2. Introduction
• Encephalitis is an acute inflammatory process affecting the
brain parenchyma
– Meningoencephalitis
– Encephalomyelitis
– Encephalomyeloradiculitis
• Viral infection is the most common and important cause, with
over 100 viruses implicated worldwide
• Incidence of 3.5-7.4 per 100,000 persons per year
• ~20,000 cases reported anually in USA
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4. Causes of viral encephalitis
• Herpes viruses – HSV-1, HSV-2, varicella zoster virus,
cytomegalovirus, Epstein-Barr virus, human herpes virus 6
• Adenoviruses
• Influenza A
• Enteroviruses, poliovirus
• Measles, mumps, and rubella viruses
• Rabies
• Arboviruses – examples: Japanese encephalitis; St. Louis
encephalitis virus; West Nile encephalitis virus; Eastern,
Western and Venzuelan equine encephalitis virus; tick
borne encephalitis virus
• Bunyaviruses – examples: La Crosse strain of California virus
• Reoviruses – example: Colorado tick fever virus
• Arenaviruses – example: lymphocytic choriomeningitis
virus
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5. What is ARBOVIRUS?
• Arboviruses = arthropod-borne viruses
• Arboviruses are maintained in nature through
biological transmission between susceptible
vertebrate hosts by blood-feeding arthropods
• Vertebrate infection occurs when the infected
arthropod takes a blood meal
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6. Major Arboviruses that cause
encephalitis.
• Flaviviridae
– Japanese encephalitis
– St. Louis encephalitis
– West Nile
• Togaviridae
– Eastern equine encephalitis
– Western equine encephalitis
• Bunyaviridae
– La Crosse encephalitis
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8. •Flavivirus related to St. Louis
encephalitis
•Most important cause of arboviral
encephalitis worldwide, with over
45,000 cases reported annually
•Transmitted by culex mosquito,
which breeds in rice fields
•Mosquitoes become infected by
feeding on domestic pigs and wild
birds infected with Japanese
encephalitis virus. Infected
mosquitoes transmit virus to humans
and animals during the feeding
process.
Japanese Encephalitis
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9. •Flavivirus
•Primary host – wild birds
•Principal arthropod vector –
mosquitoes
•Geographic distribution -
Africa, Middle East, Western
Asia, Europe, Australia,
North America, Central
America
West Nile Virus
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12. Eastern Equine Encephalitis
• Togavirus
• Caused by a virus
transmitted to humans and
horses by the bite of an
infected mosquito.
• 200 confirmed cases in the
US 1964-present
• Human cases occur
relatively infrequently,
largely because the primary
transmission cycle takes
place in swamp areas
where populations tend to
be limited.
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13. Western Equine Encephalitis
• Togavirus
• Mosquito-borne
• 639 confirmed cases
in the US since 1964
• Important cause of
encephalitis in horses
and humans in North
America, mainly in
the Western parts of
the US and Canada
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14. La Crosse Encephalitis
• Bunyavirus
• On average 75 cases per
year reported to the CDC
• Most cases occur in
children under 16 years old
• Zoonotic pathogen that
cycles between the
daytime biting treehole
mosquito, and vertebrate
amplifier hosts (chipmunk,
tree squirrel) in deciduous
forest habitats
• 1963 – isolated in La
Crosse, WI from the brain
of a child who died from
encephalitis
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15. Summary – Confirmed and Probable
Human Cases in the US
Virus Years Total cases
Eastern Equine 1964-2000 182
Western Equine 1964-2000 649
La Crosse 1964-2000 2,776
St. Louis 1964-2000 4,482
West Nile 1999-present > 9,800
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16. Other viruses that commonly cause viral
encephalitis
Herpes simplex virus type 1 (HSV-1), which is responsible for cold sores
HSV-2, which is responsible for genital herpes
Varicella zoster virus, which causes chicken pox and shingles
Epstein-Barr virus, which causes mononucleosis
Childhood viruses that can cause encephalitis include:
Measles (rubeola)
German measles (rubella)
Mumps
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17. But, not all cases of encephalitis is
caused by virus.
Some others include
BACTERIA
NON INFECTIOUS CAUSES
(ALLERGIC REACTIONS OR
TOXIN)
FUNGUS
PARASITE
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19. 90% of people with
encephalitis have flu-
like symptoms,
(fever, sore throat,
cough, and malaise.)
If the person has meningitis and
encephalitis, he or she may have a
headache, stiff neck, vomiting,
and be bothered by light
possible hallucinations,
agitation, and personality
changes.
Infants may have
bulging in the
fontanels or soft
spots on the skull.
change in
consciousness,
ranging from mild
confusion to coma
Have trouble in
understanding words.
Coordinating voluntary
muscle movements
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20. Diagnosis
Encephalitis is a serious condition, so you
should see a doctor if you or your child start
having symptoms. You are usually diagnosed
and treated in a hospital at first. After doing
a physical exam, a doctor may take the
following steps to diagnose the condition
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21. • Brain imaging. Brain imaging is often the first test if symptoms and patient
history suggest the possibility of encephalitis. The images may reveal
swelling of the brain or another condition that may be causing the
symptoms, such as a tumor. Technologies may include magnetic resonance
imaging (MRI), which can produce detailed cross-sectional and 3-D images
of the brain, or computerized tomography (CT), which produces cross-
sectional images.
• Electroencephalogram (EEG). Doctor may order an EEG, a test in which a
series of electrodes are affixed to the scalp. The EEG records the electrical
activity of the brain. Certain abnormal patterns in this activity may be
consistent with a diagnosis of encephalitis. EEG may show sharp waves in
one or both of temporal lobes.
• Blood and other specimens culture: A minimum of 20 mL of blood in each
of two to three separate cultures per each 24- hour period is necessary for
the detection of most bacteremias.
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22. A lumbar puncture
Or spinal tap, is a procedure to collect
cerebrospinal fluid to check for the
presence of disease or injury.
A spinal needle is inserted, usually
between the 3rd and 4th lumbar
vertebrae in the lower spine. Once the
needle is properly positioned in the
subarachnoid space (the space between
the spinal cord and its covering, the
meninges), pressures can be measured
and fluid can be collected for testing.
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23. MRI brain (T2W image): right
temporal lobe high signal in a
patient with herpes encephalitis
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24. Treatment
Viral encephalitis is a serious medical condition.
Although there are no specific medications to treat
it, people with symptoms are often given the
antiviral medication acyclovir (Zovirax). It works
against herpes simplex and varicella-zoster viruses.
Acyclovir (Zovirax) -- treats encephalitis caused by HSV, VZV, and EBV
Ganciclovir (Cytovene) -- treats encephalitis caused by
cytomegalovirus and HSV1
Anticonvulsant medications -- prevent and treat seizures that may
happen with encephalitis
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25. Nutrition and Dietary Supplements
• Eat antioxidant foods, including fruits (such as
blueberries, cherries, and tomatoes), and vegetables
(such as squash and bell peppers).
• Avoid refined foods, such as white breads, pastas, and
especially sugar.
• Eat fewer red meats and more lean meats, cold-water
fish, tofu (soy, if no allergy), or beans for protein.
• Use healthy oils in foods, such as olive oil or vegetable
oil.
• Avoid caffeine, alcohol, and tobacco.
• Drink 6 - 8 glasses of filtered water daily.
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26. Supplements
• Omega-3 fatty acids, such as fish oil, one to three times
daily, to help decrease inflammation and boost the
immune system. Fish oil may increase the risk of
bleeding, especially if you take blood-thinners such as
warfarin (Coumadin), clopidogrel (Plavix), or aspirin.
• Vitamin C, 500 - 1,000 mg 1-3 daily, as an antioxidant
and to boost the immune system.
• Probiotic supplement (containing Lactobacillus
acidophilus), for digestive and immune system health.
If you are taking antibiotics, taking probiotics as well
may help you avoid some side effects such as diarrhea.
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27. Acupuncture
• A study of a small number of people
with complications from encephalitis
suggests that acupuncture on the
scalp may reduce severe
complications and symptoms. Some
practitioners believe that scalp
acupuncture works for people with
encephalitis because all meridians
converge at the head, and the method
can stimulate and regulate qi (energy)
throughout the entire body. More
research is needed.
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