Factors Affecting the Ovilarval Density of Aedes Spp. Mosquitoes in Selected Rice Fields of Mu^oz, Nueva Ecija

Variables among the macroclimate, microclimate and rice canopy categories and three other different farming systems were evaluated on their effects to the egg and larval density of Aedes spp. mosquitoes known as transmitters of animal and human diseases. No statistical difference in egg density （#eggs/mL） among farming systems （P = 0.345） were observed. However, there was significant difference in larval density （#1arvae/mL） among farming systems （P 〈 0.001） particularly between organic and conventional farms and between organic and mixed farms at （P 〈 0.05）. Among the variables in the macroclimate category, wind velocity and ambient temperature significantly influenced larval density in conventional farms. Among the variables in the microclimate category, water temperature significantly contributed to larval density in both the mixed and conventional farms whereas water turbidity, in conventional farms. Among the variables in the rice canopy category, the number of tillers per plant was a significant contributor to larval density in all farm types. No variable among the environmental exposure categories affected the larval density in organic farms.

Current resistance status of Aedes aegypti and Aedes albopictus populations in Penang Island,Malaysia

Objective:To determine the current insecticide resistance status of Aedes(Ae.)aegypti and Ae.albopictus to four insecticides,namely 0.05%deltamethrin,0.75%permethrin,5%malathion and 0.25%pirimiphos-methyl using the World Health Organisation(WHO)susceptibility test kit.Methods:Adult bioassays were carried out using the standard protocol of the World Health Organisation.All F1 generation urban and suburban field strains of Ae.aegypti and Ae.albopictus were tested against pyrethroid and organophosphate insecticides,including the presence of piperonyl butoxide(PBO)in four replicates of 25 non-blood-fed female mosquitoes ranging from 3 to 5 days old.The Vector Control Research Unit(VCRU)laboratory strain served as a reference strain.Results:In this study,0.05%deltamethrin demonstrated a lower value of knockdown time when 50%of the mosquito population died(KT50)and knockdown time when 95%of the mosquito population died(KT95),which is significantly more effective compared to 0.75%permethrin against adult female Ae.aegypti(urban and suburban)and Ae.albopictus(urban and suburban)(ANOVA,P<0.01).Meanwhile,5%malathion was a more effective insecticide,amounting to the shorter KT50 and KT95 compared to 0.25%pirimiphos-methyl against Ae.aegypti(urban and suburban)and Ae.albopictus(urban and suburban).Ae.aegypti urban and Ae.aegypti suburban performed a higher resistance ratio(RR)towards both 0.05%deltamethrin and 0.75%permethrin due to the wide use of permethrin in dengue vector control programs in Malaysia.However,Ae.albopictus urban and suburban have lower resistance than Ae.aegypti urban and suburban towards 0.05%deltamethrin and 0.75%permethrin at 24 hours post-treatment.The addition of PBO with these insecticides successfully reduced knockdown time(KT50 and KT95)values of most of the Ae.aegypti and Ae.albopictus field strains except PBO+0.75%permethrin against Ae.aegypti suburban.Conclusions:The addition of PBO to insecticides has significantly reduced the knockdown time(KT50 and KT95)values on most of Ae.aegypti and Ae.albopictus urban strain except PBO+5%malathion against Ae.albopictus urban strain and PBO+0.75%permethrin against Ae.albopictus suburban strain in comparison to exposure to insecticides without PBO.Ae.aegypti showed a higher resistance ratio of 50(RR50)when compared with the VCRU laboratory reference strain(susceptible strain)at the exposure to the deltamethrin,including with pre-exposure to PBO.This study found that the addition of PBO with organophosphates(5%malathion and 0.25%pirimiphos-methyl)was significantly more effective than pyrethroids against Ae.aegypti and Ae.albopictus(urban and suburban)due to their high mortality rate at 24 hours.It can be concluded that the usage of PBO can help reduce resistance alteration in Aedes mosquitoes.

Surveillance of arthropod-borne viruses in Benin,West Africa 2020–2021:detection of dengue virus 3 in Aedes aegypti(Diptera:Culicidae)

Dear Editor,Dengue virus(DENV,family Flaviviridae,genus Flavivirus)serotypes 1 to 4(DENV-1,-2,-3,and-4)are responsible for more than 100 million infections per year worldwide.Symptoms of DENV infection can be diverse,reaching from an acute febrile illness to the more severe,sometimes fatal dengue haemorrhagic fever/dengue shock syndrome.

2023年德阳市登革热媒介伊蚊监测结果分析

目的掌握德阳市登革热媒介伊蚊的种类构成、密度季节消长、区域及生境分布等本底信息,为制定媒介伊蚊控制措施并开展登革热预警预测及风险评估提供科学依据。方法根据《全国病媒生物监测方案》及《四川省登革热防控技术方案(2023版)》等,分别采用布雷图指数法和双层叠帐法对2023年德阳市蚊幼孳生情况和成蚊密度开展监测。采用WPS 2016软件录入并整理数据,SPSS 25.0软件进行t检验、Mann-Whitney U检验或Kruskal-Wallis H检验、卡方检验相关分析。结果蚊幼孳生:共调查3600户,积水数8507个,其中阳性数为697个;BI值为19.36,室外高于室内(Z=3.61,P<0.01);CI为8.19%,室内外差异无统计学意义(χ^(2)=1.17,P=0.28);蚊幼孳生高峰在7—9月且布雷图指数到达高值≥20,废旧轮胎堆放地、废品站、工地等生境更易出现伊蚊孳生(均P<0.05)。成蚊密度:5—10月共捕获407只白纹伊蚊,平均密度为3.77只/(人·h);8月为密度峰值,达6.61只/(人·h)。结论2023年德阳市部分季节和生境的白纹伊蚊蚊幼孳生和成蚊密度较高,且在7—9月,有登革热疫情暴发风险,应针对性采取控制措施,防控登革热疫情发生与传播风险。

食蚊鱼(Gambusia spp.)入侵生态学研究进展

食蚊鱼(Gambusia spp.)是原产于北美洲的著名入侵物种,它对蚊类幼虫具有很强的捕食压力,被作为疟疾防治生物工具而在全世界温带和热带地区扩散。近20多年来的研究认为,食蚊鱼通过食物竞争和捕食等机制威胁引入地的无脊椎动物、鱼类、两栖类的生存,显著影响引入地的生物多样性。它们具有广泛的生境适应性、生长迅速、卵胎生、高生殖率、对生殖生态条件无特殊要求等特点。另外,它们的个体野外寿命不超过2 a,种群更新速度快,种群内形成春季和夏季两个繁殖群体,并具有不同的繁殖生物学特点,因而形成复杂的世代结构。遗传上,雌鱼具有混交及能长期贮存精子的特点,能快速建立种群并克服奠基效应。这些种群通过快速适应性进化而形成一定规模的地理群体。当前,由于食蚊鱼在预防疟疾的工作中仍具有不可替代的作用,它会借助于人力的作用而继续扩散。为减轻它对非目标地区和非目标生物的影响,应进一步深入开展其入侵生态学研究。

诱蚊诱卵器法监测不同类型住宅小区中白纹伊蚊结果分析

目的分析上海市徐汇区不同住宅小区中诱蚊诱卵器监测结果,为制定科学、高效的住宅小区中白纹伊蚊密度控制策略提供理论依据,减少登革热在本地区的传播风险。方法使用诱蚊诱卵器在168个住宅小区中于6—10月每2周开展一次监测,按照3种住宅类型和8个监测轮次记录诱蚊诱卵器阳性率,采用Shapiro-Wilk检验进行诱蚊诱卵器阳性率的正态分布分析,采用Kruslal-Wallis检验和Mann-Whitney U检验进行诱蚊诱卵器阳性率的非参数检验分析,采用Spearman相关分析进行诱蚊诱卵器阳性率和住宅小区绿化率及物业费的相关性分析。结果平均诱蚊诱卵器阳性率为5.17%;8个监测轮次中,第3次(7月)的诱蚊诱卵器阳性率最高,为6.62%,第8次(10月)最低,为2.98%,并在第6次(9月)小幅上升为4.92%;3类住宅小区中,普通小区的平均诱蚊诱卵器阳性率为5.80%,高于高层小区的3.94%,且差异有统计学意义(P<0.001),低密度小区诱蚊诱卵器阳性率为5.10%,介于两者之间且差异均无统计学意义;同时,诱蚊诱卵器阳性率与物业费存在显著的负相关性,与绿化率无相关性。结论住宅小区诱蚊诱卵器阳性率在7月出现最高峰,在9月出现次高峰;普通小区的平均诱蚊诱卵器阳性率显著高于高层小区,且阳性率与物业费呈显著负相关;各住宅小区可根据物业人员蚊虫控制能力,有针对性地开展白纹伊蚊防控工作。

ralb34k2-1刺激小鼠RAW264.7巨噬细胞对蛋白质PTM代谢物修饰及DENV-2易感性的影响

目的探讨白纹伊蚊唾液蛋白34k2-1(ralb34k2-1)刺激的小鼠单核巨噬细胞白血病细胞(RAW264.7细胞)胞内蛋白翻译后代谢修饰(PTMs)的变化及对2型登革病毒(DENV-2)易感性的影响。方法利用抗乙酰化、乳酰化、琥珀酰化、巴豆酰化和丙二酰化的泛特异性抗体,通过免疫印迹法(Western blot)检测ralb34k2-1蛋白刺激后不同时相的RAW264.7细胞蛋白质翻译后代谢物修饰的情况,酶联免疫吸附双抗体夹心法(ELISA)检测细胞内外的乳酸含量;用2 mg/L ralb34k2-1预处理RAW264.7细胞24 h后、继续培养2 d、再用DENV-2感染细胞,通过实时荧光定量多聚核苷酸链式反应(RT-qPCR)检测感染18 h和36 h后的病毒核酸变化,分析ralb34k2-1预处理后对病毒易感性的影响;检测感染前后胞内白细胞介素1β-(IL-1β)、白细胞介素10-(IL-10)、肿瘤坏死因子β-(TGF-β)、诱导性一氧化氮合酶(iNOS)和精氨酸酶1(Arg-1)mRNA的相对表达情况,分析ralb34k2-1预处理对细胞免疫状态及细胞极化的影响。结果胞内不同的代谢物对蛋白质的修饰程度主要表现为乳酰化修饰>乙酰化修饰>琥珀酰化修饰;在时相上,除琥珀酰修饰外,随时间的延长其余代谢物对蛋白质的修饰有增多的趋势,其中以6 h乳酰化修饰最多;ralb34k2-1刺激对细胞的乳酸产生无明显影响;经ralb34k2-1预处理后胞内DENV-E相对表达量较对照组高5倍以上,IL-10 mRNA的相对表达在感染前后均保持高水平(6~8倍);在感染前iNOS/Arg比值为3.46±1.59,但受ralb34k2蛋白预处理的细胞在感染后表现iNOS表达下调的趋势。结论蚊唾液ralb34k2蛋白可能通过调控PTM代谢物修饰的方式,改变细胞的免疫状态从而增强登革病毒的易感性。

16种市售驱蚊产品对白纹伊蚊驱避效果比较

为了明确驱蚊产品的有效驱蚊时间,为消费者选择驱蚊产品提供依据.招募12名志愿者,利用Arm-in-cage方法测试了16种市售驱蚊产品对白纹伊蚊的驱避效果.结果显示:有效驱避时间达4 h的有2种,均含化学合成物,分别为15%避蚊胺和10%驱蚊酯;达3 h的有1种,仅含植物源驱蚊成分;达2 h的有3种,达1 h的4种;<1 h的有6种,其中5种为植物源驱蚊产品.含有人工合成驱蚊成分的8种驱蚊产品中,人工合成驱蚊成分含量越高,驱蚊时间越长,少数植物源驱蚊产品效果较好.5种驱蚊产品的驱蚊效果在不同实验人员之间存在显著差异(P<0.05).结论:相比于化学合成驱避剂,植物源驱避剂的驱蚊效果稍差,但是少数植物源驱避剂的驱蚊时间也可以达到3 h.

Ovicidal and repellent activities of botanical extracts against Culex quinquefasciatus,Aedes aegypti and Anopheles stephensi(Diptera:Culicidae)

Objective:To determine the ovicidal and repellent activities of methanol leaf extract of Ervatamia coronaria(E.coronaria) and Caeslpinia pulckerrima(C.pulcherrima) against Culex quinquefasciatus(Cx.quinquefasciatus),Aedes aegypti(Ae.aegypti) and Anopheles stephensi(An. stephensi).Methods:The ovicidal activity was determined against three mosquito species at various concentrations ranging from 50-450 ppm under the laboratory conditions.The hatch rates were assessed 48 h after treatment.The repellent efficacy was determined against three mosquito species at three concentrations viz.,1.0,2.5 and 5.0 mg/cm under the laboratory conditions. Results:The crude extract of E.coronaria exerted zero hatchability(100%mortality) at 250.200 and 150 ppm for Cx.quinqitefasciatus,Ae.aegypti and An.stephensi,respectively.The crude extract of C.pulchenima exerted zero hatchability(100%mortality) at 375.300 and 225 ppm for Cx.quinquefasciatus,Ae.aegypti and An.Stephensi,respectively.The methanol extract of E. coronaria found to be more repellenct than C.pukherrima extract.A higher concentration of 5.0 mg/cm^2 provided 100%protection up to 150.180 and 210 min against Cx.quinquefasciatus,Ae. aegypti and An.stephensi,respectively.The results clearly showed that repellent activity was dose dependent.Conclusions:From the results it can be concluded the crude extracts of E.coronaria and C.pukherrima are an excellent potential for controlling Cx.quinquefasciatus,Ae.aegypti and An.stephensi mosquitoes.

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.

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.

Larvicidal activity,inhibition effect on development,histopathological alteration and morphological aberration induced by seaweed extracts in Aedes aegypti(Diptera:Culicidae)

Objective:To investigate the larvicidal activity,inhibition effect on development,histopathological alteration and morphological aberration induced by the extracts derived from seaweeds Bryopsis pennuta(B.pennata),Sargassum binderi(S.binderi) and Padina australis in Aedes aegypti(Ae.aegypti) larvae and to characterize the phytochetnical components of the three seaweeds.Methods:Larvicidal activity of the seaweeds towards the larvae of Ae.aegypti was determined according to WHO.The inhibition effect of seaweeds was assessed by determining the mortality,adult emergence rate,larval and pupa duration of the treated larvae.Histopathological effect on midgut epithelium of larvae and morphological aberration induced by the methanol extracts were examined.Phytochemical analysis was done to determine the presence of alkaloids,saponins,steroids and terpenoids in the seaweeds.Results:Chloroform partition of B.pennata extract exhibited the strongest larvicidal activity(LC_(50) = 82.55 μg/mL).followed by methanol extract of B.pennata(LC_(50) = 160.07 μg/mL) and chloroform partition of S.binderi extract(LC_(50) = 192.43 μg/mL).The methanol extract of S.bituleri exhibited the strongest effect on prolongation of larval period(1.5-fold longer as compared to control) and resulted in strongest inhibition effect in adult emergence(98.67%).The histopathological study showed that larvae treated with seaweed extracts had cytopathological alteration of the midgut epithelium.The morphological observation revealed that the anal papillae and terminal spiracles of larvae were the common sites of aberrations.Conclusions:The study provided information on various effects of seaweed extracts on Ae.aegypti.Further investigation on identifying the active compounds and their mechanisms of action is recommended.

Susceptibility of Aedes albopictus from dengue outbreak areas to temephos and Bacillus thuringiensis subsp.israelensis

Objective:To monitor the current duration of the application rates in vector programme and the level of Aedes albopictus larvae susceptibility from three selected areas in northeast district of Penang on two selected larvicides,temephos and Bacillus thuringiensis subsp.israelensis(Bti) which are commonly used by Penang Health Department for vector control.Methods:The mosquito larvae were tested against two types of larvicides:(1) temephos(Abate&#174;) with diagnostic dosage(0.012 mg/L) and operational dosage(1 mg/L) and(2)Bacillus thuringiensis subsp.israelensis(Vecto Bac&#174;WG) with operational dosage ranging from 6 000 international toxic units per L to 24 000 international toxic unit per L.A total of 20 late third and early forth instar larvae were selected and transferred into paper cup sized 300 m L using wide-mouthed pipette.The larvae were distributed into each 300 m L paper cup containing 50 m L of aged tap water.The experiment was replicated five times for each concentration tested.Each test was repeated three times.The mortality was recorded after 24 h of exposure and recorded lethal time was based on 2 h for temephos and 6 h for Bti.The control consisted of ethanol for temephos and only seasoned water for Bti.Results:The result showed that Aedes albopictus from Flat Hamna,Kampung Sungai Gelugor and Kampung Tanjung Tokong were still susceptible to Bti and temephos.However,higher lethal time and resistance ratio were detected in strain from Flat Hamna which was a known dengue hot spot area in northeast of Penang.Conclusions:The application of temephos and Bti in vector control activity in these selected localities is still relevant in the control of Aedes larvae populations.

Toxicity and sub-lethal effect of endemic plants from family Anacardiaceae on oviposition behavior of Aedes albopictus

Objective: To evaluate the lethal concentration, oviposition deterrence and ovicidal activity of acetone extracts of Melanochyla fasciculiflora(M. fasciculiflora) leaf and Gluta renghas(G. renghas) leaf against Aedes albopictus(Ae. albopictus). Methods: To determine the lethal concentration of Anacardiaceae, ten test concentrations of the extracts ranging from 200 to 650 mg/L were selected for larvicidal bioassays and 25 early fourth instar larvae were exposed to the extracts for 24 h. The sub-lethal concentrations used for oviposition deterrence was the value of LC25, LC50 and LC75 from above study which is 235 mg/L, 470 mg/L and 705 mg/L for M. fasciculiflora extract and 187.5 mg/L, 375 mg/L and 562.5 mg/L for G. renghas extract, respectively. Twenty gravid Ae. albopictus were allowed to oviposit in different treated concentrations. For oviciding procedure, a total of 300 eggs of Ae. albopictus were soaked in solution with each treated concentration as mentioned above for 24 h. After 24 h, eggs were sieved and soaked in seasoned water, and hatching rates were calculated. For comparison, only seasoned water was used in control experiment.Results: G. renghas demonstrated lower LC50 value of 372.80 mg/L compared to M. fasciculiflora(467.90 mg/L). The activity index of negative oviposition revealed the deterrent effect and thus, caused a remarkable negative response resulting in oviposition of fewer eggs compared with control(without plant extract). The acetone extract of M. fasciculiflora was more effective than G. renghas extract in displaying oviposition deterrence potential since the latter did not possess the deterring effect within the concentration range tested. However, both plant extracts exhibited excellent oviciding effect as 92.33% of eggs failed to be hatched when treated with 705.0 mg/L of M. fasciculiflora and 86.67% with 562.5 mg/L of G. renghas. The oviposition deterrence and percentage of egg mortality were directly proportional to the concentrations of extracts in both plants tested. Conclusions: These results clearly indicate that the acetone extract of G. renghas could be served as potential larvicide, whereas M. fasciculiflora has better sub-lethal effect for oviposition deterrence and against Ae. albopictus as an oviciding agent.

Bioactivity of seagrass against the dengue fever mosquito Aedes aegypti larvae

Objective:To identify the larvieidal activity of the seagrass extracts.Methods:Seagrass extracts,Syringodium isoelifolium(.S.isoetifolium),Cymodocea serrulata and Hulophila beccarii,were dissolved in DMSO to prepare a graded series of concentration.Batches of 25 early 4th instars larvae of Aedes aegypti(Ae.aegypti) were transferred to 250 ml.enamel bowl containing199 mL of distilled water and 1 mL of plant extracts(0.01 mg- 0.1 mg).After 24 h the mortality rate was identified with the formulae[(%of lest mortality-%of control mortality)/(100-%of control morlality)]× 100.Each experiment was conducted with three replicates and a concurrent control group.A control group consisted of 1 mL of DMSO and 199 mL of distilled water only.Results:The root extract of S.isoelifolium showed maximum larvicidal activity with minimum concentration of extract of LC_(50)= 0.0604 ± 0.0040)μg/mL with lower confidence limit(LCL)-upper confidence limit(UCL) =(0.051-0.071) and LC_(90)=0.0972 μg/mL followed by leaf extract of S.isoelifolium showed LC_(50)=(0.062 ± 0.005)μ'g/mL.The regression equation of pool and leaf extract of S.isoelifolium for4th instar larvae were Y =4.909- 1.32x(R^2= 0.909) and Y= 2.066+ 1.2x(R^2 =0.897) respectively.The results of the preliminary photochemical constituents shows the presence of saponin,steroids,terpenoid,phenols,protein and sugars.Conclusions:from the present study the ethanolic extracts of seagrass of S.isoelifolium possesses lead compound for development of larvieidal activity.

Growth inhibitory effect of phenolic extracts of Ziziphus jujuba Mill.in dengue vector Aedes aegypti(L)in parent and F1 generation

Objective: To evaluate the lethal and emergence inhibitory effect of alkaloid, phenolic and terpenoid extracts of Ziziphus jujuba(Z. jujuba; Rhamnaceae) against Aedes aegypti(Diptera: Culicidae), and to explore the effect of the most effective fraction on developmental and biochemical parameters of the dengue vector. Methods: The fourth instar larvae of Aedes aegypti were exposed to alkaloid, phenolic and terpenoid extracts from Z. jujuba leaves to test their toxicity and emergence inhibitory effects. Phenolic extract, being the most effective was further tested against the mosquitoes for their growth inhibitory effect supported by biochemical changes in the parent and F1 generation. Results: While the different secondary metabolite fractions i.e., alkaloid, phenolics and terpenoid caused mortality at larval and pupal stages, the LC_(50) value was the lowest for phenolic fraction. Further study carried out with the phenolic fraction revealed that it affected growth by decreasing adult life span, fertility and fecundity of the mosquitoes. The reduction in growth was also accompanied by decrease in carbohydrate and lipid levels. Conclusions: It is concluded that the phenolic extract of the leaves of Z. jujuba is a potential candidate for control of Aedes mosquitoes.

Larvicidal activity of the pericarp extract of Garcinia mangostana against dengue vector Aedes aegypti in Sri Lanka

Objective:To assess the larvicidal activity of mangosteen(Garcinia mangostana)against larval stages of Aedes aegypti mosquitoes.Methods:A crude extract was prepared in ethanol from powdered mangosteen pericarps.A concentration gradient(0.01-4.92 g/L)was prepared from the stock solution.Seven batches of 25 third instar larvae of Aedes aegypti were used for larval bioassays.Larval mortality rates were observed after one and 24 hours.Cholesterol and total lipid contents in 20 randomly selected dead larvae at each trial were assessed by colorimetric method.The experimental setup was repeated five times.The General Linear Model and Probit analysis were used to evaluate the relationship of mortality with cholesterol level,total lipid level and cholesterol to total lipid ratio.Results:The percentage mortalities significantly varied with different concentrations(F_(7,32)=385.737;P<0.001).The LC50 and LC99 values were(0.041±0.006)g/L and(10.616±1.758)g/L,respectively after 24 hours.There was no mortality recorded within the one-hour exposure time.Only the cholesterol content(F_(5,24)=173.245;P<0.001)in larvae exposed to different concentrations denoted a significantly decreasing trend within 24-hour exposure.Larvae that were exposed to the lowest concentration(0.55 g/L)showed a higher cholesterol level(22.67±1.33)μg.Conclusions:The Garcinia mangostana extract acts as an effective sterol carrier protein inhibitor that inhibits cholesterol uptake in Aedes aegypti mosquitoes.Hence,it could be explored for use as a key source for the development of an environment-friendly plant-based larvicide.

Evaluation of Cuban Bacillus thuringiensis(Berliner,1911)(Bacillales:Bacillacea)isolates with larvicidal activity against Aedes aegypti(Linnaeus,1762)(Diptera:Culicidae)

Objective:To evaluate 11 Cuban native Bacillus(B.)thuringiensis isolates in order to select one with the best larvicidal activity against Aedes(Ae.)aegypti and low cytotoxicity.Methods:The cry and cyt genes of the isolates(A21,A51,L95,L910,M29,R84,R85,R87,R89,U81 and X48)were amplified by PCR.The influence of organic matter and NaCl on the larvicidal activity was tested by bioassays.Cytotoxicity was assayed on peritoneal macrophages of BALB/c mice.Results:The cyt1(Aa,Ab,Ba),cyt2,cry4aA,cry4Ba,cry11(Aa,Ba,Bb)and cry10 genes were identified in all native Cuban isolates.The larvicidal activity(LC_(90))of seven isolates was affected by the presence of organic matter in the water,while A21,A51,L910,R84,U81 and X48 had better LC_(50),LC_(90),LC_(95) than the 266/29-Ⅶ-98 control strain.The LC_(50) of two isolates was affected by the presence of NaCl and A21,A51,R85 isolate had better larvicidal activity than the 266/29-Ⅶ-98 control strain.In terms of toxicity against macrophages,the extracts of nine isolates were less cytotoxic than the control strains.Conclusions:Native isolate A21 had the main virulence factors against Ae.aegypti larvae,displayed a good larvicidal activity in presence of different factors related with Ae.aegypti breeding sites,and had low citotoxicity against macrophages.These results can contribute to the improvement of existing biological control strategies and the development of new biolarvicides.

Residual effects of TMOF-Bti formulations against 1^(st) instar Aedes aegypti Linnaeus larvae outside laboratory

Objective:To evaluate the effectiveness and residual effects of trypsin modulating ecstatic factor-Bacillus thuringiensis israeliensis(TMOF-Bti) formulations against Aedes aegypti(Ae. aegypti)(L) larvae at UKM Campus Kuala Lumpur.Methods:Twenty first instar Ae.aegypti larvae were added in each bucket containing 4 L of water supplied with crushed dried-leaf powder as their source of food.Combination of TMOF-Bti in rice husk formulation with the following weights viz 10,25,50 and 100 mg,respectively in duplicate was distributed in the buckets;while TMOF-Bti in wettable powder formulation each weighing viz 2,5,10 and 20 mg,respectively in duplicate was also placed in the buckets.The control buckets run in duplicate with 4 L of water and 20 first instar Ae.aegypti larvae.All buckets were covered with mosquito netting.Larval mortality was recorded after 24 hours and weekly for five weeks.A new batch of 20 1^(st) instar larvae Ae.aegypti was introduced into each bucket weekly without additional TMOF-Bti rice husk formulation or wettable powder.The experiment was repeated for four times.Results:The result of the study showed that all formulations were very effective on the first two weeks by giving 100% larval mortality for all concentrations applied.The TMOF(2%) + Bti(2%) had a good residual effect until the end of 3^(rd) week,TMOF(4%) + Bti(4%) until 4^(th) week,wettable powder TMOF(20%) + Bti(20%) until the third week.Condusions:From the results it can be concluded that the TMOF-Bti formulations can be utilized in dengue vector control.

Recent advances on pathogenesis,diagnosis,prevention,immunological aspects,and vectors of dengue:A review

Dengue is a vector-borne disease caused by the dengue virus(DENV)of family Flaviviridae.Dengue fever is common in both developed and developing countries.Globally,approximately 400 million cases of dengue fever are reported annually,resulting in approximately 22000 fatalities.Dengue cases in India have progressively increased in the last decade.In recent years,substantial progress has been made in understanding various aspects of dengue,including its pathogenesis,diagnosis,prevention strategies,immunological responses,and the role of vectors in its transmission.The transmission of a positive RNA virus occurs through Aedes mosquitoes,specifically Aedes aegypti and Aedes albopictus.This virus is associated with a wide spectrum of symptoms,ranging from mild undifferentiated fever to severe hemorrhagic fever and shock,posing a potential threat to human health.There are 4 types of antigenically distinct dengue serotypes(DENV-1 to DENV-4)and among them,DENV-2 is more lethal and extremely severe.To overcome the severity of dengue,Dengvaxia is administered to children 9 to 16 years old with evidence of previous dengue infection.The diagnosis of dengue is carried out by ELISA-based non-structural protein(NS1)and immunoglobulin tests.However,there are no specific biomarkers to identify severe disease progression.Climatic factors and temperature play an important role in complex interaction among host,vector,and virus to manifest the severity of dengue.There is a need for the refinement of climate-based disease forecasting models in India to effectively control the spread of dengue.The mosquito repellent should be used periodically to kill or repel the Aedes mosquito to prevent the spread of dengue in humans.