Penilla R P, Rodríguez A D, Hemingway J, Torres J L, Arredondo-Jiménez J I, Rodríguez M H
Centro de Investigación de Paludismo, Tapachula, Chiapas, México.
Med Vet Entomol. 1998 Jul;12(3):217-33. doi: 10.1046/j.1365-2915.1998.00123.x.
A high level of DDT resistance and low levels of resistance to organophosphorus, carbamate and pyrethroid insecticides were detected by discriminating dose assays in field populations of Anopheles albimanus in Chiapas, southern Mexico, prior to a large-scale resistance management project described by Hemingway et al. (1997). Biochemical assays showed that the DDT resistance was caused by elevated levels of glutathione S-transferase (GST) activity leading to increased rates of metabolism of DDT to DDE. The numbers of individuals with elevated GST and DDT resistance were well correlated, suggesting that this is the only major DDT resistance mechanism in this population. The carbamate resistance in this population is conferred by an altered acetylcholinesterase (AChE)-based resistance mechanism. The level of resistance observed in the bioassays correlates with the frequency of individuals homozygous for the altered AChE allele. This suggests that the level of resistance conferred by this mechanism in its heterozygous state is below the level of detection by the WHO carbamate discriminating dosage bioassay. The low levels of organophosphate (OP) and pyrethroid resistance could be conferred by either the elevated esterase or monooxygenase enzymes. The esterases were elevated only with the substrate pNPA, and are unlikely to be causing broad spectrum OP resistance. The altered AChE mechanism may also be contributing to the OP but not the pyrethroid resistance. Significant differences in resistance gene frequencies were obtained from the F1 mosquitoes resulting from adults obtained by different collection methods. This may be caused by different insecticide selection pressures on the insects immediately prior to collection, or may be an indication that the indoor- and outdoor-resting A. albimanus collections are not from a randomly mating single population. The underlying genetic variability of the populations is currently being investigated by molecular methods.
在墨西哥南部恰帕斯州白纹伊蚊的野外种群中，通过区分剂量试验检测到了对滴滴涕的高抗性水平以及对有机磷、氨基甲酸酯和拟除虫菊酯类杀虫剂的低抗性水平，这是在海明威等人（1997年）描述的大规模抗性管理项目之前进行的。生化分析表明，滴滴涕抗性是由谷胱甘肽S - 转移酶（GST）活性水平升高导致滴滴涕代谢为DDE的速率增加所致。GST水平升高且具有滴滴涕抗性的个体数量高度相关，这表明这是该种群中唯一主要的滴滴涕抗性机制。该种群中的氨基甲酸酯抗性是由基于乙酰胆碱酯酶（AChE）改变的抗性机制赋予的。在生物测定中观察到的抗性水平与携带改变的AChE等位基因的纯合个体频率相关。这表明该机制在杂合状态下赋予的抗性水平低于世卫组织氨基甲酸酯区分剂量生物测定的检测水平。低水平的有机磷（OP）和拟除虫菊酯抗性可能是由酯酶或单加氧酶水平升高所致。酯酶仅在底物对硝基苯乙酸（pNPA）存在时升高，不太可能导致广谱OP抗性。改变的AChE机制也可能导致OP抗性，但不会导致拟除虫菊酯抗性。通过不同采集方法获得的成虫所产生的F1代蚊子的抗性基因频率存在显著差异。这可能是由于采集前昆虫受到的不同杀虫剂选择压力所致，或者可能表明室内和室外栖息的白纹伊蚊种群并非来自随机交配的单一群体。目前正在通过分子方法研究这些种群潜在的遗传变异性。
