Japanese Encephalitis

EPIDEMIOLOGY PREVENTION & CONTROL

JAPANESE ENCEPHALITIS • • • • • • •

Mosquito-borne encephalitis Zoonotic disease Genus-Group B arbovirus or Flavi virus Family-Flaviviridae Vector-Culicine mosquito Epidemic in Japan in 1924 to1970 ICD-A83.0

ARBOVIRUS • Arthropod borne virus • Viruses that multiplies in tissues of arthropods & transmitted to susceptible vertebrate hosts by bite of the hematophagous arthropods after an extrinsic incubation period • Yellow fever • Tropical & temperate zones • India 2 in 1951 , 40 in 1975

INCIDENCE • 50,000 cases occur annually • China contributes > 50% and India 20%. • Annual incidence 10 to 100 cases per 100 000 • 15,000 deaths annually (WHO , 5-35% case fatality rate) and 9000 disabled • In India in 2000, 2593 cases, 556 deaths

PROBLEM STATEMENT--WORLD • Leading cause of viral encephalitis & neurological infection in Asia Reasons • Extensive paddy cultivation • Existence of piggeries • Climatic factors

EPIDEMIOLOGY

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Endemic in (1) China and Korea, (2) the Indian sub-continent consisting of India, parts of Bangladesh, southern Nepal, and Sri Lanka, and (3) the southeast Asian countries of Burma, Thailand, Cambodia, Laos, Vietnam, Malaysia, Indonesia and the Philippines

IN INDIA • • • • • • •

1955-Pondicherry & Vellore North & South Arcot,Chithoor 1964-Madurai , West bengal 1978-Karnataka, Assam, Bihar, UP 1996-Outbreak in Kerala Occurred in 25 States / Union Territories Epidemic prone areas-Westbengal, Karnataka, AP,Assam, TN, UP, Bihar, Goa ,Manipur. • Population at risk > 160 million

Occurance of JE outbreaks in India (1950-2000)

Source - VCRC Pondicherry

Source – VCRC - Pondicherry

TAMIL NADU • 1980 –Thiruvannamalai, Darmapuri, Namakkal, Trichy, Dindigul, Tirunelveli • 1991 – Epidemic in South arcot • Past five years -Viluppuram, Cuddalore, Perambalur • South arcot – Incidence - 4.7/ 100,000. • Thanjavur - Incidence - 0.4/100,000. Ratio of Pig : Cattle – 1: 400, • In South Arcot dt.-- 1:4

EPIDEMIOLOGICAL FEATURES Cycles of transmission Pig

Mosquito

Ardeid bird

Pig

Mosquito

Man – Incidental dead end host No man to man transmission

Mosquito Ardeid bird

Man

ANIMAL HOST Pigs – Amplifier host • No symptoms • High titre viraemia • Mosquitoes are infected In endemic areas – 12 to 44 % pigs infected Cattle & Buffaloes - Mosquito attractants - Brakes for transmission Horse - Signs of encephalitis

BIRDS Ardeid birds (Pond herons & Cattle egrets) - Maintanence / reservoir host Black crowned night herons – Amplifying host Poultry, Ducks, pigeons

VECTORS Culex tritaeniorynchus, C.vishnui, C.gelidus Anopheles, Mansonoides, Aedes Breeds in irrigated rice fields In Springs, peak in June to Sep Feeds outdoors – In dusk and evening Zoophillic, Zoophagic Extrinsic incub period – 9 -12 days Infective for lifetime Vertical transmission

JE IN MAN Encephalitis in young children & > 60 yrs

High in males then females Sub clinical infections Overt disease 1: 300 to 1: 1000 Tip of Iceberg IP 5 – 15 days CFR – 20 – 40 % Up to 60 % Damage to CNS – 30%

Infection in man-Reasons:

1. Vector abundance 2. Adequate man - Mosquito contact (increased biting rate) 3. Longevity of vector Dengue fever & JE – Mutually exclusive CLINICAL FEATURES 3 STAGES Prodromal Stage - 1 to 6 days

Acute encephalitic stage Altered sensorium,Convulsions,Coma Late Stage Mental impairment,paresis

DIAGNOSIS CSF IFA – Detects Ag on second day RPHA – with in 10 days of onset PCR – Viral genome Innoculation in infant mice Serum - for antibody HI, CF,NT,Immunodiffusion Based on 4 fold rise of IgG titre in paired sera collected at interval of 15 to 20 days

TESTS IN SURVEILLANCE 1. MACELISA – Ab. after 7th day of illness Detection of Ab. in serum & CSF

Sensitivity 84 % 2

IF in CSF 58 % Completed in 2 – 3 hrs Both in surveillance programme

NPV 40 %

VACCINATION For population at risk Killed mouse brain vaccine Primary-2 doses 1ml SC 7-14days Booster-in 6-12 months Revaccinations after 3 yrs 1988-EPI Thailand Live attenuated vaccine in China SA 14-14-2 Chimeric vaccine

Drawbacks: Production limited & expensive Multiple doses,short term protection Time lag in immunity 80-90% coverage Neurological rx

RISK GROUPS Residents of rural are in endemic area Duty military presonnel Expatriates in rural areas CDC recommends vaccine for 4 weeks or more or in epidemics 0,7 & 30 (or) 0 ,7,14 Last dose – 10 days before travelling

VECTOR CONTROL Aerial or ground fogging with ULV – Indoor residual spray Villages in 2—3 Km-spray as prevention Nearby villages-Surveillance

ANTI LARVAL MEASURES Environmental control: Eliminate breeding places Source reduction Water management Biological control : Larvivorous fish - Gambusia affinis, Lebister reticulatus Biocides

Anti Adult Measures Genetic control Protection against mosquito bites Integrated vector control Utilisation of all methods to bring about an effective degree of vector suppression in a cost effective manner. Pig control Seggregation, Slaughtering, Vaccination

CONTROL & PEVENTIVE MEASURES IN TN Regular vaccination in Perambalur Dt Children 1 – 14 years 3 Doses before 2 years 3 Booster doses at 4, 8, 11 years Vaccine coverage 82 – 94 % Anticipatory spray during premonsoon JE Endemic villages with deaths – Fogging Residual spray

SURVEILLANCE Human Encephalitis On clinical and lab diagnosis Encephalitis in epidemics In monsoon & Post monsoon Sentinel Animals Vector surveillance Vector abundance Pigs Vector infection rate Cattle Dusk index Goats Ag. Capture ELISA

PROBLEM / CONSTRAINTS 1. 2. 3. 4. 5. 6. 7. 8.

Paddy cultivation Source reduction Pig rearing Migration of birds No Policy on vaccination Lack of epidemiological data No effective surveillance system Appropriate control measures

LIST OF REFERENCES State of art of new vaccines – Research & development – www.who.int www.pon.nic.in / vcrc JE in TN – ICMR Bulletin, Vol: 28 No - 4 April 1998 CDC - Travellers health – Health information for international travel 2003 - 2004

Cont..

Health & FW Dept. – Govt. of TN – Dept. of public health & preventive medicine – www.tn health.org Management of JE – Module for medical officers JE – www.unimas.my