A survey on malaria in mobile Cambodians in Aranyaprathet,Sa Kaeo Province,Thailand

A cross-sectional survey of the malaria prevalence among mobile Cambodians in Aranyaprathet, at the Thai-Cambodia border, was conducted in November 2000. A total of 666 asymptomatic, mobile Cambodians who worked as traders and laborers were studied. The overall prevalence rate was 2.4%, with 93.75% of the infections being due to Plasmodium vivax and 6.25% due to Plasmodium falciparum. Almost all cases had low level of parasitemia (1+) and no sexual stages were found. Factors associated with malaria infection included being male, being in the 10-59 year age group, having a lower level of education and frequent trans-border crossing. Both groups of migrant workers (traders and laborers) had an equal chance of infection.     

Sensitivity of Plasmodium vivax to chloroquine in Sa Kaeo Province,Thailand

Following a recent, abrupt local increase in the incidence of vivax malaria, a study was conducted in order to evaluate the efficacy of chloroquine for the treatment of 26 adult patients with acute vivax malaria in Sa Kaeo Province, Thailand. The chloroquine sensitivity of Plasmodium vivax has been assessed in parallel, using a growth inhibition method. Blood samples for the in vitro tests were taken prior to the administration of the standard treatment with chloroquine--in total 25 mg base/kg over 3 days--and primaquine 0.25 mg base/kg once daily for 14 days. The efficacy has been assessed according to the WHO standard in vivo test. The cure rate was 100%. No recrudescence was observed during the follow-up period of 28 days. The mean fever clearance time (FCT) was 40 h, the mean parasite clearance time (PCT) was 49 h. Mean IC(50) and IC(90) of the parasites were 28 and 171 nM, respectively. These results show that local P. vivax is still sensitive to chloroquine. The epidemic outbreak was therefore obviously not due to the presence of chloroquine-resistant P. vivax.     

Incrimination of Anopheles dirus as a vector of malaria in Dibrugarh district, Assam

Anopheles nigerrimus, A. vagus, A. dirus, A. karwari and A. kochi were the most abundant species among 12 anopheline species collected during the course of entomological studies carried out from July to September, 1988 in an area endemic for malaria under Tengakhat PHC of Dibrugarh district, Assam. Sporozoites were detected in the salivary glands of one specimen of A. dirus, Peyton & Harrison (A. balabacensis) which constituted about 18.11 per cent of the total anopheline collection.     

Astrodaucus persicus as a new source of bioinsectisides against malaria vector,Anopheles stephensi

Objective: To determine the larvicidal activities of petroleum ether, chloroform, ethyl acetate and methanol fractions of roots and fruits extracts of Astrodaucus persicus from Apiaceae family against malaria vector, Anopheles stephensi(An. stephensi).Methods: Twenty five third instar larvae of An. stephensi were exposed to various concentrations(10–160 g/L) of fractions and were assayed according to World Health Organization protocol. The larval mortality was calculated after 24 h treatment.Results: Among tested fractions, the highest larvicidal efficacy was observed from ethyl acetate fraction of fruits extract with 50% and 90% mortality values(LC_(50) and LC_(90)) of34.49 g/L and 108.61 g/L, respectively. Chloroform fraction of fruits extract was the second larvicidal sample with LC_(50) of 45.11 g/L and LC_(90) of 139.36 g/L. Petroleum ether fractions of fruits and roots and methanol fraction of fruits showed moderate toxicity against An. stephensi.Conclusions: Astrodaucus persicus is a potential source of valuable and natural larvicidal compounds against malaria vector, An. stephensi and can be used in mosquitoes control programs as an alternative to synthetic insecticides.     

2005-2019年贵州省传疟媒介按蚊密度及种群监测

目的 了解2005-2019年贵州省传疟媒介按蚊密度、种群构成及生境分布,为制定全省输入性疟疾传播风险防控措施提供参考依据.方法 2005-2019年在贵州省分别采用人帐诱法和诱蚊灯法开展按蚊密度及按蚊种群监测,对捕获的按蚊进行形态学分类鉴定并计数,并对按蚊生境分布进行分析.结果 2005-2019年贵州省传疟按蚊密度...     

Confirmation of Anopheles varuna in vietnam, previously misidentified and mistargeted as the malaria vector Anopheles minimus.

Malaria control programs in Southeast Asia are faced with several questions concerning vector behavior and species identification, which need to be answered to consolidate and further improve the results of control practices. The vector system in Southeast Asia is complex because of the number of species potentially involved in malaria transmission. Additionally, the follow-up and evaluation of preventive control measures are hampered by the misidentification of vectors due to overlapping morphological characters of the female mosquitoes. In central Vietnam, control practices are aimed at 2 main species, Anopheles dirus s.l. and Anopheles minimus s.l. These reputed vectors were studied in an area of Binh Thuan Province of south-central Vietnam. Different collection methods were used to capture mosquitoes quarterly during a 1-year period. Mosquitoes were identified in the field and later subjected to detailed morphological examination and polymerase chain reaction-restriction fragment length polymorphism analysis. What was thought to be an unusual morphotype of An. minimus was shown to be Anopheles varuna, and most specimens identified as the former species in the field proved to be the latter species. Very few An. minimus individuals were found during the study period. The population of An. varuna was found to be highly zoophilic, and based on this behavior, it cannot be considered a vector in Vietnam. Because this species was previously being misidentified as An. minimus, a nonvector was mistargeted as a malaria vector in Binh Thuan Province. Anopheles dirus, which was found positive for Plasmodium falciparum circumsporozoite via enzyme-linked immunosorbent assay, is clearly the main vector in this area. Despite the fact that several potential secondary vectors were found during the study, the primary target for vector control in the region should be An. dirus.     

Incrimination of Anopheles aconitus Donitz as a vector of epidemic malaria in Bangladesh.

In 1989-91, post-monsoon epidemics of vivax malaria occurred in the central flood plain near Dhaka. Anopheles philippinensis, the usual vector in the paddy field habitat, was not present, but 1.4% of parous An. aconitus were infective. This is only the second time An. aconitus has been incriminated as a vector in Bangladesh. We speculate that the surprising increase in lowland malaria may have been caused by environmental change that favored the survival of An. aconitus.     

Is Anopheles mascarensis a new malaria vector in Madagascar?

Anopheles mascarensis De Meillon, 1947, a mosquito that is native to Madagascar, is reported for the first time to act as a vector of Plasmodium falciparum malaria. From September 1989 to March 1990, 2, 499 An. mascarensis specimens from different regions of Madagascar were tested by an enzyme-linked immunosorbent assay (ELISA), using monoclonal antibodies against the circumsporozoite (CS) protein of the four human species of Plasmodium. The salivary glands of 237 specimens were also dissected. Fourteen of 1,864 specimens obtained from Sainte Marie island on the Malagasy east coast were found by ELISA to be positive for the CS protein of P. falciparum. In addition, two of 237 specimens that were dissected were observed to have sporozoites in the salivary glands. These sporozoites were identified as P. falciparum by ELISA. In the other regions studied, no positive specimens were found. Due to observed behavioral differences between east coast and highland populations of An. mascarensis, the possible presence of a species complex is discussed.     

Irritability of malaria vector, Anopheles sacharovi to different insecticides in a malaria-prone area

ObjectiveTo determine the susceptibility and irritability level of malaria vector Anopheles sacharovi (An. sachrovi) to different insecticides in a malaria-prone area.MethodsSusceptibility and irritability levels of field collected strain of An. sacharovi to WHO standard papers of DDT 4%, dieldrin 0.4%, malathion 5%, fenitrothion 1%, permethrin 0.75%, and deltamethrin 0.05% were determined in East Azerbaijan of Iran during reemerging of malaria as described by WHO.ResultsResults showed that at the diagnostic dose of insecticides this species exhibited resistance to DDT, tolerant to dieldrin and but somehow susceptible to fenitrothion, malathion, permethrin and deltamethrin. The results of irritability of this species to DDT, lambdacyhalothrin, permethrin cyfluthrin and deltamethrin revealed that DDT had had the most and deltamethrin the least irritancy effect. The average number of take offs/fly/minutes for DDT was 0.8±0.2. The order of irritability for permethrin, lambdacyhalothrin, cyfluthrin and deltamethrin were 0.7±0.2, 0.5±0.2, 0.5±0.3, and 0.2±0.1, respectively.ConclusionsResults of this study reveals the responsiveness of the main malaria vector to different insecticides. This phenomenon is depending on several factors such as type and background of insecticide used previously, insecticide properties, and physiology of the species. Careful monitoring of insecticide resistance and irritability level of species could provide a clue for appropriate selection of insecticide for malaria control.     

Attractiveness of pregnant women to the malaria vector, Anopheles arabiensis, in Sudan

The attractiveness of pregnant women for mosquitoes was investigated in a peri-urban site in New Halfa, eastern Sudan, in September-October 2003. For 20 nights, the mosquitoes feeding on nine pregnant and nine non-pregnant women sleeping under untreated bednets were collected. The women slept outdoors, in the yards of nine houses, each yard holding one pregnant and one non-pregnant woman. In general, each pregnant woman attracted significantly more Anopheles arabiensis (the main vector of Plasmodium falciparum in the area) than each non-pregnant women, with mean biting rates of 0.94 and 0.49 bites/woman-night, respectively (P = 0.005). In contrast, the two groups of women attracted similar numbers of the other mosquito species collected, which were all culicine. Impregnated bednets need to be used in the study area, at least by the pregnant women (who appear to be at particularly high risk of acquiring malaria).     

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)     

湖北省主要传疟媒介按蚊生态习性及密度分析

目的了解近年来湖北省主要传疟媒介按蚊季节消长、栖息、吸血和孳生地等生态习性及其密度变化情况,为消除疟疾前蚊媒防制工作提供依据。方法于2012年7—9月,选择京山县、广水市和随州市曾都区为调查点,采用人工叮咬、帐诱捕蚊和灯诱3种方式进行媒介按蚊密度监测和生态习性调查。对调查资料进行描述性分析和方差分析检验。结果调查捕获的传疟按蚊均为中华按蚊,未发现嗜人按蚊。京山县人诱密度成蚊密度7月份最高,为7.50只/(人·h);曾都区帐诱密度8月份最高,为0.18只/帐;广水市灯诱密度7月份最高,为9.67只/夜。中华按蚊幼虫密度在不同孳生地以8月下旬和9月上旬为高。结论湖北省原嗜人按蚊和中华按蚊复合媒介区,现已很少发现有嗜人按蚊的存在,中华按蚊幼虫孳生地以稻田为主,中华按蚊幼虫密度和成蚊密度季节消长基本一致。     

Biting rhythms of malaria vector Anopheles culicifacies in Kheda district, Gujarat.

All night collections on bovine baits were made in 6 villages of Kheda district, Gujarat. During 70 all night bait collections from January to December 1989, a total of 2290 An. culicifacies were collected. An. culicifacies mostly exhibited bimodal rhythms with a seasonal shift in peak biting activities. During the cold season most biting occurred just after dusk and during the warm season late at night. An. culicifacies was more active during moonless hours and its activity showed no correlation with temperature and humidity during most part of the year.     

Olfactory responses in a gustatory organ of the malaria vector mosquito Anopheles gambiae

The proboscis is an important head appendage in insects that has primarily been thought to process gustatory information during food intake. Indeed, in Drosophila and other insects in which they have been identified, most gustatory receptors are expressed in proboscis neurons. Our previous characterization of the expression of AgOR7, a highly conserved odorant receptor (OR) of the Afrotropical malaria vector mosquito Anopheles gambiae in the labellum at the tip of the proboscis was suggestive of a potential olfactory function in this mosquito appendage. To test this hypothesis, we used electrophysiological recording and neuronal tracing, and carried out a molecular characterization of candidate OR expression in the labellum of A. gambiae. These studies have uncovered a set of labial olfactory responses to a small spectrum of human-related odorants, such as isovaleric acid, butylamine, and several ketones and oxocarboxylic acids. Molecular analyses indicated that at least 24 conventional OR genes are expressed throughout the proboscis. Furthermore, to more fully examine AgOR expression within this tissue, we characterized the AgOR profile within a single labial olfactory sensillum. This study provides compelling data to support the hypothesis that a cryptic set of olfactory neurons that respond to a small set of odorants are present in the mouth parts of hematophagous mosquitoes. This result is consistent with an important role for the labellum in the close-range discrimination of bloodmeal hosts that directly impacts the ability of A. gambiae to transmit malaria and other diseases.