Coordenação Geral de Vigilância de Aboviroses, Secretaria de Vigilância em Saúde, Ministério da Saúde, Edifício PO 700, SRTV 702, Via W 5 Norte, Brasília/Distrito Federal, CEP 70723-040, Brazil.
Laboratório de Parasitologia Médica e Biologia de Vetores, Faculdade de Medicina, Universidade de Brasília, Campus Universitário Darcy Ribeiro, Asa Norte, Brasília/Distrito Federal, CEP 70910-900, Brazil.
Parasit Vectors. 2020 Oct 27;13(1):531. doi: 10.1186/s13071-020-04406-6.
Chemical mosquito control using malathion has been applied in Brazil since 1985. To obtain chemical control effectiveness, vector susceptibility insecticide monitoring is required. This study aimed to describe bioassay standardizations and determine the susceptibility profile of Ae. aegypti populations to malathion and pyriproxyfen, used on a national scale in Brazil between 2017 and 2018, and discuss the observed impacts in arbovirus control.
The diagnostic-doses (DD) of pyriproxyfen and malathion were determined as the double of adult emergence inhibition (EI) and lethal doses for 99% of the Rockefeller reference strain, respectively. To monitor natural populations, sampling was performed in 132 Brazilian cities, using egg traps. Colonies were raised in the laboratory for one or two generations (F1 or F2) and submitted to susceptibility tests, where larvae were exposed to the pyriproxyfen DD (0.03 µg/l) and adults, to the malathion DD determined in the present study (20 µg), in addition to the one established by the World Health Organization (WHO) DD (50 µg) in a bottle assay. Dose-response (DR) bioassays with pyriproxyfen were performed on populations that did not achieve 98% EI in the DD assays.
Susceptibility alterations to pyriproxyfen were recorded in six (4.5%) Ae. aegypti populations from the states of Bahia and Ceará, with Resistance Ratios (RR) ranging from 1.51 to 3.58. Concerning malathion, 73 (55.3%) populations distributed throughout the country were resistant when exposed to the local DD 20 µg/bottle. On the other hand, no population was resistant, and only 10 (7.6%) populations in eight states were considered as exhibiting decreased susceptibility (mortality ratios between 90 and 98%) when exposed to the WHO DD (50 µg/bottle).
The feasibility of conducting an insecticide resistance monitoring action on a nation-wide scale was confirmed herein, employing standardized and strongly coordinated sampling methods and laboratory bioassays. Brazilian Ae. aegypti populations exhibiting decreased susceptibility to pyriproxyfen were identified. The local DD for malathion was more sensitive than the WHO DD for early decreased susceptibility detection.
自 1985 年以来，巴西一直在使用马拉硫磷进行化学蚊虫控制。为了获得化学控制效果，需要对蚊虫的敏感性进行杀虫剂监测。本研究旨在描述生物测定标准化，并确定 2017 年至 2018 年在巴西全国范围内使用的吡丙醚和马拉硫磷对埃及伊蚊种群的敏感性概况，并讨论在虫媒病毒控制中观察到的影响。
吡丙醚和马拉硫磷的诊断剂量（DD）分别确定为成虫抑制率（EI）的两倍和洛克菲勒参考株的致死剂量的两倍。为了监测自然种群，在 132 个巴西城市使用卵阱进行了抽样。将种群在实验室中饲养一代或两代（F1 或 F2），并进行敏感性测试，其中幼虫暴露于吡丙醚的 DD（0.03 µg/l）和成虫暴露于本研究中确定的马拉硫磷 DD（20 µg），以及世界卫生组织（WHO）DD（50 µg）在瓶试验中。在 DD 试验中未达到 98% EI 的种群中进行了吡丙醚的剂量反应（DR）生物测定。
在来自巴伊亚州和塞阿拉州的六个（4.5%）埃及伊蚊种群中记录到对吡丙醚的敏感性改变，抗性比（RR）范围为 1.51 至 3.58。关于马拉硫磷，全国共有 73 个（55.3%）种群对当地 DD 20 µg/瓶表现出抗性。另一方面，没有种群表现出抗性，只有 10 个（7.6%）种群在八个州被认为对 WHO DD（50 µg/瓶）表现出敏感性降低（死亡率在 90%至 98%之间）。
本研究证实了在全国范围内进行杀虫剂抗性监测行动的可行性，采用了标准化和高度协调的抽样方法和实验室生物测定。鉴定出对吡丙醚敏感性降低的巴西埃及伊蚊种群。马拉硫磷的本地 DD 比 WHO DD 更敏感，可早期检测到敏感性降低。
