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 × 106
daltons
• Antigenic Structure:
Hemagglutinins, Complement
Fixing and Neutralising Antigens
7. Taxonomy Of Some Important
Arboviruses
FAMILY GENUS IMPORTANT SPECIES
Togaviridae Alphavirus Chikungunya, Mayaro, O’nyong-nyong,
EEE,WEE,VEE virus etc
Flaviviridae Flavivirus Japanese Encephalitis, West Nile, Dengue, KFD,
MVE, Yellow fever
Bunyaviridae Bunyavirus
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
Rhabdoviridae Vesiculovirus Vesicular stomatitis virus, Chandipura virus
9. Geographic Distribution
• Endemic in temperate and tropical regions of
Asia
• Reduced prevalence in Japan
• Has not occurred in U.S
•
• India - Epidemics
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)
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
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
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
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
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
JE virus infection occurs throughout the temperate and tropical regions of Asia. Although initially prevalent in Japan in the late 1800’s, control methods (vaccination and pesticides) have reduced the incidence of the disease in this country. 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. Photo shows distribution of Japanese encephalitis.
JE in pigs causes high mortality for newborn piglets. However there is close to zero mortality for adult pigs. Death from JE in equines is rare; when outbreaks occur, mortality rates of 5% or less have been reported. JE can be quite severe for humans. One in 300 infections results in symptomatic disease and mortality rates can vary from 5-35% depending on intensive care facilities of the region. Approximately 33-50% of the patients with symptomatic disease, who survive, have major neurologic sequelae within 1 year. This can include seizures, paresis or movement disorders. Children (ages 2-10 years) and the elderly are at the highest risk.
Human cases of JE may be suspected in persons visiting endemic areas and demonstrating neurological sign accompanied by a fever. A tentative diagnosis of JE can be based on a four-fold rise in antibody titer using several methods, such as hemagglutination inhibition (HI), immunofluoresent antibody titer (IFA), complement fixation (CF) or IgG ELISA. Caution should be used when interpreting these results since cross-reactivity can occur with other flaviviruses. Additionally, the antibody response may have already peaked by the time the patient presented for care and there for fail to demonstrate a rise in titer. Additionally, demonstration of JE specific IgM in serum or CSF may be useful in acute phases of the disease. Definitive diagnosis of JE is done by viral isolation. Samples of CSF can be used. Brain tissue can be used for virus isolation in post-mortem situations. There is no specific treatment for JE and supportive care is recommended.
The mortality rate in piglets can be quite high from JE. This reduction in number of offspring can have an great economic impact for the swine market. Additionally, equine deaths due to an outbreak of JE can result in a 2-5% mortality rate. These losses can impact the income potentially provided by these animals. Although JE is not currently found in the U.S., the transmitting vectors are, as is the potential for the disease. Since humans are also quite susceptible to JE, the need for immunization of the population and treatment of affected persons can lead to an great economic demand to the public and the medical community. Additionally, vector control measures will be needed to aid and protect the population.