Insecticide resistance in disease vectors of public health importance

Vector-borne diseases are a global problem--a trend that may only increase if global temperature rises and demographic trends continue--and their economic and social impact are enormous. Insecticides play a vital role in the fight against these diseases by controlling the vectors themselves in order to improve public health; however, resistance to commonly used insecticides is on the rise. This perspective outlines the major classes of disease vector control agents and the mechanisms of resistance that have evolved, arguing that effective resistance management strategies must carefully monitor resistance in field populations and use combinations of the limited modes of action available to best effect. Moreover, the development of novel insecticide classes for control of adult mosquitoes and other vectors becomes increasingly important.     

球形芽孢杆菌Ts—1对十种蚊幼虫毒效测定

用球形芽孢杆菌Ts—1冻干菌粉,对国内10种蚊幼虫生物测定的结果表明,不同蚊种之间敏感性有很大差异。库蚊属蚊虫(特别是淡色库蚊和致倦库蚊)对Ts—1敏感性很高,按蚊其次,而伊蚊属除东乡伊蚊外对Ts—1均不敏感。此外,同一蚊种不同地理株之间,对Ts一1的敏感性也有显著差异。     

豫南罗索线虫感染库蚊、伊蚊和阿蚊的实验研究

试验的伊蚊、库蚊和阿蚊,对豫南罗索线虫均表现敏感,当蚊幼与线幼虫数之比为1:5时,4种伊蚊的感染率均在95％以上;致倦库蚊和三带喙库蚊的感染率分别为98.6％和97.1％,骚扰阿蚊为66.4％。线虫在蚊体内发育良好,感染度亦较高,表明此线虫具有应用前景。     

球形芽孢杆菌(Ts—1)在水体中消长动态以及对蚊幼虫的残效

本实验观察了球形芽孢杆菌(Ts—1)在清水和污水中细菌和芽孢数量消长动态和残效。在水体中,细菌和芽孢均以指数函数衰减。污水对Ts—1生长存活无害,但对致倦库蚊幼虫残效期较清水中为短。水体中死亡虫体对保持球形芽孢杆菌的残效有重要作用。     

Receptor-binding affinity and larvicidal activity of tetrahydroquinoline-type ecdysone agonists against Aedes albopictus

Tetrahydroquinolines (THQs), a class of nonsteroidal ecdysone agonists, are good candidates for novel mosquito control agents because they specifically bind to mosquito ecdysone receptors (EcRs). We have recently performed quantitative structure–activity relationship (QSAR) analyses of THQs to elucidate the physicochemical properties important for the ligand–receptor interaction. Based on previous QSAR results, here, we newly synthesized 15 THQ analogs with a heteroaryl group at the acyl moiety and evaluated their binding affinity against Aedes albopictus EcRs. We also measured the larvicidal activity of the combined set of previously and newly synthesized compounds against A. albopictus to examine the contribution of receptor-binding to larvicidal activity. Multiple regression analyses showed that the binding affinity and the molecular hydrophobicity of THQs are the key determinants of their larvicidal activity.     

四川罗索线虫对中华按蚊幼虫自然感染的观察

在乐山四川罗索线虫自5至12月寄生于中华按蚊幼虫,感染率为0.36～43.33％,以6、7 月最高.感染强度为1～8条。5～10月,月平均温度17～24℃是线虫繁殖和侵入的适宜时期。8℃(12月份)以下虽不能侵入,但可在宿主体内寄生。     

Effects of radiation on the fitness,sterility and arbovirus susceptibility of a Wolbachia-free Aedes albopictus strain for use in the sterile insect technique

BACKGROUND

The sterile insect technique (SIT) is a green and species-specific insect pest control technique that suppresses target populations by releasing factory-reared, radiosterilized males into the wild. Once released, it is important to be able to distinguish the released males from the wild males for monitoring purposes. Several methods to mark the sterile males exist. However, most have limitations due to monetary, process efficiency, or insect quality. Aedes albopictus is naturally infected with Wolbachia at a high prevalence, therefore the elimination of Wolbachia can serve as a biomarker to distinguish factory-reared male mosquitoes from wild conspecifics.

RESULTS

In this study, a Wolbachia-free Ae. albopictus GT strain was developed and its fitness evaluated, which was found to be comparable to the wild GUA strain. In addition, GT male mosquitoes were irradiated at the adult stage and a dose of 20 Gy or more induced over 99% sterility. Moreover, a dose of 30 Gy (almost completely sterilizing male and female mosquitoes) had limited effects on the mating competitiveness of GT males and the vector competence of GT females, respectively. However, radiation reduced mosquito longevity, regardless of sex.

CONCLUSION

Our results indicate that the Ae. albopictus GT strain can be distinguished from wild mosquitoes based on Wolbachia status and shows similar fitness, radio-sensitivity and arbovirus susceptibility to the GUA strain, indicating that it is feasible to use the GT strain to suppress Ae. albopictus populations for SIT programmes. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

苏云金杆菌H-14对致倦库蚊子_1代的影响

用14×10~3/ml的BtH-14菌液处理亲代第4龄致倦库蚊幼,观察其子_1代生命表特征。经与对照组比较,处理组蚊虫的净生殖率降低16.49％,雌蚊年均产卵量减少33％,世代周期延长约9天。     

West Nile virus in North America: perspectives on epidemiology and intervention

West Nile virus (WNV) invaded New York in 1999 and rapidly swept across the North American continent to the West Coast, north into southern Canada and south into Latin America, with minimal genetic change. Regional epidemics in equines and humans typically have included a year of viral introduction with minimal activity, successful overwintering, explosive amplification to epidemic levels the following year and then rapid subsidence. Overwintering possibly included long-term mosquito or avian infections, continued low-level transmission at southern latitudes and dispersal by south-north migrants. Explosive amplification has been associated with infections in several corvid species and other urban birds that produce elevated viremias capable of efficiently infecting even moderately susceptible mosquito species. Intervention has included mass vaccination of equines, and proactive and reactive mosquito control. Proactive mosquito control in areas with established infrastructure has been successful in reducing case incidence.     

苏云金杆菌Bt-59菌株Cry/Cyt毒素蛋白鉴定及杀虫活性

苏云金杆菌以色列亚种（Bacillus thuringiensis subsp.israelensis，Bti）是防治蚊幼虫的重要病原细菌，不同菌株间毒素蛋白种类和分布不尽相同。本研究利用苏云金杆菌以色列亚种Bt-59菌株的全基因组数据，对潜在的毒素基因种类、分布及菌株杀虫活性进行了分析。结果表明，Bt-59菌株除了含有Bti标准菌株主要毒素基因外，还含有Cry4-like基因，且Cry10Aa和Cyt1Ca基因在质粒4上发生了易位。质粒5上的Cry60Aa和Cry60Ba基因编码的毒素蛋白含有ETX_MTX2结构域，并与苏云金杆菌jegathesan亚种的同源蛋白一致性为100%。Cyt1Ca蛋白除了含有Bac_thur_toxin结构域外，还含有2个串联的RicinB_lectin_2结构域。菌株Bt-59对蚊幼虫具有较高的杀虫活性，对白纹伊蚊Aedes albopictus和淡色库蚊Culex pipiens pallens的LC₅₀分别为1.239 μL/L和0.341 μL/L。研究结果明确了菌株Bt-59毒素蛋白的种类和特征，为菌株遗传改良提供理论基础。     

稻田放养满江红对蚊虫孳生影响的初步观察

实验室笼内研究表明,容器水面覆盖细绿萍可阻止库蚊在其中产卵,但对中华按蚊产卵无显著作用。1987年在湖南桂东县对放养细绿萍的稻田观察结果,库蚊(主要是三带喙库蚊)幼虫密度明显比对照田为低,而且随着覆盖面积比例扩大而下降率愈大,当覆盖面积达到95％时,平均下降率达78.96％,但对按蚊幼虫密度下降率甚微,这与实验室观察结果相符。在桂东县,养萍稻田每亩可收鲜萍1500-2000公斤,可用作禽畜饲料或其他作物基肥。养萍稻田也可使稻谷增产8％左右。由于养萍既可减少库蚊幼虫孳生,也有较好的经济效益,是在稻田蚊虫综合治理中值得采用的方法之一。