马来丝虫微丝蚴定量注射感染中华按蚊和致倦库蚊的实验观察

本文报告采用改进的微量注射技术和较为精细的计数方法,以2—10条微丝蚴/蚊,定量注射感染中华按蚊和致倦库蚊,找出了这两种蚊虫的微丝蚴感染量与感染期幼丝虫阳性率、幼丝虫平均发育成熟率之间的定量关系;比较了在注射感染条件下两种蚊虫对马来丝虫易感性的差异。     

Quantitative studies on the development of inoculated Brugia malayi microfilariae in Anopheles sinensis and Culex quinquefasciatus

Definite numbers of B. malayi mf were inoculated into An. sinensis and Cx. quinquefasciatus, and their subsequent development was observed. The relationships between the dosage and the L3 positive rate on the one hand and the average filarial maturity rate on the other were defined. At the same dosages of 4 and 10 mf/mosquito, the L3 positive rates and the average filarial maturity rates in An. sinensis were much higher than those in Cx. quinquefasciatus (p less than 0.01). It was demonstrated that the immune response to filariae of the mosquitos was the main factor resulting in these differences. The intensity of the immune response not only varied with the species, but also declined with the aging of mosquitos. The results of our experiment might be useful to studies on the dynamics of filariasis transmission and the interaction between filariae and their insect hosts.     

注射感染马来丝虫微丝蚴在蚊虫体内早期...

This paper reports the early development and variation of inoculated Brugia malayi microfilariae in 3 groups of mosquitoes, i. e. young Anopheles sinensis, young Culex quinquefasciatus and old Cx. quinquefasciatus. Significant differences were observed among these groups. Sixty hours after inoculation, the percentage of normally developing filarial larvae in young An. sinensis was 72.3%; the percentage of melanized microfilariae in young Cx. quinquefasciatus was 75.4% and the percentage of filarial larvae which developed abnormally or remained in diapause status in old Cx. quinquefasciatus was 67.1%, each being much higher than that in the other groups. It was suggested that the immune competence of the mosquitoes had influence upon the filarial development. The intensity of the immune response not only varied with the species, but also diminished with the aging of mosquitoes.     

聚合酶链反应检测蚊体内马来丝虫幼虫的实验

目的　建立一种特异、灵敏和简捷的聚合酶链反应 (PCR)检测蚊体内马来丝虫幼虫的方法。方法　在应用一种新的模板纯化处理技术 (Microcon 10 0 )基础上 ,采用适应于检测我国马来丝虫的两套DNA扩增引物(P1、P2与P3、P4) ,对实验感染马来丝虫的中华按蚊进行扩增检测。结果　两套引物均可检出蚊体内不同发育期幼丝虫 (L1、L2 和L3) ,其灵敏度达 1只蚊体内 1/ 6 4条L1和 2 0 0只群体蚊中含有 1只感染蚊 (体内有 1条L3)的水平 ,而对犬恶丝虫及未感染蚊却不能扩增出特异条带。结论　初步建立特异、灵敏和简捷的PCR检测蚊体内马来丝虫幼虫的方法。     

不同日龄致倦库蚊对马来丝虫易感性的比较研究

不同日龄致倦库蚊分别经胸内接种马来丝虫微丝蚴后,比较观察了蚊虫体内微丝蚴的黑化率、(?)虫率以及感染性蚊虫的比率。接种后第3、4、5、9d解剖接种蚊虫,结果表明,1～2日龄蚊虫体内微丝蚴黑化率显著高于15～16日龄蚊虫,分别为84.1％和57.5％。三期幼虫率则相反,分别为1.5％和3.7％。黑化的微丝蚴主要分布在蚊虫腹部,占72.3％和69.1％。     

Limitation and facilitation in the vectors and other aspects of the dynamics of filarial transmission: the need for vector control against Anopheles-transmitted filariasis

In certain filaria-mosquito combinations, the number of infective, third-stage larvae (L(3)) that develop in a mosquito is not proportional to the number of microfilariae (mff) ingested by that mosquito. As the number of mff ingested increases, the yield of L(3) per microfilaria may either increase (in a process known as 'facilitation') or decrease (in a process known as 'limitation'). Each ingested microfilaria that is successful (in terms of reaching the haemocoel) increases (facilitation) or decreases (limitation) the 'permeability' of the stomach wall for the next microfilaria. Limitation is seen in some culicine mosquitoes, especially the Aedes spp. that transmit Wuchereria bancrofti, which, in consequence, become relatively more efficient as vectors as they ingest fewer mff. This phenomenon makes the interruption of filarial transmission by Aedes spp. particularly difficult. As the survival of anopheline mosquitoes is adversely affected by filarial infection, the use of mass drug administrations (MDA) to reduce the prevalence and intensity of microfilaraemias may increase the mean lifespan of some of the local Anopheles species. If these same species also act as vectors of malarial parasites, effective, drug-based control of W. bancrofti may worsen the problem posed by malaria. Therefore, wherever malaria and bancroftian filariasis are co-endemic and caused by parasites transmitted by the same species of mosquito, MDA should be augmented by interventions (use of bednets or house-spraying) against adult Anopheles.     

Preliminary observations on the development of larval filariae in Toxorhynchites species

Brugia malayi and B. Pahangi microfilariae from gerbil intraperitoneal infections were inoculated into the thorax of male and female Toxorhynchites amboinesis and developed into third-stage larvae as early as 11 days. In a comparative study with Aedes togoi fed on microfilaremic gerbils, third-stage larvae were found at 10 days. Some third-stage larvae of B. malayi inoculated into gerbils developed to advanced stages. Third-stage larvae of Wuchereria bancrofti were recovered in low numbers from Tx. amboinesis and Tx. aurifluus inoculated with microfilariae recovered from human blood by membrane filtration. Development of all filarial species was similar in both male and female mosquitoes. Toxorhynchites species are plant feeders and therefore reduce the hazards of laboratory transmission of pathogenic agents. Because of their large size, manipulations with this mosquito species are easy and the size allows for a larger inoculum to be used. This group of mosquitoes should develop into useful laboratory vectors for the transmission of arthropod-borne diseases.     

注射感染马来丝虫微丝蚴在蚊虫体内早期发育的观察

本文报告经注射感染的马来丝虫微丝蚴在幼龄中华按蚊、幼龄致倦库蚊和老龄致倦库蚊体内早期发育变化的情况。接种后60h,幼丝虫在这三类蚊虫体内的发育已有明显差异。幼龄中华按蚊体内正常发育的幼丝虫比例最高(72.3％);幼龄致倦库蚊体内黑化幼丝虫的比例最高(75.4％);而老龄致倦库蚊体内以滞育或畸形的幼丝虫比例最高(67.1％)。实验表明,蚊虫的免疫是影响幼丝虫发育的一个重要因素。免疫反应的强度在不同的蚊种间有显著差异,且随蚊虫日龄的增加而下降。     

Persistence of Brugia malayi DNA in vector and non-vector mosquitoes: implications for xenomonitoring and transmission monitoring of lymphatic filariasis

Xenomonitoring (detection of filarial larvae or their DNA in mosquitoes) is a sensitive marker for assessing the endemicity of filariasis and a useful tool for evaluating elimination programs. To examine the fate of microfilariae (mf) and filarial DNA in vector competent and non-competent mosquito strains, we compared the detection of Brugia malayi parasites by dissection and by quantitative real-time polymerase chain reaction (PCR) in three different mosquito strains. We conclude that PCR is much more sensitive than dissection for detecting filarial larvae, especially their remnants in mosquitoes. However, parasite DNA can be detected in both vector and non-vector mosquitoes for two weeks or longer after they ingest mf-positive blood. Thus, although xenomonitoring with vector and non-vector mosquito species may be a sensitive method for indirectly detecting filarial parasites in human populations, positive test results for parasite DNA in mosquitoes do not necessarily prove that transmission is ongoing in the study area.     

应用DNA探针检测蚊体内丝虫幼虫的研究

本文用人工合成的寡核苷酸探针，经斑点杂交法检测蚊体内马来丝虫幼虫。可测到丝虫和微丝蚴２ｎｇ的ＤＮＡ量，不与其它动物丝虫标本发生交叉反应。将单个蚊直接压于硝酸纤维素膜上进行检测，感染蚊中含有１条感染期幼虫就可出现阳性反应。将一组蚊虫在裂解液中研磨集体检测时，在２０只蚊虫中有１只感染蚊即可检出。显示该探针可用于马来丝虫地区的蚊媒监测。