Japanese encephalitis: problem in India

Japanese encephalitis is a mosquito-borne viral encephalitis.It  is endemic in many regions of India.

The virus is particularly common in  areas where rice cultivation occurs.

The irrigated rice fields attract the natural avian vertebrate hosts.They  are breeding sites  for mosquitoes such as    Culex  tritaeniorhyncus.

The mosquito which carries the Japanese Encephalitis virus

Culex tritaeniorhyncus

How  does the disease spread?

Mosquitoes transmit the virus to humans. Humans get the disease.But humans don’t  transmit the infection. Pigs and horses are amplifier hosts (that is the virus multiplies in their bodies ).

So vaccination of these additional amplifier hosts may definitely reduce virus transmission.

When does Japanese encephalitis occur?

In India, Japanese encephalitis outbreaks have been reported in most states  and Union territories.

It occurs throughout the year.Significantly highest incidences occur   during monsoon and post-monsoon period.

Who are  most likely to get Japanese encephalitis?

In endemic areas   unvaccinated children are most often affected.

But travelers of all ages   may also be affected.

Statistics  which give you a  better perspective

Most   human cases  of JE (Japanese encephalitis) may be asymptomatic. Overt encephalitis may occur  in 1 of 20-1000 cases.

However, the encephalitis  when it occurs is severe.

 Fatality being as high as 25%.

Significantly children constitute an unfortunately high percentage of the fatalities.

World Health Organization (WHO) estimates  that there  occurs at least 50,000, reported fatal cases in Asia every year.

Of this  at least, 10,000 are children.

Serious neuropsychiatric sequelae  may be observed in   the  encephalitis  survivors in up to 30% cases.

Out of many  causes of encephalitis, JE is the most significant one which is vaccine preventable.

 

How can JE be Prevented?

• Public health campaigns to raise awareness
• Surveillance  for cases of encephalitis
• Vector(mosquito)  control
• Vaccination.

Who needs Japanese encephalitis vaccine

• Children and  adults in endemic , epidemic zones
• Travellers to endemic zones
• A spending month or longer in  endemic  area during the transmission season.
• Amplifier host vaccination( Pigs, horses)

 

Vaccination in India

1)Live  stable, neuro attenuated  strain of cell culture derived  SA-14-14-2 vaccine.

Recent Indian data on efficacy /effectiveness  suggests the need for two doses of vaccines for  primary vaccination schedule.

• Primary immunization

Children less than 3 years:

2 doses of 0.25 ml.1st dose at 9 months along with measles vaccine.

2nd dose at 16 or 18 months at the time of first DTP booster.

Children more than 3 years,  adolescents, adults less than 50 years:2 doses of 0.5 ml on days 0 and 28.

• Booster  Doses

Long-term protective efficacy and requirement for boosters are still not fully determined

 Adults have been recommended for a booster after 12 months.

 

 2)Purified Japanese encephalitis Inactivated Vaccine(Human)

• It contains the  JEV strain  821564-XY in a purified and inactivated form.
• Indicated above one year of age.

Composition

• JEV strain  821564-XY in a purified and inactivated form.
• Aluminium hydroxide gel
• Thiomersal(preservative)
• Phosphate Buffered solution

Site and route: Intramuscularly into deltoid  of upper arm of adults

Children :anterolateral thigh

 

Primary vaccination dosage and schedule: 

2 dose 0.5 ml each

First dose: Day 0

Second dose:28 days after the first dose

One dose  offers >98% protection 

You might need  a booster:

• when visiting  an  endemic area , with chance of re-exposure
• more than one year has passed, since primary vaccination was given.

 

Possible Adverse  effects  of JE vaccine:

• Fever
• headache
•  myalgia
• hypersensitivity reaction.

 

 

Contraindications of Japanese Encephalitis vaccine:

• Patient with known or suspected hypersensitivity  to vaccine components.
• Severe allergic reaction after previous dose  of vaccine.
• A patient who has fever.

 

The Big picture  on Japanese encephalitis vaccine

The  risk of JE associated encephalitis, it’s resultant mortalities and serious morbidity  is  on one side.This is  weighed against the relatively safe vaccine with few side effects.The balance of  facts makes this  vaccine a  very important vehicle to fight the endemic nature of the disease in India.

There’s a need for public awareness and vector control measures.These are the backbone of effective prevention.Prevention, as usual, is the best policy.Stay informed, take charge and make an informed decision.

Is your home mosquito Free?

Let me know in the comments section below.

 

 

 

Reference:

• VermaR.Hum Vaccin Immunother. 2012 Apr;8(4):491-3. doi: 10.4161/hv.18925. Epub 2012 Feb 28. Japanese encephalitis vaccine: need of the hour in endemic states
• Best of Indian Pediatrics vol1. Devendra Mishra, Dheeraj  Shah
• Harrison’s Principles of Internal Medicine