Japanese Encephalitis:Epidemiology, Prevention and

Control

Dr. Dilip Kumar Das

Associate Professor, Community Medicine

Burdwan Medical College, West Bengal

JE : Global Burden

A disease of public health importance:

- Epidemic potential- Epidemic potential - High case fatality- High case fatality - Complications leading to life long sequelae- Complications leading to life long sequelae

Previously disease of East Asia - Japan, Korea and China

Recent years spread to SEA - Thailand, Indonesia, India, Vietnam, Myanmar and Sri Lanka.

Estimated 43,000 cases with 11,000 deaths and 9,000 disabilities occur / year globally

JE in India : Historical Background

1952 - First evidence of JE viral activity by VRC (NIV) 1955 - First human case of JE 1956 - First viral isolation from mosquitoes 1958 - First viral isolation from JE case

1973 - First outbreak in Bankura & Burdwan in West Bengal 1976 - Repeat outbreak in Burdwan 1978 - Several states reported outbreaks of JE 2003 - JE prevention and control under integrated NVBDCP

JE endemic areas in India

Uttar PradeshAndhra PradeshAssamBiharGoaKarnatakaMaharashtraTamilnaduWest BengalKeralaJharkhandOrissaManipurPunjabHaryana

Agent-Host-Vector-Environment

Agent: JE is a viral disease - an Arbovirus (Flavivirus) Closely linked antigenically to other flaviviruses Single serotype, but geographic strains differ by RNA

sequencing Neurotorpic and primarily affects central nervous system

Host: JE virus is primarily zoonotic in its natural cycle. Natural hosts: Animals and Birds - Pigs: amplifier host - allow manifold virus multiplication

without suffering from disease & maintain prolonged viraemia. - Cattle and buffaloes: ‘mosquito attractants’ Man is an accidental ‘dead-end’ host. -usual age group below 15 years with no sex predilection

Vectors: Culex tritaeniorhynchus, C. vishnui and C. pseudovishnui. Breeding habit: Irrigated rice fields, shallow ditches and pools etc. Resting habit: Exophilic but may rest indoor in extreme summer Feeding habit: Zoophilic and outdoor as well as indoor feeders The average life span of mosquito is about 21 days Flight Range: long distance (1 - 3 kms or even more)

Environment: Mainly prevalent in rural areas Outbreak is a seasonal phenomenon Mosquito vector prefers large and clean water collections for

breeding - paddy cultivation areas offer typical favourable situation Rural setting offers the amplifier hosts in abundance Occurrence in monsoon and post-monsoon season: in north India

from May-October, in southern part from August to November

How Japanese Encephalitis is transmitted?

Transmission Cycle: Pig – Mosquito – Pig Bird – Mosquito – Bird Due to prolonged viraemia, mosquitoes get

opportunity to pick up infection from pigs easily. After an extrinsic incubation period of 9 –12 days Infected

female mosquito transmits the virus to other hosts Man is a dead end in transmission cycle due to low

and short-lived viraemia. Mosquitoes do not get infection from JE patient.

Clinical Manifestations High ratio of symptomatic to asymptomatic infections

(1:250 to 1:1000) Incubation period : 6-16 days

Course of the disease can be divided into three stages:

Prodromal stage - Acute onset - fever, chills, headache and malaise

Acute encephalitic stage - High fever (38 to 40.7o C), neck rigidity, photophobia, nausea, vomiting,

seizures and altered sensorium. - Variable neurological signs appear (cranial nerve palsies, tremors, ataxia,

abnormal reflexes, paralysis, delirium and ultimately coma)

Late stage and sequelae - Active inflammation subsides, neurological signs stable

- Sequelae: Parkinsonism, paralysis and mental retardation

Case Fatality Rate: Exceeds 25%

Case Definitions for JE Diagnosis and Reporting

Suspect case

Febrile illness of variable severity associated with neurological symptoms ranging from headache to meningitis or encephalitis. 

Symptoms can include headache, fever, meningeal signs, stupor, disorientation, coma, tremors, paralysis (generalized), hypertonia , loss of coordination.

- (Patient with fever, altered sensorium lasting more than 6 hours, no skin rash and other known causes of encephalitis excluded)

Probable Case

A suspected case with presumptive laboratory results: Detection of an acute phase anti-viral antibody response

through one of the following - - Elevated and stable JE antibody titres in serum through

ELISA or HI or virus neutralization assays OR - IgM antibody to the virus in serum 

Confirmed Case

A suspect case with confirmed laboratory result : - Detection of JE virus, antigen or genome in tissue, blood or

other body fluid by immuno-chemistry, immuno-fluorescence or PCR, or

- JE virus specific IgM in CSF or - Four fold or greater rise in paired sera (acute & convalescent

phases) through IgM/IgG ELISA, HI or virus neutralization test

Management

Mainly symptomatic & supportive Therapeutic norms for the supportive

therapy are not established Fluid and electrolyte balance Reduction of intra-cranial pressure Control of convulsions, if present Maintenance of airway is crucial

Prevention and Control of JE

Early diagnosis and proper management of JE cases

Strengthening of referral mechanism

Integrated Vector Management:

- - Insecticide residual spray not recommended - Reduction of breeding sources: Water management system with

intermittent irrigation system; incorporation of neem products in rice fields

- Anti-larval operations wherever feasible: larvivorous fish, biolarvicides

- Fogging with Malathion for immediate killing of mosquitoes during outbreak

- Reduction in man-vector contact: personal protection with ITNs, repellents, clothing etc. and exploring possibility of segregation of pigs, mosquito proofing of piggeries.

Prevention and Control of JE

Behaviour Change Communication for community participation and inter-sectoral convergence

Capacity building through training on case management and control of JE

Vaccination of children in JE endemic areas (1 and 15 years)

Operational research

Monitoring and Evaluation

Vaccination against JE

Killed VaccineKilled Vaccine:

2 doses of 1 ml each (0.5 ml <3 years age); 7-14 days interval; Sub-cutaneously Booster dose after few months (preferably 1 month)

but within one year Revaccination after three years

Live Vaccine :

SA –14 –14 – 2 Freeze-dried Single dose of 0.5 ml; Sub-cutaneously Routine Immunisation: 16 – 24 months Pilot Basis : Children of 1- 15 years

Gaps and Challenges of the Prevention and Control of JE

Outdoor habit of the vector – variation in vector bionomics

Scattered distribution of cases spread over relatively large areas

Role of different reservoir hosts Specific vectors for different geographical and

ecological areas Immune status of various population groups is not

known making it difficult to delineate vulnerable population groups.

Gaps and Challenges of the Prevention and Control of JE

Difficulties in segregation of pigs Inadequate surveillance Efficient rapid diagnostics for field use not available Inadequate epidemic forecasting & preparedness Lack of supervision & monitoring. Limited inter-sectoral convergence and community

participation JE immunization programme-supply of vaccines and

cold chain arrangements, cost factor, coverage.

National Vector Borne Disease Control Programme

MalariaFilaria

Kala-azarJapanese Encephalitis

Dengue

National Vector Borne Disease Control Programme

Vision:

A well-informed and self-sustained, healthy India free from vector borne diseases with equitable access to quality health care

Mission:

Integrated and accelerated action towards reducing Integrated and accelerated action towards reducing mortality on account of Malaria, Japanese mortality on account of Malaria, Japanese Encephalitis, Dengue by half and elimination of Kala-Encephalitis, Dengue by half and elimination of Kala-azar by 2010 and elimination of Lymphatic Filariasis azar by 2010 and elimination of Lymphatic Filariasis by 2015 by 2015

Strategies of NVBDCP

1. Parasite Elimination and Disease Management

• Early case detection and complete treatment

• Strengthening of referral services

• Epidemic preparedness and rapid response

2. Integrated Vector Management

for Transmission Risk Reduction

• Indoor residual spraying in selected high risk areas

• Use of insecticide treated bed nets

• Use of larvivorous fish

• Anti larval measures in urban areas

• Minor environmental engineering

Strategies of NVBDCP

3. Supporting Interventions

• Behaviour Change Communication

• Public Private Partnership

• Human Resource Development through Capacity Building

• Operational Research

• Monitoring and Evaluation through periodic reviews/field visits and web based Management Information System