Sibling Species Composition and Susceptibility Status of Anopheles gambiae s.l. to Insecticides Used for Indoor Residual Spraying in Eastern Uganda.

IF 1.4 Q3 PARASITOLOGY
Julius Iga, Stephen Ochaya, Richard Echodu, Elizabeth A Opiyo, Alex K Musiime, Angella Nakamaanya, Geoffrey M Malinga
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引用次数: 0

Abstract

Background: Malaria remains one of the most critical disease causing morbidity and mortality in Uganda. Indoor residual spraying (IRS) and the use of insecticide-treated bed nets are currently the predominant malaria vector control interventions. However, the emergence and spread of insecticide resistance among malaria vectors threaten the continued effectiveness of these interventions to control the disease, particularly in high transmission areas. To inform decisions on vector control, the current study evaluated the Anopheles malaria vector species and their susceptibility levels to 0.1% bendiocarb and 0.25% pirimiphos-methyl insecticides used in IRS intervention program in Namutumba district, Eastern Uganda.

Methods: Anopheles larvae were collected between March and May 2017 from different breeding sites in the parishes of Nsinze and Nawaikona in Nsinze sub-county and reared to adults to assess the susceptibility status of populations in the study area. Mosquitoes were identified using morphological keys and species-specific polymerase chain reaction (PCR) assays. Susceptibility tests were conducted on 2- to 5-day-old non-blood-fed adult female Anopheles that emerged using insecticide-impregnated papers with 0.1% bendiocarb and 0.25% pirimiphos-methyl following standard World Health Organization (WHO) insecticide susceptibility bioassays. A Log-probit regression model was used to derive the knock-down rates for 50% and 95% of exposed mosquitoes.

Results: A total of 700 mosquito larvae were collected from different breeding sites. Morphological identification showed that 500 individuals that emerged belonged to Anopheles gambiae sensu lato (s.l.), the main malaria vector. The PCR results showed that the dominant sibling species under the A. gambiae complex was Anopheles arabiensis 99.5% (395/397). WHO bioassay tests revealed that the population of mosquitoes exhibited high levels of susceptibility (24-hour post-exposure mortality 98-100%) to both insecticides tested. The median knock-down time, KDT50, ranged from 6.6 to 81.4 minutes, while the KDT95 ranged from 21.6 to 118.9 minutes for 0.25% pirimiphos-methyl. The KDT50 for 0.1% bendiocarb ranged from 2.8 to 62.9 minutes, whereas the KDT95 ranged from 36.0 to 88.5 minutes.

Conclusions: These findings indicate that bendiocarb and pirimiphos-methyl are still effective against the major malaria vector, A. arabiensis in Nsinze sub-county, Namutumba district, Uganda and can be effectively used for IRS. The study has provided baseline information on the insecticide susceptibility status on malaria vectors in the study area. However, routine continuous monitoring program of insecticide susceptibility and malaria vector composition is required so as to guide future decisions on insecticide use for IRS intervention toward malaria elimination and to track future changes in vector population.

Abstract Image

Abstract Image

乌干达东部地区冈比亚按蚊兄弟种组成及对室内滞留喷洒杀虫剂的敏感性
背景:疟疾仍然是造成乌干达发病率和死亡率的最严重疾病之一。室内滞留喷洒和使用经杀虫剂处理的蚊帐是目前主要的疟疾病媒控制干预措施。然而,疟疾病媒中杀虫剂耐药性的出现和蔓延威胁到这些控制疾病的干预措施的持续有效性,特别是在高传播地区。为了为媒介控制决策提供信息,本研究评估了乌干达东部Namutumba地区IRS干预规划中使用的疟媒按蚊种类及其对0.1%苯虫威和0.25%吡虫磷-甲基杀虫剂的敏感性。方法:于2017年3 - 5月在宁泽县宁泽县和纳威科纳县的不同孳生地点采集按蚊幼虫,饲养成蚊,评估研究区种群易感状况。利用形态键和种特异性聚合酶链反应(PCR)对蚊虫进行鉴定。按照世界卫生组织(WHO)标准的杀虫剂敏感性生物测定法,对2 ~ 5日龄非吸血雌性按蚊进行药敏试验,采用0.1%苯虫威和0.25%吡虫磷-甲基杀虫剂浸渍纸。采用Log-probit回归模型计算了50%和95%暴露蚊子的杀灭率。结果:在不同孳生地点共捕获蚊幼虫700只。形态鉴定显示,共发现500只冈比亚按蚊(Anopheles gambiae sensu lato, s.l)。PCR结果显示,冈比亚按蚊复合体下的优势兄弟种为阿拉伯按蚊,占99.5%(395/397)。世卫组织生物测定试验显示,蚊子种群对所测两种杀虫剂表现出高度敏感性(接触后24小时死亡率为98-100%)。中位敲除时间KDT50在6.6 - 81.4分钟之间,而0.25%甲基吡硫磷的KDT95在21.6 - 118.9分钟之间。0.1%恶虫威的KDT50在2.8 ~ 62.9分钟之间,KDT95在36.0 ~ 88.5分钟之间。结论:本研究结果表明,在乌干达纳木图姆巴区Nsinze副县,苯虫威和甲基吡虫磷对主要疟疾媒介阿拉比伊蚊仍有一定的防治效果,可以有效地应用于IRS。该研究为研究地区疟疾病媒对杀虫剂的敏感性状况提供了基线信息。然而,需要对杀虫剂敏感性和疟疾病媒组成进行常规连续监测,以指导未来在IRS干预中使用杀虫剂的决策,以消除疟疾,并跟踪未来病媒种群的变化。
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来源期刊
Journal of Parasitology Research
Journal of Parasitology Research Medicine-Infectious Diseases
CiteScore
3.50
自引率
9.10%
发文量
49
审稿时长
13 weeks
期刊介绍: Journal of Parasitology Research is a peer-reviewed, Open Access journal that publishes original research articles, review articles, and clinical studies in all areas of basic and applied parasitology. Articles covering host-parasite relationships and parasitic diseases will be considered, as well as studies on disease vectors. Articles highlighting social and economic issues around the impact of parasites are also encouraged. As an international, Open Access publication, Journal of Parasitology Research aims to foster learning and collaboration between countries and communities.
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