JAPANESE ENCEPHALITIS

Dr Ubaid N P

JR Community Medicine,

Pariyaram Medical College

EPIDEMIOLOGY

▪ Agent

▪ Geographical Distribution

▪ Hosts

▪ Transmission

▪ Morbidity and Mortality

INTRODUCTION

▪ SYNONYMS: Japanese B Encephalitis, Arbovirus B Encephalitis, Mosquito-Borne Encephalitis, Russian Autumnal Encephalitis, Brain Fever, Summer Encephalitis.

▪ Definition: JE is an inapparent to acute arboviral infection of horses, pigs and humans. It’s a zoonotic disease i.e. infecting mainly animals and incidentally man.

JE - GLOBAL SCENARIO

▪ Major public health disease in Asia

▪ Virus first isolated in Japan in 1935

▪ As per WHO estimates 50,000 serious cases and 10,000 each year

▪ Disease is prevalent in Indian Sub-continent, Nepal, India, Sri Lanka and some areas in Bangladesh

▪ Other SE Asian countries reporting cases include: Myanmar, Thailand, Cambodia, China, Indonesia, Laos, Vietnam, Malaysia, Philippines, Taiwan, Hong Kong and Korea 4

JE ENDEMIC AREAS IN INDIA

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Number of endemic districts: 135;14 states Population: 330 million

JE affected areas

• Andhra Pradesh

• Assam

• Bihar

• Haryana

• Kerala

• Karnataka

• Maharashtra

• Manipur

• Nagaland

• Tamil Nadu

• Uttar Pradesh

• West Bengal

AGENT

▪ Zoonotic disease

▪ Family: Flaviviridae

▪ Genus: Flavivirus

HOSTS

• Horses are the primary affected domestic animals of JE though essentially a dead-end host; other

equids (donkeys) are also susceptible

• Pigs act as “amplifiers” of the virus producing high viraemias which infect mosquito vectors

• The natural maintenance reservoir for JE virus are birds of the family Ardeidae (herons andegrets)

Contd..

EGRET {RESERVOIR HOST}

POND HERON

LIFE CYCLE OF JAPANESE ENCEPHALITIS

Mosquito Vectors

▪ C. Tritaeniorhynchus

▪ C. Vishnui

▪ C. Gelidus

▪ Anopheles

Culex tritaeniorhynchus(Cx vishnui group)

Breeding Habitat

▪ Rice fields

▪ Shallow pools

▪ Ditches

A TYPICAL BREEDING HABITAT FOR MOSQUITOES

DYNAMICS OF JE TRANSMISSION

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EnvironmentVector Mosquito

Host - Amplifying Host - Carrier

Victim-Accidental

Full Recovery DeathRecovery with residual

complications

Morbidity/Mortality

▪ Swine– High mortality in piglets– Death rare in adult pigs

▪ Equine– Morbidity: 2%, during an outbreak– Mortality: 5%

▪ Humans– Mortality: 20-40%– Serious neurologic sequelae: 33-50%

PATHOGENESIS

Virus enters the body through the bite of the insect vector - mosquitoes

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After multiplication in local & regional LN, viremia of varying duration ensues

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Virus is transported to target organ (brain) via blood

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Virus proliferate & damage the neuronal tissue, thereby elicits nervous manifestations

JE IN MAN : CLINICAL FEATURES

• Incubation Period - 5 to 15 days

• Only 1 in 300 to 1 in 1000 infections develop into encephalitis, rest asymptomatic

• Course of disease- 3 stages:

a) Prodromal stage: Fever, headache, GIT disturbances malaise. Duration- 1 to 6 days.b) Acute encephalitic stage: Fever - 38 to 40.7°C, nuchal rigidity, focal CNS signs, convulsion & altered sensorium progressing in many cases to coma.c) Late stage and sequelae: Temperature & ESR touch normal level, neurological signs become stationary or tend to improve

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Case Fatality Rate (CFR) :

•Varies between 20-40% but it may reach 58% & over , higher in children

• 30-50% of the people that survive the infection develop paralysis, brain damage, or other serious permanent sequelae

• Average period between the onset of illness & death is about 9 days

• In utero infection possible: Abortion of fetus

Diagnosis and Treatment In Man:

▪ Clinical

▪ Laboratory Tests–Tentative diagnosis▪ Antibody titer : HI, IFA, CF, ELISA▪ JE-specific IgM in serum or CSF

–Definitive diagnosis▪ Virus isolation : CSF sample, brain▪ Treatment:- No Specific treatment

- Supportive care

Vector control reduces transmission

IN AFFECTED VILLAGES:

-Aerial or ground fogging with ultra low volume insecticides(eg.Malathion,Fenitrothion)

-Indoor residual spray - Spraying should cover vegetation around houses, breeding sites & animal shelters

IN UNAFFECTED 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

PREVENTION AND CONTROL

AGRICULTURAL PRACTICES :

- water management practice of Paddy cultivation-

At least one dry day every week - conserve water, reduce larval population increase rice grain yield, and reduce the emission of methane into the environment thereby reducing the Global warming effect.

Using neem products as fertilizers will also reduce the mosquito population

Vaccines

▪ Three types of JE vaccine in large scale use are:

1. Mouse brain derived, purified & inactivated vaccine – Nakayama or Beijing strains

2. Cell culture derived inactivated vaccine – Beijing P3 strain

3. Cell culture derived, live attenuated vaccine – SA-14-14 strain

Vaccination for travellers

Vaccination in swine's

Guidelines for management of AES including JE in India(2009)

Case Definition : Suspected case. Acute onset of fever (≤ 7 days). change in mental status With/ withouto New onset of seizures (excluding febrile seizures)o Other early clinical findings - may include irritability, somnolence or abnormal behaviour greater than that seen with usual febrile illness

Laboratory confirmed case

A suspected case with any one of the following markers

▪ Presence of IgM antibody in serum and/or CSF to a specific virus including JE/Entero virus or others

▪ Four fold difference in IgG antibody titre in paired sera

▪ virus isolation from brain tissue

▪ Antigenic detection by immunofluroscence

▪ Nucleic acid detection by PCR

Probable CasesSuspected case in close geographic and temporal relationship to a laboratory-confirmed case of JE in an outbreakAcute Encephalitis Syndrome due to other agent - A suspected case in which diagnostic testing is performed and an etiological agent other than JE is identifiedAcute Encephalitis Syndrome due to unknown agent - A suspected case in which no diagnostic testing is performed / no etiologicaI agent was identified / test results were indeterminate

THANK YOU