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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.


Ngassa Mbenda H.G.,National Institute of Malaria Research | Ngassa Mbenda H.G.,University of Witwatersrand | Das A.,National Institute of Malaria Research | Das A.,Center for Research in Medical Entomology
Infection, Genetics and Evolution | Year: 2016

Understanding the population genetics of genes which shape resistance to antimalarial drugs can help in devising novel control strategies. The high spread of the resistant strains of the malaria parasite Plasmodium falciparum pose a greater challenge than before to the control programs across the world. Specific mutations in the P. falciparum chloroquine resistant transporter gene “Pfcrt” have been associated with resistance to not only chloroquine, but also to amodiaquine, one of the artemisinin partners used in Cameroon for the treatment of uncomplicated malaria. We here present data on genetic variation at the Single Nucleotide Polymorphisms (SNPs) level in the Pfcrt gene in five distinct geographical settings of the Southern-Cameroon (the most malaria endemic part), i.e. Ebolowa, Yaounde, Bertoua, Douala and Kye-ossi (a city bordering Cameroon and two others African countries). Two novel mutations, hitherto unreported (in Cameroon) were found in the Pfcrt gene and variable genetic diversity was observed across the populations. High linkage disequilibrium was found between few SNPs including one of the novel mutations suggesting a synergistic work for conferring/maintaining a higher level of resistance. The inference of evolutionary pattern of this gene in Cameroon based on the genetic diversity data depicts a signature of Darwinian positive natural selection on these loci. Observation of novel mutations might traduce new variants in chloroquine/or amodiaquine resistance (proposal awaiting an experimental verification) and signal of positive selection can be the result of drug pressure exerted by misuse of chloroquine (though officially banned from the country) and/or amodiaquine. Our findings thus, provide a baseline understanding of the evolution of a malaria drug resistant gene in Cameroon and suggest a successful establishment of chloroquine-resistant strains which requires urgent attention of the malaria control program in Cameroon. © 2016 Elsevier B.V.


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.


Gowri Sankar S.,Anna University | Dhananjeyan K.J.,Center for Research in Medical Entomology | Paramasivan R.,Center for Research in Medical Entomology | Thenmozhi V.,Center for Research in Medical Entomology | And 2 more authors.
Clinical Microbiology and Infection | Year: 2012

The usefulness of detecting circulating non-structural protein 1 (NS1) IgM antibodies for diagnosing acute dengue virus infection was evaluated during an outbreak investigation along with other routinely used laboratory diagnostic methods. For the first time, the samples were also tested for NS1 antigen detection. NS1 IgM antibody detects all the serum samples that were positive for NS1 antigen detection within first 5days of infection. The sensitivity of the NS1 IgM ELISA was higher when compared with RT-PCR and therefore, it could be used for early diagnosis. © 2011 The Authors. Clinical Microbiology and Infection © 2011 European Society of Clinical Microbiology and Infectious Diseases.


Asnet Mary J.,Lady Doak College | Paramasivan R.,Center for Research in Medical Entomology | Tyagi B.K.,Center for Research in Medical Entomology | Surender M.,Biotechnology Information Center | Shenbagarathai R.,Lady Doak College
Journal of Biomolecular Structure and Dynamics | Year: 2013

Chikungunya fever is one of the reemerging vector-borne diseases. It has become a major global health problem especially in the developing countries. There are no vaccines or specific antiviral drugs available to date. This study reports small molecule inhibitors of envelope glycoprotein 2 (E2 glycoprotein) which are predicted based on Chikungunya virus-host interactions. E2 glycoprotein of Chikungunya virus interacts at 216 residue of the host receptor protein which plays a vital role in initiating infection. Understanding the structural aspects of E2 glycoprotein is crucial to develop specific inhibitors to prevent the virus binding from host receptors. In silico method was adopted to predict the sequence motifs of envelope protein, as the method like yeast two hybrid system is laborious, time consuming, and costly. The E2 glycoprotein structure of the Indian isolate was modeled using two templates (2XFC and 3JOC) and then validated. The class III PDZ domain binding motif was found to be identified at 213-216 amino acids. The corresponding peptide structures which recognize the PDZ domain binding motif were identified by the literature search and were used for generating five point pharmacophore model (ADDDR) containing acceptor, donor and aromatic ring features. Databases such as Asinex, TosLab and Maybridge were searched for the matches for the predicted pharmacophore model. Two compounds were identified as lead molecules as their glide score is > 5 kcal/mol. Since the pharmacophore model is developed based on Chikungunya virus-host interaction, it can be used for designing promising antiviral lead compounds for the treatment of Chikungunya fever. © 2012 Taylor and Francis.


Samuel P.P.,Center for Research in Medical Entomology | Thenmozhi V.,Center for Research in Medical Entomology | Nagaraj J.,Center for Research in Medical Entomology | Kumar T.D.,Directorate of Health Services | Tyagi B.K.,Center for Research in Medical Entomology
Journal of Vector Borne Diseases | Year: 2014

Background & objectives: A longitudinal, entomological and virological study was conducted from 2007 to 2010 in four dengue fever affected areas of Thiruvananthapuram district, Kerala to understand the risk factors involved in the dengue transmission.Methods: Aedes surveys were carried out seasonally in the selected localities both indoors and peridomestic sites. Water holding containers were sampled for the presence of immature. Outdoor and indoor resting/landing mosquitoes were collected. Blood meal identification was performed by gel diffusion test and viral assay using the ELISA test.Results: The species found were Aedes (Stegomyia) aegypti (Linn.), Ae. (Stegomyia) albopictus (Skuse) and Ae. (Stegomyia) vittatus (Bigot). Aedes aegypti and Ae. albopictus immature stages were also found during the study period. Aedes aegypti was the only prevalent species in the water-starved Vizhinjam, a rural coastal area with breteau index (BI) ranging from 40 to 271. Aedes albopictus was recorded in rest of the three surveyed localities— two urban and one rural ghat areas of Thiruvananthapuram district.Interpretation & conclusion: The vector control measures should be focused mainly on source reduction of water storage containers present in both outdoor (Ae. albopictus and Ae. vittatus) and indoor (Ae. aegypti). To achieve effective vector management, a public health response beyond routine larviciding or focal spraying is essential throughout the year. © 2014 Malaria Research Center. All Rights reserved.


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.


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.


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.


Muniaraj M.,Center for Research in Medical Entomology | Sathish Babu R.,Center for Research in Medical Entomology
Tropical Biomedicine | Year: 2014

The vector mosquitoes, Aedes aegypti and Aedes albopictus of dengue and Chikungunya fever are closely associated with human habitations and adapted to feed on human blood. They undergo larval and pupal development in natural and artificial freshwater collections in the urban and peri-urban environment. Although reports are available about the feeding behaviour of the thriving mosquito larvae, much information is still required to understand the successful survival of Aedes mosquitoes in small and temporary water collections. This study was undertaken to determine the co-existence and prevalence of Philodina roseola and other Bdelloid rotifers in the container habitats of Ae. aegypti mosquitoes. The investigation was conducted in 43 villages which belong to four districts in South India, affected by the epidemic of either dengue or Chikungunya fever. A total of 2093 houses and 12980 containers were examined for Aedes breeding and those containers with Aedes larvae were chosen for further investigation. The investigation showed that, the P. roseola was found associated in 502 (98.2%) containers, P. roseola along with other Philodina sp. in 126 containers (25%) and P. roseola along with other Philodina sp. and other Bdelloid rotifers found in 93 containers (19%). Since the members of the genus Philodina can survive desiccation, reproduce by parthenogenesis, can be transported by wind easily and more importantly, it can incorporate the genome of other organisms including viruses, understanding the coexistence and relationship of Philodina sp. with Aedes larvae would be helpful in the control of Aedes breeding and the control measures can be designed keeping the association of Bdelloids with Aedes in mind.

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