Mosquito vector management with botanicals-the most effective weapons in controlling mosquito-borne diseases

Dear editor,Mosquito-borne diseases,viz.,malaria,filariasis,dengue hemorrhagic fever,chikungunya,Japanese encephalitis etc.,created huge impact on humans over the world,and the chemical insecticides remain the mainstay of effective control.But,indiscriminate and rampant use of the chemical insecticides in controlling mosquito vectors,in order to prevent diseases vectored by them,has resulted problems related to the adverse environmental effects for their(insecticides)potential toxicity,high operational cost,community acceptance,and the development of insecticide resistance among the vectors.The factors mentioned above prompted the search for new means of control strategies.Currently,the botanicals(viz.,plant extracts,essential oils and phytochemicals)with mosquitocidal potential

Exploration of larvicidal and adult emergence inhibition activities of Ricinus communis seed extract against three potential mosquito vectors in Kolkata,India

Objective:To determine the larvicidal and adult emergence inhibition activities of castor （Ricinus communis） seed extract against three potential mosquito vectors Anopheles stephensi（An. slephensi）,Culex quinquefasciatus（Cx.quinquefasciatus） and Aedes albopictus（Ae.albopictus） in India.Methods:The R.communis seed extract was tested,employing WHO procedure,against fourth larval instars of the three mosquito species for 24 h and larval mortalities were recorded at various concentrations（2-64μg/mL）:the 24 h LC50 values of the R.communis seed extract were determined following Probit analysis.The larval killing,antipupation and adult emergence inhibition rates of the test extract,using a single concentration of 2μLC50,were studied at different time periods（24-72 h）:the extract toxicity was tested against a fish.Oreochromis niloticus（O.niloticus）.Results:The R.communis seed extract exhibited larvicidal effects with 100%killing activities at concentrations 32-64μg/mL,and with LC50 values 7.10.11.64 and 16.84μg/mL for Cx.quinquefasciatus,An.stephensi and Ae.albopictus larvae,respectively. When the larvae were treated with the extract at a single concentration of 2×LC50,significant differences were observed,compared to control groups,in rate of pupation（P【0.001） as well as in adult formation（P【0.001）.Conclusions:The present findings suggest that the R.communis seed extract provided an excellent potential for controlling An.stephensi,Cx.quinquefasciatus and Ae. albopictus mosquito vectors.

Evaluation of larvicidal activity of Pongamia pinnata extracts against three mosquito vectors

Objective:To evaluate the mosquito larvicidal activity of Pongamia pinnata(P.pinnata)extracts against three mosquito vectors.Methods:The methanol and hydroalcohol extracts of bark part of P.pinnata L were tested against fourth instar larvae of Culex quinqnefasciatus,Aedes aegypti and Anopheles stephensi.The mortality was observed 24 h and 48 h after treatment,data was subjected to probit analysis to determine lethal concentration(LC_(50)and LC_(90))to kill 50 and 90 percent of treated larvae of tested species.Results:The larval mortality was found in both methanol and hydroalcohol extracts of P.pinnata against Culex quinquefascialus,Aedes aegypti and Anopheles stephensi with LC_(50)values of 84.8,118.2 and 151.7 ppm;97.7,128.3 and 513 ppm.The highest larval mortality was found in methanol extract of P.pinnala when comparable to the hydroalcohol extract.Conclusions:These results suggest that both methanol and hyrdoalcohol extracts have the potential to be used as an ideal ecofriendly approach for the control of disease vectors.This could lead to isolation of novel natural larvicidal compounds.

Larvicidal and repellent activities of Sida acuta Burm.F.(Family:Malvaceae) against three important vector mosquitoes

Objective:To determine the larvicidal and repellent activities of Sida acuta Burm.F.（Family: Malvaceae）extract against Culex quinquefasciatus,Aedes aegypti and Anopheles stephensi. Methods:Twenty five late III instar larve of three mosquito species were exposed to various concentrations（15-90 mg/L） and were assayed in the laboratory by using the protocol of WHO 2005:the 24 h LC50 values of the Sida acuta leaf extract was determined following Probit analysis. The repellent efficacy was determined against three mosquito species at three concentrations viz.,1.0,2.5 and 5.0 mg/cm2 under the laboratory conditions.Results:Results showed varying degree of larvicidal activity of crude extract of Sida acuta against three important mosquitoes with LC50 values ranging between 38 to 48 mg/L.The crude extract had strong repellent action against three species of mosquitoes as it provided 100%protection against Anopheles stephensi for 180 min followed by Aedes aegypti（150 min） and Culex quinquefasciatus（120 min）.Conclusions: From the results it can be concluded the crude extract of Sida acuta was an excellent potential for controlling Culex quinquefasciatus,Aedes aegypti and Anopleles stephensi mosquitoes.

Citrus-based essential oils could be used for dengue vector mosquitoes control

Dear Editor The mosquitoes Aedes aegypli(I,) and Aedes albopictus (Skuse)(Diptera:Culicidae) are important vectors of dengue fever in tropical and subtropical parts of the world. Chemical control has been considered as an effective tool for their management in different areas of the world.However, injudicious use of the chemicals result in environmental pollution,ill effects to humans and other animals,and the development of insecticide resistance,which ultimately limits the efficacy of many insecticides!’].Essential oils can be used for mosquito control with no harmful effects to the ecosystem and non-target organisms.Essentials oils from different plants have been found very

4种灭幼剂对广州市白纹伊蚊幼虫和蛹的杀灭效果

目的 了解常用灭蚊幼剂对广州市白纹伊蚊幼虫和蛹的杀灭效果,为登革热等蚊媒传染病媒介控制中合理使用杀虫剂提供参考依据。方法 采用《卫生杀虫剂现场药效测定与评价杀蚊幼剂》(GB/T 31711—2015)中容器实验法,分别测试4种灭蚊幼剂对白纹伊蚊幼虫和蛹的杀灭效果。结果 4种常用灭蚊幼剂对白纹伊蚊幼虫均有良好杀灭效果,96 h死亡率为95.00%~100.00%;对蚊蛹的杀灭效果差别较大,其中倍硫磷、高效氟氯氰菊酯对蚊蛹杀灭效果显著,72 h死亡率为88.33%~100.00%,吡虫啉对蚊蛹杀灭效果较差,72 h死亡率为16.67%,苏云金杆菌对蚊蛹几乎无效。结论 灭蚊工作中处置难以清除的孳生水体时,应当根据孳生蚊虫的生活史不同阶段合理投药。

第七届世界军人运动会病媒生物防治的经验和教训

大规模集会可能增加媒介疾病传播风险。国外报道大规模集会病媒生物防治经验教训的文献很少。中国通常在大规模集会开展病媒生物防治保障工作投入较多资金及人力用于提升病媒防治水平,以达到控制媒介骚扰和疾病的目标;相关成功经验报道较多,但失误和教训甚少提及。第七届世界军人运动会于2019年10月在武汉举行。军动会有51个竞赛场馆及205个重点保障场所,分布于全市15个城区。蚊媒及其传播疾病防控是最重要的目标之一,武汉成功达到目标,但也有失误和教训。本文总结武汉军运会有害生物防治保障工作中的成功经验,并着重反思其中不足。为提高大规模集会病媒生物防治的效率,建议:①用相关法规推动城市病媒生物防治;②开展应用研究,解决保障工作中遇到的技术及管理问题;③倡导求真务实的工作作风,现场防治工作务求有的放矢;④重视监测质量,制定并严格执行质量控制方案。

在“同一健康”下浙江省病媒生物可持续控制“无四害村”的实践

目的系统总结浙江省农村病媒生物可持续控制的实践经验。方法回顾“同一健康”(One Health)理念和媒介生物可持续控制策略的提出和变迁,阐述浙江实践的依据、前提、基础和发展历程。结果从“无蚊村”“无蝇村”“无蚊蝇村”“无四害村”再到“无蚊单位”建设,提出了农村病媒生物可持续控制创新理念,强调的是“环境—宿主媒介—人类健康”。结论浙江农村病媒生物可持续控制探索是媒介生物及相关传染病可持续控制策略的成功实践,在当前全球严峻的病媒生物性传染病防控形势下,需要全球各部门合作和统一行动。政府首先应该负起责任,整治健康环境。新时代爱国卫生运动应该从城市扩展到农村,进一步提高农村健康环境,为传染病防控服务。

On the Range of Action of Adult Culex pipiens s.l.

Mosquitoes are an interesting topic due to their medical importance, as they play an active role in the transmission of many pathogens and parasites, acting as vectors for various pathologies that are deadly to humans, such as dengue, yellow fever, chikungunya, West Nile virus, encephalitis and malaria, among many others that are less common. In terms of morbidity and mortality caused by vector-borne diseases, mosquitoes are the most dangerous animals for humanity and, although they also play a role in the ecosystem as a food source for other organisms, their importance for public health cannot be overlooked. As highly efficient vectors, they put more than three billion people at risk, mainly in tropical and subtropical regions as well as in Europe, since heat waves and flooding are becoming more frequent and severe, and summers are getting longer and warmer, accelerating mosquito development, biting rates, and the incubation of the pathogens within their bodies. Female mosquitoes bite to acquire proteins for the development of their ovaries and eggs and, in the process, acquire pathogens and/or parasites from one vertebrate host and transmit them to another, usually after a short period of replication. Three of their four life stages are lived in still freshwater, so it is crucial to understand their range of action when they reach adulthood and leave the water, in order to plan and implement local prevention measures. A set of georeferenced abundance data collected in mainland Portugal over seven years was linked to cartographed water bodies in a geographic information system to estimate the distances at which Culex pipiens s.l. had a significant presence, with criteria based on the size of the catches. The result allows for an estimate of the fly range of those mosquitoes, which can be used to focus countermeasures.

Larvicidal and repellent potential of Moringa oleifera against malarial vector,Anopheles stephensi Liston(Insecta:Diptera:Culicidae)

Objective:To evaluate the larvicidal and pupicidal potential of the methanolic extracts from Moringa oleifera(M.oleifera) plant seeds against malarial vector Anopheles stephensi(A.stephensi) mosquitoes at different concentrations(20,40,60,80 and 100 ppm).Methods:M.oleifera was collected from the area of around Bharathiar University,Coimbatore.The dried plant materials were powdered by an electrical blender.From each sample,100 g of the plant material were extracted with 300 mL of methanol for 8 h in a Soxhlet apparatus.The extracts were evaporated to dryness in rotary vacuum evaporator to yield 122 mg and 110 mg of dark greenish material(residue) from Arcang amara and Ocimum basilicum,respectively.One gram of the each plant residue was dissolved separately in 100 mL of acetone(stock solution) from which different concentrations, i.e.,20,40,60,80 and 100 ppm were prepared.Results:Larvicidal activity of M.oleifera exhibited in the first to fourth instar larvae of the A.stephensi,and the LC_(50) and LC_(90) values were 57.79 ppm and 125.93 ppm for the first instar,63.90 ppm and 133.07 ppm for the second inslar,72.45 ppm and 139.82 ppm for the third instar,78.93 ppm and 143.20 ppm for the fourth instar,respectively. During the pupal stage the methanolic extract of M.oleifera showed that the LC_(50),and LC_(90) values were 67.77 ppm and 141.00 ppm,respectively.Conclusions:The present study indicates that the phytochemicals derived from M.oleifera seeds extracts are effective mosquito vector control agents and the plant extracts may be used for further integrated pest management programs.

Chemical composition and larvicidal activity of leaf essential oil from Clausena anisata (Willd.) Hook.f.ex Benth (Rutaceae) against three mosquito species

Objective:To determine the mosquito larvicidal activity of leaf essential oil and their chemical constituents from Clausena anisata（C.anisata）（Willd.） Hook.f.ex Benth.against Culex quinquefasciatus,Aedes aegypti and Anopheles Stephensi.Methods:Essential oil was obtained by hydro-distillation and the chemical composition of the leaf essential oil was analyzed using gas chromatography—mass spectrometry.The mosquitoes were reared in the vector control laboratory and twenty lateⅢinstar larvae of three mosquito species were exposed to based on the wide range and narrow range tests,essential oil was tested at 50.100.150,200 and 250 ppm and each compound was tested at various concentration（5-75 ppm） and were assayed in the laboratory by using the protocol of WHO 2005:the 24 h LC50 values of the C.anisata leaf essential oil and their major compounds were determined following Probit analysis.Results:The oil contained were mainlyβ-pinene（32.8%）,sabinene（28.3%）,germacrene-D（12.7%）,estragole （6.4%） and linalool（5.9%）.The essential oil from the leaves of C.anisata exhibited significant larvicidal activity,with 24 h LC50 values of 140.96,130.19 and 119.59 ppm.respectively.The five pure constituents extracted from the C.anisata leaf essential oil were also tested individually against three mosquito larvae.The LC50 values ofβ-pinene,sabinene,germacrene-D,estragole and linalool appeared to be most effective against Anopheles stephensi(LC50-23.17,19.67,16.95. 11.01,35.17 ppm) followed by Aedes aegypti(LC50-27.69,21.20,18.76,12.70,38.64 ppm) and Culex quinquefasciatus(LC50-32.23,25.01.21.28,14.01,42.28).Conclusions:The essential oil of C. anisata contains five major compounds and has remarkable larvicidal properties,which may be considered as a potent source for the production of natural larvicides.

Plant-mediated synthesis of nanoparticles:A newer and safer tool against mosquito-borne diseases?

Prevention and control of mosquito-borne diseases is a key challenge of huge public health importance.Plant-mediated synthesis of nanoparticles has recently gained attention as a cheap,rapid and eco-friendly method to control mosquito vector populations,with special reference to young instars.Furthermore,plant-fabricated nanoparticles have been successfully employed as dengue virus growth inhibitors.In this Editorial,parasitologists,entomologists and researchers in drug nanosynthesis are encouraged to deal with a number of crucial challenges of public health importance.

Seasonal abundance and potential of Japanese encephalitis virus infection in mosquitoes at the nesting colony of ardeid birds,Thailand

Objective:To investigate the abundance and seasonal dynamics of mosquitoes,and to detect Japanese encephalitis virus(JEV)in these mosquitoes at the nesting colony of ardeid birds.Methods:Mosquitoes were collected bimonthly from July 2009 to May 2010 by Centers for Disease Control.Light traps and dry ice,as a source of CO_2,were employed to attract mosquitoes.Mosquitoes were first identified,pooled into groups of upto 50 mosquitoes by species,and tested for JEV infection by viral isolation and reverse transcriptase polymerase chain reaction.Results:A total of 20370 mosquitoes comprising 14 species in five genera were collected.The five most abundant mosquito species collected were Culex tritaeniorhynchus(95.46%),Culex vishnui(2.68%),Culex gelidus(0.72%),Anopheles peditaeniatus(0.58%)and Culex quinquefasciatus(0.22%).Mosquito peak densities were observed in July.All of 416 mosquito pools were negative for JEV.Conclusions:This study provides new information about mosquito species and status of JEV infection in mosquitoes in Thailand.Further study should be done to continue a close survey for the presence of this virus in the ardeid birds.

Larvicidal and irritant activities of hexane leaf extracts of Citrus sinensis against dengue vector Aedes aegypti L.

Objective:To assess the larvicidal and irritant activities of the hexane extracts of leaves of Citrus sinensis(C.sinensis)against the early fourth instars and female adults of Aedes aegypti(Ae.aegypti).Methods:The larvicidal potential of the prepared leaf extract was evaluated against early fourth instar larvae of Ae.aegypli using WHO protocol.The mortality counts were made after 24 h and LC_(50)and LG_(50)values were calculated.The efficacy of extract as mosquito irritant was assessed by contact irritancy assays.Extract-impregnated paper was placed on a glass plate over which a perspex funnel with a hole on the top was kept inverted.Single female adult,3-day old unfed/blood-fed,was released inside the funnel.After 3 min of acclimatization time,the time taken for the first take-off and total number of flights undertaken during 15 min were scored.Results:The citrus leaf extracts from hexane possessed moderate larvicidal efficiency against dengue vector.The bioassays resulted in an LC_(50)and LC_(90)value of 446.84 and 1370.96 ppm,respectively after 24 h of exposure.However,the extracts were proved to be remarkable irritant against adults Ae.aegypti,more pronounced effects being observed on blood-fed females than unfed females.The extract-impregnated paper was thus proved to be 7-11 times more irritable as compared with the control paper.Conclusions:The hexane extracts from C.sinensis leaves are proved to be reasonably larvicidal But remarkably irritant against dengue vector.Further studies are needed to identify the possible role of extract as adulticide,oviposition deterrent and ovicidal agent.The isolation of active ingredient from the extract could help in formulating strategies for mosquito control.

2020-2022年中国登革热时空分布及相关环境因素分析

目的分析2020—2022年中国登革热时空分布及环境因素特征。方法采用描述性流行病学方法分析中国本地和输入性登革热分布的时空特征以及环境特征。结果2020—2022年中国5个省发生1185例本地病例和19个省发生217例输入性病例。登革热具有季节性特征,本地病例高峰期为9—11月,输入性病例高峰期为6—11月。97.64%的本地病例发生在云南和广西。云南边境缅甸的登革热输入是其登革热本地暴发的主要原因。67.28%的输入性病例分布在广东、福建、云南和浙江,83.41%的输入性病例来自东南亚国家。广东的人口和经济条件是2020—2022年其输入性病例居首位的主要原因。结论我国登革热仍是由输入引起的本地暴发,具有显著的地方性和季节性特征,各地要做好蚊媒、登革热以及相关环境因素监测,贯彻落实蚊媒可持续控制措施。

Astrodaucus persicus as a new source of bioinsectisides against malaria vector, Anopheles stephensi

Objective: To determine the larvicidal activities of petroleum ether, chloroform, ethyl acetate and methanol fractions of roots and fruits extracts of Astrodaucus persicus from Apiaceae family against malaria vector, Anopheles stephensi(An. stephensi).Methods: Twenty five third instar larvae of An. stephensi were exposed to various concentrations(10–160 g/L) of fractions and were assayed according to World Health Organization protocol. The larval mortality was calculated after 24 h treatment.Results: Among tested fractions, the highest larvicidal efficacy was observed from ethyl acetate fraction of fruits extract with 50% and 90% mortality values(LC_(50) and LC_(90)) of34.49 g/L and 108.61 g/L, respectively. Chloroform fraction of fruits extract was the second larvicidal sample with LC_(50) of 45.11 g/L and LC_(90) of 139.36 g/L. Petroleum ether fractions of fruits and roots and methanol fraction of fruits showed moderate toxicity against An. stephensi.Conclusions: Astrodaucus persicus is a potential source of valuable and natural larvicidal compounds against malaria vector, An. stephensi and can be used in mosquitoes control programs as an alternative to synthetic insecticides.

Stage-structured models for interacting wild and sterile mosquitoes

Using the sterile insect technique,in which sterile mosquitoes are released to reduce or eradicate the wild mosquito population,is an effective weapon to prevent transmission of mosquito-borne diseases. To study the impact of the sterile insect technique on the disease transmissions,we formulate stage-structured discrete-time mathematical models,based on difference equations,for the interactive dynamics of the wild and sterile mosquitoes. We incorporate different strategies for releasing sterile mosquitoes,investigate the model dynamics,and compare the impact of the different release strategies.Numerical examples are also provided to demonstrate dynamical features of the models.

2021年和2022年马鞍山市鼠与蚊病原学监测分析

目的掌握马鞍山市鼠与蚊病原感染情况,为病媒传播疾病防控工作提供科学依据。方法鼠类、蚊类监测方法及实验室检测方法参照《全国病媒生物病原学监测方案(试行)》(中疾控传发[2020]13号)《全国病媒生物监测实施方案(中疾控传防发[2016]56号)》执行;采用Excel 2013和SPSS 16.0软件进行数据整理分析,QGIS 3.30.0绘制病例地区分布图,P<0.05差异有统计学意义。结果2021年和2022年共捕获鼠类486只,涉及城镇居民区、农村居民区、重点行业、农田、林地5类生境,在农村居民区生境的褐家鼠、黑线姬鼠和小家鼠中检测出汉坦病毒阳性,阳性率为1.23%(6/486);蚊类共捕获10762只,分为489组,涉及居民区、牲畜棚、农户、公园、医院5类生境,其中牲畜棚、农户、医院3类生境中检出致倦库蚊和三带喙库蚊共16组乙脑病毒阳性,阳性率为3.27%(16/489)。结论依据病原学监测结果,提示需在重点地区开展综合措施降低媒介传染病的发生风险。

蚊媒黄病毒传播机制及疫苗与药物研发进展

蚊媒病毒可通过蚊虫叮咬在宿主和蚊虫媒介之间传播循环。由蚊媒传播的病毒达数百种之多,每年可造成数亿人感染,这些病毒感染可引起严重的人类疾病,如出血热、关节炎、脑炎和脑膜炎等,严重者可导致死亡。蚊媒病毒大部分为RNA病毒,其中黄病毒科的蚊媒病毒流行最为广泛,包括登革病毒、寨卡病毒、黄热病毒、乙型脑炎病毒和西尼罗病毒等。目前虽然已有针对少数蚊媒黄病毒的有效疫苗,例如预防黄热病病毒和乙型脑炎病毒的疫苗,但仍然没有针对大多数蚊媒黄病毒的有效预防性疫苗和抗病毒疗法。因此,全面了解蚊媒黄病毒在脊椎动物宿主与蚊虫之间的感染与传播的机制,可能为抗蚊媒黄病毒的疫苗与药物研发提供新的思路与目标,从而使我们能够更有效地预测和控制蚊媒黄病毒在自然界传播和流行,为应对蚊媒黄病毒造成的公共卫生威胁提供新的解决方案。本文首先描述了蚊媒黄病毒的生物学特性和流行病学特性,接下来介绍了蚊媒黄病毒的传播途径与媒介模型,并进一步全面总结了目前对蚊媒黄病毒在宿主和媒介之间传播机制及病毒在蚊虫媒介中的感染机制的研究,同时针对蚊媒黄病毒的新型疫苗研发和药物筛选策略,对未来针对蚊媒黄病毒的机制研究与抗病毒策略开发进行了展望。

云南省中华按蚊、杰普尔按蚊种群与环境因素关系的地理信息系统分析

目的研究云南省南部地区中华按蚊(Anopheles sinensis)和杰普尔按蚊(An.jeyporiensis)与地理环境因素的关系,探讨在云南省南部地区西部开发新村镇建设中对疟疾媒介蚊虫种群的可能影响。方法应用地理信息系统对云南省南部勐腊县的龙塘村及东方红村的中华按蚊和杰普尔按蚊种群与环境因素之间的关系进行分析。结果各样点中华按蚊优势度可以用线性模型拟合,线性模型为d=0.3621-3.26×10-4×DTF-8.0854×10-7×KFA(R2=0.642,F检验,P=0.000);DTF与样点中华按蚊优势度呈负相关(Person=-0.683,P=0.002),而KFA与样点中华按蚊优势度也呈负相关关系(Person=-0.735,P=0.001)。各样点杰普尔按蚊种群密度可以用线性模型拟合,线性模型为Ni=263-0.0541×KRL(R2=0.633,F检验,P=0.000),KRL与样点杰普尔按蚊种群密度呈负相关关系(Person=-0.825,P=0.000)。各样点杰普尔按蚊优势度可以用线性模型拟合,线性模型为d=7.9204×10-4×DTF-0.0232(R2=0.267,F检验,P=0.023),DTF与样点杰普尔按蚊优势度呈正相关关系(Person=0.562,P=0.012)。结论在云南省南部地区西部开发的新村镇建设中,相关环境因素的变化有可能会引起中华按蚊和杰普尔按蚊2种媒介蚊虫种群的变化。