形形色色的灭蚊术

生物灭蚊就是利用动植物和微生物灭蚊。动物中的蛙蟾、柳条鱼、蜘蛛、蝙蝠等都是灭蚊的精兵骁将。如一只蝙蝠一昼夜可捕食蚊子250—300只,一条柳条鱼一昼夜可捕食孑孓达500余条。有些热带植物如澳大利亚的一种淡黄色食蚊蘑菇,它的冠部表面会分泌一种带粘液的有气味的液体,30米内的蚊子闻到气味后,就会飞扑过去,被粘住而被液体消化掉。近年来,国内外科学家研究发现,球形芽胞杆菌、灭蚊链球菌、白僵菌、苏云金杆菌、绿僵菌等多种微生     

简讯

苏云金杆菌以色列变种灭蚊幼虫的室内毒效测定及现场效果观察长期使用滴滴涕灭蚊,使蚊子产生了抗药性,不但未能消灭蚊虫,反而污染了环境,杀灭了一些蚊虫的天敌,致使蚊子大量孳生。对此,我们于1982—1984年采用     

黄鳝摄食蚊幼虫的研究

蚊虫是疟疾、丝虫病、流行性乙型脑炎和登革炎传播媒介,消灭蚊子有助于减少人类疾病的传染。然而 ,长期的化学药物防治使蚊虫产生抗药性 ,而且污染环境2-4 ,因此有人进行生物防治的研究和应用,但国内外未见利用黄鳝灭蚊幼的报道。进行黄鳝摄食蚊幼虫的研究5-10 ,可为生物灭蚊的研究提出一条新的思路 ,并积累基础资料。       

稀有鮈鲫对库蚊幼虫摄食量的研究

利用某些鱼类的摄食来控制蚊子数量,是预防以蚊为传播媒介的疾病之重要途径。迄今为止,对以(Gambusia affinis Baird et Girard)为代表的灭蚊鱼类的研究已深入到“鱼—蚊—稻田”生物控制系统阶段,并且在许多地区已成功地应用了几十年,但在我国对灭蚊鱼方面的研究尚不多。       

介绍一个课外小组活动内客——测试诱蚊缸的效果

一、活动目的进一步了解蚊子的产卵习性,从而运用到除四害中去,提高灭蚊的效果;并能启发青少年自己设计实验方法的思路。     

吞食孑孓的黄颡鱼

一.引言蚊子对人们的危害,大家都是不言而喻的。它不仅吸人们的血,而且还给人类带来可怕的疾病。那应如何消灭蚊子呢?消灭蚊子的方法一般不外乎用化学药剂“DDT”、“666”等,另外用人工捕杀及填塞污水沟等等也可从防止蚊子的繁殖。但这些方法在实际应用上有某些限制,并且也是不够经济的。如蚊子幼虫     

通过基因工程开发灭蚊毒素

通过基因工程开发灭蚊毒素Ｌｉｕ等通过基因工程技术在革兰氏阴性菌Ａｓｔｉｃｃａｃａｕｌｉｓｅｘｃｅｎｔｒｉｃｕｓ中产生了原来由Ｂ．ｓｐｈａｅｒｉｃｕｓ产生的能杀死蚊子幼虫的毒素（ＮａｔＢｉｏｔｅｃｈｎｏｌ１９９６,１４,３４３—４７）。浮选鉴定法表明,...     

蚊子嗅觉系统的最新研究进展

由于蚊子传播疟疾、登革热、黄热病等多种疾病,严重威胁着人类的健康及生活.现有的化学防治手段不但效果不理想,而且导致蚊子抗性增强,环境污染,并危害到其它生物种群.蚊子的行为很大程度上依赖于它们的嗅觉系统,因而根据蚊子的嗅觉系统的研究来利用化学生态手段去防治蚊子成了近期的研究热点.这一方法不但对环境更加友好,而且对蚊子专一性强,避免伤害其它生物.本文根据近期关于蚊子嗅觉系统的研究,尤其针对蚊子气味结合蛋白(odorant binding protein,OBP)、气味受体(odorant receptor,OR)蛋白和驱蚊胺(DEET)的最新研究结果进行了综述.     

球形芽孢杆菌的发酵试验

一些球形芽孢杆菌因能杀灭蚊子幼虫而受到重视,目前已分离出30多个有效菌株。1981年我们首次从国内分离到一株有高度灭蚊效果的球形芽孢杆菌。但目前这类菌还没有进行大规模工业化生产,也没有通用的商品     

孑孓灵制剂的灭蚊效果

蚊虫是传染疟疾、丝虫病、脑炎等疾病的媒介,是人类的大敌。化学杀虫剂灭蚊虽有显著效果,但对环境的污染,以及蚊虫产生抗药性等已成为较突出的问题。近几年来,国内外利用微生物方法灭蚊的研究进展迅速,我国已筛     

Avian malaria: a new lease of life for an old experimental model to study the evolutionary ecology of Plasmodium

Avian malaria has historically played an important role as a model in the study of human malaria, being a stimulus for the development of medical parasitology. Avian malaria has recently come back to the research scene as a unique animal model to understand the ecology and evolution of the disease, both in the field and in the laboratory. Avian malaria is highly prevalent in birds and mosquitoes around the world and is amenable to laboratory experimentation at each stage of the parasite''s life cycle. Here, we take stock of 5 years of experimental laboratory research carried out using Plasmodium relictum SGS1, the most prevalent avian malaria lineage in Europe, and its natural vector, the mosquito Culex pipiens. For this purpose, we compile and analyse data obtained in our laboratory in 14 different experiments. We provide statistical relationships between different infection-related parameters, including parasitaemia, gametocytaemia, host morbidity (anaemia) and transmission rates to mosquitoes. This analysis provides a wide-ranging picture of the within-host and between-host parameters that may bear on malaria transmission and epidemiology.     

Transgenic mosquitoes and malaria transmission

As the malaria burden persists in most parts of the developing world, the concept of implementation of new strategies such as the use of genetically modified mosquitoes to control the disease continues to gain support. In Africa, which suffers most from malaria, mosquito vector populations are spread almost throughout the entire continent, and the parasite reservoir is big and continuously increasing. Moreover, malaria is transmitted by many species of anophelines with specific seasonal and geographical patterns. Therefore, a well designed, evolutionarily robust and publicly accepted plan aiming at population reduction or replacement is required. The task is twofold: to engineer mosquitoes with a genetic trait that confers resistance to malaria or causes population suppression; and, to drive the new trait through field populations. This review examines these two issues, and describes the groundwork that has been done towards understanding of the complex relation between the parasite and its vector.     

The multifaceted mosquito anti-Plasmodium response

Plasmodium development within its mosquito vector is an essential step in malaria transmission, as illustrated in world regions where malaria was successfully eradicated via vector control. The innate immune system of most mosquitoes is able to completely clear a Plasmodium infection, preventing parasite transmission to humans. Understanding the biological basis of this phenomenon is expected to inspire new strategies to curb malaria incidence in countries where vector control via insecticides is unpractical, or inefficient because insecticide resistance genes have spread across mosquito populations. Several aspects of mosquito biology that condition the success of the parasite in colonizing its vector begin to be understood at the molecular level, and a wealth of recently published data highlights the multifaceted nature of the mosquito response against parasite invasion. In this brief review, we attempt to provide an integrated view of the challenges faced by the parasite to successfully invade its mosquito host, and discuss the possible intervention strategies that could exploit this knowledge for the fight against human malaria.     

Hemolytic C-type lectin CEL-III from sea cucumber expressed in transgenic mosquitoes impairs malaria parasite development

The midgut environment of anopheline mosquitoes plays an important role in the development of the malaria parasite. Using genetic manipulation of anopheline mosquitoes to change the environment in the mosquito midgut may inhibit development of the malaria parasite, thus blocking malaria transmission. Here we generate transgenic Anopheles stephensi mosquitoes that express the C-type lectin CEL-III from the sea cucumber, Cucumaria echinata, in a midgut-specific manner. CEL-III has strong and rapid hemolytic activity toward human and rat erythrocytes in the presence of serum. Importantly, CEL-III binds to ookinetes, leading to strong inhibition of ookinete formation in vitro with an IC(50) of 15 nM. Thus, CEL-III exhibits not only hemolytic activity but also cytotoxicity toward ookinetes. In these transgenic mosquitoes, sporogonic development of Plasmodium berghei is severely impaired. Moderate, but significant inhibition was found against Plasmodium falciparum. To our knowledge, this is the first demonstration of stably engineered anophelines that affect the Plasmodium transmission dynamics of human malaria. Although our laboratory-based research does not have immediate applications to block natural malaria transmission, these findings have significant implications for the generation of refractory mosquitoes to all species of human Plasmodium and elucidation of mosquito-parasite interactions.     

The Dutch school of malaria research

An epidemic of tertian malaria in some coastal areas of The Netherlands resulted in the setting up of official measures in 1920. A scientific and a propaganda commission were charged with control. Efforts were made to reduce mosquito populations by adult and larval spraying. After the discovery that infected mosquitoes were to be found only inside houses, control operations were focussed against adult mosquitoes. Some later discoveries resulted in a more effective control. a) Spraying ditches with Paris green did not prevent adult mosquitoes from entering the control area. b) Anopheles maculipennis turned out to be a complex of species, with A. atroparvus as the vector. The latter preferred brackish water and did not go into full hibernation. The closing of the Zuyder Sea and the expected desalinization gave hope for less suitable conditions for the vector. c) Plasmodium vivax normally had an incubation period of 8 months. d) Pyrethrum was an effective but short-lasting insecticide. e) Healthy parasite carriers could infect mosquitoes. This knowledge was applied through an extensive system of investigation, including spleen examination of schoolchildren. Suspected houses were sprayed bimonthly from August to November, during which period infected mosquitoes were likely to be present. This system worked extremely well, and during the next epidemic from 1943 to 1947 the thus treated towns remained virtually free of malaria! DDT became available and was either sprayed in suspected houses as before, or through wide-spread coverage of all houses. The epidemic subsided whatever method employed and not only due to the use of DDT. The number of cases even went down to the point of no return and the last case of Dutch malaria was recorded in 1959. The wealth of experience on house-spray control, parasite and mosquito biology and experimental malaria of the Dutch malariologists has had its impact on the international bodies engaged in the battle against malaria.     

Synthetic propeptide inhibits mosquito midgut chitinase and blocks sporogonic development of malaria parasite

Incessant transmission of the parasite by mosquitoes makes most attempts to control malaria fail. Blocking of parasite transmission by mosquitoes therefore is a rational strategy to combat the disease. Upon ingestion of blood meal mosquitoes secrete chitinase into the midgut. This mosquito chitinase is a zymogen which is activated by the removal of a propeptide from the N-terminal. Since the midgut peritrophic matrix acts as a physical barrier, the activated chitinase is likely to contribute to the further development of the malaria parasite in the mosquito. Earlier it has been shown that inhibiting chitinase activity in the mosquito midgut blocked sporogonic development of the malaria parasite. Since synthetic propeptides of several zymogens have been found to be potent inhibitors of their respective enzymes, we tested propeptide of mosquito midgut chitinase as an inhibitor and found that the propeptide almost completely inhibited the recombinant or purified native Anopheles gambiae chitinase. We also examined the effect of the inhibitory peptide on malaria parasite development. The result showed that the synthetic propeptide blocked the development of human malaria parasite Plasmodium falciparum in the African malaria vector An. gambiae and avian malaria parasite Plasmodium gallinaceum in Aedes aegypti mosquitoes. This study implies that the expression of inhibitory mosquito midgut chitinase propeptide in response to blood meal may alter the mosquito's vectorial capacity. This may lead to developing novel strategies for controlling the spread of malaria.     

Dynamics of malaria transmission model with sterile mosquitoes

In this paper, a malaria transmission model with sterile mosquitoes is considered. We first formulate a simple SEIR malaria transmission model as our baseline model. Then sterile mosquitoes are introduced into the baseline model. We consider the case that the release rate of sterile mosquitoes is proportional to the wild mosquito population size. To investigate the impact of releasing sterile mosquitoes on the malaria transmission, the dynamics of the baseline model and the models with the sterile mosquitoes are discussed. We derive formulas of the reproductive numbers and explore the existence of endemic equilibrium as the reproductive number is more than unity for these models. It is shown that both the baseline model and the models with the sterile mosquitoes undergo backward bifurcations. Based on theoretical analysis and numerical simulation, we investigate the impact of releasing sterile mosquitoes on malaria transmission.     

The role of Pvs28 in sporozoite development in Anopheles sinensis and its longevity in BALB/c mice

To develop a vivax malaria vaccine for blocking malarial transmission, the ookinete surface protein Pvs28 was cloned from Korean malaria patients using polymerase chain reaction. The Pvs28 gene consists of 726 bp and encodes 241 amino acids. It was subcloned into the expression vector pQE30 and expressed in Escherichia coli. The expressed recombinant protein, rPvs28, has a molecular weight of about 28 kDa in SDS–PAGE analysis. A monoclonal antibody against rPvs28 was produced using BALB/c mice. It inhibited sporozoite development in Anopheles sinensis mosquitoes (n = 81) which is one of the malaria vectors in Korea, with relatively high antibody titer against rPv28 persisting for more than 6 months. These results indicate that rPvs28 induces an immune response in mice that effectively blocks sporozoite development in mosquitoes. Therefore it could be a vaccine candidate for preventing vivax malaria in Korea.     

The effect of Plasmodium yoelii nigeriensis infection on the feeding persistence of Anopheles stephensi Liston throughout the sporogonic cycle.

Vector-borne parasites such as malaria have been shown to modify the feeding behaviour of their invertebrate hosts so as to increase the probability of transmission. However, evolutionary consideration of developmental changes in malaria within Anopheles mosquitoes suggests that the nature of altered feeding by mosquitoes should differ depending on the developmental stage of the parasite. We present laboratory evidence that the feeding persistence of female Anopheles stephensi towards a human host is decreased in the presence of Plasmodium yoelii nigeriensis oocysts (which cannot be transmitted), but increased when the malaria has developed into transmissible sporozoites in the salivary glands. In ten-minute trials, 33% of uninfected mosquitoes gave up their feeding attempt before the test period had ended, 53% of those harbouring oocysts had given up, but only 20% of those infected with sporozoites gave up by this time. We conclude that changes in feeding behaviour of mosquitoes mediated by parasite infection are sensitive to the developmental stage of the parasite and that these changes have important implications for malaria epidemiology.     

Insecticide-treated plastic tarpaulins for control of malaria vectors in refugee camps

Spraying of canvas tents with residual pyrethroid insecticide is an established method of malaria vector control in tented refugee camps. In recent years, plastic sheeting (polythene tarpaulins) has replaced canvas as the utilitarian shelter material for displaced populations in complex emergencies. Advances in technology enable polythene sheeting to be impregnated with pyrethroid during manufacture. The efficacy of such material against mosquitoes when erected as shelters under typical refugee camp conditions is unknown. Tests were undertaken with free-flying mosquitoes on entomological study platforms in an Afghan refugee camp to compare the insecticidal efficacy of plastic tarpaulin sprayed with deltamethrin on its inner surface (target dose 30 mg/m2), tarpaulin impregnated with deltamethrin (initially > or = 30 mg/m2) during manufacture, and a tent made from the factory impregnated tarpaulin material. Preliminary tests done in the laboratory with Anopheles stephensi Liston (Diptera: Culicidae) showed that 1-min exposure to factory-impregnated tarpaulins would give 100% mortality even after outdoor weathering in a temperate climate for 12 weeks. Outdoor platform tests with the erected materials (baited with human subjects) produced mosquito mortality rates between 86-100% for sprayed or factory-impregnated tarpaulins and tents (average approximately 40 anophelines and approximately 200 culicines/per platform/night), whereas control mortality (with untreated tarpaulin) was no more than 5%. Fewer than 20% of mosquitoes blood-fed on human subjects under either insecticide-treated or non-treated shelters. The tarpaulin shelter was a poor barrier to host-seeking mosquitoes and treatment with insecticide did not reduce the proportion blood-feeding. Even so, the deployment of insecticide-impregnated tarpaulins in refugee camps, if used by the majority of refugees, has the potential to control malaria by killing high proportions of mosquitoes and so reducing the average life expectancy of vectors (greatly reducing vectorial capacity), rather than by directly protecting refugees from mosquito bites. Mass coverage with deltamethrin-sprayed or impregnated tarpaulins or tents has strong potential for preventing malaria in displaced populations affected by conflict.