不同地理株嗜人按蚊对间日疟原虫的易感性

目的 比较我国不同地理株嗜人按蚊对间日疟原虫的易感性. 方法在我国间日疟流行区采集间日疟病例血样,采用体外人工膜饲感染系统在实验室同时体外人工感染广东、辽宁、江苏3个不同地理株的嗜人按蚊,在感染后的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 共配对感染江苏、广东和辽宁地理株嗜人按蚊35批,感染7～9 d 3种按蚊卵囊阳性率分别为68.57%、60.00%和68.57%,感染后14 d子孢子阳性率分别为22.86%、14.29%和22.86%,3种按蚊感染卵囊和子孢子差异无统计学意义(P＞0.05).在感染后7～9 d分别解剖江苏、辽宁、广东株嗜人按蚊228、235只和228只,卵囊阳性蚊比例分别为28.07%、25.11%和26.75%.在感染后14 d分别解剖江苏、辽宁、广东株嗜人按蚊150、142只和135只,子孢子阳性蚊比例分别为10.67%、8.45%和11.85%,三者间卵囊和子孢子阳性蚊比例差异均无统计学意义(P均＞0.05).江苏、广东、辽宁株嗜人按蚊子孢子感染度差异无统计学意义(P＞0.05).结论 广东、辽宁、江苏3个不同地理株嗜人按蚊均对间日疟原虫易感.     

套式PCR检测蚊体内疟原虫的研究

目的建立一种敏感、特异而快速的检测蚊体内疟原虫的方法。方法采用套式PCR方法,对人工感染间日疟原虫的嗜人按蚊、感染恶性疟和混合感染间日疟与恶性疟的大劣按蚊以及流行季节现场捕获的中华按蚊体内的疟原虫进行检测。结果28批人工感染间日疟原虫的嗜人按蚊、2批人工感染恶性疟的大劣按蚊和1批混合感染间日疟与恶性疟的大劣按蚊的检测结果与镜检结果符合率为100%;589只现场捕获的中华按蚊中,发现间日疟原虫阳性2只,阳性率为0.34%。结论本方法能快速而敏感地检出蚊体内不同种疟原虫。     

中华按蚊和嗜人按蚊对间日疟原虫的易感性观察

近年来,我省疟疾流行病学调查结果显示,以中华按蚊为单一媒介的地区,间日疟发病率较低,而以中华按蚊和嗜人按蚊共存的地区,间日疟发病率则较高.为了解中华按蚊和嗜人按蚊对间日疟原虫的易感性,我们在六合县程桥地区医院进行了此项观察.材料和方法1 实验蚊虫 用同日龄羽化后2d未经吸血的雌性中华按蚊和嗜人按蚁为实验材料,两种蚊虫由本所养蛇室提供.2 病例选择 选择发作2次以上的间日疟志愿者,分别在病程的间歇期、发作期采10ml静脉血,用肝素抗凝.3 感染方法 采用人体胎盘膜体外膜饲法,     

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。     

复方蒿甲醚抑制蚊体内间日疟原虫孢子增殖观察

间日疟现症病人用复方蒿甲醚片,于治疗前及治疗后５、１２和２４ｈ分别以大劣按蚊叮咬吸血感染,结果用药前按蚊的唾腺子孢子阳性率为７５．８２％,用药后５ｈ有极少数吸血按蚊的胃壁卵囊阳性,但唾腺中均未检出子孢子。服药后患者血内疟原虫无性体及有性体较治疗前迅速减少,表明复方蒿甲醚能迅速杀灭红内期间日疟原虫,并能抑制其在蚊体内的孢子增殖。     

复方蒿甲醚抑制蚊体间日疟原虫孢子增殖观察

间日疟现症病人用复方蒿甲醚片,于治疗前及治疗后５,１２和２４ｈ分别以大劣按蚊叮咬吸血感染,结果用药前按蚊的唾腺子孢子阳性率为７５．８２％,用药后５ｈ有极少数吸血按蚊的胃壁卵囊阳性,但唾腺中均未检出子孢子。服药后患者血内疟原虫无性体及有性体较治疗前迅速减少,表明复方蒿甲醚能迅速杀灭红内期间日疟原虫,并能抑制其在蚊体内的孢子增殖。     

广西微小按蚊和中华按蚊对海南株间日疟原虫易感性研究

广西微小按蚊中华按蚊感染海南株间日疟原虫，发现广西微小按蚊对海南株间日疟原虫易感性较高，卵囊阳性率为８５．２％，腺感染率为７０．６％，中华按蚊卵囊阳性率为１．９％，腺感染率为０；而对照组海南大劣按蚊卵囊阳性率为３８．０％，腺感染率为５６．５％。     

山东中华按蚊传播间日疟的研究

本文报告了１９７３～１９９４年山东中华按蚊传播日间疟的系统研究结果，７０年代暴发流行期间感染率为０．４７％，病家蚊经饲养后解剖感染率为１３．２％，实验观察人工感染蚊虫感染率为３６．１％，其中腺子孢子阳性率为１７％，胃部囊合阳性率为２３．３％，鲁东半岛疟疾非暴发流行区与鲁西南易暴发流行区中华蚊按对间日疟原虫的易感染性无显著性差异，间日疟原虫在中华按蚊体内发育的起点温度为１４．９℃，有效积温为１０５．     

广西微小按蚊和中华按蚊对海南株间日疟原虫易感性研究

广西微小按蚊和中华按蚊感染海南株间日疟原虫，发现广西微小按蚊对海南株间日疟原虫易感性较高，卵囊阳性率为８５．２％（２３／２７），腺感染率为７０．６％（１２／１７）；中华按蚊卵囊阳性率为１．９％（２／１０６），腺感染率为０（０／９３）；而对照组海南大劣按蚊卵囊阳性率为３８．０％（３５／９２），腺感染率为５６．５％（３９／６９）。     

对间日疟原虫配子体活力周期性的实验研究

1983年7～9月间,对我国滇南地区5例自然感染的间日疟病例,以驯化的中华按蚊为媒介,每8小时离体吸血1次,以卵囊阳性率和感染度(每阳性蚊卵囊均数)判定配子体活力的强弱。结果发现间日疟原虫配子体活力有明显的周期性,蚊媒的感染高峰似见于病人血液中出现发育中滋养体和成熟滋养体为主的发作间歇期,低谷则见于以成熟裂殖体和幼年滋养体为主的临床发作期,显示配子体的活力周期与无性体的裂体增殖周期有相当密切的关系。除1例外,在实验过程中均见一完全不能使蚊媒感染的无感染期,由此证明,周围血液内的配子体对蚊媒并不始终均具感染性。从蚊媒感染率的消长曲线和各期无性体组成的相互关系推断,配子体活力周期比无性体的裂体增殖周期略长。     

Prevention of sporogony of Plasmodium vivax in Anopheles dirus mosquitoes by transmission-blocking antimalarials

The sporontocidal activity of four dihydroacridine-diones (WR-233602, WR-243251, WR-250547, and WR-250548) and three fluoroquinolones (WR-279135, WR-279298, and WR-279288) was determined against naturally circulating isolates of Plasmodium vivax. Laboratory-reared Anopheles dirus mosquitoes were infected with P. vivax by feeding them on gametocytemic volunteers reporting to local malaria clinics in Kanchanaburi and Tak provinces, Thailand. Four days after the infectious feed, mosquitoes were re-fed on uninfected mice treated 90 minutes previously with a given drug at a dose of 100 mg base drug/kg mouse body weight. Sporontocidal activity was determined by assessing both oocyst and sporozoite development. None of the fluoroquinolones exhibited sporontocidal activity against P. vivax, whereas all 4 dihydroacridine-diones affected sporogonic development to some degree. WR-233602 affected oocyst development, but had no impact on sporozoite production, WR-250548 affected oocyst development and had a limited effect on sporozoite production, and WR-243251 and WR-250547 had a marked impact on all phases of sporogony. These data demonstrate that experimental dihydroacridine-diones are capable of interrupting the sporogonic development of P. vivax. These compounds may be useful in preventing malaria transmission.     

Comparative susceptibility of anopheline mosquitoes in Rondonia, Brazil to infection by Plasmodium vivax

Seven anopheline species from Costa Marques, Rondonia, Brazil were compared with Anopheles darlingi for susceptibility to infection by Plasmodium vivax. Laboratory-reared F1 progeny of field-collected An. darlingi and the test anopheline species were fed at the same time on the same patients, all of whom had gametocytes in peripheral blood before treatment. Mosquitoes were dissected on day 8 after infection for oocysts and on days 14-16 after infection for sporozoites. The mean numbers of P. vivax oocysts and the percent of salivary gland infections for An. darlingi and An. deaneorum were similar and far exceeded those found in the other anopheline species tested. Anopheles albitarsis and An. mediopunctatus were less susceptible to infection by oocyst measurements than An. darlingi. However, for oocyst-infected An. albitarsis and An. mediopunctatus, the percent of mosquitoes with salivary gland infections and the numbers of sporozoites in the salivary glands were similar to An. darlingi. Anopheles triannulatus and An. oswaldoi were both susceptible to P. vivax infection, but the sporozoite infection rates and the numbers of sporozoites observed in the salivary glands were very low. Anopheles braziliensis and An. benarrochi both developed oocysts, but were never observed to have sporozoites in the salivary glands. These studies implicate some anopheline species as potential malaria vectors, but also show that species previously incriminated by ELISA techniques are not vectors of malaria parasites in Costa Marques, Rondonia, Brazil.     

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.     

Effects of anticoagulants on Plasmodium vivax oocyst development in Anopheles albimanus mosquitoes

Artificial membrane feeding (AMF) assays are used to determine malaria transmission-blocking activity in Anopheles. The purpose of this study was to determine the effect of the most widely used anticoagulants, EDTA and heparin, on development of the Plasmodium vivax sporogonic cycle. Blood samples collected from 60 patients carrying P. vivax infections were used to feed An. albimanus using AMF. Seven days after feeding, mosquitoes were dissected to assess mosquito infection. Mosquitoes fed with blood containing EDTA showed a lower mean oocyst number as compared with those fed blood with heparin. However, this effect was minimized upon reduction of EDTA concentrations in the serum. This result may be explained by the fact that microgametocytes require Ca(2+), Mn(2+), and Mg(+2) to activate enzymes important for exflagellation process and for motility of ookinetes. We therefore recommend that heparin be used as the anticoagulant of choice for blood used in AMF assays.     

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。     

Mosquito infection studies with Aotus monkeys and humans infected with the Chesson strain of Plasmodiun vivax

Oocyst counts were compared between mosquitoes that fed on humans versus mosquitoes that fed on Aotus monkeys, both of which were infected with the Chesson strain of Plasmodium vivax. Oocyst counts obtained from mosquitoes fed on humans were almost 10-fold higher in number. Mosquitoes were more likely to be infected and with a higher rate of infection when they fed on monkeys before the peak in the asexual parasite count. Mosquitoes that fed on humans were more likely to be more heavily infected when fed after the peak in the asexual count. Of several species of owl monkeys, Aotus vociferans was infected at a higher frequency. On the basis of oocyst counts, Anopheles dirus were the most susceptible and An. maculatus were the least susceptible of the mosquito species tested.     

Susceptibility of two karyotypic forms of Anopheles aconitus (Diptera: Culicidae) to Plasmodium falciparum and P. vivax

Four laboratory-raised colonies of two karyotypic forms of Anopheles aconitus, i.e., Form B (Chiang Mai and Phet Buri strains) and C (Chiang Mai and Mae Hong Son strains), were experimentally infected with Plasmodium falciparum and P. vivax using an artificial membrane feeding technique and dissected eight and 12 days after feeding for oocyst and sporozoite rates, respectively. The results revealed that An. aconitus Form B and C were susceptible to P. falciparum and P. vivax, i.e., Form B (Chiang Mai and Phet Buri strains/P. falciparum and P. vivax) and Form C (Chiang Mai and Mae Hong Son strains/P. vivax). Comparative statistical analyses of the oocyst rates, average number of oocysts per infected midgut and sporozoite rates among all strains of An. aconitus Form B and C to the ingroup control vectors, An. minimus A and C, exhibited mostly no significant differences, confirming the high potential vector of the two Plasmodium species. The sporozoite-like crystals found in the median lobe of the salivary glands, which could be a misleading factor in the identification of true sporozoites in salivary glands were found in both An. aconitus Form B and C.     

Changing scenario of malaria in central India, the replacement of Plasmodium vivax by Plasmodium falciparum (1986-2000)

OBJECTIVES: Since 1986, we have been studying the changing epidemiology of malaria in a forest belt of Mandla, which has the highest number of malaria cases in central India (Madhya Pradesh) to define the epidemiological characteristics of the infection with each Plasmodium species in different seasons of the year. Our long-term objective was to determine the dynamics of Plasmodium vivax vs.P. falciparum infections. METHODS: Five villages underwent fortnightly surveillance of fever cases. Drugs were distributed within 24 h after results of blood smears became available as per Indian National Anti-Malaria Programme. Indoor resting mosquitoes were also collected fortnightly. RESULTS: The only two Plasmodium species encountered were P. vivax and P. falciparum in both children and adults. Relatively more malaria infections were recorded in children (< or =14 years) than adults (>14 years) (chi2=89.94, P<0.00001). However, there were significant falling trends in P. vivax from 1986 to 2000 in both age groups (< or =14 years from 63 to 13, P<0.0001 and >14 years from 84 to 7, P<0.0001). The indoor resting density of Anopheles culicifacies, an efficient vector resistant to both dichlorodiphenyltrichloroethane (DDT) (4%) and hexachlorocyclohexane (HCH) (0.4%), was very high throughout this period in all villages (52.35 +/- 31.8, range 5-200 per man hour). Anopheles fluviatilis was present in small numbers 0.78 +/- 1.24 (range 0-7 per man hour). CONCLUSION: Major contributors of the changing epidemiology of malaria in this area are changing drug sensitivity along with insecticide sensitivity.     

Comparison of experimental infectivity and development of Plasmodium vivax in Anopheles sacharovi and An. superpictus in Turkey

A study has been made of the infectivity and the sporogenic development of Plasmodium vivax in Anopheles sacharovi and An. superpictus under experimental conditions. An. superpictus showed a slightly lower rate of feeding on human bait, oocyst development, and sporozoite infection of the salivary glands, with ratios of 89.3:100, 89:100, and 98:100, respectively. An. superpictus completed sporogony in 10-14 days with an average of 11.7 days, and An. sacharovi within 8-12 days with an average of 9.8 days. The survival of infected An. superpictus averaged 16.5 days postinfection while An. sacharovi averaged 11.6 days. Under laboratory conditions, An. sacharovi was a more competent vector of P. vivax than An. superpictus.