Barros Antonio Thadeu M, Gomes Alberto, Koller Wilson W
Embrapa Pantanal, Rua 21 de Setembro, 1880. Corumbá, MS, 79320-900, Brasil.
Rev Bras Parasitol Vet. 2007 Jul-Sep;16(3):145-51. doi: 10.1590/s1984-29612007000300006.
Horn fly susceptibility to insecticides was evaluated in the state of Mato Grosso do Sul, Brazil, from October 2000 to September 2002. Insecticide bioassays (n=57) were conducted in 38 ranches from 14 municipalities throughout the state. Horn flies from wild populations were collected on cattle and exposed to filter papers impregnated with cypermethrin, permethrin, or diazinon and mortality was assessed after two hours. Resistance to cypermethrin was detected in all populations, with resistance ratios (RR) ranging from 27.6 to 91.3-fold. Permethrin bioassays provided apparently low levels of resistance (RR<5), however, resistant flies were found in 96.9% of the populations based on diagnostic concentrations. From both pyrethroid bioassays, resistance was detected in 97.4% of the populations. On the other hand, a high susceptibility to diazinon (RR< or =1.1) was detected in all populations. Pyrethroid products, most cypermethrin (92.3%) and deltamethrin (66.7%), were used in all ranches controlling horn flies (97.5%). Insecticide treatments, usually incorrectly applied, were routinely delivered by manual backpack sprayers in most ranches (84.5%). This profile of insecticide use helps to explain the widespread resistance of horn flies to pyrethroids in the state as well as their high susceptibility to the organophosphate. Inadequate control practices contribute to aggravate the resistance problem and its consequences.
2000年10月至2002年9月期间，在巴西南马托格罗索州对厩螫蝇对杀虫剂的敏感性进行了评估。在该州14个市的38个牧场进行了杀虫剂生物测定（n = 57）。从牛身上采集野生种群的厩螫蝇，将其暴露于浸渍有氯氰菊酯、氯菊酯或二嗪农的滤纸上，两小时后评估死亡率。在所有种群中均检测到对氯氰菊酯的抗性，抗性比率（RR）范围为27.6至91.3倍。氯菊酯生物测定显示抗性水平明显较低（RR < 5），然而，根据诊断浓度，在96.9%的种群中发现了抗性苍蝇。从两种拟除虫菊酯生物测定中，在97.4%的种群中检测到抗性。另一方面，在所有种群中均检测到对二嗪农的高敏感性（RR ≤ 1.1）。在所有控制厩螫蝇的牧场（97.5%）中都使用了拟除虫菊酯产品，其中大部分是氯氰菊酯（92.3%）和溴氰菊酯（66.7%）。在大多数牧场（84.5%），杀虫剂处理通常使用手动背负式喷雾器进行，且施用方式通常不正确。这种杀虫剂使用情况有助于解释该州厩螫蝇对拟除虫菊酯的广泛抗性以及它们对有机磷的高敏感性。控制措施不当加剧了抗性问题及其后果。
