Lind Eva Osterman, Uggla Arvid, Waller Peter, Höglund Johan
Department of Parasitology (SWEPAR), Swedish University of Agricultural Sciences and National Veterinary Institute, SE-751 89 Uppsala, Sweden.
Vet Parasitol. 2005 Mar 31;128(3-4):261-9. doi: 10.1016/j.vetpar.2004.11.029.
The aim of this study was to investigate the suitability of a larval development assay (LDA) for the determination of anthelmintic resistance in cyathostomin nematode populations of the horse. In addition, comparison of results between geographic regions, types of horse establishment, and the use of anthelmintics in Sweden, was established. Seventy horse herds from different parts of Sweden were sampled, and strongyle eggs from the faeces of 54 of those were investigated by an LDA (DrenchRite). The following anthelmintics were tested: thiabendazole (TBZ), levamisole (LEV), ivermectin monosaccharide (IVM-MS), ivermectin aglycone (IVM-AG) and pyrantel (PYR). The LC50 values for TBZ and LEV were generally lower than those previously reported in other LDA studies on horse nematodes. This could be related to the infrequent use of these compounds for the past 20 years in Sweden. In this study, there was a great variation within and between assay plates that could not be explained. Still the LC50 values differed significantly between the regions for all anthelmintics, except for pyrantel. The highest LC50s were observed in parasite populations from the south of Sweden. There were no significant differences between riding schools and studs. Limitations of this technique exist, namely the lack of established cut-off values for susceptible and resistant populations and interpretation problems related to multi-species infections. Although there are advantages with LDA such as the possibility of testing several compounds simultaneously without interference with the deworming programmes on the farms, we conclude that LDA currently is not a reliable alternative to the faecal egg count reduction test (FECRT).
本研究的目的是调查幼虫发育试验（LDA）用于测定马圆线虫种群抗蠕虫药耐药性的适用性。此外，还对瑞典不同地理区域、马场类型以及抗蠕虫药使用情况的结果进行了比较。从瑞典不同地区采集了70个马群的样本，其中54个马群粪便中的圆线虫卵通过LDA（DrenchRite）进行了检测。测试了以下抗蠕虫药：噻苯达唑（TBZ）、左旋咪唑（LEV）、伊维菌素单糖（IVM-MS）、伊维菌素糖苷配基（IVM-AG）和噻嘧啶（PYR）。TBZ和LEV的半数致死浓度（LC50）值通常低于此前其他关于马线虫的LDA研究报告的值。这可能与这些化合物在瑞典过去20年中使用频率较低有关。在本研究中，试验平板内部和之间存在很大差异，无法解释。不过，除噻嘧啶外，所有抗蠕虫药的LC50值在不同地区之间仍存在显著差异。在瑞典南部的寄生虫种群中观察到最高的LC50值。骑术学校和种马场之间没有显著差异。该技术存在局限性，即缺乏针对易感和耐药种群的既定临界值以及与多物种感染相关的解释问题。尽管LDA有一些优点，例如可以同时测试几种化合物而不干扰农场的驱虫计划，但我们得出结论，目前LDA并非粪便虫卵计数减少试验（FECRT）的可靠替代方法。
