Detection and anatomical localization of Plasmodium falciparum circumsporozoite protein and sporozoites in the afrotropical malaria vector Anopheles gambiae s.l

Salivary glands from Anopheles gambiae s.l. collected in Burkina Faso, West Africa, were analyzed by both microscopic examination and immunoradiometric assay to determine the Plasmodium falciparum sporozoite rates. Using the same mosquito samples, the immunoassay revealed positive salivary glands with low sporozoite loads, which were frequently missed by microscopy. A closer agreement between both techniques was found using salivary glands with high sporozoite loads. We also found a number of mosquitoes with uninfected salivary glands which harbored the circumsporozoite antigen in their thoraces. In a particular village these mosquitoes represented 43.5% of all sporozoite antigen carrying specimens.     

发作期与间歇期间日疟原虫在不同按蚊体内发育差异的研究

目的  比较临床发作期与间歇期间日疟原虫在中华按蚊和嗜人按蚊体内发育的差异。方法在我国间日疟流行区分别采集临床发作期与间歇期间日疟病例的血样，采用体外人工膜饲感染系统在实验室同时体外人工感染中华按蚊和嗜人按蚊，在感染后7～9 d和14 d分别解剖蚊胃和唾液腺，并检测蚊体内的卵囊和子孢子数。结果临床发作期间日疟原虫感染中华按蚊的卵囊阳性率和阳性蚊比率、子孢子阳性蚊比率和感染度均低于间歇期间日疟原虫感染，临床发作期间日疟原虫感染嗜人按蚊的子孢子阳性率、阳性蚊比率和卵囊阳性蚊比率均低于间歇期间日疟原虫感染，而子孢子感染度则高于间歇期疟原虫感染。结论临床发作期与间歇期间日疟原虫体外人工感染中华按蚊、嗜人按蚊卵囊和子孢子有差异     

Population biology and antimalarial resistance: The transmission of antimalarial drug resistance in Plasmodium falciparum

Malaria morbidity and mortality continue to increase across sub-Saharan Africa. This is largely as a result of the continued use of chloroquine and sulfadoxine-pyrimethamine, despite widespread resistance. Although eliminating the asexual stages of Plasmodium falciparum is the focus of treatment of individual symptomatic patients, at a population level, reducing the carriage of gametocytes - the sexual stage responsible for infection of the mosquito vector - is necessary to limit the transmission of malaria parasites and the spread of antimalarial resistance. The probability of a mosquito being infected depends on the prevalence, duration and density of viable gametocyte carriage in the human host, although additional humoral and leukocyte factors also affect transmissibility. There is a log-sigmoid relationship between gametocyte density in the patients' blood and infectivity to the mosquito. The infectivity and thus transmission potential associated with a particular antimalarial treatment can be characterised as a function of blood gametocyte density and time, summing these over the acute and all subsequent recrudescences of that infection. Gametocyte carriage and infectivity to mosquitoes is consistently higher in patients infected with drug resistant compared with drug sensitive malaria parasites. It is the ratio of transmission potential in drug resistant versus sensitive infections that drives the spread of resistance. Early access to highly effective antimalarial treatment reduces the risk of disease progression and limits gametocyte carriage. The remarkable spread of sulfadoxine-pyrimethamine (SP) resistance across vast regions results from the very high post-treatment prevalence and density of gametocyte carriage following SP treatment. In areas of low intensity malaria transmission, the gametocyte-reducing effect of widespread use of artemisinin-based combination therapy has resulted in a sustained decrease in malaria transmission and a decrease in the spread of resistance. Malaria treatment policy should be based primarily on therapeutic efficacy against asexual stages, but should also consider transmission reduction potential. Artemisinin-based combination therapies are the only antimalarials currently available which rapidly reduce both asexual and gametocyte stages of the P. falciparum lifecycle.     

Malaria vector incrimination in three rural riverine villages in the Brazilian Amazon

Vector incrimination studies were conducted from April 2003 to February 2005 at three riverine villages 1.5 km to 7.0 km apart, along the Matapi River, Amapa State, Brazil. A total of 113,117 mosquitoes were collected and placed in pools of 相似文献   

Insecticide treated nets: impact on vector populations and relevance of initial intensity of transmission and pyrethroid resistance

Insecticide treated bednets locate a deposit of a quick-acting insecticide of low human toxicity between a sleeper and host-seeking mosquitoes. Thus a chemical barrier is added to the often incomplete physical barrier provided by the net. Treated nets may be considered as mosquito traps baited by the odour of the sleeper. Trials in Assam, Tanzania and elsewhere have shown that when a whole community is provided with treated nets, so many mosquitoes of anthropophilic species are killed by contact with the nets that the density and/or sporozoite rate of the vector population is reduced. In order to gain this "mass" or community effect, in addition to widespread personal protection, and thus to achieve the full potential of the treated net method, a high per cent coverage of the community is needed. This suggests that organised free provision of treated nets, comparable to a house spraying programme, is likely to be more cost-effective than trying to market nets and insecticide to very poor rural people. In areas with high malaria transmission, where acquisition of immunity to malaria is very important, it has been argued that vector control (without vector eradication) could, in the long run, make the situation worse by preventing the normal build-up of immunity. However, our data from Tanzania do not support this idea--3-4 years after provision of nets (which are re-treated annually) young children are still showing clear health benefits; older children are not "paying" for this by showing worse impact of malaria. There is less malaria morbidity in a highland area where malaria transmission is about 15x less intense than in a nearby lowland area. The per cent impact of treated nets malaria morbidity in both area was very similar. At present only pyrethroids are used for net treatment which suggested that emergence of pyrethroid resistance would have a disastrous effect. However, in West Africa, where there is now a high frequency of the kdr resistance gene in Anopheles gambiae, it is reported that treated nets continue to have a powerful impact on vector populations. In Tanzania, pyrethroid resistance has not been detected in malaria vectors, but it has emerged in bedbugs after seven years use of treated nets.     

云南湄公河流域上游河谷地区疟疾媒介传疟作用研究

目的通过观察蚊媒季节消长、嗜血习性、叮咬行为和疟疾子孢子率以研究出它们在云南湄公河上游河谷地带传疟作用的关系. 方法村内采取诱蚊灯和人工诱捕方法捕蚊;现场采取显微镜解剖蚊虫的方法观察唾腺子孢子,实验室采用ELISA技术检测蚊虫体内环子孢子蛋白(CSP). 结果村内共捕获16种按蚊.现场显微镜解剖7种按蚊,1 010只经产蚊中,发现了7只唾液腺感染子孢子;ELISA方法检测现场捕回的8种按蚊,5 154只各龄期蚊中,发现11只环子孢子蛋白阳性蚊.微小按蚊、中华按蚊、多斑按蚊子孢子阳性率(包括ELISA环子孢子蛋白阳性和镜检唾腺子孢子感染蚊)分别是0.37%、0.22%、0.32%, 昆虫接种率分别估算为9.82、3.97、2.69.这些蚊媒叮咬活动起始于黄昏,并整夜有活动,但微小按蚊夜间活动高峰出现于子夜,中华按蚊和多斑按蚊的高峰则在2100之前.它们的人血指数都在80%以上. 结论以上结果显示微小按蚊、中华按蚊和多斑按蚊是湄公河上游河谷地带的重要传疟媒介.     

Trial of pyrethroid impregnated bednets in an area of Tanzania holoendemic for malaria. Part 2. Effects on the malaria vector population.

The malaria vector population consisted mainly of Anopheles gambiae s.s. with a small contribution from An. funestus and An. rivulorum. The mosquitoes coming to bite in bedrooms were monitored with light traps set beside untreated bednets. When impregnated bednets were provided for all the other beds in a village the Anopheles populations declined but the Culex quinquefasciatus populations were unaffected. The survival of An. gambiae (as measured by the mean number of ovarian dilatations) and the sporozoite rate declined following introduction of the nets and the estimated sporozoite inoculation rates into people not under their nets declined by more than 90%. The net introductions caused sharp declines in the number of mosquitoes resting indoors, but the evidence was inconclusive regarding diversion to outdoor resting, animal biting, earlier biting or outdoor biting. DDT spraying greatly reduced the Anopheles populations.     

双氢青蒿对约氏疟原虫在蚊体内发育的影响

目的：观察双氢青蒿素（dihydroqinghaosu，DQHS）对约氏疟原虫在斯氏按蚊体内发育的影响。方法：受染疟原虫小鼠一次性经口灌喂不同浓度DQHS药液后，供蚊虫吸血，应用光镜和电镜观察对照组和用药组的疟原虫在蚊体内的发育情况。结果：DQHS对疟原虫配子体有一定的抑制作用，其作用强度与配子体成熟程度和用药剂量不同有关。未成熟配子体对药物较敏感；随着药物剂量的增加，卵囊和子孢子的阳性率和密度随之逐渐下降；但180mg或240mg／kg用药组对子孢子密度的影响的差别无显著性意义。电镜观察60mg／kg作用16h后，用药组的蚊胃上卵囊（12d－13d解剖蚊），出现膜受损，甚至胞质空泡化。120mg／kg药量对蚊体内3日龄卵囊作用16h，卵囊仍继续发育，比较对照组和用药组的卵囊和子孢子密度, 两组间差别无显著意义(P > 0. 05) ; 两组卵囊超微结构形态亦无明显差异。结论: DQHS 影响约氏疟原虫配子体感染性而减少蚊媒传播, 但对蚊体内子孢子增殖期不起直接的抑制作用。     

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。     

Plasmodium coatneyi: observations on periodicity, mosquito infection, and transmission to Macaca mulatta monkeys.

Plasmodium coatneyi has adapted well to experimental studies with Macaca mulatta monkeys and Anopheles dirus mosquitoes. Studies were made to determine 1) the course of asexual parasitemia, 2) periods when infective gametocytes were produced, 3) the laboratory-reared mosquitoes susceptible to infection, 4) the mosquito most capable of transmitting the infection to monkeys via bite, 5) the pattern of recrudescence, and 6) the prepatent periods following the bites of infected An. dirus mosquitoes. The period when infective gametocytes are produced is concentrated primarily in the first week when parasitemia exceeds 1,000/microl. Mosquitoes were more heavily infected on days when the asexual parasite counts were highest. Gametocyte counts were generally low. Mature forms of the parasite markedly sequestered giving a pattern of high-low periodicity. Anopheles dirus and An. freeborni mosquitoes were nearly equal in terms of their ability to support oocyst development. Other species (An. stephensi, An. maculatus, and An. gambiae.) were less supportive. High sporozoite densities in the salivary glands were frequently produced in An. dirus and sporozoite transmission was obtained via the bites of these mosquitoes after 12-18 days of extrinsic incubation. Prepatent periods ranged from 10 to 15 days. The presence of frequent parasitic recrudescences suggests mechanisms similar to that seen in human infections with P. falciparum. It is proposed that P. coatneyi in M. mulatta monkeys can be a suitable model for studies on cerebral pathology, vaccine efficacy, and the testing of antimalarial drugs.     

Transmission-blocking activity of tafenoquine (WR-238605) and artelinic acid against naturally circulating strains of Plasmodium vivax in Thailand

The sporontocidal activity of tafenoquine (WR-238605) and artelinic acid was determined against naturally circulating isolates of Plasmodium vivax in western Thailand. Primaquine was used as a negative control and a dihydroacridine-dione (WR-250547) was used as a positive control. Laboratory-reared Anopheles dirus mosquitoes were infected with P. vivax by allowing mosquitoes to feed on blood (placed in an artificial-membrane feeding apparatus) collected from gametocytemic volunteers reporting to local malaria clinics in Tak province, Thailand. Four days post-infection, mosquitoes were refed on uninfected mice treated 90 minutes earlier with a given drug. Drug activity was determined by assessing oocyst and sporozoite development. Neither primaquine nor artelinic acid affected oocyst or sporozoite development at a dose of 100 mg of base drug/kg of mouse body weight. In contrast, tafenoquine and WR-250547 affected sporogonic development at doses as low as 25.0 and 0.39 mg/kg, respectively. The potential role of these compounds in the prevention of malaria transmission is discussed, as are alternative strategies for the use of transmission-blocking antimalarial drugs.     

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...     

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.     

传疟按蚊抗药性研究进展

我国卫生部于2010年5月印发《中国消除疟疾行动计划（2010-2020年）》,提出在2020年,将全面彻底消除疟疾.控制及消除疟疾的关键在于传播媒介的控制,而按蚊为疟疾主要传播媒介,传疟媒介对杀虫剂的抗药性直接导致了疟疾发病的死灰复燃.为了全面了解疟疾蚊媒的抗药性现状和产生机制,该文对国内外传疟按蚊抗药性现状、产生机制和检测方法进行综述.     

Potential vectors of malaria and their different susceptibility to Plasmodium falciparum and Plasmodium vivax in northern Brazil identified by immunoassay

During the period from May 1983 to July 1985 we conducted an epidemiological study to determine potential vectors of malaria in 6 districts in the state of Pará in northern Brazil. The examination of random human blood smears, prepared at the time of mosquito capture, indicated overall human infection rates of 16.7% and 10.9% for Plasmodium falciparum and P. vivax, respectively. Two immunoassays, the immunoradiometric assay (IRMA) and the enzyme-linked immunosorbent assay (ELISA), based on the use of species-specific antisporozoite monoclonal antibodies, were used to analyze a total of 9,040 field-collected Anopheles mosquitoes for plasmodial infection. P. falciparum sporozoite antigen was detected in A. darlingi at rates varying from 2.7% to 4.2%, and in small numbers of A. oswaldoi collected in 1 of the districts. In contrast, sporozoite antigen of P. vivax was found in A. darlingi, A. triannulatus, A. nuneztovari, and A. albitarsis at rates ranging from 0.9% to 12.0%. By dissection, sporozoites were found in the salivary glands of these same 4 species at rates ranging from 0.8% to 2.2%. The latter 3 species had not previously been implicated as malaria vectors of any significance in northern Brazil.     

不同密度间日疟原虫对中华按蚊的感染性观察

目的观察不同密度间日疟原虫对中华按蚊的感染性。方法：对蚊传人工感染滇南间日疟原虫的３８例志愿者，于原虫出现日及各次临床发作时抽取病人静脉血，用离体吸血法感染中华按蚊，以显微镜下在蚊胃壁查见卵囊为感染阳性。结果：虫现期原虫不能使按蚊获得感染。原虫密度高于１００／μｌ以上的初发病例，对按蚊的感染率和感染程度随病程的延长和原虫密度的增高而上升；复发期间日疟原虫对按蚊的感染率和感染程度远远高于初发病例，其原虫密度只要在１／μｌ以上即可使按蚊获得感染；原虫密度大于１０００／μｌ的初发病例和大于１００／μｌ的各组复发病例均能使按蚊获得较高的感染率、蚊胃阳性率及卵囊指数。结论：间日疟临床发作期是传播疟疾最危险的时期，复发病例是疟疾扩散过程中危险性较大的传染源；选择实验感染病例时，初发病例以虫数高于１０００／μｌ、复发病例高于１００／μｌ者为佳。     

Unexpected anthropophily in the potential secondary malaria vectors Anopheles coustani s.l. and Anopheles squamosus in Macha, Zambia

Anopheles coustani s.l. and Anopheles squamosus are sub-Saharan mosquito species that have been implicated in malaria transmission. Although generally believed to be of negligible importance due to their overwhelmingly zoophilic behavior, An. coustani s.l. and An. squamosus made up a large proportion of the anophelines collected by human landing catches during the 2007-2008 and 2008-2009 rainy seasons in Macha, Zambia. Further, polymerase chain reaction-based blood meal identification showed that the majority of blood meals from these mosquito species caught in human-baited Centers for Disease Control light traps were from human hosts. Although no An. coustani s.l. or An. squamosus were found to be positive for Plasmodium, the demonstrated anthropophilic tendencies of these mosquitoes in southern Zambia suggest their potential as secondary malaria vectors.     

Application of a biochemical key to study transmission of malaria and Bancroftian filariasis in sibling species of the Anopheles gambiae complex in north-eastern Tanzania

A biochemical key was applied in order to study transmission of malaria and Bancroftian filariasis in Anopheles gambiae sensu stricto, An. arabiensis and An. merus in different localities in north-eastern Tanzania. The technique was found to be a useful additional taxonomic tool for field entomologists. Significant differences between species in the rate of infection with Bancroftian filariasis were obtained between An. gambiae s.s. and An. funestus (P less than 0.005) and between An. funestus and An. arabiensis (P less than 0.0001). There were also significant differences between most of the investigated localities in the rate of filarial infection. However, there were no significant differences between the three species or between localities with respect to malaria sporozoite rates. Possible reasons for the observed variation between species and localities with respect to vectorial activity for Bancroftian filariasis are discussed.     

Infectiousness of the Human Population to Anopheles arabiensis by Direct Skin Feeding in an Area Hypoendemic for Malaria in Senegal

Direct skin feeding experiments are sensitive assays to determine human infectiousness to mosquitoes but are rarely used in malaria epidemiological surveys. We determined the infectiousness of inhabitants of a malaria hypoendemic area in Senegal. Gametocyte prevalence by microscopy was 13.5% (26 of 192). Of all individuals who were gametocyte positive, 44.4% (11 of 25) infected ≥ 1 Anopheles arabiensis mosquito and 10.8% (54 of 500) of mosquitoes became infected. Of all individuals who were gametocyte negative by microscopy, 4.3% (7 of 162) infected ≥ 1 mosquito and 0.4% (12 of 3240) of mosquitoes became infected. The 18.2% (12 of 66) of all mosquito infections was a result of submicroscopic gametocyte carriage and two individuals without asexual parasites or gametocytes by microscopy were infectious to mosquitoes. When infectivity and local demography was taken into account, children 5–14 years of age contributed 50.8% of the human infectious reservoir for malaria. Adults and submicroscopic gametocyte carriers may contribute considerably to onward malaria transmission in our setting.     

巢氏PCR判定西藏疟疾流行区传疟媒介

目的确定西藏墨脱县疟疾流行区的疟疾传播媒介。方法根据2005、2006和2007年疟疾发病情况,在墨脱县选择了3个疟疾发病较高的自然村,采用人诱、牛诱、灯诱及清晨人房全捕等方法捕获成蚊,经形态学鉴定后麻醉处死,密封干燥,带回实验室-20℃冻存备用,采用混合样本法随机抽取10只多斑按蚊复合体为一份混合标本,提取蚊虫DNA。根据文献采用巢氏PCR扩增疟原虫小亚单位核糖体脱氧核糖核酸(SSUrDNA),并对阳性结果克隆测序,比对证实。结果共捕获按蚊5345只,其中多斑按蚊复合体5190只,带足按蚊155只,提取的360份多斑按蚊复合体混合样本DNA中发现子孢子阳性扩增样品2份,种型鉴定2份阳性混合样本均为伪威氏按蚊,PCR产物经克隆测序,NCBIBLAST同源性比对证实为疟原虫SSurDNA基因片段。结论多斑按蚊复合体中的伪威氏按蚊为西藏林芝疟疾流行区的传疟媒介。