weight and nematode faecal egg counts (FEC): targeted selective treatment (TST) or suppressive treatment, both with monepantel. Lambs of the TST group were treated individually when they presented with a packed cell volume (PCV) ≤20%. On 7 October 2016, the lambs were allocated to clean pastures, where they grazed in separated paddocks by group until late February 2017. The experimental area was contaminated with nematodes that were introduced with the experimental Ile de France and Santa Ines lambs, naturally infected with gastrointestinal nematodes. To maintain the grazing lambs in the suppressive treatment group and their pasture as free of worms as possible, these lambs were treated with anthelmintics before being allocated to their paddock and then were periodically treated with monepantel. However, the use of a suppressive treatment regimen that included monepantel over a period of 3 months resulted in the emergence of a population of resistant H. contortus. In the TST group, there was a rapid and progressive reduction in the efficacy of monepantel, which at the end of the experiment was only 76%. The Ile de France lambs were all treated one or more times during the experiment, whereas only two Santa Ines lambs in the TST required treatment. In conclusion, a population of H. contortus resistant to monepantel emerged quickly during the rainy season, even when sheep were submitted to selective treatment.
本研究考察了在包括莫能菌素的抑制性或选择性治疗方案下，羔羊体内捻转血矛线虫对驱虫药的抗药性发展情况。根据体重和线虫粪便虫卵计数（FEC），将20只法兰西岛羊和20只圣伊内斯羊分配到两种驱虫治疗方案中：靶向选择性治疗（TST）或抑制性治疗，两种方案均使用莫能菌素。TST组的羔羊在血细胞比容（PCV）≤20%时进行个体治疗。2016年10月7日，将羔羊分配到干净的牧场，在那里它们按组在分开的围场中放牧，直到2017年2月底。实验区域被随着实验用的自然感染胃肠道线虫的法兰西岛羊和圣伊内斯羊引入的线虫污染。为使抑制性治疗组的放牧羔羊及其牧场尽可能无虫，这些羔羊在分配到围场前用驱虫药治疗，然后定期用莫能菌素治疗。然而，在3个月的时间里使用包括莫能菌素的抑制性治疗方案导致了一群抗药的捻转血矛线虫的出现。在TST组，莫能菌素的疗效迅速且逐渐降低，在实验结束时仅为76%。法兰西岛羊在实验期间均接受了一次或多次治疗，而TST组中只有两只圣伊内斯羊需要治疗。总之，即使绵羊接受了选择性治疗，在雨季期间仍迅速出现了对莫能菌素耐药的捻转血矛线虫群体。
