CSIRO Agriculture and Food, St. Lucia, Brisbane, Queensland 4067, Australia; School of Veterinary Science, The University of Queensland, Gatton, Queensland 4343, Australia.
CSIRO Agriculture and Food, St. Lucia, Brisbane, Queensland 4067, Australia.
Vet Parasitol. 2024 Dec;332:110326. doi: 10.1016/j.vetpar.2024.110326. Epub 2024 Oct 5.
Control of the sheep blowfly relies largely on the use of insecticides applied prophylactically in advance of expected fly activity. However, the blowfly has shown an ability to develop resistance to some of these insecticides. Recent reports of the co-occurrence of resistance to both dicyclanil and imidacloprid in in vitro bioassays with field-collected fly strains has raised the possibility that the two resistances may represent cross-resistance linked by a common mechanism. We investigated this by imposing insecticide selection pressure on larvae of two insecticide-resistant field strains over a number of generations using either dicyclanil or imidacloprid and then measuring changes in sensitivity to both the selecting chemical and the alternate chemical. Larvae selected over six generations with each chemical showed significant increases in resistance to the selecting chemical: resistance ratios at the IC 5.5 - 8.1-fold higher for dicyclanil, and 3.1 - 3.8-fold for imidacloprid. The larvae also showed significant increases in levels of resistance towards the alternate chemical: resistance ratios 2.6 - 3.1-fold higher towards dicyclanil following selection with imidacloprid, and 2.2 - 3.2-fold higher towards imidacloprid following selection with dicyclanil. The increases in resistance to both chemicals after exposure to either suggests a common mechanism of resistance, at least in our laboratory-selected populations. Assays with the cytochrome P450 inhibitor aminobenzotriazole showed that this synergist was able to remove the increased resistance to both compounds in strains selected with either compound, suggesting that cytochrome P450 is responsible for the resistance observed to both chemicals. Our results confirm that cross-resistance exists between dicyclanil and imidacloprid in the sheep blowfly, and hence the two compounds should be considered as related entities in insecticide rotation strategies for flystrike control.
对绵羊狂蝇的控制主要依赖于在预期蝇类活动之前预防性地使用杀虫剂。然而，狂蝇已经显示出对一些杀虫剂产生抗性的能力。最近有报道称，在体外生物测定中，田间采集的蝇株对双氰胺和吡虫啉同时表现出抗性，这增加了两种抗性可能代表通过共同机制产生的交叉抗性的可能性。我们通过在几代时间内对两种抗药性田间菌株的幼虫施加杀虫剂选择压力，使用双氰胺或吡虫啉来研究这种情况，然后测量对选择化学物质和替代化学物质的敏感性变化。用每种化学物质选择了六代的幼虫对选择化学物质的抗性显著增加：双氰胺的抗性比增加了 8.1 倍，吡虫啉的抗性比增加了 3.1 倍。幼虫对替代化学物质的抗性水平也显著增加：在用吡虫啉选择后，对双氰胺的抗性比增加了 2.6 倍至 3.1 倍，在用双氰胺选择后，对吡虫啉的抗性比增加了 2.2 倍至 3.2 倍。在接触任一种化学物质后，对这两种化学物质的抗性增加表明至少在我们的实验室选择的种群中存在一种共同的抗性机制。用细胞色素 P450 抑制剂氨基苯并三唑进行的测定表明，这种增效剂能够去除用任何一种化合物选择的菌株对这两种化合物增加的抗性，这表明细胞色素 P450 是对这两种化学物质观察到的抗性的原因。我们的结果证实了绵羊狂蝇中双氰胺和吡虫啉之间存在交叉抗性，因此在控制蝇蛆病的杀虫剂轮换策略中，这两种化合物应被视为相关实体。
