Japanese Encephalitis: Epidemiology, Prevention and Control

1. Japanese Encephalitis:Epidemiology, Prevention and Control Dr Monjori Mitra

2. JE : Global Burden • A disease of public health importance: - Epidemic potential - High case fatality - 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

4. JE endemic areas in India Uttar Pradesh Andhra Pradesh Assam Bihar Goa Karnataka Maharashtra Tamilnadu West Bengal Kerala Jharkhand Orissa Manipur Punjab Haryana

5. 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

6. 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

7. 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.

8. 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%

9. Case Definitions for JE Diagnosis and Reporting Suspect case Acute Encephalitis Syndrome 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)

10. 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

11. Disease Burden • Leading cause of viral encephalitis in Asia • 35,000-50,000 cases annually (Source:CDC,2004)

12. Death and disability from JE • Up to 30% of all patients with JE die. • For those that survive the illness, more than 30% cases are left with disability. • Disability is both physical and cognitive.

14. 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

15. Preventive strategies • Surveillance for cases of encephalitis • Vector control • vaccination

16. 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.

17. Vaccination • Not an outbreak response vaccine • Universal vaccine for JE endemic areas • All children from 1 – 15 years should be vaccinated • Phillipines study shows acceptable efficacy when coadministered with measles vaccine at 9 months. • Travellers vaccine in JE endemic areas when expected to stay for 4 weeks and should complete the doses prior to 1 week before travel.

20. JE VACCINE • INACTIVATED MOUSE BRAIN VACCINE • It is expensive vaccine, complicated dosing schedule, side effect of this vaccine. • Inactivated Mouse brain vaccine • 3-5 US dollars/dose • 9 – 15 US dollars/per child • The ‘mouse brain vaccine’ manufactured by killing populations of mice was being manufactured by Central Research Institute, Kasauli. • LIVE ATTENUATED VACCINE • SA 14 - 14-2 (Chinese live attenuated vaccine at affordable cost, safe, effective). • This vaccine was developed in China and has been used there since 1988. • it has been licensed and used in South Korea and Nepal and licensed in Sri Lanka. • It also appears feasible that a single dose of vaccine will provide life-long protection.

22. 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.

23. 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.

24. Strategies of National Vector Borne Disease Control Programme 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

25. 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

26. Strategy • A one time mass campaign targeting all children in the age group of 1-15 years in the districts. • Followed by integration of the JE vaccine into the Routine Immunization Program to cover the new cohort (children attaining more than 1 year of age) in the districts covered previously under the JE vaccination campaign. These children would be administered the JE vaccine between 1-2 years of age along with the DPT booster dose, under the Routine Immunization Programme. • A special campaign has been planned for 2010 in selected districts in the country to cover left outs and new cohorts. • Age distribution pattern of the lab confirmed JE cases will be reviewed to further inform strategy.

27. JE vaccination coverage 2006-2009