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.

Chemical composition and larvicidal activity of essential oil of Origanum majorana(Lamiaceae) cultivated in Morocco against Culex pipiens(Diptera:Culicidae)

Objective:To evaluate the larvicidal activity of essential oil of Origanum mtijoruna(Lamiaceae)cultivated in Morocco against Culex pipiens(Diptera:Culicidae).Methods:The analysis and the identification of the various constituents of essential oil were carried out by gas chromatography coupled with mass spectrometry.Biological test was performed according to a standard methodology inspired by the World Health Organization protocol with slight modification.Results:This oil mainly consisted of monoterpene and sesquiterpenes.The majority compounds are 4-terpinene(28.96%),y-terpinene(18.57%),α-terpinene(12.72%) and sabinene(8.02%).The lethal concentrations(LC_(50) and LC_(90)) measured for the essential oil Origanum majorana,were respectively of the order of 258.71 mg/L and 580.49 mg/L.Conclusions:The results could be useful in search for newer,safer,and more effective natural larvicidal agents.

Larvicidal activity of Cyclamen(Myrsinaceae) extracts against the larvae of West Nile virus vector Culex pipiens L.(Diptera:Culicidae)

Objeclive:To evaluate the larvicidal activity of the tuber extracts isolated from two species of Cyclamen（Cyxltimen mimbile Hildebr.and Cyclamen alpinum Dammann ex.Sprcnger） against Culex pipiens L.（Diptera:Culicidae）.Methods:Twenty young（first-second） or older（third- fourth） instars of tile Culex pipiens were exposed to various concentrations（100 to I 000 ppm） of the extracts.Mortality was recorded after 12-,24-,48-.72- and 96-h of exposure.Results:We determined that the young larval stages were more susceptible to the extracts in comparison with the older larval stages.A comparison of LC90 and LC90 values has shown that Cyclamen mimbile was more active than Cyclamen alpinum.Conclusions:This study is the first to report on the larvicidal activity of the extracts of Cyclamen species against Culex pipiens.More studies are needed to isolate and identify the active components involved,their mode of action,and effects on other mosquito and pest species.

The morphological variations of Culex pipiens(Diptera:Culicidae) in central Iran

Objective:To determine the variations in morphological characters of Culex pipiens complex and identify the species complex.Methods:A study was carried out from April to October 2009 in Yazd Province,Iran.This study was performed in two randomly selected rural villages in Yazd County using different sampling methods such as larval collection,hand catch,pyrethrum space spray,light trap,and pit shelter collections.The data were analyzed using SPSS software Ver. 16.ANOVA and Tukey’s post-hoc test was used to compare the ratios of the samples.Results: The average of the DV/D ration was 0.090±0.007 and the range was 0-0.33.The average D/V ratio was 1.07±0.02,with maximum 1.6 and minimum 0.6.The costa and subcosta intersection were observed beyond the bifurcation of R2+3 in most of the specimens.The bifurcations of R2+3 and M1+3 veins were not on one direction in all samples.The range of the R-Ceh7R2+3 ratio was 2.42-7.91.The average ratio of cross wing was 2.25±0.04 with a range of 1.36-3.70.Conclusions: More populations of Culex pipiens from different areas of Iran need to be studied to gain complete information about the taxonomy and ecology of the species.

Study on the cytoplasmic incompatibility in some natural population of Culex pipiens complex in China and Japan

The cytoplasmic incompatibility in the field population of Culex pipiens complex from China and Japan was studied. The results of the crossing experiments between 11 different strains suggest that some Japanese strains might be possible to be used for control Chinese strains by using male sterile technique, and the heavy infection of wolbachiae in mosquitoes may have some relations with the cytoplasmic incompatibility in the field population of Cx. pipiens complex.

Climatic and Physiographic Variables to Evaluate Culex pipiens s.l. Risk and Habitat

Using a geographic information system (GIS), the relations between a georeferenced data set of Culex pipiens s.l. collected in Portugal mainland during seven years (2006-2012) and meteorological and physiographic parameters are evaluated. This work is one of the results of a long-term surveillance program of pernicious insects that act as vectors of various diseases;its focus is on the possibility of prevention that can be achieved with abundance data. The focus on Culex pipiens is justified by its abundance and its competence as a vector for numerous health issues. The cumulative distribution of monthly captures by each meteorological parameter allows to compute thresholds corresponding to mosquito massive presence related to 90% of the captures. Using the weather parameters measured in the network of weather stations across the country, a monthly average of each parameter of interest (temperature, humidity, etc.) is computed and an interpolation of the results is made to produce raster maps corresponding to each month. The previously obtained thresholds are applied to each map, producing spatial masks with the relevant zones for each parameter. The intersection of the various masks for each month shows the most densely populated area of Culex, and the ensemble allows us to observe the evolution of mosquito presence through the critical season, which is from May to October at these latitudes. In parallel, mosquito abundance data are related to physiographic parameters. The relative distribution of female mosquitoes across land cover types in each month allows identifying which classes and seasons are most relevant. Orthometric altitude related to the presence of 90% of the catches shows the limits reached by mosquitoes in each month. The results are applied to the previously obtained climate envelopes, delimiting critical areas where the level of risk of transmission of the pathogens for which Culex pipiens is a competent vector is high and countermeasures should be concentrated, allowing its planning, and targeting on a monthly basis. The described procedure can be used with other relevant vectors in any region of the world, whenever abundance data is available.

Comparative study of the effect of Bacillus thuringiensis on larval populations of Culex pipiens L.(Diptera-Culicidae)of the City of Tlemcen(Algeria)

In the cities of Algeria, Culex pipiens L. (Diptera: Culicidae) is the mosquito which presents most interest because of its wide geographical distribution and of its abundance which engender a strong nuisance. Besides, its role of vector of the virus West Nile arouses a particular interest in the Mediterranean Basin. These insects are generally controlled by conventional insecticides for the greater part, chemicals which cause in the long term side effects (effects on the not aimed bodies and the resistance of the aimed species). A research for the effect of the bioinsecticide Bacillus thuringiensis (granulated commercial shape in 200 IUT1/mg) was realized on préimaginales populations of the artificial deposits sites (taken directly of them natural the deposits sites) and cleansed populations (stemming from a breeding) having never been handled previously, taking into account local weather and physico-chemical conditions. Analyses of variance, allowed to determine the combined effect of the factor measure and of the factor time which by increasing, increase the efficiency of the product. The results of the rates of mortalities registered after treatment allowed to loosen the DL50 and the DL90 for every embryonic stage. From the results, we estimated the degree of sensibility of the larva populations of Culex pipiens which have proved heterogeneous in partial tolerance in Bacillus thuringiensis for the populations of the sensitive artificial and homogeneous the deposits sites for those stemming from the breeding.

三种植物提取物对蚊的毒杀效果比较

用60%乙醇分别提取了苍耳(Xanthium sibiricum)子与艾蒿(Artemisia argyi)、紫茉莉(Mirabilis jalapa)的叶和茎提取物,并用浸渍法和三角烧瓶熏蒸法测定了提取物对尖音库蚊(Culex pipiens)复组蚊的幼虫和成虫杀虫和驱避效果。结果表明,苍耳子、艾蒿叶与茎和紫茉莉叶与茎植物提取物对蚊的IV龄幼虫毒杀作用的LC50值分别是0.373 6、1.630 7、2.715 5、6.841 1和3.981 8 mg/mL,对成虫毒杀作用的LC50值分别是0.017 85、0.042 85、0.018 09、0.034 40和0.068 74 g/250 mL;5种提取物对幼虫的毒杀作用由强到弱依次是苍耳子、艾蒿叶、艾蒿茎、紫茉莉茎、紫茉莉叶,对成虫的毒杀作用由强到弱依次是苍耳子、艾蒿茎、紫茉莉叶、艾蒿叶、紫茉莉茎。

Co-circulation of Aedes flavivirus,Culex flavivirus,and Quang Binh virus in Shanghai,China

Background:With increases in global travel and trade,the spread of arboviruses is undoubtedly alarming.Pathogen detection in field-caught mosquitoes can provide the earliest possible warning of transmission.Insect-specific flavivirus(ISFV)has been first detected in 1991 and documented worldwide in the latest ten years.Although infection with ISFVs is apparently limited to insects,an increase in the infection rate of mosquito-borne flaviviruses may be able to induce cytopathic effects in vertebrate cells during co-infection with other human pathogens.However,little is known whether ISFVs persist in most regions of China.Methods:During the mosquito activity season in 2016,a surveillance program was carried out to detect ISFVs in mosquitoes in metropolitan Shanghai,China.The presence of ISFVs was randomly tested in different species of mosquitoes using RT-PCR-based and hemi-nested PCR assays,following by the sequencing of PCR products.Sequences from positive pooled samples were compared with those deposited in GenBank.Thereafter,sequences of representative insect flaviviruses were used for further phylogenetic and molecular evolutionary analyses.Results:Our investigations showed:(1)the presence of Aedes flavivirus(AEFV)in 11/161 pooled samples(nine pools in Songjiang District,one pool in Huangpu District,and one pool in Qingpu District)of Aedes albopictus,(2)the presence of Quang Binh virus(QBV)in 10/195 pooled samples(all in Chongming District)of Culex tritaeniorhynchus;and(3)the presence of Culex flavivirus(CxFV)in 9/228 pooled samples(six pools in Pudong New Area,two pools in Huangpu District,and one pool in Chongming District)of Cx.pipiens.Furthermore,phylogenetic analyses of the gene sequences of envelope proteins indicated that Shanghai CxFV strains belonged to the Asia/USA genotype.The overall maximum likelihood estimation values(and 95%confidence interval)for CxFV,QBV,and AEFV in mosquitoes collected in Shanghai in 2016 were 1.34(0.66-2.45),1.65(0.87-2.85),and 1.51(0.77-2.70)per 1000,respectively.Conclusions:This study reveals the presence and the geographical distribution of ISFVs,and determines the genetic variation and the infection rate of ISFVs in Shanghai,China.At least,three insect flaviviruses including ISFVs,AEFV,CxFV,and QBV,co-circulate in this area.To our knowledge,this is the first report of AEFV in China.

Experimental infections of mosquitoes with severe fever with thrombocytopenia syndrome virus

Background:Severe fever with thrombocytopenia syndrome(SFTS)is a newly identified emerging infectious disease,which is caused by a novel bunyavirus(termed SFTSV)in Asia.Although mosquitoes have not been identified as the primary vectors,as revealed by epidemiological surveys,their role in transmitting this SFTSV as a suspicious vector has not been validated.Findings:In this study,we conducted experimental infections of mosquitoes with SFTSV to examine the role of mosquitoes in the transmission of the virus.We did not detect viral replication in Culex pipiens pallens,Aedes aegyptis and Anopheles sinensis as revealed by qRT-PCR assay.In addition,we failed to isolate SFTSV from the Vero cells cultured with suspensions of SFTSV-infected mosquitoes.Conclusion:The results of the present study demonstrate little possibility that mosquitoes act as vectors for the emerging pathogen SFTSV.