The stable fly, Stomoxys calcitrans, is a globally important pest causing stress, economic losses and transmission of pathogens in livestock. Control on commercial farms relies predominantly on the use of insecticides, with pyrethroids being the most frequently used class of insecticides in industrialised countries. Here, laboratory isolates were obtained from four dairy farms in Brandenburg (Germany) and tested for phenotypic resistance to deltamethrin in comparison to a susceptible reference isolate using topical application. Individual flies were subsequently genotyped using allele-specific real-time PCRs. Phenotypic resistance was observed in all four field isolates with resistance ratios between 46 and 119 compared to the susceptible laboratory strain. At position 1014 of the voltage-sensitive sodium channel, allele-specific PCRs detected the wild-type, kdr-his and kdr genotypes encoding leucine, histidine and phenylalanine, respectively. In the susceptible laboratory isolate, only the wild-type was identified. On the farms with very high LD₅₀ values, the kdr variant was most prevalent and logistic regression analysis revealed that the kdr variant increased the odds to survive exposure to deltamethrin more than the kdr-his genotype. Flies carrying two resistance alleles were less susceptible than flies that also carried one wild-type allele. In three out of four field isolates, the allele frequencies were significantly different from the expectations of the Hardy–Weinberg equilibrium suggesting ongoing selection. The data show that the phenotype can be largely explained by the kdr genotype and represent high frequencies of the L1014F kdr and L1014H kdr-his variants conferring high levels of resistance in northern Germany.

稳定的果蝇 Stomoxys calcitrans 是一种全球重要的害虫，可造成压力、经济损失和病原体在牲畜中传播。对商业农场的控制主要依赖于杀虫剂的使用，其中拟除虫菊酯是工业化国家最常用的杀虫剂类别。在这里，从勃兰登堡州（德国）的四个奶牛场获得实验室分离株，并使用局部应用测试了对溴氰菊酯的表型耐药性。随后使用等位基因特异性实时 PCR 对个体果蝇进行基因分型。与易感实验室菌株相比，在所有四种田间分离株中观察到表型抗性，抗性比在 46 到 119 之间。在电压敏感钠通道的 1014 位，等位基因特异性 PCR 分别检测到编码亮氨酸、组氨酸和苯丙氨酸的野生型 kdr-his 和 kdr 基因型。在易感实验室分离株中，仅鉴定出野生型。在 LD₅₀ 值非常高的农场中，kdr 变体最为普遍，logistic 回归分析显示，kdr 变体比 kdr-his 基因型更能增加暴露于溴氰菊酯的存活几率。携带两个抗性等位基因的果蝇比同样携带一个野生型等位基因的果蝇更不敏感。在四个田间分离株中的三个中，等位基因频率与 Hardy-Weinberg 平衡的预期显着不同，表明正在进行选择。 数据显示，该表型在很大程度上可以用 kdr 基因型来解释，并且代表了 L1014F kdr 和 L1014H kdr-his 变体的高频，在德国北部赋予了高水平的耐药性。