ABSTRACT
With global warming, mosquitoes and mosquito-borne diseases are spreading rapidly in many regions across the world and producing substantial morbidity and mortality.According to recent studies, mosquito population structure, density and distribution in urban environment are under dynamical changes with continuous urbanization and the consequent environment changes.Surface sewers and under-ground catch basins are becoming major mosquito breeding habitats. Population structure in surface sewers varies with the environment, Aedes albopictus is the dominant species in residential areas.Charac-terized with high population density and mobility, residential areas are easier for mosquito-borne disease spreading, so more attention should be paid to Aedes albopictus control in urban residential areas.Increased underground garages and subway traffic generated new breeding habitats and over wintering sites for mosquitoes in urban environment, control measures should be taken for such environments, since urban underground spaces are always the transit hub of vehicles, which may facilitate the spread of mosquito and its vectored virus, particularly, Culex molestus, Aedes albopictus and Culex tritaeniorhynchus can all be found breeding in underground catch basins.Frequent reports of Culex tritaeniorhynchus breeding in urban surface and underground environment suggest that Culex tritaeniorhynchus is gradually adapted to the new urbanized habitats, which may produce great effect for mosquito population structures in urban environment.Breeding habitats management is the most effective measures for mosquito control, qualified mosquito surveillance can help understand the fluctuation of mosquito species and provide timely warning, at the same time, regular risk assessment for mosquito-borne disease is essential for disease control and prevention.
ABSTRACT
Background & objectives: Bagaza virus (BAGV), a flavivirus synonymous with Israel turkey meningoencephalitis virus, has been found to circulate in India. BAGV has recently been held responsible for inducing febrile illness in humans and causing unusually high mortality to wild birds in Spain. A study was therefore, undertaken to determine its replication kinetics in certain mosquitoes and to determine vector competence and potential of the mosquitoes to transmit BAGV experimentally. Methods: Aedes aegypti, Culex tritaeniorhynchus and Cx quinquefasciatus mosquitoes were inoculated with BAGV; samples were harvested every day and titrated in BHK-21 cell line. Vector competence and experimental transmission were determined by examining the saliva of infected mosquitoes for virus and induction of sickness in suckling mice, respectively. Results: Cx. tritaeniorhynchus and Ae. aegypti mosquitoes yielded 5 log10 and 4.67 log10 TCID50/ml of virus on day 3 post-infection (PI), respectively while Cx. quinquefasciatus yielded a titre of 4 log10TCID50/ml on day 4 PI. BAGV was detected in saliva of all the infected mosquitoes demonstrating their vector competence. Experimental transmission of BAGV to infant mice as well as transovarial transmission was demonstrated by Cx. tritaeniorhynchus but not by Ae. aegypti and Cx. quinquefasciatus mosquitoes. Interpretation & conclusions: Replication of BAGV to high titres and dissemination to saliva in three most prevalent mosquitoes in India is of immense public health importance. Though no major outbreak involving man has been reported yet, BAGV has a potential to cause outbreaks in future.
ABSTRACT
To determine the larvicidal activity of various extracts of Gymnema sylvestre against the Japanese Encephalitis vector, Culex tritaeniorynchus in Tamilnadu, India. To identify the active principle present in the promising fraction obtained in Chlorofom:Methanol extract of Fraction 2. The G. sylvestre leaf extracts were tested, employing WHO procedure against fourth instar larvae of C. tritaeniorhynchus and the larval mortalities were recorded at various concentrations (6.25, 12.5, 25.0, 50 and 100 µg/mL); the 24h LC50 values of the G. Sylvestre leaf extracts were determined following Probit analysis. It was noteworthy that treatment level 100 µg/mL exhibited highest mortality rates for the three different crude extracts and was significantly different from the mean mortalities recorded for the other concentrations. The LC50 values of 34.756 µg/mL (24.475-51.41), 31.351 µg/mL (20.634-47.043) and 28.577 µg/mL (25.159-32.308) were calculated for acetone, chloroform and methanol extract with the chi-square values of 10.301, 31.351 and 4.093 respectively. The present investigation proved that G. Sylvestre could be possibly utilized as an important component in the Vector Control Program.
O presente trabalho é para identificar a atividade larvicida de vários extratos da Gymnema sylvestre contra o vetor da encefalite japonesa, Culex tritaeniorhynchus em Tamilnadu, Índia. Com este propósito o princípio ativo presente na fração mais promissora foi obtida através de um extrato clorofórmio:metanol da fração 2. Os extratos das folhas do G. sylvestre foram testados empregando o procedimento da WHO contra estágios quaternários da larva do C. tritaeniorhynchus e as mortalidades larvais foram registradas após várias concentrações (6,25, 12,5, 25,0 e 100; 34,756 µg/mL (24,475-51,41), 31,351 µg/mL (20,634-47,043) e 28,577 µg/mL (25,159-32,308) g/mL); os valores de LC50 de 24 horas dos extratos das folhas de G. sylvestre foram determinados seguindo a análise Probit. Foi notado que o nível de tratamento de 100 µg/mL exibiu a mortalidade mais alta para os três diferentes extratos crus e foi significantemente diferente das mortalidades médias registradas para as outras concentrações. Os valores de LC50 de 34,756 µg/mL (24,475-51,41), 31,351 µg/mL (20,634-47,043) e 28,577 µg/mL (25,159-32,308) foram calculados para os extratos de acetona, clorofórmio e metanol com os valores de qui-quadrado de 10,301, 31,351 e 4,093 respectivamente. A presente investigação mostra que o G. sylvestre pode ser usado como componente importante no programa de controle do vetor.
Subject(s)
Animals , Culex , Gymnema sylvestre/chemistry , Insect Vectors , Insecticides , Plant Extracts , Saponins , Culex/classification , Encephalitis, Japanese/transmission , India , Insect Vectors/classification , Plant Leaves/chemistry , Saponins/isolation & purificationABSTRACT
Objective: This study was undertaken to assess the larvicidal and ovicidal potential of the crude methanol, benzene and acetone solvent extracts from the medicinal plant Pemphis acidula (Pe. acidula) against the medically important mosquito vectors, Culex tritaeniorhynchus (Cx. tritaeniorhynchus) and Anopheles subpictus (An. subpictus) were exposed to various concentrations and (Diptera: Culicidae). Methods: Twenty five late third instar of Cx. tritaeniorhynchus and An. subpictus were exposed to various concentrations and were assayed in the laboratory by using the protocol of WHO 2005. The larval mortality was observed 24 h of treatment. Hundred eggs of Cx. tritaeniorhynchus and An. subpictus were exposed to various concentrations and were assayed in the laboratory by using the protocol of Su and Mulla 1998. The ovicidal activity was observed 48 h of treatment. Results: The LC50 and LC90 values being 10.81and 20.64 and 22.10 and 43.71 ppm and hundred percent of egg mortality was observed at 350 and 400 ppm methanol extract of Pe. acidula against Cx. tritaeniorhynchus and An. subpictus, respectively. Conclusion: These results suggest that the leaf extracts have the potential to be used as an ideal ecofriendly approach for the control of mosquitoes.
ABSTRACT
Background & objectives: Mosquitoes transmit serious human diseases, causing millions of deaths every year and the development of resistance to chemical insecticides resulting in rebounding vectorial capacity. Plants may be alternative sources of mosquito control agents. The present study assessed the role of larvicidal activities of hexane, chloroform, ethyl acetate, acetone, and methanol dried leaf and bark extracts of Annona squamosa L., Chrysanthemum indicum L., and Tridax procumbens L. against the fourth instar larvae of malaria vector, Anopheles subpictus Grassi and Japanese encephalitis vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae). Methods: Larvicidal activities of three medicinal plant extracts were studied in the range of 4.69 to 1000 mg/l in the laboratory bioassays against early 4th instar larvae of An. subpictus and Cx. tritaeniorhynchus. The mortality data were subjected to probit analysis to determine the lethal concentrations (LC50 and LC90) to kill 50 and 90 per cent of the treated larvae of the respective species. Results: All plant extracts showed moderate effects after 24 h of exposure; however, the highest toxic effect of bark methanol extract of A. squamosa, leaf ethyl acetate extract of C. indicum and leaf acetone extract of T. procumbens against the larvae of An. subpictus (LC50 = 93.80, 39.98 and 51.57 mg/l) and bark methanol extract of A. squamosa, leaf methanol extract of C. indicum and leaf ethyl acetate extract of T. procumbens against the larvae of Cx. tritaeniorhynchus (LC50 =104.94, 42.29 and 69.16 mg/l) respectively. Interpretation & Conclusions: Our data suggest that the bark ethyl acetate and methanol extract of A. squamosa, leaf ethyl acetate and methanol extract of C. indicum, acetone and ethyl acetate extract of T. procumbens have the potential to be used as an ecofriendly approach for the control of the An. subpictus, and Cx. tritaeniorhynchus.
Subject(s)
Acetates/chemistry , Animals , Annona/chemistry , Anopheles/drug effects , Asteraceae/chemistry , Chrysanthemum/chemistry , Culex/drug effects , Dose-Response Relationship, Drug , Humans , Insecticides/chemistry , Insecticides/pharmacology , Larva/drug effects , Malaria/prevention & control , Methanol/chemistry , Plant Bark/chemistry , Plant Extracts/chemistry , Plant Extracts/pharmacologyABSTRACT
Background & objectives: Climatic attributes have been associated with relative mosquito abundance and transmission of mosquito borne infections in many parts of the world, especially in warm and tropical climatic regions. The main objectives of this study were to assess the change in seasonal pattern of Japanese encephalitis (JE) vectors, their density, to elucidate whether the lagged climate variables (precipitation, temperature and humidity) are associated with JE vector density, and to determine if temperature and precipitation are similarly important for the rise in the number of potential mosquito vectors for JE virus in the temperate climate of Andhra Pradesh, India. Methods: Mosquito samples were collected from Kurnool district of Andhra Pradesh using hand catch and light-trap methods during 2002 to 2006. The type and abundance of recovered species were compared to ecological correlates. In each geographic area, temperature and precipitation are the two possible proxy variables for mosquito density, in conjunction with other seasonal factors for JE epidemics. Results: Out of the various mosquito species collected, Culex gelidus and Cx. tritaeniorhynchus were noticed in high numbers. There was considerably high prevalence of Cx. gelidus (68.05%) in urban area than in rural areas whereas, Cx. tritaeniorhynchus (57.51%) was found to be more in rural areas than in the urban area. It is noticed that the factors such as rainfall and temperature were found to be correlated with the per man hour (PMH) density, whereas the humidity was inversely correlated with the PMH. Interpretation & conclusion: The environmental and eco-climatic factors are assisting in enhancing the breeding of these mosquitoes in Kurnool district of Andhra Pradesh, India. Both Cx. tritaeniorhyncus and Cx. gelidus are quite adaptable to these environmental conditions and this necessitates immediate control measures in both rural and urban areas of Kurnool district.
ABSTRACT
A sectional survey with histochemical technique was carried out on Culex tritae-niorhynchus larvae infected with Coelomomyces indica in comparison to the noninfected larvae. Studies were pursued by using micrograph and imaging analysis. The results showed that the glycogen, protein and nucleic acid (RNA and DNA)reaction in the infected group were less than those of the control group. The gray level assessment in tissue imaging showed marked difference between the two groups. It is suggested that C. indica has significant effect on the above biochemical elements of the mosquito larvae, which might be considered an important mechanism in the pathogenicity of the fungus.