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Chowdhury P.,Arbovirology Group | Chowdhury P.,Tocklai Tea Research Institute | Topno R.,Arbovirology Group | Khan S.A.,Arbovirology Group | Mahanta J.,Arbovirology Group
Advances in Virology | Year: 2015

West Nile Virus (WNV) is a pathogenic arbovirus that belongs to genus Flavivirus under family Flaviviridae. Till now there are no approved vaccines against WNV for human use. In this study, the effect of two alkylating agents, formaldehyde and β-PL, generally used for inactivated vaccine preparation, was assessed on the basis of antigenic and immunogenic potential of the inactivated WNV. Lineage 5 WNV isolates were inactivated by both formalin and β-PL treatments. Inactivation was confirmed by repeated passage in BHK-21 cell line and infant mice. Viruses inactivated by both the treatments showed higher antigenicity. Immune response in mice model showed serum anti-WNV antibody titre was moderately higher in formalin inactivated antigen compared to β-PL inactivated antigen. However, no significant differences were observed in neutralization antibody titre. In conclusion, we can state that both formaldehyde and β-PL inactivation processes were found to be equally efficient for inactivation of WNV. However, they need to be compared with other inactivating agents along with study on cell mediated immune response. © 2015 Pritom Chowdhury et al.

Khan S.A.,Arbovirology Group | Borah J.,Arbovirology Group | Chowdhury P.,Tocklai Tea Research Institute | Dutta P.,Arbovirology Group | Mahanta J.,Arbovirology Group
Transactions of the Royal Society of Tropical Medicine and Hygiene | Year: 2015

Background: Japanese encephalitis virus (JEV) is one of the major etiological agents responsible for causing large numbers of acute encephalitis syndrome (AES) cases in the northeastern region of India. This study was carried out to establish and characterize the circulating strain of JEV in the region in order to understand the disease epidemiology. Methods: Virus isolation was attempted from 121 patients that presented with AES. Phylogenetic analysis was done using the Kimura-2-Parameter model based on envelope and pre-membrane gene sequence. A pathogenecity study was done in the Swiss albino mice model and assessed by Kaplan-Meier survival analysis. Results: The phylogenetic analysis of the two JEV isolates obtained placed them within genotype (G)III, where they form a subclade within the Vellore group of Indian JEV strains. Neutralization assays suggested similarity between the study isolates and prototype Vellore JEV strain P20778. Pathogenesis in mice suggested that the circulating GIII JEV strains were neuroinvasive. Conclusions: This study showed that a pathogenic GIII JEV strain was circulating in the northeastern region of India. This finding is important as it is contrary to the belief that GI is gradually replacing GIII as the dominant genotype in Asia. © The Author 2015.

Roy S.,Tocklai Tea Research Institute | Muraleedharan N.,Tocklai Tea Research Institute | Mukhopadhyay A.,North Bengal University
Experimental and Applied Acarology | Year: 2014

Oligonychus coffeae Nietner (Acari: Tetranychidae), the red spider mite (RSM), is a major pest of tea (Camellia sinensis) in most tea-producing countries. Nymphs and adults of RSM lacerate cells, producing minute characteristic reddish brown marks on the upper surface of mature leaves, which turn red in severe cases of infestation, resulting in crop loss. The pest is present on tea all the year round, although numbers vary depending on season. Their number increases as the weather warms up and decreases markedly once rains set in. Under optimal conditions there may be 22 overlapping generations in a year. Parthenogenesis is known to occur; consequently, all mite stages can be found at a given time. Their infestation is mainly confined to the upper surface of the mature leaves and could readily be identified by the bronzing of the leaf. There are several naturally occurring insect predators, such as coccinellid and staphylinid larvae, lacewing larvae, and mite predators, most importantly species of the families Phytoseiidae and Stigmaeidae. Integrated management has been adopted to control this mite pest, involving cultural, mechanical, physical, biological and chemical methods. This review collates the most important works carried out on biology, ecology and management of O. coffeae. Also the scope of future studies for better management of this regular mite pest of tea is discussed. © 2014 Springer International Publishing Switzerland.

Bhuyan L.P.,Tocklai Tea Research Institute | Borah P.,Tocklai Tea Research Institute | Sabhapondit S.,Tocklai Tea Research Institute | Gogoi R.,Tocklai Tea Research Institute | Bhattacharyya P.,Indian Statistical Institute
Journal of Food Science and Technology | Year: 2015

The spatial distribution of theaflavin and thearubigin fractions and their impact on black tea quality were investigated using multivariate and geostatistics techniques. Black tea samples were collected from tea gardens of six geographical regions of Assam and West Bengal, India. Total theaflavin (TF) and its four fractions of upper Assam, south bank and North Bank teas were higher than the other regions. Simple theaflavin showed highest significant correlation with tasters’ quality. Low molecular weight thearubigins of south bank and North Bank were significantly higher than other regions. Total thearubigin (TR) and its fractions revealed significant positive correlation with tasters’ organoleptic valuations. Tea tasters’ parameters were significantly and positively correlated with each other. The semivariogram for quality parameters were best represented by gaussian models. The nugget/sill ratio indicated a strong/moderate spatial dependence of the studied parameters. Spatial variation of tea quality parameters may be used for quality assessment in the tea growing areas of India. © 2015 Association of Food Scientists & Technologists (India)

Roy S.,Tocklai Tea Research Institute | Rahman A.,Tocklai Tea Research Institute
Zoology and Ecology | Year: 2014

The tea aphid Toxoptera aurantii Boyer (Sternorrhyncha: Aphididae) is a major pest of the tea plant (Camellia sinensis (L.)). Micraspis discolor (F.) and Menochilus sexmaculatus (F.) (Coleoptera: Coccinellidae) are the most common predators of these pests in tea plantations of North East India. A laboratory study was conducted to evaluate the suitability of the tea aphid Toxoptera aurantii, as prey for these two ladybird beetles. The life cycle of M. sexmaculatus was found to be shorter than that of M. discolor. Aphid consumption by M. sexmaculatus was significantly higher than that by M. discolor. Aphid consumption by larvae of M. discolor and M. sexmaculatus was noticed to be higher in later instars. Females of both ladybird species consumed a significantly greater number of aphids per day than males. As for biological parameters and the predatory potential of the two ladybird species, the study results proved that M. discolor and M. sexmaculatus are effective biocontrol agents of the tea aphid and can be used in integrated pest management programs successfully. © 2014 Nature Research Centre.

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