japanese encephalitis

brief discussion on japanese encephalitis, it's epidemiology, management and prevention strategies

1. JAPANESE ENCEPHALITIS
Speaker:
Dr. Pallab Kanti Nath
MD Anesthesiology
Medical College, Kolkata

2. “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.

3. ARBOVIRUS (ABV):
•Viruses of vertebrates biologically transmitted
by hematophagus insect vectors
•Special characteristic: Ability to multiply in
arthropods
•Worldwide in distribution but far more
numerous in tropical than in temperate zones
•India: Over 40 ABV detected, >10 are known
to produce human disease

4. Virus classification:
•Family: Flaviviridae
•Genus: Flavivirus
•Virions: Spherical, lipoprotein-enveloped
particles being 40-50nm in diameter, 3
structural and 7 non-structural proteins
•Genome: Single stranded positive sense RNA of
molecular weight 3 × 10
6
daltons
•Antigenic Structure:
Hemagglutinins, Complement
Fixing and Neutralising Antigens

5. FLAVIVIRUS

6. FLAVIVIRUS

7. Taxonomy Of Some Important
Arboviruses
FAMILY GENUS IMPORTANT SPECIES
TogaviridaeAlphavirus Chikungunya, Mayaro, O’nyong-nyong,
EEE,WEE,VEE virus etc
FlaviviridaeFlavivirus Japanese Encephalitis, West Nile, Dengue, KFD,
MVE, Yellow fever
BunyaviridaeBunyavirus
Phlebovirus
Nairovirus
Hantavirus
California encephalitis, Oropouche, Turlock
Rift valley fever, Sandfly fever virus
Ganjam virus, Nairobi sheep disease virus
Prospect hill, Hantan, Seoul, Puumala
Reoviridae Orbivirus African horse sickness, Blue tongue viruses
RhabdoviridaeVesiculovirusVesicular stomatitis virus, Chandipura virus

8. EPIDEMIOLOGY
•Geographical Distribution
•Hosts
•Transmission
•Morbidity and Mortality

9. Geographic Distribution
•Endemic in temperate and tropical regions of
Asia
•Reduced prevalence in Japan
•Has not occurred in U.S
•
•India - Epidemics

10. 10
Distribution of Japanese encephalitis in AsiaDistribution of Japanese encephalitis in Asia

11. 11
JE ENDEMIC AREAS IN INDIA
Number of endemic districts: 135;
Population: 330 million
JE affected
areas
•Andhra Pradesh
•Assam
•Bihar
•Haryana
•Kerala
•Karnataka
•Maharashtra
•Manipur
•Nagaland
•Tamil Nadu
•Uttar Pradesh
•West Bengal

12. 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 and
egrets)

13. EGRET

14. POND HERON

15. • Humans are vulnerable to this disease
•humans are dead-end host
…Although they (birds) do not demonstrate
clinical disease they do generate high
viraemias upon infection

16. TRANSMISSION
JE presents two recognised epidemiologic patterns
in Asia:
•Late summer/early autumn-associated epidemic
disease of northern temperate areas
- Large numbers of mosquitoes feed on Ardeid birds
(spring season)
- Ardeid birds migrate between rural and urban
ecosystems introducing JE virus(spring season);
these birds also amplify virus
- Increased vector activity leads to spill-over and
infection of swine by mosquito vectors shared by
birds and pigs

17. - Infection of pigs produces additional amplification
of virus
- with profusion of JE virus circulating, mosquitoes of
horses and humans also transmit agent to these
hosts; usually sporadic & localised epizootics or
epidemics (late summer or early autumn)
• Year-round endemic disease of southern tropical
areas
- continual cycle between birds, swine & mosquitoes
- principal vectors: Culex tritaeniorhynchus and Culex
gelidus

18.  Actual transmission of JE virus occurs by means of
Mosquitoes
-Culex tritaeniorhynchus has a wide host range
(birds, horses, swine and humans)
-oviposits in flooded fields
(fish ponds, rice paddies and ditches)
-most active at twilight hours

19. Culex tritaeniorhynchus

20. A TYPICAL BREEDING HABITAT FOR
MOSQUITOES

21. LIFE CYCLE OF JAPANESE ENCEPHALITIS

22. Morbidity/Mortality
•Swine
–High mortality in piglets
–Death rare in adult pigs
•Equine
–Morbidity: 2%, during an outbreak
–Mortality: 5%
•Humans
–Mortality: 5-35%
–Serious neurologic sequelae: 33-50%

23. PATHOGENESIS

24. 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 and
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

25. 25
 Case Fatality Rate (CFR) :
-Varies between 20-40% but it may reach 58% or
more, (higher in children)
 30-50% of the people that survive the infection
may 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

26. Differential Diagnosis
•Meningitis
•Febrile Convulsions
•Rey’s Syndrome
•Rabies
•Cerebral Malaria
•Toxic Encephalopathy

27. Diagnosis and Treatment
•Clinical
•Laboratory Tests
–Tentative diagnosis
•Antibody titer : eg. ELISA
•JE-specific IgM in serum or CSF
–Definitive diagnosis
•Virus isolation : CSF sample, brain
–Treatment
- No Specific treatment
- Supportive care

28. A} SANITARY PROPHYLAXIS:
 Housing of animals in-doors in screened
stabling can provide protection from
mosquitoes
- Especially during active JE outbreaks &
during peak vector activity (usually dusk
to dawn)
-Insecticides, repellants & fans also
provide protection

29. 29
PREVENTION AND CONTROL
•Personal protective
measures and mosquito
elimination are the most
important
•Travellers going to endemic
areas may consider
vaccination

30. 30
Prevention of Mosquito Bites
•Avoid going to areas with water
accumulation (eg rice fields) during dusk and
dawn when the mosquitoes are most active
•Wear light-coloured, long-sleeved clothing
and trousers
•Apply mosquito-repellents over exposed
parts of the body and clothes every 4 to 6
hours

31. 31
Prevention of Mosquito Bites
• Place of accommodation should
have mosquito nets
•Use insecticides or coil incenses
to repel mosquitoes
•Install mosquito nets to doors and
windows so that mosquitoes can’t
get in

32. 32
•Put all used cans and bottles into
covered dustbins
•Change water for plants at least
once a week, leaving no water in
the saucers underneath flower
pots
Prevent mosquito breeding

33. 33
•Keep all drains free from
blockage
•Cover tightly all water
containers, wells and water
storage tanks
•Top up all defective ground
surfacers to prevent the
accumulation of stagnant
water
Prevent mosquito breeding

34. 34
JE Vaccination
•Prevent encephalitis from JE virus
•Recommended for use in
endemic areas

35.  VACCINATION
- 3 types of JE vaccines:
1. Mouse Brain-derived Purified &
Inactivated Vaccine (Nakayama or
Beijing strain of JE virus)
2. Cell Culture Derived Inactivated JE
Vaccine (Beijing P-3 strain)
3. Cell Culture Derived, Live Attenuated
Vaccine ( SA 14 – 14 – 2 strain of JE virus)

36. 36
Contraindictions for JE vaccination
•History of previous severe allergic reaction
•Infant< 1yr of age
•Pregnancy

37. Economic Impact
1} Animals:
–Porcine
•High mortality in piglets
–Equine
•Up to 5% mortality rate
2} Humans:
•Medical cost for immunization and
medical treatment

38. “THANK
YOU”