Low-resolution genome map of the malaria mosquito Anopheles gambiae.

We have microdissected divisions of the Anopheles gambiae polytene chromosomes, digested the DNAs with a restriction enzyme, and PCR-amplified the DNA fragments to generate a set of pooled probes, each corresponding to approximately 2% of the mosquito genome. These divisional probes were shown to have high complexity. Except for those derived from near the centromeres, they hybridize specifically with their chromosomal sites of origin. Thus, they can be used to map cloned DNAs by a dot blot procedure, which is much more convenient than in situ hybridization to polytene chromosomes. We discuss additional potential uses of these probes, such as easier isolation of molecular markers and genes, including those that cross-hybridize with clones available from other insects. It is expected that the probes will substantially accelerate molecular genetic analysis of this most important malaria vector.     

Spatio-temporal distribution of malaria vectors (Diptera: Culicidae) across different climatic zones of Iran

Malaria is a main vector-borne public health problem in Iran. The last studies on Iranian mosquitoes show 31 Anopheles species including different sibling species and genotypes, eight of them are reported to play role in malaria transmission. The objective of this study is to provide a reference for malaria vectors of Iran and to map their spatial and temporal distribution in different climatic zones. Shape files of administrative boundaries and climates of Iran were provided by National Cartographic Center. Data on distribution and seasonal activity of malaria vectors were obtained from different sources and a databank in district level was created in Excel 2003, inserted to the shape files and analyzed by ArcGIS 9.2 to provide the maps. Anopheles culicifacies Giles s.l., Anopheles dthali Patton, Anopheles fluviatilis James s.l., Anopheles maculipennis Meigen s.l., Anopheles sacharovi Favre, Anopheles stephensi Liston, and Anopheles superpictus Grassi have been introduced as primary and secondary malaria vectors and Anopheles pulcherrimus Theobald as a suspected vector in Iran. Temporal distribution of anopheline mosquitoes is restricted to April-December in northern Iran, however mosquitoes can be found during the year in southern region. Spatial distribution of malaria vectors is different based on species, thus six of them (except for Anopheles maculipennis s.l. and Anopheles sacharovi) are reported from endemic malarious area in southern and southeastern areas of Iran. The climate of this part is usually warm and humid, which makes it favorable for mosquito rearing and malaria transmission. Correlation between climate conditions and vector distribution can help to predict the potential range of activity for each species and preparedness for malaria epidemics.     

Polymorphisms detected by random PCR distinguish between different chromosomal forms of Anopheles gambiae.

We have applied PCR amplification using random primers to distinguish between incipient species of the malaria vector Anopheles gambiae. Individuals belonging to three chromosomally characterized West African forms of this mosquito, which are important epidemiologically as they differ in vectorial capacity, were sampled both from laboratory stocks and from wild populations collected in three localities. The techniques used allowed for the unambiguous classification of the mosquitoes, providing a tool for rapid and efficient diagnosis, which previously relied on cytological examination of polytene chromosomes.     

Distribution and chromosomal polymorphism of the malaria vector Anopheles dirus species D

Preliminary results indicate that species D of the Anopheles dirus complex is widespread west of the Thai-Burma border in Burma and Bangladesh. A chromosomal study of An. dirus species D in these areas has revealed that this malaria vector is highly polymorphic for chromosomal rearrangements in salivary gland polytene chromosomes. The data from the limited number of wild-caught samples suggest that different geographically isolated populations may occur with respect to the frequency of inversions 2La, 3Ra and 3La. The distribution of chromosomal polymorphisms may be associated with the geography and epidemiology of human malaria in this region.     

斑须按蚊唾液腺中疟原虫配子体激活因子的活性动态

目的　探讨斑须按蚊生长、发育过程唾液腺中疟原虫配子体激活因子的活性动态。方法　应用体外雄配子体出丝分析方法 ,检测雌性斑须按蚊羽化后、吸血及产卵前后唾液腺中疟原虫配子体激活因子对柏氏疟原虫雄配子体出丝诱导活性的变化。结果　羽化后未吸血组斑须按蚊唾液腺配子体激活因子活性与按蚊生长、发育呈同步变化 ;吸血后未产卵组按蚊唾液腺抽提物的配子体激活因子活性在吸血后显著下降 ,吸血后第 8天恢复到吸血前水平 ;而吸血后产卵组按蚊唾液腺抽提物的配子体激活因子活性在吸血后第 4天恢复到吸血前水平。结论　吸血后斑须按蚊唾液腺配子体激活因子的消长与按蚊产卵相关。     

Bio-ecology of malaria vectors in an endemic area,Southeast of Iran

Objective:To determine some bio-ecological aspects of malaria vectors in Jask County,where is targeted for malaria elimination in the national program.Methods:Mosquitoes were collected monthly during 2013-2014 using different collection methods.Subsequently,ELISA test was used to detect the human blood index of mosquitoes.The susceptibility status of Anopheles stephensi was evaluated against the diagnostic dosages of seven WHO recommended insecticides.Results:A total of 3 650 female and 4 736 Anopheles larvae were collected including Anopheles stephensi,Anopheles culicifacies s.l.,Anopheles dthali.Anopheles fluviatilis s.l.,Anopheles moghulensis and Anopheles turkhodi species.Anopheles stephensi was the dominant collected species on human baits and indoors with high rate of unfed and gravid specimens in internal and external window traps.Human blood index was calculated as 14.3%for this species.It was also found to be resistant to DDT and Dieldrin.Conclusions:The collected species had a wide range of habitats,and resting behaviors.With regarding to the presence of most important malaria vectors in Jask.control of the disease may be so complicated;as based on the weather condition it can be transmitted during the whole year,except for cold months.With this strong potential of transmission,existing population movements in the area may lead to imported cases of malaria and local outbreak(s).So,more specific studies on malaria vectors in high risk areas of Jask County are recommended.     

Bacteria of the genus Asaia stably associate with Anopheles stephensi, an Asian malarial mosquito vector

Here, we show that an alpha-proteobacterium of the genus Asaia is stably associated with larvae and adults of Anopheles stephensi, an important mosquito vector of Plasmodium vivax, a main malaria agent in Asia. Asaia bacteria dominate mosquito-associated microbiota, as shown by 16S rRNA gene abundance, quantitative PCR, transmission electron microscopy and in situ-hybridization of 16S rRNA genes. In adult mosquitoes, Asaia sp. is present in high population density in the female gut and in the male reproductive tract. Asaia sp. from An. stephensi has been cultured in cell-free media and then transformed with foreign DNA. A green fluorescent protein-tagged Asaia sp. strain effectively lodged in the female gut and salivary glands, sites that are crucial for Plasmodium sp. development and transmission. The larval gut and the male reproductive system were also colonized by the transformed Asaia sp. strain. As an efficient inducible colonizer of mosquitoes that transmit Plasmodium sp., Asaia sp. may be a candidate for malaria control.     

A point survey of periurban and urban malaria in Karachi

A point survey of malaria in Karachi revealed a concentration of malaria cases in the periurban perimeter and marginal areas where immigrating groups, including Afghan refugees and Biharis from Bangladesh are concentrated. Populations of Anopheles stephensi, Karachi's main vector, were low, and were feeding chiefly on buffaloes which are also concentrated along the periurban perimeter. Maintenance of malaria transmission in periurban zones may depend on immigration of susceptibles, bovid hosts which help maintain zoophilic vector populations, and mosquito breeding sites in water tanks or buffalo hoofprints. The vector's switch to man-biting behaviour may occur either due to a 'spillover' effect from buffalo corrals to surrounding houses, or when buffaloes become less available for biting. Four types of chromosome inversions were found in the Karachi An. stephensi; as this species is not a vector in similar habitats in Lahore and Pondicherry where such inversions are not prevalent, it is likely that its status as a vector is related to chromosomal polymorphism influencing behaviour.     

Re-ingestion of Plasmodium berghei sporozoites after delivery into the host by mosquitoes

Malaria-infected mosquitoes feeding on a mammalian host inject sporozoites into the skin to induce a malaria infection. The numbers of sporozoites ultimately able to reach the liver may be important determinants of the characteristics of the ensuing blood infection. Because feeding mosquitoes not only inject sporozoites into the host but concomitantly ingest blood to obtain their bloodmeal, some sporozoites are re-ingested by the feeding mosquito. We studied transmission of fluorescent Plasmodium berghei sporozoites injected into mice by Anopheles stephensi mosquitoes and found that the numbers of sporozoites re-ingested by mosquitoes are comparable to numbers previously reported to be delivered directly into mice. Thus, re-ingestion of sporozoites likely plays a significant role in transmission dynamics of malaria by mosquitoes, and may account for the failure of some sporozoite-infected mosquitoes to induce a blood infection.     

Entomological and epidemiological attributes for malaria transmission and implementation of vector control in southern Iran

Bashagard is an important malaria endemic area in south of Iran. An epidemiological and entomological survey was performed during 2002-2010. The aim of study was to determine malaria situation, species composition of anopheline mosquitoes and susceptibility status of main vectors to insecticides/larvicides. A total of 13,490 malaria cases were recorded, Plasmodium vivax (99.64%), P. falciparum (0.35%) and mix cases (0.01%). The highest and lowest Annual Parasite Incidence (API) were observed in 2007 (145.72/1000) and 2009 (6.29/1000), respectively. Anopheles culicifacies, An. dthali, An. stephensi, An. superpictus, An. fluviatilis, An. moghulensis, An. turkhudi and An. apoci were collected from the area. Two peak activities occur in April and October. The first five species were confirmed as malaria vectors in Iran. No indication of sporozoite in mosquitoes using molecular method was performed. Susceptibility tests using diagnostic dose of insecticides and larvicides showed only resistance of An. stephensi to DDT. Tolerance in An. stephensi to deltamethrin and bendiocarb is reported. The same phenomenon was observed in An. culicifacies to DDT, propoxur and deltamethrin, and in An. dthali to malathion and deltamethrin. Larvae of vectors were susceptible to all larvicides, except for An. stephensi that exhibited tolerance to fenthion. In conclusion it should be emphasized that malaria transmission is a complex process in Bashagard. This event is attributed to five proven vectors with different behaviors which are active in the area. Regarding tolerance of vectors to deltamethrin, resistance management is suggested by using new insecticide with novel mode of action.     

Toward Anopheles transformation: Minos element activity in anopheline cells and embryos

The ability of the Minos transposable element to function as a transformation vector in anopheline mosquitoes was assessed. Two recently established Anopheles gambiae cell lines were stably transformed by using marked Minos transposons in the presence of a helper plasmid expressing transposase. The markers were either the green fluorescent protein or the hygromycin B phosphotransferase gene driven by the Drosophila Hsp70 promoter. Cloning and sequencing of the integration sites demonstrated that insertions in the cell genome occurred through the action of Minos transposase. Furthermore, an interplasmid transposition assay established that Minos transposase is active in the cytoplasmic environment of Anopheles stephensi embryos: interplasmid transposition events isolated from injected preblastoderm embryos were identified as Minos transposase-mediated integrations, and no events were recorded in the absence of an active transposase. These results demonstrate that Minos vectors are suitable candidates for germ-line transformation of anopheline mosquitoes.     

Evaluation of the action of ivermectin on blood-sucking mosquitoes

The effect of Ivomec, a formulation of ivermectin administered by various routes: through biological membrane and feeder animal was assessed. Higher insecticidal effect was obtained by feeding mosquitoes with blood containing ivermectin through biological membrane. Anopheles stephensi females were the most sensitive of 3 species under study. Their total death after feeding was observed at 1 ppm, while for Aedes aegypti the lethal dose was 2.5 ppm and for An. sacharovi, 50 ppm. Subcutaneous injection of the drug to rabbits at the dose 0.34 mg/kg wt with further feeding on it of 3 Anopheles species demonstrated the highest drug sensitivity of An. stephensi mosquitoes. Death rates among the females fed on the rabbit 4-6 days after injection of the drug were 93, 70 and 79%, respectively. Death rates among An. sacharovi and An. atroparvus differed only slightly from that of the control group. In some experiments ivermectin effect on female fertility and larvae hatching from ova can be traced. Probably, increasing the preparation dose, administered to an animal-feeder, may change significantly characteristics of the malaria carrier natural population. Moreover, further use of ivermectin versus helminths and mosquitoes in zootechnical practice may produce a side-effect on mosquitoes, feeding recurrently on domestic animals, thus increasing the effect of malaria zoological control.     

Resistance status of main malaria vector,Liston (Diptera:Culicidae) to insecticides in a malaria Endemic Area,Southern Iran

Objective: To evaluate the susceptibility of Anopheles stephensi(An. stephensi) Liston, the main malaria vector in southern Iran, to WHO recommended insecticides. Methods: Larvae of An. stephensi were collected from three different larval habitats in both urban and rural area of Bandar Abbas city and one rural area in Rudan county southern Iran. WHO standard method was used for evaluation of adult and larval mosquito susceptibility. Bendiocarb, permethrin, lambda-cyhalothrin, deltamethrin as insecticide and temephos and chlorpyriphos as larvicide were used at the diagnostic dosages recommended by WHO. Results: Findings of this study showed all larval populations of An. stephensi were completely susceptible to temephos and candidate for resistance to chlorpyriphos. Adult mosquitoes in rural areas of Bandar Abbas city were resistant to pyrethroid and carbamate insecticides. Conclusion: Comparison of the results of this survey with previous studies indicates that the resistance to pyrethroids and carbamates in this malaria endemic region is increasing. Wide use of pesticides in agriculture is certainly effective in increasing resistance. The inter-sectoral coordination and collaboration in health and agriculture seem to be necessary to manage insecticide resistance in malaria vectors.     

Enhanced malaria parasite transmission from helminth co-infected mice

Helminth infections are prevalent in malaria-endemic areas, yet the potential for helminths to alter malaria transmission has not been closely examined. We used the Echinostoma caproni-Plasmodium yoelii murine model of co-infection to assess the impact of helminth co-infection on malaria transmission. In four replicate experiments, Anopheles stephensi mosquitoes exposed to co-infected mice five days post-malaria infection had a higher rate of infectivity (80.1%, n = 241) than those exposed to malaria only-infected mice (72.0%, n = 232, P = 0.039). Intensity of malaria parasite transmission was also greater, with approximately two-fold more oocysts (geometric mean = 19.2 versus 10.5, P = 0.004) and an increase in sporozoite burden observed in mosquitoes exposed to co-infected mice. Malaria parasite prevalence and anemia were similar between co-infected and malaria only-infected mice, which suggested that enhanced malaria parasite transmission was due to helminth-induced modulation of host responses.     

Population cytogenetics of the malaria vector Anopheles leucosphyrus group

Until recently, very little was known of Anopheles species complexes and their relationships to epidemiology and malaria transmission in Southeast Asia. During the past eight years, extensive studies on the genetics of natural populations of anopheline mosquitoes in this region, involving the interdisciplinary efforts of taxonomists, operational entomologists and biologists, have revealed groups of cryptic species of Anopheles vectors, particularly the An. leucos phyrus group. This species group comprise seventeen species and two subspecies widely distributed in the forested areas of Southeast Asia. Among these species. An. dirus Peyton and Harrison, has been shown by cytogenetic and morphological studies to be a complex of at least seven isomorphic species, provisionally designated species A, B, C, D, E, F and takasagoensis, on the Southeast Asian mainland. Cytological identification of these species is based on distinct banding patterns of salivary gland polytene chromosomes as well as heterochromatin differences in mitotic karyotypes. The five species found in Thailand (A-D, F) exhibit distinct geographic distributions. Species A is widespread throughout Thailand except in the south. Species B had been found in sympatry with species C in southern Thailand and both seem to show north-south clinal geographic variation. Species D is common on the west side of southern Thailand and along the Thai-Burmese border in sympatry with species A. Species F, An. nemophilous Peyton and Ramalingam, has been found in a population at the Thai-Malaysian border in this study although it was known to be common in southern and western Thailand and Peninsular Malaysia. Species E is known only from western India. The five species found in Thailand also exhibit seasonal variation in relative abundance and different nocturnal biting cycles. Chromosomal polymorphisms have been observed in mitotic and polytene chromosomes of An. dirus A and D. Species B and C also show heterochromatin variation in the sex chromosomes, but are monomorphic for the standard sequence in polytene chromosomes. These biological characteristics of the An. dirus complex may have implications for understanding the epidemiology of malaria in Southeast Asia. Recent cytogenetic studies of wild-caught samples of An. leucosphyrus from Sumatra, Kalimantan and southern Thailand have revealed the presence of two distinct species within this taxon. Species A is widely distributed in southern Thailand, East Malaysia and Kalimantan, while species B is confined to Sumatra. The two isomorphic species are vectors of human malaria within their range of distribution.(ABSTRACT TRUNCATED AT 400 WORDS)     

斯氏按蚊血淋巴前酚氧化酶差异表达与疟原虫卵囊黑化关系的研究

目的　探讨斯氏按蚊血淋巴前酚氧化酶与疟原虫卵囊黑化的相互关系。方法　斯氏按蚊分吸糖水组、吸正常小白鼠血组、吸约氏疟原虫感染血组和吸硝喹糖水组 ,挤压法收集雌斯氏按蚊血淋巴 ,解剖后取吸硝喹糖水蚊第 1、2和 3天斯氏按蚊中肠 ,超声提取中肠蛋白 ,Bradford法检测血淋巴总蛋白浓度 ,继而对血淋巴和中肠蛋白进行SDS -PAGE ,Western印迹电转移后检测前酚氧化酶。结果　四组血淋巴前酚氧化酶和用药后中肠前酚氧化酶均呈现一条阳性蛋白带 ,分子量分别均约 6 6kDa,与吸糖水组比较 ,吸正常小白鼠血组血淋巴前酚氧化酶表达增强 ,而感染后血淋巴前酚氧化酶表显著增强。硝喹诱导黑化后血淋巴前酚氧化酶表达水平呈逐日下调趋势 ,而硝喹诱导黑化过程中中肠前酚氧化酶量逐渐增加。结论　斯氏按蚊血淋巴前酚氧化酶参与疟原虫卵囊黑化反应。     

斯氏按蚊配子体激活因子活性变化与产卵的关系

目的探讨斯氏按蚊唾液腺中疟原虫配子体激活因子的变化趋势与蚊卵发育及产出的关系。方法应用体外雄配子体出丝观察方法检测雌性斯氏按蚊唾液腺抽提物及卵巢匀浆上清中配子体激活因子对伯氏疟原虫雄配子体出丝诱导活性的动态变化;分别采用聚丙烯酰胺凝胶电泳和Bradford蛋白分析法检测两器官蛋白成分或含量的变化。结果吸血后按蚊唾液腺抽提物的出丝诱导活性显著下降,未产卵组和产卵组按蚊的活性分别于吸血后第8日和第4日恢复到吸血前水平;卵巢匀浆上清的诱导活性亦在吸血后下降,吸血后第2日显著升高,未产卵组保持该活性水平至吸血后第8日,产卵组诱导活性于吸血后第4日(产卵翌日)回落。两组按蚊唾液腺蛋白组成未见明显区别;吸血后第2日,卵巢的蛋白含量达到峰值,未产卵组按蚊卵巢蛋白含量维持在高水平直至吸血后第6日,而产卵组按蚊卵巢蛋白含量在吸血后第4日则恢复到吸血前的水平。结论按蚊唾液腺中配子体激活因子的消长与雌蚊体内蚊卵的发育、成熟及产出之间存在某种内在的生理联系。     

2020—2021年焦作市传疟媒介种群及密度监测结果分析

目的 了解焦作市消除疟疾后传疟媒介种群及密度情况,为消除疟疾后传疟媒介的控制和输入性疟疾再传播风险评估提供科学依据。方法 2020—2021年选择焦作市共7个县（市、区）作为传疟媒介监测点,使用诱蚊灯法及人帐诱法开展种群及密度监测,挑选大中型水体环境共20处,采用勺捕法开展蚊虫孳生地调查。结果 7个县（市、区）中除解放区外均捕获有中华按蚊。2020年媒介种群监测共捕获蚊虫8 116只,其中中华按蚊构成比为21.76%,修武县捕获中华按蚊数量最多（1 262只）,沁阳市捕获中华按蚊构成比最高（40.39%）;室内环境中中华按蚊数量多,而室外环境中中华按蚊构成比高;密度监测共捕捉蚊虫802只,平均密度为30.55只/人·小时,其中中华按蚊136只,平均密度为5.18只/人·小时;在稻田环境中捕获按蚊孑孓126条,其余水体未发现。2021年种群监测捕捉蚊虫10 852只,中华按蚊构成比为1.67%,修武县捕获中华按蚊数量最多（179只）,构成比最高（1.99%）;室内环境捕获中华按蚊数量及构成比均高于室外环境;密度监测共捕获蚊虫3 662只,平均密度为130.79只/人·小时,其中中华按蚊1...     

江苏省消除疟疾阶段媒介监测结果分析

目的 分析江苏省消除疟疾阶段媒介监测结果,为输入性疟疾在本地传播的风险评估和消除疟疾后监测提供科学依据。方法 2011-2017年每年6-10月,在江苏省媒介按蚊监测点采用半通宵人饵诱捕法、室外全通宵诱蚊灯法诱捕按蚊,进行按蚊种群和密度监测;采用WHO推荐的强迫接触筒法进行杀虫剂抗性监测。结果 2011-2017年,在江苏省7个媒介按蚊监测点采用半通宵人饵诱捕法共捕获中华按蚊5 106只,年均叮人率分别为1.075、0.786、1.057、0.787、0.790、1.797只/（人·h）和1.185只/（人·h）;采用室外全通宵诱蚊灯法共捕获中华按蚊28 186只,年均灯诱密度分别为57.950、50.932、14.800、4.405、58.070、72.406只/（灯·夜）和17.145只/（灯·夜）。2012年中华按蚊对溴氰菊酯、DDT和马拉硫磷的敏感性、抗性指数均为R级。结论 江苏省传疟媒介主要为中华按蚊,未发现嗜人按蚊;部分疟疾流行区中华按蚊已对溴氰菊酯、DDT和马拉硫磷产生高度抗性。