Japanese encephalitis epidemiology

japanese encephalitis

1. Epidemiology of Japanese Encephalitis Dr Utpal Sharma Demonstrator Department of Community Medicine FAAMCH, Barpeta

2. Introduction Japanese Encephalitis (JE) is a mosquito borne zoonotic viral disease involving the animals and humans. The virus is maintained in a transmission cycle between mosquito vectors and vertebrate hosts In nature, the virus is maintained in ardied birds and other animals particularly pigs. Horses are the primary affected domestic animals of JE and essentially a dead-end host, other equids are also susceptible Pigs act as important amplifiers of the virus producing high viraemias which infect mosquito vectors

3. JE transmission cycle

4. Ecology & Natural cycle of JE

5. What is Japanese encephalitis??? In humans causes inflammation of the membranes around the brain But why Japanese…… The virus was first isolated in Japan in 1935 from a fatal human case of encephalitis. In 1938, the virus was first isolated from its primary vector species, Culex tritaeniorhynchus . The first historic mention of JE occurred during the late 1870’s…… “summer encephalitis” Again in 1924, disease hit Japan with 6,125 human cases resulting in 3,797 human deaths (62% case-fatality rate).

6. And the journey continues…. 1940-1978: Disease spread with epidemics in China, Korea and India 1955: Disease was first time recognised in India 1972: Outbreaks reported in UP, Assam, West Bengal 1983-1987 : Vaccine available in U.S. on investigational basis

7. Why so worried about JE…??? Presence of one clinical case in the community suggests that 300 to 1000 people have been infected. It is a disease of public health importance because..... ....of its epidemic potential and high case fatality rate ( 20-40%) . .....most infections occur among children In a sizeable proportion of those who survive, are left with permanent neurological and/or psychiatric sequelae . The incidence of Japanese encephalitis has shown an increasing trend in recent times..... .......the disease is fast becoming a major public health problem in India It is a preventable disease and no specific antiviral treatment

8. JE around the globe….. Infection occurs throughout the temperate and tropical regions of Asia. Reduced the incidence of the disease in Japan since 1800’s …. ………probably due to control methods (vaccination and pesticides) Currently, the disease occurs in China, India, Nepal, Philippines, Sri Lanka and Northern Thailand. Occasionally sporadic cases of disease occur in Indonesia and northern Australia. An estimated 50,000 cases of JE occur globally each year, with 10,000 deaths and nearly 15,000 disabled. The disease has not occurred in the rest of the world.

9. Global distribution of JE

10. JE in India In India, JE was first recorded in Vellore and Pondicherry in mid 1950s (1955) The first major outbreak of JE occurred in 1973 in Bankura & Burdwan districts of West Bengal. In1976, wide spread outbreaks were reported from Andhra Pradesh, Assam, Karnataka,Tamil Nadu, Uttar Pradesh and West Bengal. The worst ever recorded outbreak in India was reported from Uttar Pradesh during 1988 when 4485 cases with 1413 deaths were recorded from eight districts with case fatality rate of 31.5%. The highly affected states include Andhra Pradesh, Assam, Bihar, Goa, Karnataka, Manipur, Tamil Nadu, Uttar Pradesh and West Bengal.

11. Distribution of JE in India

12. The hot spots…..

13. Endemic areas in India

14. To be noted……. Outbreaks of JE usually coincide with monsoons and post-monsoon period when the vector density is high. However, in endemic areas, sporadic cases may occur throughout the year. Case fatality rate in newly affected areas ranges from 10 – 70%. However, with early detection and management of cases it has come down to an average of approximately 20%.

15. Type A / Type B JE Type A Japanese Encephalitis Type B Japanese Encephalitis Encephalitis lethargica Von Economos disease Unknown etiology Vector borne disease Viral infection of CNS

16. Assam

17. Epidemiological Triad Organisms harboring the pathogens Agency that carries and transmits the pathogens Microbes causing disease External factors allowing transmission

18. Agent : ARBOVIRUSES Japanese encephalitis virus belongs to the family Flaviviridae , which are single - stranded RNA viruses. Viruses of vertebrates transmitted by hematophagus insect vectors Special characteristic: Ability to multiply in arthropods M ore numerous in tropical than in temperate zones

19. Vector of Transmission The virus is transmitted by the bites of mosquitoes of the Culex vishnui complex; Culex tritaeniorhynchus Culex vishnui Culex pseudovishnui .....with individual vector species differing in specific geographic areas. In India and many endemic areas in Asia, Culex tritaeniorhyncus is the principal vector. This species feeds outdoors beginning at dusk and during evening hours until dawn. In temperate zones, the vectors present in greatest numbers from June through September and inactive during winter months

20. Breeding places It breeds in...... water pools, Shallow ditches flooded rice fields, and stable collections of water Primarily outdoor resting in vegetation and shadowed places but may rest indoors in summers Flight range : 1-3 kms

21. Mode of transmission Humans get infected by the bite of the infected Culex mosquitoes Man to man transmission does not occur The infection does not spread from human beings to the mosquitoes No reports of accidental laboratory infection, congenital infection or transmission from infected organ donors

22. Hosts..... Natural reservoir of infection Amplifier Hosts Manifold virus multiplication without suffering from disease and maintain prolonged viraemia Accidental Host Dead end Host The virus has no specific age or sex predilection Pond heron

23. Environment.... Transmission related principally to temperature and humidity conducive to breeding and survival of the vector Immune status of various population groups Specific vectors for different geographical and ecological areas (rural, and agricultural locations) Increased Rainfall In temperate locations, transmission usually starts in April and may last until October Piggeries within 4-5 kms from human dwellings

24. Factors favouring outrbreak …..

25. Pathogenesis of the disease

26. Control and Prevention of the threat….. ………Japanese Encephalitis

27. Control measures Control measures involves 2 strategies: Control of the reservoir Control of the vector Control of reservoir: - Birds and various vertebrate animals acts as reservoirs - Practically impossible to take care of reservoirs - Pigs acts as amplifying hosts - Pig rearing should be discouraged in areas where rice cultivation is widespread

28. Cont…. Control of vector: Insecticide spraying is subtle option as vector mosquitoes breeds in paddy fields Eco management (intermittent irrigation) of paddy fields can be done - Ultra low volume insecticide spraying by fogging has been found helpful to some extent - Sterile male technique is a novel approach IN AFFECTED VILLAGES: -Aerial or ground fogging with ultra low volume insecticides -Indoor residual spray - Spraying should cover vegetation around houses, breeding sites & animal shelters IN UNINFECTED VILLAGES : - Those falling within 2-3 km radius of infected villages should also receive spraying as a preventive measure Use of mosquito nets should be advocated

29. Few ways to control vectors….

30. Prevention 4 types of vaccines are available for use against JE….. Mouse brain derived killed vaccine Cell culture based killed vaccine Live attenuated vaccine Live chimeric vaccine

31. Mouse brain derived killed vaccine Nakayama or Beijing strains are used Widely used vaccine in the past Primary dose followed by boosters Expensive and ideal for travelers Has severe adverse effects Banned from 2007 in India and in many other countries

32. Purified inactivated vaccine V ero cell derived purified inactivated vaccine Indigenous vaccine, made using strains obtained from kolar,Karnataka 2 doses intramuscularly 28 days apart for routine immunization and single dose of 0.5 ml during epidemics 98% seroconversion after 2 doses Launched officially in October, 2013 Available in markets but not yet introduced into routine immunization schedule

33. Live attenuated vaccine Also called as SA 14-14-2 vaccine Presently used in India Two doses of 0.5 ml subcutaneously Safer upto 15 years of age Not recommended for adults Highly effective for use during mass campaigns

34. Once Again………

35. Preventive and control measures Reducing the vector density and in taking personal protection against mosquito Reduction in mosquito breeding sites Piggeries and cattle may be kept away (4-5 kms ) from human dwellings Vaccination of all children in endemic areas

36. Challenges in Prevention and control JE Outdoor habit of the vector 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

37. NVBDCP & National programme for prevention and control of JE /AES 1 st case of JE in India was reported on 1955, from vellore 1 st major epidemic outbreak was reported from Burdwan district of West Bengal, in 1973 Since then, many outbreaks have been reported from 171 districts in 19 states of India A major epidemic was reported in 2005, from eastern UP with 6000 cases and more than 1000 deaths This led to introduction of vaccine in high endemic areas of the country by NVBDCP, in the year 2006

38. NVBDCP & National programme for prevention and control of JE /AES NVBDCP also developed guidelines for surveillance and case management of JE during the same year, 2006 Guidelines were updated again in 2009 In November, 2011, GOI developed a new programme for control and prevention of JE/AES This programme works under the NVBDCP Ministry of Health & Family Welfare(MOHFW) monitors the works of the programme

39. Goals and objectives Goal is to reduce morbidity, mortality and disability due to JE/AES Objectives: 1) strengthen & expand JE vaccination 2) strengthen surveillance, vector control, case management and timely referral of serious & complicated cases 3) estimate disability burden & to provide rehabilitation services 4) improve nutritional status of children at risk for JE/AES 5) carrying out intensified IEC/BCC activities regarding JE/AES

40. Activities…. JE vaccination has been introduced into the routine immunization schedule in 132 endemic districts More areas are added based on epidemiological surveillance 50 sentinel sites and 13 apex centres has been established for JE reporting and research Regular trainings are conducted for paediatricians , District medical officers and others regarding JE management & surveillance Entomology centres has been established throughout the country for research on vector mosquitoes

41. Vaccination Mass JE vaccination campaigns are first conducted in endemic districts where, all children in the age group of 1 to 15 years will be vaccinated Later, JE vaccination is introduced into the routine immunization schedule of that district 2 doses, 0.5 ml, subcutaneously… 1 st dose along with measles vaccine at 9 months of age 2 nd dose along with the booster dose of measles at 18-24 months of age.

42. Thank you