Ultrasensitive qualitative detection of Japanese encephalitis
virus by reverse transcription coupled real time polymerase
One of the
leading causes of acute encephalopathy in children in the
tropics is Japanese encephalitis (JE). An arbovirus, the
Japanese encephalitis virus is transmitted by Culex mosquitoes
and is a member of genus Flavivirus of the family Flaviviridae.
The RNA genome of the JE virus is positive sense,
single-stranded, approximately 11 Kb in length, and contains one
long open reading frame.
JE virus is
related to Murray Valley encephalitis virus. The virus is
neurotropic and predominately affects the thalamus, anterior
horns of the spinal cord, cerebral cortex, and cerebellum. It
mainly affects children <15 years of age and is mostly
asymptomatic. The occasional symptomatic child typically
presents with a neurological syndrome characterized by altered
sensorium, seizures, and features of intracranial hypertension.
Though no antiviral drug is available against JE, effective
supportive management can improve the outcome. Control of JE
involves efficient vector control and appropriate use of
primates can develop similar pathological lesions to those in
human when infected with JE virus; they are considered dead-end
hosts for JE. Most horses infected by JE virus show mild
clinical signs, including fever, anorexia and depression.
However, the mortality rate is high when JE infected horses show
neurological symptoms (Ihara et al., 1997). Seroepidemiological
survey of Asian monkeys has also shown widespread infection of
these primates with JE virus (Yuwono et al., 1984). The virus
can also infect birds, pigs and donkeys. Currently, the virus is
mainly detected in East Asia, southeast Russia, India, Papua New
Guinea and the Torres Strait Islands.
methods of JE diagnosis, including hemagglutination-inhibition
and complement fixation tests for antibody assay, have been
ineffective because of low sensitivity. Although a new
immunoassay was developed to detect earlier, virus-specific IgM
antibodies in the serum and cerebrospinal fluid (CSF) of acute
and convalescent-phase patients, this new assay also suffered
from low sensitivity and non-specific reaction. Reverse
transcription-polymerase chain reaction (RT-PCR) has been used
to detect Flavivirus rapidly and specifically.
Help confirm the disease causing agent
Shorten the time required to confirm a clinical
diagnosis of JE infection.
Help ensure that animal populations are free of JE virus
Early prevention of spread of the virus
Minimize personnel exposure to the virus
Safety monitoring of biological products and vaccines
that derive from horses and primates
Ihara, T., Kano, R., Nakajima, Y., Sugiura, T., Imagawa, H.,
Izuchi, T. and Samjima, T. (1997) Detection of antibody to
Japanese encephalitis virus (JEV) by enzyme-linked immunosorbent
assay (ELISA). J. Equine Sci. 8: 25-28.
Yuwono, J., Suharyono,
W., Koiman, I., Tsuchiya, Y. and Tagaya, I. (1984)
Seroepidemiological survey on dengue and Japanese encephalitis
virus infections in Asian monkeys. Southeast Asian J Trop Med
Public Health. 15:194-20
0.5 ml whole blood in EDTA (purple top) or ACD (yellow top)
tube, or 0.5 ml fresh or frozen CNS tissue, or 0.5 ml CSF, serum
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specimen acceptability and shipping instructions.
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Qualitative reverse transcription coupled real time PCR