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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 - High case fatality - PowerPoint PPT Presentation
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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