Young K E, Garza V, Snowden K, Dobson R J, Powell D, Craig T M
Department of Veterinary Pathobiology, Texas A and M University, College Station 77843, USA.
Vet Parasitol. 1999 Aug 31;85(2-3):205-14; discussion 215-25. doi: 10.1016/s0304-4017(99)00100-4.
Diversity of parasite populations was compared between two herds of horses, one a regularly treated herd the other a feral herd which has bad no anthelmintic treatment for at least 25 years. Eggs obtained from fecal samples of both herds were tested for anthelmintic resistance by use of an in-vitro larval hatch/development assay (LDA), DrenchRite. A fecal egg reduction test was also performed with the domesticated herd using fenbendazole, pyrantel pamoate and ivermectin. Cyathostomes were the predominant group of worms present in both herds. Trichostrongylus axei was seen in both herds, but Strongylus equinus, Strongylus vulgaris, Gyalocephalus capitatus, Poteriostomum spp. and Strongyloides westeri were only found in the feral horses. Larvae of Strongylus edentatus were found in a single domesticated horse. Fecal egg reduction tests with the domesticated herd showed a 32% egg count reduction for fenbendazole, a 93% reduction with pyrantel, and a 99% reduction with ivermectin. From the LDA, anthelmintic resistance was evaluated by determining the resistance ratio of the domesticated herd compared with the feral herd. For benzimidazoles in the domesticated herd, 45% of the cyathostome population was 9.4 times more tolerant than the feral herd's parasite population. The parasite population in the domesticated herd was 1.5 times more tolerant to Levamisole, and 1.7 times more tolerant to the benzimidazole/levamisole combination than the parasite population within the feral herd. 9% of the parasite population in the domesticated herd was 90 times more tolerant to avermectins than the feral herd's parasite population, even though a subpopulation of worms in the feral herd were tolerant to low concentrations of avermectins despite never being previously exposed to this class of anthelmintic.
比较了两群马的寄生虫种群多样性，一群是定期接受治疗的马群，另一群是野生马群，该野生马群至少25年未进行驱虫治疗。通过体外幼虫孵化/发育试验（LDA）即DrenchRite，对两群马粪便样本中获得的虫卵进行驱虫抗性检测。还对家养马群使用芬苯达唑、吡喹酮和伊维菌素进行了粪便虫卵减少试验。圆线虫是两群马中主要的蠕虫种类。两群马中均发现了艾氏毛圆线虫，但马圆线虫、普通圆线虫、头状杯环线虫、波口线虫属和韦氏类圆线虫仅在野生马中发现。在一匹家养马中发现了无齿圆线虫的幼虫。对家养马群进行的粪便虫卵减少试验显示，芬苯达唑使虫卵计数减少了32%，吡喹酮减少了93%，伊维菌素减少了99%。通过LDA，通过确定家养马群与野生马群的抗性比率来评估驱虫抗性。在家养马群中，45%的圆线虫种群对苯并咪唑的耐受性比野生马群的寄生虫种群高9.4倍。家养马群中的寄生虫种群对左旋咪唑的耐受性比野生马群高1.5倍，对苯并咪唑/左旋咪唑组合的耐受性比野生马群中的寄生虫种群高1.7倍。家养马群中9%的寄生虫种群对阿维菌素的耐受性比野生马群的寄生虫种群高90倍，尽管野生马群中的一部分蠕虫亚群尽管从未接触过此类驱虫药，但对低浓度的阿维菌素有耐受性。
