Centro de Investigaciones en Microbiología y Parasitología Tropical (CIMPAT), Departamento de Ciencias Biológicas, Universidad de Los Andes, Bogotá D.C., Colombia.
Laboratorio de Entomología, Instituto Nacional de Salud, Bogotá D.C., Colombia.
Parasit Vectors. 2020 Apr 3;13(1):163. doi: 10.1186/s13071-020-04048-8.
Triatomine bugs are responsible for the vectorial transmission of the parasite Trypanosoma cruzi, etiological agent of Chagas disease, a zoonosis affecting 10 million people and with 25 million at risk of infection. Several triatomine species of the genus Rhodnius have been found inhabiting palm crowns where insects can find shelter in leaves axils and blood from palm-associated vertebrates. Rhodnius prolixus insects have been collected in oil palms in Colombia, and high T. cruzi infection rates were found. Since pest control is carried out in oil palm plantations, continuous exposure to insecticides could be occurring in these triatomines. Some insecticides suggested for pest control in oil palm plantations are also recommended for triatomine control in human dwellings. In this study, our objective was to assess if triatomines inhabiting oil palms exhibit resistance to deltamethrin, an insecticide used for vector control.
Rhodnius prolixus nymphs were sampled in oil palms located in Tauramena, Colombia. To determine deltamethrin resistance, biological and biochemical assays were carried out on fifth-instar nymphs from the F1 generation. For biological assays, pure and commercial deltamethrin were used, and in biochemical assays, activities of detoxifying enzymes related to pyrethroid resistance, such as oxidases, esterases and transferases, were quantified.
Deltamethrin lethal dosage 50 and 90 in R. prolixus from oil palms was significantly higher than in those from a susceptible colony suggesting possible deltamethrin resistance. Moreover, mortality with commercial deltamethrin was very low in insects from oil palms. In biochemical assays, the activity of evaluated detoxifying enzymes was significantly higher in R. prolixus from oil palms than in those from the susceptible colony.
Possible deltamethrin resistance found in R. prolixus insects from oil palms could threaten traditional vector control strategies in urban settings if insecticide-resistant triatomines can migrate from oil palms plantations. In palm oil producer countries such as Colombia, the oil palm plantations are growing constantly during the last years. We suggest that pest control strategies in oil palm crops should include triatomine surveillance and toxicological monitoring, especially in zones with several Chagas disease cases.
三锥虫是寄生虫克氏锥虫的载体，克氏锥虫是一种引起恰加斯病的病原体，这种人畜共患病影响了 1000 万人，有 2500 万人面临感染风险。几种 Rhodnius 属的三锥虫已经在棕榈树冠中被发现，昆虫可以在那里的叶子腋部找到庇护所，并从与棕榈有关的脊椎动物身上吸血。在哥伦比亚的油棕种植园中已经收集到了 Rhodnius prolixus 昆虫，并且发现了很高的 T. cruzi 感染率。由于在油棕种植园中进行了害虫防治，这些三锥虫可能会不断接触杀虫剂。一些建议用于油棕种植园害虫防治的杀虫剂也被推荐用于人类住宅中的三锥虫防治。在这项研究中，我们的目的是评估栖息在油棕树上的三锥虫是否对用于病媒控制的除虫菊酯产生抗药性。
在哥伦比亚的 Tauramena 采集了栖息在油棕树上的 Rhodnius prolixus 若虫。为了确定对除虫菊酯的抗药性，对来自 F1 代的第五龄若虫进行了生物和生化测定。在生物测定中，使用了纯除虫菊酯和商业除虫菊酯，在生化测定中，量化了与拟除虫菊酯抗性相关的解毒酶的活性，如氧化酶、酯酶和转移酶。
来自油棕的 Rhodnius prolixus 的除虫菊酯致死剂量 50 和 90 明显高于来自易感群体的致死剂量，表明可能存在除虫菊酯抗性。此外，来自油棕的昆虫对商业除虫菊酯的死亡率非常低。在生化测定中，来自油棕的 Rhodnius prolixus 中评估的解毒酶的活性明显高于来自易感群体的活性。
如果能从油棕种植园迁移的抗药性三锥虫威胁到城市环境中的传统病媒控制策略，那么在来自油棕的 Rhodnius prolixus 昆虫中发现的可能的除虫菊酯抗性可能会构成威胁。在哥伦比亚等棕榈油生产国，油棕种植园在过去几年中不断增长。我们建议，在油棕作物中，害虫防治策略应包括三锥虫监测和毒理学监测，特别是在有几个恰加斯病病例的地区。
