Kaplan Ray M
Department of Medical Microbiology and Parasitology, College of Veterinary Medicine, University of Georgia, Athens 30602, USA.
Vet Res. 2002 Sep-Oct;33(5):491-507. doi: 10.1051/vetres:2002035.
Suppressive anthelmintic treatment strategies originally designed to control Strongylus vulgaris in horses were extremely successful in reducing morbidity and mortality from parasitic disease. Unfortunately, this strategy has inadvertently resulted in the selection of drug-resistant cyathostomes (Cyathostominea), which are now considered the principal parasitic pathogens of horses. Resistance in the cyathostomes to benzimidazole drugs is highly prevalent throughout the world, and resistance to pyrantel appears to be increasingly common. However, there are still no reports of ivermectin resistance in nematode parasites of horses despite 20 years of use. It is unknown why resistance to ivermectin has not yet emerged, but considering that ivermectin is the single most commonly used anthelmintic in horses most parasitologists agree that resistance is inevitable. The fecal egg count reduction test is considered the gold standard for clinical diagnosis of anthelmintic resistance in horses, but diagnosis is complicated by lack of an accepted standard for the performance of this test or for the analysis and interpretation of data. Presently there is very little data available on the molecular mechanisms of anthelmintic resistance in cyathostomes; beta-tubulin gene is the only anthelmintic-resistance associated gene that has been cloned. The increasingly high prevalence of anthelmintic-resistant cyathostomes must be taken into account when designing worm control programs for horses. Strategies to decelerate further selection for drug resistance thereby extending the lifetime of currently effective anthelmintics should be implemented whenever possible. Considering the nature of the equine industry in which horses often graze shared pastures with horses from diverse locations, transmission and widespread dispersal of resistant parasites is virtually assured. A proactive approach to this problem centered on understanding the molecular basis of anthelmintic resistance in cyathostomes is required if we are to expect chemical control of nematodes in horses to remain a viable element of parasite control in the future.
最初设计用于控制马体内普通圆线虫的驱虫治疗策略在降低寄生虫病的发病率和死亡率方面极为成功。不幸的是，这一策略无意中导致了对药物耐药的杯状线虫（杯状亚目）的出现，它们现在被认为是马的主要寄生虫病原体。杯状线虫对苯并咪唑类药物的耐药性在全球范围内高度普遍，对噻嘧啶的耐药性似乎也越来越常见。然而，尽管已使用了20年，但马的线虫寄生虫对伊维菌素耐药的情况仍未见报道。尚不清楚为何尚未出现对伊维菌素的耐药性，但考虑到伊维菌素是马最常用的单一驱虫药，大多数寄生虫学家都认为耐药性是不可避免的。粪便虫卵计数减少试验被认为是马驱虫药耐药性临床诊断的金标准，但由于缺乏该试验操作或数据的分析与解释的公认标准，诊断变得复杂。目前关于杯状线虫驱虫药耐药分子机制的数据非常少；β-微管蛋白基因是唯一已被克隆的与驱虫药耐药相关的基因。在设计马的蠕虫控制方案时，必须考虑到驱虫药耐药杯状线虫的患病率日益升高。应尽可能实施减缓对耐药性进一步选择从而延长当前有效驱虫药使用寿命的策略。考虑到养马业的性质，即马匹经常与来自不同地区的马在共同牧场放牧，耐药寄生虫的传播和广泛扩散几乎是必然的。如果我们期望未来马线虫的化学控制仍能作为寄生虫控制的一个可行要素，就需要采取一种积极主动的方法来解决这个问题，其核心是了解杯状线虫驱虫药耐药的分子基础。
