Mosquitoes are vectors for many important diseases. Being a vector means that it carries a disease from one host to another. Many of these diseases have a distribution, high, and a high number of cases but some do not, Japanese Encephalitis is also one of the diseases transmitted by mosquito vector. JEV has been isolated from ten species of the genus Culex, three species of Anopheles and three species of Mansonia in India. Of these the largest numbers of isolates have come from two species. Culex tritaeniorhyn and Cx vishnui are incriminated as major vectors in Southern India. By large in whole of South East Asia and India, maximum number of JEV isola-tion have been done from members of Culex vishnui group of mosquitoes which include three species i.e.. Cx. tritaeniarhynchus Giles, Cx. vishnui Theobald and Cx. pseudovishnui Colless.

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COMSATS Institute of Information Technology, Abbottabad
Course title General Virology
Assignment number 01
Assignment Japanese Encephalitis Virus
Submitted by Zohaib HUSSAIN
Registration number Sp13-bty-001
Submitted To Dr. Sidra Rehman
Date of submission Tuesday, September 29, 2015

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Japanese encephalitis virus
Vector of disease
Mosquitoes are vectors for many important diseases. Being a vector means that it carries a
disease from one host to another. Many of these diseases have a distribution, high, and a high
number of cases but some do not, Japanese Encephalitis is also one of the diseases transmitted by
mosquito vector. JEV has been isolated from ten species of the genus Culex, three species of
Anopheles and three species of Mansonia in India. Of these the largest numbers of isolates have
come from two species. Culex tritaeniorhyn and Cx vishnui are incriminated as major vectors in
Southern India. By large in whole of South East Asia and India, maximum number of JEV isola-
tion have been done from members of Culex vishnui group of mosquitoes which include three
species i.e.. Cx. tritaeniarhynchus Giles, Cx. vishnui Theobald and Cx. pseudovishnui Colless.
.Morphology of disease
Three morphologically distinct structures, inner core, envelope, and surface projections, were
observed in purified Japanese encephalitis virus virions by electron microscopy. The average
diameter of each structure was 29.8 ± 2.5, 44.8 ± 3.2, and 53.1 ± 4.5 nm, respectively. It is
Enveloped, icosahedral nucleocapsid symmetry, spherical particles and 40 to 60 nm in diameter.
The causative agent for Japanese encephalitis virus is an enveloped virus of the
genus flavivirus and is closely related to the West Nile virus and the St. Louis encephalitis virus.
The positive sense single-stranded RNA genome is packaged in the capsid which is formed by
the capsid protein. The outer envelope is formed by envelope protein and is the protective
antigen. It aids in entry of the virus into the inside of the cell. The genome also encodes several

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nonstructural proteins (NS1, NS2a, NS2b, NS3, N4a, NS4b, NS5). NS1 is produced as secretory
form also. NS3 is a putative helicase, and NS5 is the viral polymerase.
Virus name (virus species located in Japanese encephalitis virus group)
Species Name Japanese encephalitis virus
The ICTVdB virus code 00.026.0.01.019.04.001
Genus Flavivirus
Family Flaviviridae
Phylogenetic ancestor and viral evolution
The virus appears to have originated from its ancestral virus in the mid-1500s in the Indonesia-
Malaysia region and evolved there into five different genotypes and spread across Asia. The
mean evolutionary rate has been estimated to be 4.35×10−4 (range: 3.4906×10−4 to 5.303×10−4)
nucleotide substitutions per site per year.
Phylogenetic tree topology
The phylogenetic tree topology obtained using thirteen complete genome sequences of JEV was
reproduced with the envelope, NS1, NS3, and NS5 genes and revealed extensive divergence
between the two Indian strains included. A more exhaustive analysis of JEV evolution using 107
envelope sequences available for isolates from different geographic locations worldwide
revealed five distinct genotypes of JEV, displaying a minimum nucleotide divergence of 7% with
high bootstrap support values.

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The tree also revealed overall clustering of strains based on geographic location, as well as
multiple introductions of JEV into the Indian subcontinent. Nonsynonymous nucleotide
divergence rates of the envelope gene estimated that the ancestor common to all JEV genotypes
arose within the last three hundred years.

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References:
https://en.wikipedia.org/wiki/Japanese_encephalitis#Evolution
http://ictvdb.bio-mirror.cn/Ictv/fs_flavi.htm#00.026.0.01.019.
https://www.clarku.edu/~tlivdahl/page19/kasia/vectordiseases.html#Japanese_Encephalitis
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC355558/
https://en.wikipedia.org/wiki/Japanese_encephalitis#Virology
https://en.wikipedia.org/wiki/Flavivirus
http://ictvdb.bio-mirror.cn/Ictv/va_indxJ.htm
http://www.ncbi.nlm.nih.gov/pubmed/11561712
Book Mosquito Vectors of Japanese Encephalitis Virus from Northern India by Bina Pani Das