Mosquito larva distribution and natural Wolbachia infection in campus areas of Nakhon Ratchasima,Thailand

Objective:To determine the prevalence of mosquito larvae in campus areas and the infection rate of endosymbiotic bacteria,Wolbachia in mosquito larvae.Method:The mosquito larvae samples were collected in residential areas and academic buildings of Suranaree University of Technology located in Northeastern Thailand during 2017-2018.Mosquito species identification was performed using GLOBE mosquito protocols and Rattanarithikul&Panthusiri’s keys.The gene encoding for the surface protein of Wolbachia was amplified by PCR and confirmed by DNA sequencing.Results:Armigeres sp.is the highest proportion of mosquito larvae followed by Culex spp.,Aedes albopictus,Aedes aegypti,and Toxorynchites spp.,respectively.Aedes aegypti have breeding sites mostly in the containers found indoors,whereas the main breeding sites of Aedes albopictus were found in both outdoors and indoors.The House Index and Breteau Index for Aedes spp.was more than 5%and 20%,respectively,in both areas,indicating that these areas are dengue sensitive.The highest proportion of Wolbachia infection was found in the larvae of Culex spp.(86.21%),followed by Aedes albopictus(69.23%)and rarely detected in Aedes aegypti(9.09%).Conclusion:The present study reported the first natural infection of Wolbachia in mosquito larvae in Thailand.Our result suggested that the mosquito species containing higher proportion of Wolbachia are less likely to be vectors for dengue.Therefore,Wolbachia transfection in mosquito larvae could be applied as a biocontrol for dengue and other mosquito-borne disease prevention.

Lead levels of Culex mosquito larvae inhabiting lead utilizing factory

Objective:To determine lead level primarily in Culex quinquefasciatus(Cx.quinquefasciatus), and Culex gelidus(Cx.gelidus) larvae inhabiting lead consuming factories,and to putatively estimate eco-toxicological impact of effluents from the firms.Methods:Third instars larvae were sampled by standard dipping method and lead concentrations in the larvae and their respective surrounding factory aquatic environments were determined through standard atomic absorption spectrophotometry(AAS).Results:Cx.quinquefasciatus was the most abundant species followed by Cx.gelidus.The levels of lead were higher in the Cx.quinquefasciatus(1.08-47.47μg/g),than in the wastewaters surface(0.01-0.78 μg/mL) from the factories or closer areas around factories. Other species were not reaching the.criteria for lead determination.Conclusions:The Cx. quinquefasciatus larvae can bio-accumulate the metal and can potentially serve as a biomarker of lead contamination,to complemente conventional techniques.

Evaluation of entomopathogenic Bacillus sphaericus isolated from Lombok beach area against mosquito larvae

Objective: To isolate, characterize and evaluate toxicity of Bacillus sphaericus(B. sphaericus) from beach area of Lombok Island.Methods: Soil was collected from determined locations and suspended in sterile physiological saline water. After heat shock was applied, suspension was spread on NYSM agar medium. Colonies grown were then observed and isolated. Colony, cell morphology,and biochemical/physiological characteristics were tested and compared to B. sphaericus2362 as standard. Initial toxicity testing was done against three species of mosquito larvae(Culex quinquefasciatus, Anopheles aconitus and Aedes aegypti) and isolates that showed more than 50% larvae killing will be assayed to obtain LC_(50) and LC_(90)values within 48 h.PCR technique were conducted to obtain 16 s r DNA amplicon for sequencing and to detect toxin-expressing genes(using multiplex PCR).Results: Twenty isolates of B. sphaericus have been collected from 20 determined locations and their characteristics were in agreement with standard B. sphaericus characteristics. Bioassay testing showed that four isolates(namely isolate MNT, SLG, TJL2 and PLG) were mildly toxic against all larvae. The rests were either low toxic or non-toxic at all.Phylogenetic analysis showed that all four isolates were clustered with other known mildly and highly toxic strains. The multiplex PCR result showed four toxic isolates owned 1–2bands from Bin toxin genes and three bands from Mtx toxin genes, whereas 16 isolates with low to non-toxic characteristics showed only three bands from Mtx toxin genes.Conclusions: Four toxic isolates of B. sphaericus were isolated from beach area of Lombok Island. They showed mild toxicity against larvae of three mosquito species.

不同温度条件下3种卫生杀虫剂杀灭蚊幼效果研究

目的了解不同温度条件对3种卫生杀虫剂杀灭蚊幼虫效果的影响。方法采用浸渍法,将幼虫置于一定浓度杀虫剂药液中,观察不同温度下蚊幼虫的死亡情况,分析温度对杀虫时间的影响规律。结果温度对3种杀虫剂杀灭蚊幼虫效果影响不同。高效氯氰菊酯在25、30℃时杀灭蚊幼虫所需时间相对较长,约6.5 h,其他温度条件下杀灭蚊幼虫时间缩短,40℃时仅需0.5 h。倍硫磷和残杀威均随着温度的升高,杀灭蚊幼虫所需时间缩短,最短仅需0.5 h。结论不同温度条件对不同杀虫剂杀灭蚊幼虫时间的影响规律不同。这一研究结论可用于蚊媒传染病疫情防控时选择有效杀虫剂的快速筛选研究。

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。

Larvicidal efficacy of crude and fractionated extracts of Dracaena loureiri Gagnep against Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and Anopheles minimus mosquito vectors

Objective:To evaluate the larvicidal efficacy of crude and fractionated extracts of Dracaena loureiri endocarp against Aedes aegypti,Aedes albopictus,Culex quinquefasciatus,and Anopheles minimus mosquitos.Methods:Larvicidal activity was tested according to World Health Organization standard protocol.The third-stage larvae of each mosquito species were exposed to various concentrations of Dracaena loureiri crude extract and six groups of Dracaena loureiri fractionated extracts(RC-DT 009-014).Larval mortality rates were observed after 24 h and48 h of exposure.Then,a computerized probit analysis of the mortality data was performed to determine lethal concentration 50(LC_(50))and lethal concentration 90 values.Results:Anopheles minimus larvae(24-h LC_(50)77.88 mg/L)had the highest susceptibility to crude extract,whereas others(Aedes aegypti,24-h LC_(50)224.73 mg/L;Aedes albopictus,24-h LC_(50)261.75 mg/L;and Culex quinquefasciatus,24-h LC_(50)282.86 mg/L)were significantly less susceptible.The most effective groups of fractionated extracts were RC-DT 012 and RC-DT 013.The mosquito species most susceptible to fractionated extracts was Culex quinquefasciatus,with 24-h LC_(50)values of 0.66 and 0.94 mg/L for RC-DT 012 and RC-DT 013,respectively.Conclusions:The larvicidal activity of fractionated extracts is more effective than that of crude extract against all tested mosquito species.For the most effective alternative larvicide,purification and a phytochemical constituent analysis must be performed.

Immatures of Lutzia fuscana(Wiedemann,1820)(Diptera:Culicidae) in ricefields:implications for biological control of vector mosquitoes

Objective:Rice fields are dynamic mosquito larval habitats with assemblage of different predator taxa,including the larva of the mosquitoes Lutzia.Entomological surveillance in the ricefields is essential to evaluate the potential of these predators as biological resource to regulate vector mosquito population.In view of this,a survey of ricefields for immatures of different mosquito species including Lutzia was conducted.Methods:Survey of selected ricefields was carried out to evaluate the species composition of mosquitoes.Laboratory evaluation of the immatures of Lutzia mosquitoes was carried out to assess its predation potential using mosquitoes and chironomid as preys.Results:The survey revealed the presence of five mosquito species belonging to the genera Anopheles and Culex and the predatory immatures of the mosquito Lutzia Juscana(Wiedemann,1820).The ratio of prey and predatory larva ranged between 1.46 and 4.78 during the study period,with a significant correlation on the relative abundance of the larval stages of Lt.Juscana and Anopheles and Culex larvae.Under laboratory conditions,a single IV instar larvae of Lt.fuscana was found to consume on an average 5 to 15 equivalent instars of Anopheles sp.and Culex sp.larvae per day depending on its age.The prey consumption reduced with the larval stage approaching pupation.When provided with equal numbers of chironomid and Anopheles or Culex larvae,larva of Lt.fuscana consumed mosquito larvae significantly more compared to chironomids.Conclusion: The survey results and the preliminary study on predation are suggestive of the role of Lt.Juscana in the regulation of vector mosquito populations naturally in the ricefields.Since Lt.Juscana is common in many Asian countries,further studies on bioecology will be helpful to justify their use in mosquito control programme.

亚热带园林水体蚊虫孳生风险及规划设计对策研究

亚热带是蚊媒疾病高发地区,园林中的各类水体可能会孳生蚊虫,威胁居民健康,但目前园林设计领域缺乏对蚊虫防控的关注。文章以佛山居住区园林为例,对其中各类水体的蚊幼(孑孓)孳生情况进行实地调查,包括各类园林水景、排水系统积水和各类无意形成的积水,明确容易和不易孳生蚊虫的水体类型,并从景观设计的角度分析这些水体形成的原因,最终从园林水景设计、排水系统结构设计、景观小品设计等方面得出减少蚊幼孳生的景观设计方法,以期对今后景观设计及施工提供一定参考。

河蟹、克氏原螯虾、黄鳝摄食生态的研究

通过疫区围网养殖河蟹、黄鳝、克氏原螯虾试验 ,解剖观察食性表明 :河蟹、黄鳝、克氏原螯虾都可以摄食钉螺、蚊幼虫。为进一步验证它们的这一食性及其摄食量 ,通过模拟网栏养殖模式的数据统计表明 :河蟹每天每只能摄食蚊幼虫 6 2 4尾、钉螺 4 8个 ;克氏原螯虾每天每只能摄食蚊幼虫 17 6尾、钉螺 0 9个 ;黄鳝每天每尾摄食蚊幼虫 8 1尾、钉螺 0 7个 ;河蟹、克氏原螯虾、黄鳝摄食生态的研究为生物灭螺、灭蚊提供新的途径。

饥饿对食蚊鱼仔鱼摄食、生长和形态的影响

本文研究了饥饿胁迫下食蚊鱼仔鱼的摄食、生长和外部形态的变化规律。结果表明,在水温(28.5±1.2)℃时,仔鱼产出2h后鳔完成充气即建立巡游模式并开始觅食,摄食比率迅速达到100%,其混合营养期仅有4h。实验期间,投喂组仔鱼的摄食比率一直保持在100%;饥饿组仔鱼在饥饿0—3d内初次摄食比率同样可达到或接近100%,但第4天开始下降,第6天初次摄食比率降至0,抵达饥饿不可逆点(PNR)时间为产出后第5.5天左右。投喂组初产仔鱼对1—2龄期库蚊幼虫的摄食强度为(2.9±1.4)ind/individual·h,摄食强度随日龄显著增长;饥饿组仔鱼在饥饿0—5d内其初次摄食强度也随日龄及饥饿时间的延长显著增长,但均显著低于相应日龄的投喂组仔鱼,其初次摄食比率与初次摄食强度之间并无显著相关关系。饥饿仔鱼在PNR前约1.5d时其累计死亡率已超半数,达(64.4±18.1)%,抵达PNR后数小时内残存个体全部死亡。实验结束(6d)时投喂组仔鱼5项生长指标呈不等速增长,其中体重增长最为显著,瞬时增长率达0.0275/d,此时腹鳍发育基本完备,进入幼鱼期。而同期饥饿组仔鱼形态发育停滞,多项生长指标出现负增长,其中体高负增长最为明显,其瞬时增长率为-0.0511/d;体重次之,体长负增长则不甚明显。饥饿仔鱼在接近或处在PNR期时腹部萎缩呈弧形,体长/体高>5,而同期投喂组仔鱼体长/体高<4.5,两者差异显著,可作为鉴别饥饿仔鱼和健康仔鱼较理想的形态数量指标。

甘遂和贯众不同提取液对蚊幼虫的杀伤作用

目的 了解甘遂 (EuphorbiakansuiLiouMass)和贯众 (Dryopteriscrossirhizomz)不同提取液对蚊幼虫杀伤的作用。方法 分别采用乙醚、乙醇、丙酮、水提取两种草药干样品植物成分。用 2 %的浓度 (2g生药 / 10 0ml溶液含 )浸渍法处理致倦库蚊、白纹伊蚊敏感株Ⅲ龄末～Ⅳ龄初幼虫。结果 2 %甘遂和贯众草药的乙醚、乙醇提取液对致倦库蚊幼虫的杀伤分别高达 95 0 %± 4 4 % ,90 0 %± 3 5 % ,83 0 %± 0 6 %与 75 0 %± 2 0 %。贯众对白纹伊蚊幼虫的杀伤力强度明显优于甘遂 ,乙醚、乙醇提取液分别为 6 1 6 %± 0 6 %与 2 3 2 %±及 6 6 6 %± 1.0与30 0 %± 1 0 %。贯众丙酮的粗提物的杀伤力较差 ,均低于 10 % ,水提液对致倦库蚊、白纹伊蚊幼虫无杀伤作用。结论 甘遂和贯众的提取液对致倦库蚊有显著的杀伤作用。贯众乙醚、乙醇提取液对白纹伊蚊幼虫的杀伤作用较甘遂草药提取液的杀伤作用强。两种草药对蚊虫的毒力主要成分溶于醚及醇。

大链壶菌对蚊幼虫作用的组织学观察

目的：观察灭蚊真菌大链壶菌感染蚊幼虫后两者的组织形态学变化以了解该真菌致死蚊幼虫的机理。方法：用真菌实验室感染蚊幼虫后取不同感染程度和时间的蚊幼虫作常规组织切片，Ｈ．Ｅ．染色，然后以正常蚊幼虫为对照，用比较组织学方法观察受染蚊幼虫和菌体的组织学变化。结果：在较早的Ⅰ度感染蚊幼虫，可见蚊头，胸部组织间隙有较细的、不分隔的大链壶菌营养型菌丝体，后者进而在血体腔内大量繁殖，并侵入肌肉、脂肪体、胃、肠等组织和细胞内，被入侵处的组织发生破坏和消失；Ⅱ度感染的蚊幼虫体内，可见蚊组织被严重破坏甚至消失，菌丝体发育为生殖型，即菌丝出现分隔，变粗变短或形成圆形、卵圆形或串珠状的孢子体。感染时间较长时蚊体内正常结构大部分消失，而此时菌丝体和孢子体内的原生质和核也已消失，只剩下中空的细胞壁管道。结论：认为大链壶菌对蚊幼虫组织的直接入侵和破坏是该菌致蚊幼虫死亡的主要原因之一。

蚊幼对狼蛛的营养作用研究

研究蚊子幼虫（子孓）对拟水狼蛛（Piratasubpiraticus）的营养、繁殖作用。结果表明狼蛛对蚊幼的捕食符合HollingⅡ型功能反应；喂以蚊幼和不喂蚊幼处理狼蛛的体重增长率和生殖有极显著差异。在相同蚊幼密度下，狼蛛初始体重越小，增长率越大，经计算狼蛛每增重1mg，需消耗10．58mg蚊幼，这基本符合生态系统营养级能量流动的1／10法则；狼蛛体重大小又对褐飞虱的捕食量有明显差异，体重大的个体瞬时发现率大于体重小的个体。由此表明早期稻田存在的大量蚊子幼虫为捕食性天敌繁殖提供了充裕的营养，使天敌得以建群和繁殖，这对后期稻飞虱的自然控制起了重要作用。

28种中草药乙醇提取液对蚊幼虫的杀伤作用

目的了解丁香等28种中草药的乙醇提取液对蚊幼虫杀伤作用,寻找和开发安全有效的植物性杀虫剂。方法用乙醇分别提取28种中草药干样品植物成分。用2%的药物(每100ml溶液含2g生药)浸渍法处理致倦库蚊、白纹伊蚊敏感株Ⅲ龄末～Ⅳ龄初幼虫24h。结果13种中草药可致白纹伊蚊幼虫半数以上死亡;17种中草药可致致倦库蚊幼虫50%以上死亡,其中12种对两种幼虫都有50%以上的致死率。藜芦、漏芦和蛇床子3种药物可致白纹伊蚊幼虫全部死亡;百部等8种中草药可致库蚊幼虫全部死亡,其中藜庐等3种中草药可致两种蚊虫幼虫全部死亡。结论两种蚊虫幼虫对28种中草药的敏感性不同,其中藜芦、漏芦和蛇床子等中草药在蚊虫防治方面具有进一步开发利用的价值。

1%双硫磷砂粒剂现场灭蚊幼效果研究

目的研究1%双硫磷砂粒剂对大容器和河流孳生的淡色库蚊、废旧轮胎和雨水井中孳生的白纹伊蚊幼虫的现场杀灭效果,以及该药物控制不同类型孳生地蚊虫孳生的持效期和适宜浓度。方法用不同浓度1%双硫磷砂粒剂处理淡色库蚊和白纹伊蚊孳生地,观察2种蚊幼密度变化及持效期。结果投放0.25mg/L 1%双硫磷砂粒剂28 d后,容器内淡色库蚊幼虫密度下降率达到80%以上,持效期接近1个月,而投放2g/m2剂量于河流中,淡色库蚊幼虫密度下降80%以上的时间为11 d,持效期为12 d;对白纹伊蚊而言,1 mg/L剂量投放20 d后,对废旧轮胎和雨水井蚊幼的杀灭效果差不多,蚊幼密度下降率都接近100%。结论1%双硫磷砂粒剂对河流中淡色库蚊的有效控制时间在2周左右,1 mg/L剂量对其他孳生地的淡色库蚊和白纹伊蚊的有效控制时间均在28 d左右。

几种菊科植物提取物对蚊幼虫的光活化活性初试

对８种菊科植物２０种提取物的光活化和非光活化活性筛选，证实万寿菊根甲醇浸提物、全株乙醇浸提物和花石油醚萃取物对白纹伊蚊Ａｅｄｅｓａｌｂｏｐｉｃｔｕｓ和致倦库蚊Ｃｕｌｅｘｑｕｉｎｑｕｅｆａｓｃｉａｔｕｓ４龄幼虫有非常明显的光活化毒杀作用。值得指出的是根甲醇索氏提取物在有或无近紫外光照条件下对两种蚊幼虫都非常高效，０１ｇ／Ｌ的致死率均为１００％。

净化养殖水体疫源生态模式及经济分析

叙述了青蛙、克氏原螯虾、乌龟、河蟹、黄鳝和泥鳅对钉螺和蚊幼的摄食对比实验 ,结果表明 ,它们每天摄食多少顺序为 :对钉螺 ,克氏原螯虾 >乌龟 >河蟹 >青蛙 ;对蚊幼 ,乌龟 >克氏原螯虾 >泥鳅 >黄鳝或青蛙 >河蟹 .在疫区对金钱蟹和克氏原螯虾进行摄食钉螺的定性观察发现 :在放养了实验动物的生态小区内 ,钉螺种群数量明显减少 .通过本实验和近 8年来的研究工作 ,形成了四种水生动植物净化疫水的生态经济模式 :1)芋、蛙、鳝、鳅、蚓、菜 ;2 )莲、菜、龟或鳖、鳝、鳅 ;3)莲藕、河蟹、泥鳅 ;4)芦苇或荻、克氏原螯虾或沼虾、泥鳅。

顺式氯氰菊酯对蚊幼虫脱氧核糖核酸酶、核糖核酸酶和多酚氧化酶的影响

分别用０．６９７ｎｍｏｌ／Ｌ和１．３９３ｎｍｏｌ／Ｌ顺式氯氰菊酯处理嗜人按蚊、斯氏按蚊和白纹伊蚊３龄幼虫，待生长至４龄，测定其脱氧核糖核酸酶、核糖核酸酶和多酚氧化酶活性。与对照组相比，用药组蚊幼虫三种酶活力均有显著变化，表明顺式氯氰菊酯对蚊幼虫的这三种酶产生了明显的影响。

烯虫酯对淡色库蚊幼虫剂量效应的实验研究

目的观察烯虫酯对淡色库蚊幼虫阶段的影响。方法采用浸渍法,观察蛹死亡和正常羽化情况。结果烯虫酯第7天致蛹死亡,LC50为2.165 8×10-8mg/ml,抑制蛹羽化作用的EC50为1.8105×10-8mg/ml;第11天致蛹死亡,LC50为1.949 4×10-8mg/ml,抑制蛹羽化作用的EC50为1.860 9×10-8mg/ml。结论烯虫酯影响淡色库蚊蛹到羽化阶段,可致蛹死亡,羽化率降低。