Epidemiological Situation of Japanese Encephalitis in Nepal

Abstract

A human Japanese encephalitis (JE) case is considered to have elevated temperature (over 380C) along with
altered consciousness or unconsciousness and is generally confirmed serologically by finding of specific anti-JE
IgM in the cerebro spinal fluid. No specific treatment for JE is available. Only supportive treatment like
meticulous nursing care, introduction of Ryle’s tube if the patient is unconscious, dextrose solution if dehydration
is present, manitol injection in case of raised cranial temperature and diazepam in case of convulsion. Intra
venous fluids, indwelling catheter in conscious patient and corticosteroids unless indicated should be avoided.
Pigs, wading birds and ducks have been incriminated as important vertebrate amplifying hosts for JE virus
due to viremia in them. Man along with bovines, ovines and caprines is involved in transmission cycle as
accidental hosts and plays no role in perpetuating the virus due to the lack of viremia in them. The species Cx
tritaeniorhyncus is suspected to be the principal vector of JE in Nepal as the species is abundantly found in the
rice-field ecosystemof the endemic areas during the transmission season and JE virus isolates have been obtained
from a pool of Cx tritaeniorhyncus females. Mosquito vector become infective 14 days after acquiring the JR
virus from the viremic host. The disease was first recorded in Nepal in 1978 as an epidemic in Rupandehi
district of the Western Development Region (WDR) and Morang of the Eastern Region (EDR). At present the
disease is endemic in 24 districts.Although JE as found endemic mainly in tropical climate areas, existense and
proliferation of encephalitis causing viruses in temperate and cold climates of hills and valleys are possible.
Total of 26,667 cases and 5,381 deaths have been reported with average case fatality rate of 20.2% in an
aggregate since 1978. More than 50% of morbidity and 60% mortality occur in the age group below 15 years.
Upsurge of cases take place after the rainy season (monsoon). Cases start to appear in the month ofApril - May
and reach its peak during late August to early September and start to decline from October. There are four
designated referral laboratories, namely National Public Health Laboratory (Teku), Vector Borne Diseases
Research and Training Center (Hetauda), B.P. Koirala Institute of Medical Sciences (Dharan) and JE Laboratory
(Nepalgunj), for confirmatory diagnosis of JE. For prevention of JE infection;chemical and biological control
of vectors including environmental management at breeding sites are necessary. Segregate pigs from humans
habitation. Wear long sleeved clothes and trousersand use repellent and bed net to avoid exposure to mosquitos.
For the prevention of the disease in humans, safe and efficacious vaccines are available. Therefore immunize
population at risk against JE. Immunize pigs at the surroundings against JE. 225,000 doses of live attenuated
SA-14-14.2 JE vaccine were received in donation from Boran Pharmaceuticals, South Korea for the first time
in Nepal. Altogether 224,000 children aged between 1 to 15 years were vaccinated in Banke, Bardiya and
Kailali districts during 1999. From China also, 2,000,000 doses of inactivated vaccine were received in 2000
and a total of 481,421 children aged between 6m to 10 yrswere protected from JE during 2001/2002. Ministry
of Agriculture, Department of Livestock Services has vaccinated around 200,000 pigs against JE in terai zone
during February 2001.

Key Words: Supportive treatment, viremia, amplifying host, vectors, vaccination/immunization.