Ihler C F, Bjørn H
Department of Large Animal Clinical Sciences, Norwegian College of Veterinary Medicine, Oslo, Norway.
Vet Parasitol. 1996 Oct 15;65(1-2):117-25. doi: 10.1016/0304-4017(96)00936-3.
Ten stables were included in a study to evaluate two in vitro methods for the detection of anthelmintic resistance in cyathostomes by comparing a faecal egg count reduction test (FECRT) to a larval development assay (LDA) and an egg hatch assay (EHA). The LDA was used in seven stables and EHA in the last three. On the basis of FECR values, resistance to benzimidazoles was detected in eight of the ten small strongyle populations. Resistance to pyrantel pamoate and ivermectin was not detected. The mean concentrations that inhibited hatching in 50% of the eggs (EC50), using thiabendazole (TBZ) in an EHA, were 1.02 microM in resistant populations and 0.37 microM in susceptible or suspected resistant ones. In the LDA, TBZ concentrations preventing 50% development by first/second stage larvae to the third larval stage (LC50) were 3.8 times lower than EC50 values in resistant worm populations. Mean LC50 for morantel, levamisol, ivermectin monosaccharide and avermectin-B2 in small strongyle populations susceptible to pyrantel and ivermectin was 8.0 microM, 0.99 microM, 15.6 nM and 2.93 nM, respectively. Data on pyrantel and ivermectin resistant populations could not be obtained as no resistant populations were detected. This study concludes that in vitro tests may be useful as a supplement to FECRT for the detection of benzimidazole resistance in cyathostomes, even if reference populations to be used as controls in the assays were not available. It is suggested that EC50 values for TBZ > 0.6 microM in LDA and > 0.5 microM in EHA strongly indicate benzimidazole resistance in equine small strongyles.
一项研究纳入了10个马厩，通过比较粪便虫卵计数减少试验（FECRT）与幼虫发育试验（LDA）以及虫卵孵化试验（EHA），来评估两种检测杯状属线虫抗驱虫药能力的体外方法。7个马厩使用了LDA，后3个马厩使用了EHA。根据FECR值，在10个小型圆线虫种群中的8个检测到了对苯并咪唑的耐药性。未检测到对吡喹酮和伊维菌素的耐药性。在EHA中使用噻苯达唑（TBZ）时，使50%的虫卵孵化受到抑制的平均浓度（EC50），在耐药种群中为1.02微摩尔，在敏感或疑似耐药种群中为0.37微摩尔。在LDA中，TBZ阻止第一/二阶段幼虫发育至第三幼虫阶段的浓度（LC50），比耐药蠕虫种群中的EC50值低3.8倍。对吡喹酮和伊维菌素敏感的小型圆线虫种群中，噻嘧啶、左旋咪唑、伊维菌素单糖和阿维菌素 - B2的平均LC50分别为8.0微摩尔、0.99微摩尔、15.6纳摩尔和2.93纳摩尔。由于未检测到耐药种群，所以无法获得关于吡喹酮和伊维菌素耐药种群的数据。本研究得出结论，体外试验可作为FECRT的补充，用于检测杯状属线虫对苯并咪唑的耐药性，即便在试验中没有可作为对照的参考种群。建议LDA中TBZ的EC50值大于＞0.6微摩尔以及EHA中＞0.5微摩尔时，强烈表明马小型圆线虫对苯并咪唑耐药。
