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.

江西省口岸区域白纹伊蚊特异性病毒Aedes albopictus anphevirus基因组序列研究

目的昆虫特异性病毒在白纹伊蚊中与致病性传染病病原体如登革病毒、基孔肯雅病毒和寨卡病毒等的传播和复制有着密切联系,本文对其基因组序列进行研究,为研发新型虫媒病毒防治策略提供理论基础。方法本研究利用二代测序技术,对江西省3个口岸区域(南昌昌北机场、九江城西港和赣州陆港)采集的野外白纹伊蚊种群携带的昆虫特异性病毒进行高通量测序。结果3个白纹伊蚊种群中广泛存在昆虫特异性病毒Aedes albopictus anphevirus(AealbAV)。利用MEGAHIT软件对这些病毒reads进行组装,得到2株AealbAV全基因组序列,与美国株MW147277.1高度同源(相似度均大于98%),基因登录号分别为九江株OR715784,赣州株OR729834,南昌株仅拼接出部分序列。结论AealbAV在江西白纹伊蚊种群中普遍存在,其全基因组研究为口岸区域利用昆虫特异性病毒进行白纹伊蚊综合防治提供了理论基础。

Geographical Distribution of Arboviruses, Aedes aegypti and Aedes albopictus Vectors and Their Resistance to Insecticides in Africa: A Systematic Review

Background & Objectives: Epidemics of arboviruses such as Dengue, Chikungunya and Zika have been recorded in recent years indicating that Aedes aegypti and Aedes albopictus are both important and very active vectors in Africa. For vector control, insecticides are on the front line, unfortunately, reported resistance jeopardizes the effectiveness of this strategy. The objective of this review was to determine the geographical distribution and insecticide resistance mechanisms of Ae. aegypti and Ae. Albopictus in Africa. Methods: A systematic review of the literature in scientific databases (PubMed, Google Scholar, ScienceDirect, Hinari) allowed us to identify relevant articles on the geographical distribution of Aedes aegypti, Aedes albopictus and arboviral diseases. On the other hand, studies related to insecticides used in vector control against Aedes, associated resistances and their molecular and metabolic mechanisms. Results: A total of 94 studies met the inclusion criteria for this search. Aedes aegypti is reported in most of Africa, and Aedes albopictus in part. There is a re-emergence and outbreak of Arbovirus epidemics in West and Central Africa. The insecticides used were organochlorines, carbamates, organophosphates and pyrethroids. In Aedes, target site insensitivity and metabolic resistance would be the 2 main mechanisms of resistance to these insecticides. Interpretation & Conclusion: Resistance has been recorded in all four major classes of insecticides recommended by WHO for vector control and eradication. New vector control methods such as the use of plant extracts with larvicidal and adulticidal activities, advanced modern biotechnology techniques, and nanobiotechnology need to be developed.

Screening of Environmental Bacterial Strains for Wild Aedes Mosquito Larval Biocontrol

The effectiveness of current control measures against Aedes mosquitoes remains low, resulting in persistent epidemics in urban areas. The emergence of resistant mosquito populations to chemical insecticides highlights the need for novel, environmentally friendly, cost-effective control strategies. This study explored the potential of environmental bacterial isolates to biocontrol wild Aedes larvae. Initially, we collected bacterial samples from infectious masses of Aedes fluviatilis larvae. The isolated bacteria were identified using biochemical, enzymatic, and molecular methods, including 16S rRNA sequencing and MALDI-TOF. Previously, Aeromonas hydrophila and Bacillus thuringiensis isolated from these infectious masses showed limited Aedes larval inhibition. Consequently, we screened additional environmental isolates from the bacteriotheque. Six isolates previously identified were tested: Chromobacterium violaceum, Enterobacter cloacae, Bacillus cereus, Bacillus sphaericus, and two strains of Bacillus thuringiensis israelensis. Among these strains, B. thuringiensis and C. violaceum exhibited significant inhibitory activities against wild Aedes larvae. Bacillus thuringiensis cultures grown under daylight conditions showed a slight ability to inhibit Aedes larvae. The potential of B. thuringiensis and C. violaceum strains studied, along with optimized culture growth conditions, will be further investigated to develop bioinsecticide products to provide safer and more sustainable alternatives for controlling larvae of Aedes mosquitoes.

Modelling the probability of presence of Aedes aegypti and Aedes albopictus in Iran until 2070

Objective:To determine the suitable ecological habitats of Aedes(Ae.)aegypti and Ae.albopictus in Iran due to climate change by the 2070s.Methods:All data relating to the spatial distribution of Ae.aegypti and Ae.albopictus worldwide,which indicated the geographical coordinates of the collection sites of these mosquitoes,were extracted from online scientific websites and entered into an Excel file.The effect of climatic and environmental variables on these mosquitoes was evaluated using the MaxEnt model in the current and future climatic conditions in the 2030s,2050s,and 2070s.Results:The most suitable areas for the establishment of Ae.aegypti are located in the southern and northern coastal areas of Iran,based on the model outputs.The modelling result for suitable ecological niches of Ae.albopictus shows that in the current climatic conditions,the southern half of Iran from east to west,and parts of the northern coasts are prone to the presence of this species.In the future,some regions,such as Gilan and Golestan provinces,will have more potential to exist/establish Ae.albopictus.Also,according to the different climate change scenarios,suitable habitats for this species will gradually change to the northwest and west of the country.The temperature of the wettest season of the year(Bio8)and average annual temperature(Bio1)were the most effective factors in predicting the model for Ae.aegypti and Ae.albopictus,respectively.Conclusions:It is required to focus on entomological studies using different collection methods in the vulnerable areas of Iran.The future modelling results can also be used for long-term planning to prevent the entry and establishment of these invasive Aedes vectors in the country.

Insecticide resistance status of Aedes aegypti and Aedes albopictus in Malaysia(2010 to 2022):A review

This review aimed to determine the prevalence of the insecticide resistance status of the field-collected Aedes(Ae.)aegypti and Ae.albopictus in Malaysia from 2010 to 2022 towards carbamates,organochlorines,organophosphates and pyrethroids.Biological and environmental controls were summarized with an emphasis on the mosquito vector control strategies in Malaysia.The information in this review was extracted from several databases such as PubMed(MEDLINE),Science Direct and Scopus by using keywords including“insecticide resistance”,“carbamate resistance”,“organochlorine resistance”,“organophosphate resistance”,“pyrethroid resistance”,“Aedes”and“Malaysia”,between January 2022 and December 2022.Distribution of resistant Ae.aegypti and Ae.albopictus in Malaysia was mapped using QGIS software.Insecticide resistance in both Ae.aegypti and Ae.albopictus is widespread in Malaysia,although the rates vary by states.The most notable was the steep increase in permethrin resistance of Ae.aegypti in Selangor,Malaysia,over the past decade.Ae.albopictus also displayed moderate resistance to permethrin,though not as widespread as Ae.aegypti in Selangor,but showed sign of resistance in Sarawak,East Malaysia.Resistance towards four main classes of insecticides have been widely documented in Malaysia.The extensive resistance towards permethrin in Malaysia which is one of the current insecticides used in Malaysia suggested that policies supporting the widespread use of permethrin fogging needs further evaluation.

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.

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.

Insecticide resistance status and biochemical mechanisms involved in Aedes mosquitoes: A scoping review

Mosquitoes belonging to the genus Aedes pose a significant threat to human health on a global scenario due to their role in transmission of dengue,chikungunya,zika,and yellow fever.In absence of specific medications and vaccines against these diseases,disease prevention relies on vector control.However,in today’s world,vector control is facing major challenges due to the onset of insecticide resistance in mosquitoes.There are four main mechanisms of insecticide resistance,namely,behavioral resistance,reduced penetration/cuticular resistance,metabolic detoxification,and target site resistance;however,the latter two mechanisms have been studied widely in Aedes mosquitoes.Insecticide resistance in Aedes mosquitoes is widespread throughout the world.This review compiles the degree of insecticide resistance/susceptibility prevailing among different field populations of Aedes mosquitoes worldwide.In addition,the review has detailed the mechanisms providing the resistance phenomenon observed in nature in Aedes mosquitoes.

Larvicidal activity of Xenorhabdus and Photorhabdus bacteria against Aedes aegypti and Aedes albopictus

Objective: To evaluate the efficacy of symbiotic bacteria, Xenorhabdus indica, Xenorhabdus stockiae, Photorhabdus luminescens subsp. akhurstii and Photorhabdus luminescens subsp. hainanensis as a larvicide against Aedes aegypti and Aedes albopictus. Methods: Larvae(L3-L4) of Aedes aegypti and Aedes albopictus were given 2 m L of a suspension 107-108 CFU/m L of each symbiotic bacterium. Distilled water and Escherichia coli ATCC襅25922 were used as the control. The mortality rate of the larval mosquitoes was observed at 24, 48, 72 and 96 h. The experiment was performed in triplicates. Results: The larvae of both Aedes species started to die at 24 h exposure. Aedes aegypti showed the highest mortality rate(87%-99%), 96 h after exposure to Xenorhabdus stockiae(b NBP22.2_TH). The mortality rate of Aedes albopictus was between 82% and 96% at 96 h after exposure to Xenorhabdus indica(b KK26.2_TH). Low effectiveness of distilled water and Escherichia coli ATCC襅25922 were observed in both Aedes larvae, with a mortality rate of 2% to 12%. Conclusions: The study confirms the oral toxicity of Xenorhabdus and Photorhabdus bacteria against Aedes spp. Xenorhabdus stockiae and Xenorhabdus indica may be an alternative agent for control Aedes spp. This is basic information for further study on the mechanism of action on Aedes larvae or application to control mosquito larvae in the community.

建筑画廊:Aedes当代建筑论坛——对话乌拉·吉斯勒

Aedes当代建筑论坛是一个致力于传播建筑文化的机构,它的建筑画廊凭借独特的策展视角和成熟的运作在世界范围内享有极高声誉。该机构的概况、它所举办的四个中国建筑师参与的展览、作为成功的建筑文化传播媒体如何看待其价值判断对于公众的影响以及其机构的成功运作经验是这次访谈的主题。

西方对中国建筑的认知 柏林Aedes画廊“土木”(TU MU)展览及其背景

在过去的20年里,中国建筑的发展发生了巨大的变化,西方媒体对这一新现象的讨论也同样如此。今天,在互联网、杂志、微信、专业建筑杂志或报纸专栏中都有对中国发展的评论,而在20年前,西方媒体对中国建筑未引起任何关注。整个20世纪,中国没有出现世界知名的建筑师,也没有人能够说出一个代表当前设计理念的中国当代建筑。文章关注了这个话题,并将重点放在西方对中国建筑师不断变化的认知上。由于作者参与了这个过程,所以本文仅代表作者个人的观点,并不代表其他人的立场。

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.

Mosquito larvicidal and ovicidal properties of Eclipta alba(L.) Hassk(Asteraceae) against chikungunya vector,Aedes aegypti(Linn.)(Diptera:Culicidae)

Objective:The present study deals with the investigation of larvicidal and ovicidal activities of benzene,hexane,ethyl acetate,methanol and chloroform leaf extract of Eclipta alba（E.alba） against dengue vector,Aedes aegypti（Ae.Aegypti）.Methods:Twenty five earlyⅢinstar larvae of Ae.aegypti was exposed to various concentrations（50-300 ppm） and was assayed in the laboratory by using the protocol of WHO 2005;the 24 h LC50 values of the E.alba leaf extract was determined by Probit analysis.For ovicidal activity,slightly modified method of Su and Mulla was performed.The ovicidal activity was determined against Ae.aegypti to various concentrations ranging from 100-350 ppm under the laboratory conditions.The egg hatch rates were assessed 48 h post treatment.Results:The LC50 values of benzene,hexane,ethyl acetate,methanol and chloroform extract of E.alba against early third instar larvae of Ae.aegypti were 151.38,165.10, 154.88,127.64 and 146.28 ppm,respectively.Maximum larvicidal activity was observed in the methanol extract followed by chloroform,benzene,ethyl acetate and hexane extract.No mortality was observed in control.Among five solvent tested the methanol extract was found to be most effective for ovicidal activity against Ae.aegypti.The methanol extracts exerted 100%mortality （zero hatchability） at 300 ppm.Conclusions:From the results it can be concluded the crude extract of E.alba was an excellent potential for controlling Ae.aegypti mosquito.

Evaluation of Andrographis paniculata Burm.f.(Family.Acanthaceae) extracts against Culex quinquefasciatus(Say.) and Aedes aegypti(Linn.)(Diptera:Culicidae)

Objective:To investigate the larvicidal and ovicidal efficacy of different extracts of Andrographis paniculata（A.paniculata） against Culex quinquefasciatus（Cx.quinquefasciatus） Say and Aedes aegypti（Ae.aegypti ） L（Diptera:Culicidae）.Methods:Larvicidal efficacy of the crude leaf extracts of A.paniculata with five different solvents like benzene,hexane,ethyl acetate, methanol and chloroform was tested against the early third instar larvae of Cx.quinquefasciatus and Ae.aegypti.The ovicidal activity was determined against two mosquito species to various concentrations ranging from 50-300 ppm under the laboratory conditions.Results:The benzene, hexane,ethyl acetate,methanol and chloroform leaf extract of A.paniculata was found to be more effective against Cx.quinquefasciatus than Ae.aegypti.The LC50 values were 112.19,137.48, 118.67,102.05,91.20 ppm and 119.58,146.34,124.24,110.12,99.54 ppm respectively.Among five tested solvent,methanol and ethyl acetate crude extract was found to be most effective for ovicidal activity against two mosquito species.The extract of methanol and ethyl acetate exerted 100%mortality at 200 ppm against Cx.quinquefasciatus and at 250 ppm against Ae.aegypti. Conclusions:From the results it can be concluded the crude extract of A.paniculata was a potential for controlling Cx.quinquefasciatus and Ae.aegypti mosquitoes.

Bioefficacy of Mentha piperita essential oil against dengue fever mosquito Aedes aegypti L

Objective:To assess the larvicidal and repellent potential of the essential oil extracted from the leaves of peppermint plant,Mentha piperita(M.piperita) against the larval and adult stages of Aedes aegypti(Ae.Aegypti).Methods:The larvicidal potential of peppermint oil was evaluated against early fourth instar larvae of Ae.aegypti using WHO protocol.The mortality counts were made after 24 and 48 h,and LC_(50) and LC_(90) values were calculated.The efficacy of peppermint oil as mosquito repellent was assessed using the human-bait technique.The measured area of one arm of a human volunteer was applied with the oil and the other arm was applied with ethanol.The mosquito bites on both the arms were recorded for 3 min after every 15 min.The experiment continued for 3 h and the percent protection was calculated.Results:The essential oil extracted from M.piperita possessed excellent larvicidal efficiency against dengue vector. The bioassays showed an LC_(50) and LC_(90) value of 111.9 and 295.18 ppm,respectively after 24 h of exposure.The toxicity of the oil increased 11.8%when the larvae were exposed to the oil for 48 h.The remarkable repellent properties of M.piperita essential oil were established against adults Ae.aegypti.The application of oil resulted in 100%protection till 150 min.After next 30 min, only 1-2 bites were recorded as compared with 8-9 bites on the control arm.Conclusions:The peppermint essential oil is proved to be efficient larvicide and repellent against dengue vector. Further studies are needed to identify the possible role of oil as adulticide,oviposilion deterrent and ovicidal agent.The isolation of active ingredient from the oil could help in formulating strategies for mosquito control.

Isolation and efficacy of entomopathogenic fungus(Metarhizium anisopliae)for the control of Aedes albopictus Skuse larvae:suspected dengue vector in Pakistan

Objective:To isolate the entomopathogenic fungus Metarhixium anisopliae(M.anisopliae) in the local environment,and evaluate its efficacy against the suspected dengue vector Aedes albopictus in Pakistan.Methods:According to the standard procedure,M.anisopliae was isolated from the dead mosquitoes which were collected from the field or dead after the collection.Bioassay was performed to determine its efficacy.Results:The results indicated that M.anisopliae had larvicidal effect with LC,value 1.09×10~5 and LC_(50) value 1.90×10^(13) while it took 45.41 h to kill 50% of tested population.Conclusions:Taking long time to kill 50%population when compare with the synthetic insecticides,is the only drawback for the use of entomopathogenic fungus but these bio-pesticides are safe for the use.

Toxicity of several botanical essential oils and their combinations against females of Aedes albopictus(Skuse) and Anopheles minimus(Theobald): Oviposition deterrent, ovicidal and adulticidal efficacies

Objective: To investigate the efficacies of 12 essential oil(EO) formulations from three Zingiberaceae plants(Alpinia galanga, Curcuma zedoaria, and Zingiber cassumunar) individually and in combination with an augmenting Eucalyptus globulus(E. globulus) EO against females of Aedes albopictus(Ae. albopictus) and Anopheles minimus(An. minimus). Methods: These formulations were evaluated for their ovicidal, oviposition deterrent and adulticidal activities against Ae. albopictus and An. minimus by a topical method, a double-choice method and a WHO susceptibility test, respectively. Results: It was found that all formulations of Zingiberaceae plants EOs augmented with E. globulus EO were more effective in oviposition deterrent, ovicidal, and adulticidal activities against the two mosquito species than all of the formulations used without E. globulus EO. Their oviposition deterrent, ovicidal and adulticidal activities were equivalent to those of 10% w/v cypermethrin. In contrast, 70% v/v ethyl alcohol as a control alone was not effective at all. The highest synergistic effect in effective repellency against Ae. albopictus was achieved by 5% Alpinia galanga EO + 5% E. globulus EO and against An. minimus was 5% Zingiber cassumunar EO + 5% E. globulus EO. Moreover, the highest synergistic effects in ovicidal activities against Ae. albopictus and An. minimus were achieved by 10% Zingiber cassumunar EO + 10% E. globulus EO and 5% Curcuma zedoaria EO + 5% E. globulus EO, respectively. For the adulticidal activities, the highest synergistic effect against two mosquitoes was achieved by 5% Curcuma zedoaria EO + 5% E. globulus EO. Conclusions: These results suggest that Zingiberaceae plant EOs augmented with E. globulus EO have a high potential to be developed into oviposition deterrent, ovicidal, and adulticidal agents for controlling populations of Ae. albopictus and An. minimus.

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.

Role of Aedes aegypti and Aedes albopictus during the 2011 dengue fever epidemics in Hanoi, Vietnam

Objective: To record the human cases of dengue fever(DF) and investigate the Aedes mosquito species circulating during the Hanoi 2011 DF epidemics. Methods: 24 different outbreak points were recorded in 8 districts between August and December 2011. Results: 140 patients were hospitalized following dengue diagnostic with a predominance of males(59.3%) and the 15-34 age class. Only DENV-1(11.27%) and DENV-2(88.73%) serotypes were detected in human samples. Mosquito sampling performed in and around patients households revealed the predominance of Aedes aegypti(95.15%) versus Aedes albopictus(4.85%). There is a positive correlation between the population density of Aedes aegypti and the number of human cases and duration of outbreaks. Conclusions: This was not observed for Aedes albopictus. 3 pools of Aedes aegypti were positive with dengue virus, two with DENV-1 and one with DENV-2.