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Suryanarayana Murty U.,Indian Institute of Chemical Technology | Srinivasa Rao M.,Indian Institute of Chemical Technology | Arunachalam N.,Center for Research in Medical Entomology
Journal of Vector Borne Diseases | Year: 2010

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. Source

Sugumar S.,Vellore Institute of Technology | Clarke S.K.,Vellore Institute of Technology | Nirmala M.J.,Vellore Institute of Technology | Tyagi B.K.,Center for Research in Medical Entomology | And 2 more authors.
Bulletin of Entomological Research | Year: 2014

Filariasis is a mosquito-borne disease that causes lymphedema and the main vector is Culex quinquefasciatus. A simple measure was taken to eradicate the vector using nanoemulsion. Eucalyptus oil nanoemulsion was formulated in various ratios comprising of eucalyptus oil, tween 80 and water by ultrasonication. The stability of nanoemulsion was observed over a period of time and 1:2 ratios of eucalyptus oil (6%) and surfactant (12%) was found to be stable. The formulated eucalyptus oil nanoemulsion was characterized by transmission electron microscopy and dynamic light scattering. The nanoemulsion droplets were found to have a Z-average diameter of 9.4â nm and were spherical in shape. The larvicidal activity of eucalyptus oil nanoemulsion and bulk emulsion was tested and compared. Our nanoemulsion showed higher activity when compared to bulk emulsion. The histopathology of larvae-treated and untreated nanoemulsion was analyzed. Furthermore, biochemical assays were carried out to examine the effect of nanoemulsion on biochemical characteristics of larvae. The treated larval homogenate showed decrease in total protein content and a significant reduction in the levels of acetylcholinesterase. The levels of acid and alkaline phosphatase also showed reduction as compared to control larval homogenate. Copyright © 2013 Cambridge University Press. Source

Mariappan T.,Center for Research in Medical Entomology
Tropical Doctor | Year: 2013

Outbreaks of dengue fever (DF) have been reported from various countries. Although DF has been endemic in India from the nineteenth century, dengue haemorrhagic fever (DHF) was first reported in 1987. The first major widespread epidemic of DHF and dengue shock syndrome (DSS) was reported in 1996 with four serotypes reported to be in co-circulation. In 2012 an outbreak occurred in India during which a total of 47,029 DF cases and 242 deaths were reported - three times higher than the previous year. Twelve states reported a large number of cases, including Tamil Nadu which recorded 12,264 from various districts. We discuss methods of prevention and control. © The Author(s) 2013. Source

Kumar K.R.,Vivekananda College | Nattuthurai N.,Vivekananda College | Gopinath P.,Vivekananda College | Mariappan T.,Center for Research in Medical Entomology
Parasitology Research | Year: 2014

Mosquitoes are the major vector for the transmission of malaria, dengue fever, yellow fever, filariasis, chikungunya and Japanese encephalitis, and they accounted for global mortality and morbidity with increased resistance to common insecticides. The aim of this study was to investigate the larvicidal potential of the acetone leaf extracts of Morinda tinctoria and synthesized silver nanoparticles against third instar larvae of Culex quinquefasciatus Say (Diptera: Culicidae). Nanoparticles are being used in many commercial applications. It was found that aqueous silver ions can be reduced by aqueous extract of plant parts to generate extremely stable silver nanoparticles in water. Synthesized AgNPs were characterized by ultraviolet–visible (UV–vis) spectroscopy, Atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FT-IR) analysis. The synthesized silver nanoparticles have also been tested against the third instar larvae of C. quinquefasciatus. The leaf extract and the AgNPs high mortality values were 50 % lethal concentration (LC50) = 8.088 and 1.442 ppm against C. quinquefasciatus, respectively. The results recorded from ultraviolet–visible spectroscopy, atomic force microscopy and Fourier transform infrared spectroscopy support the biosynthesis and characterization of silver nanoparticles. These results suggest that the leaf extract of M. tinctoria and synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of C. quinquefasciatus. By this approach, it is suggestive that this rapid synthesis of nanoparticles would be proper for developing a biological process for mosquito control. © 2014, Springer-Verlag Berlin Heidelberg. Source

Arunachalam N.,Center for Research in Medical Entomology | Tana S.,Center for Health Policy and Social Change | Espino F.,Institute of Tropical Medicine | Kittayapong P.,Mahidol University | And 5 more authors.
Bulletin of the World Health Organization | Year: 2010

Objective: To study dengue vector breeding patterns under a variety of conditions in public and private spaces; to explore the ecological, biological and social (eco-bio-social) factors involved in vector breeding and viral transmission, and to define the main implications for vector control. Methods: In each of six Asian cities or periurban areas, a team randomly selected urban clusters for conducting standardized household surveys, neighbourhood background surveys and entomological surveys. They collected information on vector breeding sites, people's knowledge, attitudes and practices surrounding dengue, and the characteristics of the study areas. All premises were inspected; larval indices were used to quantify vector breeding sites, and pupal counts were used to identify productive water container types and as a proxy measure for adult vector abundance. Findings: The most productive vector breeding sites were outdoor water containers, particularly if uncovered, beneath shrubbery and unused for at least one week. Peridomestic and intradomestic areas were much more important for pupal production than commercial and public spaces other than schools and religious facilities. A complex but non-significant association was found between water supply and pupal counts, and lack of waste disposal services was associated with higher vector abundance in only one site. Greater knowledge about dengue and its transmission was associated with lower mosquito breeding and production. Vector control measures (mainly larviciding in one site) substantially reduced larval and pupal counts and "pushed" mosquito breeding to alternative containers. Conclusion: Vector breeding and the production of adult Aedes aegypti are influenced by a complex interplay of factors. Thus, to achieve effective vector management, a public health response beyond routine larviciding or focal spraying is essential. Source

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