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Japanese encephalitis epidemiology
Japanese encephalitis is a mosquito-borne viral disease that infects humans and animals. The virus is maintained in a transmission cycle between mosquito vectors, such as Culex tritaeniorhynchus, and vertebrate hosts like birds and pigs. The disease is most common in Asia and causes brain inflammation that can lead to death or long-term neurological problems in about 20-30% of cases. Prevention strategies focus on controlling the mosquito vector population and vaccinating people in endemic areas.
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Japanese encephalitis epidemiology
- 1. Epidemiology of Japanese Encephalitis DrUtpal 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
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- 4. Ecology & Naturalcycle of JE
- 5. What is Japaneseencephalitis??? 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 journeycontinues…. 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 worriedabout 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.
- 8. JE around theglobe….. 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.
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- 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 JEin India
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- 13. Endemic areas inIndia
- 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
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- 17. Epidemiological Triad Organisms harboringthe pathogens Agency that carries and transmits the pathogens Microbes causing disease External factors allowing transmission
- 18. Agent: ARBOVIRUSES Japanese encephalitisvirus 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 More 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 Itbreeds 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 reservoirof 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 relatedprincipally 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
- 25. Pathogenesis of thedisease
- 26. Control and Preventionof the threat….. ………Japanese Encephalitis
- 27. Control measures Control measuresinvolves 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: -Insecticidespraying 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 tocontrol vectors….
- 30. Prevention 4 typesof 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 derivedkilled 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 Vero 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
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- 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 andcontrol 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 & Nationalprogramme for prevention and control of JE /AES 1st case of JE in India was reported on 1955, from vellore 1st 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 & Nationalprogramme 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 vaccinationhas 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 JEvaccination 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… 1st dose along with measles vaccine at 9 months of age 2nd dose along with the booster dose of measles at 18-24 months of age.
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Editor's Notes
- #3 How JE was knw to the world Origin of terms History- global scenario Enzootic: Endemic in animals. An enzootic disease is constantly present in an animal population, but usually only affects a small number of animals at any one time.
- #6 Half a century later, also in Japan, a large JE outbreak involving >6,000 cases was documented.
- #7 In 1940, JE was first identified in China and in 1949 it was identified in Korea during a major epidemic that resulted in 5,548 human cases. In 1954 the virus was recognized in India and a major epidemic occurred in 1978 with over 6,000 human cases occurring. In 1983, in South Korea, JE immunizations started in children as young as age 3 except in endemic areas where the vaccine was recommended in children even younger. From 1983 to 1987 the JE vaccine was available in the U.S. on an investigational basis.
- #11 The Directorate of NVBDCP is monitoring JE incidence in the country since 1978 In 1978 JE cases were reported from 21 states and Union Territories..
- #14 There are 15 states that show cases of JE every yr, but these 5 states are considered under highly endemic area coz they account for total 80% cases all over India
- #15 Outbreak in ghorakpur claimed many lives upto 1000 children, worst outbreak ever 2005: Outbreak in Ghorakpur , UP 2006: Government of India introduced vaccine in UIP schedule in highly endemic states. 2009: National Program for prevention and control of JE
- #16 Symptoms of type a :high fever, sore throat, headache, lethargy, double vision, delayed physical and mental response, sleep inversion and catatonia.[3] In severe cases, patients may enter a coma-like state (akinetic mutism). Patients may also experience abnormal eye movements ("oculogyric crises"),[7] parkinsonism, upper body weakness, muscular pains, tremors, neck rigidity, and behavioral changes including psychosis. Klazomania (a vocal tic) is sometimes present
- #19 Group B arbo virus, Flavi virus, the glycoprotein envelope of the virus contains specific as well as cross reactive neutralizing epitopes
- #21 Culex vishnui subgroup is very common, widespread and breed in water with luxuriant vegetation mainly in paddy fields and the abundance is related to rice cultivation, shallow ditches and pools. These vectors are primarily outdoor resting in vegetation and other shaded places but in summer may also rest in indoors. They are in principally cattle feeders, though human and pig feeding are also recorded in some areas
- #23 Birds : Pond herons, cattle egrets, poultry birds, appear to be involved in natural transmission of JE virus. The vector mosquito species prefer cattle blood as compared to that of human beings. The pigs are “amplifier hosts” for the virus. Migratory birds may be involved in the transfer of virus one region to another Cattle :It is believed that prevalence of an enormously large population of cattle in India may act as deterrent to the spread of JE infection. Pigs : Infected pigs do not manifest many overt symptoms of the disease but allow multiplication and circulation of the virus in their blood. They are capable of infecting a large number of vector mosquito species, which in turn may transmit the virus to man after the completion of extrinsic incubation period of 9-12 days.
- #24 In endemic areas, however, most people are infected below the age of 15 years. In hyper – endemic areas, half of all Japanese encephalitis cases occur before the age of four years, and almost all before 10 years of age. Only one out of 250 to 500 JE viral infections lead to symptomatic disease. Those endemic regions where childhood JE vaccination has been widely implemented have experienced a shift in the age distribution of cases towards older children and adults (3). In India, Japanese encephalitis is considered to be largely a paediatric problem. Young children below 10 years of age are more likely to die, and if they survive, are more likely to have residual neurological sequelae