Publications (41)101.24 Total impact
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Article: Identification of structural motifs in the E2 glycoprotein of Chikungunya involved in virus-host interaction.
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ABSTRACT: 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.An animated Interactive 3D Complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:21.Journal of biomolecular structure & dynamics 10/2012; · 4.99 Impact Factor -
Article: Wolbachia endobacteria in a natural population of Culex quinquefasciatus from filariasis endemic villages of south India and its phylogenetic implication.
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ABSTRACT: Understanding Wolbachia mosquito interactions have been recognized as an important concept to develop novel vector control strategies. The prevalence of Wolbachia endobacteria in a natural population of the filariasis vector Culex quinquefasciatus was determined by the polymerase chain reaction method. Earlier workers had estimated the infection rates of Wolbachia with only one or very few individuals per species. In our study large number of specimens were assayed, and a total of 750 adult Culex quinquefasciatus mosquitoes were collected from three south Indian villages of Tirukoilur and Mugaiyur blocks, monthly for a period of five months (December 2006 to April 2007) and screened for the presence of Wolbachia. The percentage prevalence in adult males ranged from 88% to 96%; while in females from 84% to 100%. An overall prevalence of 91.2% was observed. There was no significant difference observed in the proportion of mosquitoes positive for Wolbachia between males and females, and also between different months of the survey; except during the month of February '07. The wsp gene sequence of the Wolbachia strain of Cx. quinquefasciatus detected was BLAST analysed and showed 99% sequence similarity with Wolbachia sp. of Culex pipiens isolated from different geographical regions. Phylogenetic analysis based on wsp gene fragments showed that the present Wolbachia isolate was closely related with Wolbachia from Culex pipens pipiens, Niphotettix virescens (Order: Hemiptera) and Cnaphalocrosis medinalis (Order: Lepidoptera).Tropical biomedicine 12/2011; 28(3):569-76. · 0.62 Impact Factor -
Article: Evaluation and use of NS1 IgM antibody detection for acute dengue virus diagnosis: report from an outbreak investigation.
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ABSTRACT: 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 5 days 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.Clinical Microbiology and Infection 10/2011; 18(1):E8-10. · 4.54 Impact Factor -
Article: Dengue fever caused by dengue virus serotype-3 (subtype-III) in a rural area of Madurai district, Tamil Nadu.
The Indian journal of medical research 09/2010; 132:339-42. · 1.84 Impact Factor -
Article: Studies on community knowledge and behavior following a dengue epidemic in Chennai city, Tamil Nadu, India.
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ABSTRACT: In 2001, a major dengue outbreak was recorded in Chennai city, with 737 cases (90%) out of a total of 861 cases recorded from Tamil Nadu state. A KAP survey was carried out to assess the community knowledge, attitude and practice on dengue fever (DF), following the major dengue outbreak in 2001. A pre- tested, structured questionnaire was used for data collection. The multistage cluster sampling method was employed and 640 households (HHs) were surveyed. Among the total HHs surveyed, 34.5% of HHs were aware of dengue and only 3.3% of HHs knew that virus is the causative agent for DF. Majority of the HHs (86.5%) practiced water storage and only 3% of them stored water more than 5 days. No control measures were followed to avoid mosquito breeding in the water holding containers by majority of HHs (65%). Sixty percent of HHs did not know the biting behaviour of dengue vector mosquitoes. The survey results indicate that the community knowledge was very poor on dengue, its transmission, vector breeding sources, biting behavior and preventive measures. The lack of basic knowledge of the community on dengue epidemiology and vector bionomics would be also a major cause of increasing trend of dengue in this highly populated urban environment. There is an inevitable need to organize health education programmes about dengue disease to increase community knowledge and also to sensitize the community to participate in integrated vector control programme to resolve the dengue problem.Tropical biomedicine 08/2010; 27(2):330-6. · 0.62 Impact Factor -
Article: An outbreak of dengue fever in Tirupur, Coimbatore district, Tamil Nadu.
The Indian journal of medical research 07/2010; 132:105-7. · 1.84 Impact Factor -
Article: Role of community empowerment in the elimination of lymphatic filariasis in south India.
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ABSTRACT: The World Health Assembly in 1997 has targeted the elimination of lymphatic filariasis (LF) by 2020, and in India the goal has been set for the year 2015 by annual single dose mass drug administration (MDA). The role of community empowerment in enhancing the drug compliance and bringing out the function of various methods used to disseminate the information on MDA to the villagers is focused. A longitudinal survey was carried out in nine villages in Tirukoilur block of Villupuram district, Tamil Nadu for filarial infection variables like microfilaraemia, antigenaemia, transmission indices before and after each MDA, to determine the drug impact. Prior to each MDA, health education campaigns with different approaches were carried out with community as the leading player. These IEC approaches were assessed after 4 MDAs for its perception in the community. After four rounds of MDA, there was a significant decline in the filarial infection variables. The microfilaraemia and antigenaemia declined by 59% and 67% respectively. The transmission indices lowered by 89% and 94% (in resting and landing catch of mosquitoes respectively). The decline in these variables, with a drug consumption rate of >80% was achieved due to the effective IEC campaigns prior to each MDA. After 4 MDAs almost 97% of the respondents were aware of lymphatic filariasis. The KAP survey in the rural villages revealed that the dissemination of MDA message through autorickshaw was the most effective, followed by school students' rally. Empowerment of community through the members of women self help groups and school students were observed to be integral to mass drug administration campaigns for the enhancement of drug compliance, thus leading to LF elimination.Tropical biomedicine 04/2010; 27(1):68-78. · 0.62 Impact Factor -
Article: Molecular identification of mosquito vectors using genomic DNA isolated from eggshells, larval and pupal exuvium.
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ABSTRACT: Correct and precise identification of mosquito vectors is important in many respects including development of vector control strategies. Conventional identification methods have limitations for sibling and closely related species of mosquitoes, stage and quality of the specimen used and this could be overcome by DNA-based identification methods using molecular markers such as nuclear ribosomal internal transcribed spacer (ITS) which do not demand intact or undamaged specimen. Genomic DNA is usually isolated from whole mosquito, legs, wings etc. Alternate sources for genomic DNA isolation such as eggshells, larval and pupal exuviae were explored in this study by amplifying the ITS markers. Standardization of genomic DNA extraction and ITS amplification were carried out with laboratory specimens. The same was applied to specimens collected from the field. The results show that PCR amenable genomic DNA could be isolated from fresh exuviae collected in the laboratory and not from older and/or field specimens. But exuviae of larvae and/or pupae collected in the field reared to adulthood in the laboratory yielded PCR amenable genomic DNA. The results also revealed that the ITS2 marker could very well differentiate Aedes aegypti and Aedes albopictus by producing amplicons of ~330 bp and ~520 bp, respectively. The genomic DNA from these alternate sources also supported the species-specific PCR to distinguish the Culex vishnui subgroup mosquitoes.Tropical biomedicine 04/2010; 27(1):47-53. · 0.62 Impact Factor -
Article: Article Description of a new species, Anopheles pseudosundaicus (Diptera: Culicidae) from Kerala, India
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ABSTRACT: Specimens of Anopheles pseudosundaicus, new species, belonging to the Pyretophorus Series of Anopheles (Cellia), were collected from the coastal areas of Alleppey and Kollam districts in Krerala, southwest India. Female (holotype), male (allotype), pupa and fourth-stage larva of this species are described and illustrated to distinguish it from An. subpictus Grassi and An. sundaicus. (Rodenwaldt). It differs from An. sundaicus by the absence of speckling on legs and from An. subpictus in having a complete prehumeral dark spot on costa in wings. A partial sequence of Cytochrome oxidase C subunit 1 (CO1) of mt DNA places An. pseudosundaicus phylogenetically distant from An. sundaicus and closer to An. subpictus.Zootaxa 09/2009; 2219:49-60. · 0.93 Impact Factor -
Article: Longitudinal studies of Japanese encephalitis virus infection in vector mosquitoes in Kurnool district, Andhra Pradesh, South India.
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ABSTRACT: A 4-yr (2002-2006) entomological study was carried out in Kurnool district, Andhra Pradesh state, south India, to identify the mosquito vectors of Japanese encephalitis virus (family Flaviviridae, genus Flavivirus, JEV). In total, 37,139 female mosquitoes belonging five genera and 18 species resting on vegetation were collected in villages and periurban areas at dusk. Mosquito species composition and pattern of JEV infection in mosquitoes varied in periurban and rural areas. In periurban area, Culex gelidus Theobald was abundant, making up 49.7% of total catch followed by Culex tritaeniorhynchus Giles (44.5%). In rural area, Cx. tritaeniorhynchus was predominant, making up 78.9% of total catch followed by Culex quinquefasciatus Say (10.8%), Anopheles subpictus Grassi (7.1%), and Cx. gelidus (1.1%). In light trap collections, Cx. gelidus and Cx. tritaeniorhynchus predominated in periurban and rural areas, respectively. Of 50,145 mosquitoes screened JEV isolations were made only from Cx. gelidus and Cx. tritaeniorhynchus. Based on high abundance and frequent JEV isolation, Cx. tritaeniorhynchus was found to be the principal vector in both areas, whereas Cx. gelidus plays a secondary vector role in periurban areas only.Journal of Medical Entomology 06/2009; 46(3):633-9. · 1.76 Impact Factor -
Article: Larvicidal efficacy of various formulations of Bacillus sphaericus against the resistant strain of Culex quinquefasciatus (Diptera: Culicidae) from southern India.
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ABSTRACT: Use of Bacillus sphaericus Neide (Bs) as potential biolarvicide in developing countries is limited due to development of resistance by target mosquitoes. Efforts are taken to look for appropriate formulations or combination of Bs to prevent or delay resistance problem. Here, we report the efficacy of a formulated Bs product to kill Bs resistant Culex quinquefasciatus Say larvae. The laboratory reared resistance colony was maintained by subjecting selection pressure with Bs (2362) toxin. Bioassays were conducted with lyophilized, standard formulated and Bs formulated by us (all belong to strain 2362, serotype H5a5b) against Bs resistant and susceptible colonies. The Bs resistant larvae showed a high level of resistance against lyophilized toxin with resistance ratio (RR) of 8375.2, 1055.6 and 11422.3 folds at LC(50), LC(90) and LC(95) levels, respectively, when compared with Bs susceptible larvae. With formulation of standard powder, the RR between Bs resistant and susceptible larvae were 1.01, 1.13 and 1.19 folds only at LC(50), LC(90) and LC(95) levels, respectively. This observation was comparable with our formulation prepared by a ground mixture of lyophilized Bs and a placebo (plaster of Paris). It is evident from our study, that the placebo present in our Bs 2362 formulation was responsible for increasing the efficacy of Bs lyophilized toxin against resistant larvae. The putative mechanism behind this toxicity phenomenon remains to be investigated to evolve new mosquito control strategies. A cross resistance to indigenous strain of Bs B42 (H5a5b) against Bs resistant larvae was also reported in this study.Tropical biomedicine 05/2009; 26(1):23-9. · 0.62 Impact Factor -
Article: Sero-entomological investigations on Japanese encephalitis outbreak in Gorakhpur division, Uttar Pradesh, India.
The Indian journal of medical research 04/2009; 129(3):329-32. · 1.84 Impact Factor -
Article: A study on chikungunya outbreak during 2007 in Kerala, south India.
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ABSTRACT: The first chikungunya outbreak occurred in Kerala during 2006 affecting 14 districts, followed by another during May 2007 affecting almost whole of the State. Four of the worst affected districts viz, Pathanamthitta, Idukki, Kottayam and Thrissur were surveyed during 2007 to understand the magnitude of the problem of chikungunya fever, particularly clinical signs and symptoms. A total of 1265 persons from 310 houses were surveyed door-to-door in 20 different localities representing four affected districts. The history and examination findings from 354 clinically diagnosed chikungunya cases were recorded. The symptoms recorded were fever, headache, myalgia, arthralgia, itch/rash, oedema, eye congestion, eye pain, oral ulcers, distaste, nausea, vomiting and haemorrhage. The major symptoms were fever (100%), headache (97.5%), arthralgia (99.4%) and myalgia (99.4%). A significant difference was observed in oedema, distaste, nausea and headache among different age groups and these symptoms were reported to be lower (12.2-89.8%) in younger age group than in older age group (90.4-100%). No genderwise difference was observed for any of the symptoms. In clinically diagnosed chikungunya cases higher age group (>35 years) found with higher rate of severity with symptoms of oedema, distaste, nausea and headache when compared with lower age group (1-35 yr). Chikungunya invaded Kerala State for the first time in 2006 and continues to be a major vector borne disease in the State. The clinical symptoms in affected cases highlighted high fever, sever myalgia and prolonged arthralgia, with occasional history of skin itch/rash (petechiae).The Indian journal of medical research 03/2009; 129(3):311-5. · 1.84 Impact Factor -
Article: Japanese encephalitis in Gorakhpur Division, Uttar Pradesh.
The Indian journal of medical research 01/2009; 128(6):775-7. · 1.84 Impact Factor -
Article: Ultrastructural changes in the lysosomes of the midgut epithelial cells of Culex quinquefasciatus (Diptera: Culicidae) following infection with Bacillus sphaericus IAB59 toxin
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ABSTRACT: Bacillus sphaericus (Bs) is a potential mosquito larvicide especially against Culex quinquefasciatus (Say), the vector of bancroftian filariasis. It is a gram-positive, aerobic and endospore-forming bacterium. During sporulation, it synthesizes binary endotoxins (molecular weight 42 and 51 kDa proteins) that are highly toxic to mosquito species. The mode of action of the binary toxin of this biolarvicide in the alimentary canal and the ultrastructural events in the tissues of the affected larvae have been demonstrated. Lysosomal components are the most important organelles involved in the metabolism of the foreign molecules encountered by the cells. In this paper, we report the ultrastructural changes in the midgut epithelial cells, with special emphasis on lysosomes (L), in untreated Cx. quinquefasciatus larvae and those treated with the Bs-IAB59 bacterial strain. In the Bs-treated larvae, the size of the L gradually increased, and within 16 h, fine filaments appeared and compartmentalized into small lamellar bodies, within the L. After 36 h, these lamellar bodies appeared to be collapsed, and later disintegrated in the 48th hour. In the untreated larvae, such ultrastructural changes in the L were not seen. These observations suggested that, though the target site of action of the Bs toxin is the midgut epithelial cells, ultrastructural changes in the L compartments play a vital role in the mortality of the mosquito larvae.International Journal of Tropical Insect Science 11/2008; 28(04):185 - 190. -
Article: Host feeding pattern of Japanese encephalitis virus vector mosquitoes (Diptera: Culicidae) from Kuttanadu, Kerala, India.
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ABSTRACT: Identification of blood meals of vector mosquitoes is an important tool in the epidemiological investigations of vector-borne diseases. The blood meals of three mosquito species involved in the transmission of Japanese encephalitis virus (JEV) from the Kuttanadu area, Kerala, were determined using the agarose gel diffusion technique. A total of 4959 blood smears belonging to Culex (Culex) tritaeniorhynchus Giles (3273), Cx. (Culex) gelidus Theobald (64), Mansonia (Mnd.) indiana Edwards (735) ,and Ma. (Mnd.) uniformis (Theobald) (887) were tested. Cx. tritaeniorhynchus had predominantly fed on bovids (46.4%), and a good proportion (29%) had fed on more than one host. Cx. tritaeniorhynchus was highly zoophagic, and human feeding accounted for only 1.5% of those individuals successfully tested. Cx. gelidus showed bovid feeding at 36% and pig feeding at 12.5%. The test results showed 42.3% Ma. indiana and 12.2% Ma. uniformis had fed on humans. Multiple feeding was observed in Ma. indiana and Ma. uniformis, and most of the double feedings were from bovids and ovids (7.9 and 20.1%, respectively). Pig feeding accounted for 4.8% of the feedings by Cx. tritaeniorhynchus, 5.3% of Ma. indiana, and 6.4% of Ma. uniformis. This study is significant because of the role played by these mosquitoes in the transmission of JEV in the Kuttanadu area of Kerala, India.Journal of Medical Entomology 10/2008; 45(5):927-32. · 1.76 Impact Factor -
Article: Natural vertical transmission of dengue viruses by Aedes aegypti in Chennai, Tamil Nadu, India.
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ABSTRACT: Dengue viruses are spread and maintained in an Aedes aegypti-human- Ae. aegypti cycle in urban areas of the tropics. Dengue viruses are also maintained in nature by vertical transmission by Ae. aegypti. A study was undertaken in Chennai, a known endemic city in south India, to comprehend the natural vertical transmission dynamics in Ae. aegypti and to assess its epidemiological importance. Ae. aegypti males collected in resting and landing collections were tested for dengue virus infection by antigen-capture enzyme-linked immunosorbent assay (ELISA) and further examined by insect bioassay, Toxorhynchites splendens inoculation-indirect immunofluorescence technique (Toxo-IFA) using serotype-specific monoclonal antibodies (Mabs), if found positive by ELISA. Of the 509 pools of Ae. aegypti males (n=5408) screened, 15 pools, collected in April, June- July, November-December in 2003 and March, May in 2004, were found positive for dengue virus infection and the minimum infection rate (MIR) among adult males was high in June 2003 (28.0/ 1000). Three positive pools could be serotyped as dengue-2 (2 pools) and dengue-3 (1 pool). Dengue virus isolations from wild caught males of Ae. aegypti indicate the occurrence of transovarial transmission. Vertical transmission was mainly observed in summer months when dengue infections in humans were low suggesting that dengue viruses adopt a novel strategy of surviving adverse climatic conditions.The Indian journal of medical research 05/2008; 127(4):395-7. · 1.84 Impact Factor -
Article: Desiccated vector mosquitoes used for the surveillance of Japanese encephalitis virus activity in endemic southern India.
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ABSTRACT: To monitor Japanese encephalitis virus (JEV) activity in endemic areas of Tamil Nadu, southern India, desiccated vector mosquitoes were screened for JEV antigen using ELISA, from 1996. A total of 133 233 specimens from eight index villages comprising 2816 pools (mainly Culex vishnui subgroup) were tested. Of these, 59 pools (2.1%) were positive for JEV antigen. Control measures were undertaken in positive villages accordingly. The average annual minimum infection rate was 0.8 at the beginning of the study and remained lower for nearly 8 years. A declining trend in JE cases was recorded.Tropical Medicine & International Health 03/2008; 13(2):286-90. · 2.80 Impact Factor -
Article: A focal outbreak of dengue fever in a rural area of Tamil Nadu.
The Indian journal of medical research 03/2007; 125(2):179-81. · 1.84 Impact Factor -
Article: Indian perspective on the need for new case definitions of severe dengue.
The Lancet Infectious Diseases 03/2007; 7(2):81-2. · 17.39 Impact Factor
