Arboviral encephalitis. Differential diagnosis in patients with central nervous system infections. Flashcards
what are arbovirus ?
known as arthropod-borne viruses, refer to a diverse group of viruses that are transmitted via vectors for transmission to humans such as mosquitos, ticks, or sandflies
which family of viruses does arboviral viruses occupy ?
Togaviridae,
Flaviviridae,
Bunyaviridae,
and Reoviridae
they have similar RNA genomes that permit mutations that allow them to acclimate to changing environments or host conditions
what is the etiology and transmission of arbovirus encephalitis ?
Togaviridae:
- CHIKUNGUNYA VIRUS
- transmitted to humans by infected Aedes mosquitoes, maternal-fetal transmission, and blood products
- can cause meningoencephalitis in severe infections
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EASTERN EQUINE ENCEPHALITIS (EEE) VIRUS
is transmitted via infected Culiseta melanura as well as some Aedes, Coquillettidia, and Culex mosquitoes
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WESTERN EQUINE ENCEPHALITIS (WEE) VIRUS
is transmitted by infected Culex mosquitoes.
Less than 1% of infected adults develop encephalitis
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VENEZUELAN EQUINE ENCEPHALITIS (VEE) VIRUS
has both epizootic subtypes transmitted by many mosquitoes and enzootic subtypes transmitted by infected Culex mosquitoes
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Flaviviridae family
- DENGUE VIRUS
is transmitted by Aedes aegypti or Aedes albopictus mosquitoes
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JAPANESE ENCEPHALITIS VIRUS
transmitted via mosquito Culex species, predominantly by Culex tritaeniorhynchus
mosquito also transmits the virus to pigs and aquatic birds = the principal viral-amplifying hosts
later than to humans
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MURRAY VALLEY ENCEPHALITIS (MVE) VIRUS
transmitted via Culex annulirostris mosquitoes.
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ST. LOUIS ENCEPHALITIS (SLE) VIRUS
transmitted via Culex mosquitoes
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WEST NILE VIRUS (WNV)
transmitted in an enzootic cycle between birds by mosquitoes
Virus is transmitted to humans via infected Culex mosquitos
should be suspected in individuals who have had recent mosquito exposure, organ transplantation, or blood transfusion.
Additional risk factors for symptomatic infection include immunosuppressed individuals, patients with multiple co-morbidities, and the elderly
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//POWASSAN VIRUS -TICK BORN!!! // transmitted by - Ixodes scapularis, Ixodes cookei, and Ixodes marxi.
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//TICK-BORNE ENCEPHALITIS (TBE) - TICK BORN !!! // Ixodes persulcatus and Ixodes ricinus in Europe
and Russia as well as Ixodes ovatus in Japan
Transmission is horizontally between ticks and vertebrates: small mammals and grouse, deer and sheep
Human infection is mostly due to either outdoor activities resulting in tick bites or consumption of raw milk from infected goats or, from
other infected animals (cows, sheep)
predominantly affected are adults 20 to 50 years of age, has a male predominance
occupational exposure in forestry and farming
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ZIKA VIRUS
Aedes aegypti, although it can also be transmitted by Aedes albopictus. Transmission can also occur via maternal-fetal transmission, sexual transmission, blood products, organ transplantation, and laboratory exposures
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BUNYAVIRIDAE FAMILY:
LA CROSSE ENCEPHALITIS VIRUS (LACV)
Aedes triseriatus
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CALIFORNIA ENCEPHALITIS VIRUS (CEV)
via Aedes mosquitoes
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REOVIRIDAE FAMILY:
////COLORADO TICK FEVER VIRUS - TICK BORN ///// via Dermacentor andersoni, a Rocky Mountain wood tick
incubation period for arbovirus encephalitis ?
1) togaviridiae family
A) CHICKUNGUNYA VIRUS
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B) EASTERN EQUINE ENCEPHALITIS
incubation period is 4 to 10 days after the mosquito bite
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C) WESTERN EQUINE ENCEPHALITIS
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D)VENEZUELAN EQUINE ENCEPHALITIS
1-6 days, followed by a febrile illness
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FLAVIVIRIDAE FAMILY:
DENGUE VIRUS
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JAPANESE ENCEPHALITIS VIRUS
incubation period of 5–15 days
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MURRAY VALLEY ENCEPHALITIS (MVE) VIRUS
1-4 weeks
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ST. LOUIS ENCEPHALITIS (SLE) VIRUS
4–21 days
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WEST NILE VIRUS (WNV)
2-14 days
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POWASSAN VIRUS
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TICK-BORNE ENCEPHALITIS (TBE)
Western / European subtype:
incubation period lasts from 7 to 14 day
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ZIKA VIRUS
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BUNYAVIRIDAE FAMILY:
LA CROSSE ENCEPHALITIS VIRUS (LACV)
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CALIFORNIA ENCEPHALITIS VIRUS (CEV)
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REOVIRIDAE FAMILY:
COLORADO TICK FEVER VIRUS
epidemiology of arbovirus encephalitis
1) togaviridiae family
A) CHICKUNGUNYA VIRUS
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B) EASTERN EQUINE ENCEPHALITIS -
PEAK
incidence for infection is during the months of August and September.
has the highest rate of mortality among arthropod-borne encephalitides
there are currently no vaccinations available for humans, but there is one available for horse
highest rate of mortality among arthropod-borne encephalitides, with a mortality of at least 30
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C) WESTERN EQUINE ENCEPHALITIS
can be found in North and South America
Less than 1% of infected adults develop encephalitis
no vaccinations available for humans, but there is one available for horses.
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D) VENEZUELAN EQUINE ENCEPHALITIS
has been linked to several outbreaks in North and South America
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Flaviviridae family:
DENGUE VIRUS
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JAPANESE ENCEPHALITIS VIRUS
found throughout Asia, including in far eastern Russia, Japan, China, India, Pakistan, and south-Eastern Asia
common in areas where irrigated rice fields attract the natural avian
vertebrate hosts and provide abundant breeding sites for
Culex tritaeniorhynchus mosquitoes
infection is mostly from July to September with periodic seasonal epidemics
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MURRAY VALLEY ENCEPHALITIS (MVE) VIRUS
Geographically, this virus is restricted to Australia, New Guinea, and Indonesia
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ST. LOUIS ENCEPHALITIS (SLE) VIRUS
low-level endemic infection in the western and central
United States
Culex tarsalis mosquitoes
serve as vectors in the western US,
while the more urbanized mosquitoes (Culex pipiens and Culex quinquefasciatus
) are responsible for epidemics in central and
eastern United States
polluted wastewater provides breeding habitat for
C. pipiens and C. quinquefasciatus -> urban mosquitoe
Transmission occurs in the summer months when mosquitos are active
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WEST NILE VIRUS (WNV)
important cause of endemic encephalitis in the US
one of the most distributed arboviruses
common in Africa, southern Europe, the Middle East, Asia,
Australia, and the Americas
infection tends to occur between mid-July and early September
because they prefer elevated mean temperatures and rainfall
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POWASSAN VIRUS
Most cases occur in the Northeast and Great Lakes regions in the US and follow a similar distribution as Lyme disease.
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TICK-BORNE ENCEPHALITIS (TBE)
has 4subtypes :
1) western/European subtype
2) Siberian subtype-> in all endemic areas of Russia
3) Far Eastern subtype
-> in eastern Russia, Korea, China, and parts
of Japan and the Baltic states
4) louping ill subtype -> in the British isles
Ixodes persulcatus and Ixodes ricinus in Europe and Russia
as well as Ixodes ovatus in Japan
Mortality outcomes differ with varying subtypes, with outcomes being worse in the Far Eastern group
Infection occurs between April and October, with a peak in June and July
- predominantly affected are adults 20 to 50 years of age, has a male predominance
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ZIKA VIRUS
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BUNYAVIRIDAE FAMILY:
LA CROSSE ENCEPHALITIS VIRUS (LACV)
in the US
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CALIFORNIA ENCEPHALITIS VIRUS (CEV)
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REOVIRIDAE FAMILY:
COLORADO TICK FEVER VIRUS
Geographically, this virus is limited to the western US and Canada
what are the clinical manifestation of arbovirus ?
Togaviridae family:
1) CHIKUNGUNYA VIRUS
chikungunya fever, can cause meningoencephalitis in severe infections.
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EASTERN EQUINE ENCEPHALITIS
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WESTERN EQUINE ENCEPHALITIS (WEE) VIRUS
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VENEZUELAN EQUINE ENCEPHALITIS (VEE)
febrile illness. Less than 0.5 percent of infected individuals develop neuroinvasive disease
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Flaviviridae family:
DENGUE VIRUS
Clinically, this virus can cause disease, which can be classified into 3 categories: dengue without warning signs, dengue with warning signs, and severe dengue
these viruses are directly neurotropic and can cause encephalitis
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JAPANESE ENCEPHALITIS VIRUS
earliest symptoms: lethargy and fever and, frequently, headache,
abdominal pain, nausea, and vomiting
Less than one percent of infections progress to neurological disease
Several days later, patients may experience delirium, unsteadiness,
and abnormal motor movements -> somnolence and coma
in some children: sudden convulsion after a brief febrile illness-
Seizures occur in up to 85% of children and 10% of adults
cranial nerve palsies, and
cognitive and speech impairments
severe encephalitis, leading frequently to coma and to a fatal
outcome in 25% of cases
WNV, SLE virus, and JEV can cause signs and symptoms of parkinsonism
In pregnancies it may lead to abortion
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MURRAY VALLEY ENCEPHALITIS (MVE) VIRUS
flu-like illness
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ST. LOUIS ENCEPHALITIS (SLE) VIRUS
disease severity increases with age:
•aseptic meningitis or mild encephalitis are common in children and
young adults
-> severe and fatal cases primarily affect the elderly
typically have a flu-like illness prior to developing any neurological manifestations
such as alaise, fever, headache,
and myalgias
can progress to lethargy, periods of confusion, and the onset of
tremors, clumsiness, and ataxia
-
vomiting and diarrhea are common, dysuria, urgency, and
incontinence may occur
-
characteristic finding:
altered consciousness, confusion, delirium, or
somnolence and generalized motor weakness
-
WNV, SLE virus, and JEV can cause signs and symptoms of parkinsonism
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WEST NILE VIRUS (WNV)
Most infections are asymptomatic, and less than 1% of individuals develop neurological disease
clinical manifestations are age - dependent:
•
young patients: acute febrile syndrome and mild neurologic
symptoms are more common
•
in the middle aged: aseptic meningitis and poliomyelitis-like
syndromes are seen
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and in older adults: frank encephalopathy is seen more often
fever and altered mental
status
other symptoms may be: tremors, seizures, cranial nerve palsies, and
pathologic reflexes
acute flaccid paralysis is asymmetric and can involve facial and respiratory muscles which is rarely seen in other arbovirus infections
West Nile virus also my present as Guillain-Barré syndrome with
radiculopathy - range of symptoms produced by the pinching of a nerve root in the spinal column
Skin rashes
chorioretinitis, retinal hemorrhages, and vitreitis
WNV, SLE virus, and JEV can cause signs and symptoms of parkinsonism
individuals become viremic when the virus replicates in dendritic cells and macrophages, resulting in dissemination within the human
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POWASSAN VIRUS
Powassan virus encephalitis cases are fatal.
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TICK-BORNE ENCEPHALITIS (TBE)
illness is known to be biphasic with neurological manifestations occurring during the second phase
begins with a fever–myalgia phase = arthralgia, fever, headaches, myalgia,
that lasts for 2–4 days
-> within 1 week these symptoms resolve spontaneously
some patients remission of symptoms is temporary, usually 2 to 8 days before high fever, headache, and vomiting resume
- which is the second phase
has onset of meningeal signs
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neurologic infections are benign in children, whereas severe disease occurs more often in elderly persons
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severe form may present with coma, seizures, tremors, and motor signs
-
-> spinal and medullary involvement can lead to typical limb-girdle paralysis and respiratory paralysis
Far Eastern subtype:
more severe form with higher rate of fatality
-
in children the early prodromal symptoms may be undetected, which usually is an aseptic meningitis
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the encephalitis is characterized by: altered consciousness, ataxia, tremor, paresthesias, focal signs, and, seizures
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lower motor neuron paralyses of the proximal muscles of the
extremities, trunk, and neck are common
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thrombocytopenia may develop during the initial febrile illness,
resembling the early hemorrhagic phase of some other tick-borne
flavivirus infections
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ZIKA VIRUS
Skin rashes
virus can cause multiple neurological complications, including encephalitis
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BUNYAVIRIDAE FAMILY:
LA CROSSE ENCEPHALITIS VIRUS (LACV)
many infected individuals are asymptomatic and some neuroinvasive
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CALIFORNIA ENCEPHALITIS VIRUS (CEV)
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REOVIRIDAE FAMILY:
COLORADO TICK FEVER VIRUS
what are the clinical manifestations of encephalitis ?
Some infected patients may experience a flu-like illness prior to having any neurological symptoms
Fevers, headaches, altered mental status, seizures, and focal neurological deficits
ombination of fever, headache, and altered mental status can symbolize acute encephalitis syndrome
what is the diagnosis of arbovirus ?
lumbar puncture if there are no contraindications to the procedure.
Cerebrospinal fluid (CSF) should be sent for cell count and differential, glucose concentration, protein concentration, culture, and gram stain.
results :
typically reveal lymphocytic pleocytosis, normal glucose, and elevated protein with a negative gram stain
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serology
Virus-specific IgM - through elisa
presence of IgM in CSF indicates neuroinvasive disease
and PCR of CSF
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(MRI), should also be considered when evaluating a patient for encephalitis
Electroencephalograms (EEG) are typically abnormal in patients with viral encephalitis and typically show generalized slowing.
In patients with WNV encephalitis, the most common EEG abnormality include diffuse irregular slow waves.
Brain biopsy can be considered in patients with encephalitis with neurological deterioration if other non-invasive test is nonrevealin
what is the treatment of arbovirus ?
If neuroinvasive disease is suspected or confirmed to be secondary to an arbovirus, management involves supportive care as there are no current antiviral treatment options
majority of non-invasive diseases and meningitis recover completely
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vaccination of arbovirus ?
TOGAVIRIDAE FAMILY:
CHIKUNGUNYA VIRUS,
EASTERN EQUINE ENCEPHALITIS
WESTERN EQUINE ENCEPHALITIS (WEE) VIRUS
VENEZUELAN EQUINE ENCEPHALITIS (VEE)
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Flaviviridae family:
DENGUE VIRUS
One vaccine is currently available in Latin America and Southeast Asia
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JAPANESE ENCEPHALITIS VIRUS
vaccine available in the US for individuals traveling to high-risk areas.
Vaccination -> two intramuscular doses given 28 days apart, with the
second dose administered at least 1 week prior to travel
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MURRAY VALLEY ENCEPHALITIS (MVE) VIRUS
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ST. LOUIS ENCEPHALITIS (SLE) VIRUS
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WEST NILE VIRUS (WNV)
no vaccines available for use in humans.
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POWASSAN VIRUS
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TICK-BORNE ENCEPHALITIS (TBE)
Vaccines are available in Europe and Canada
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ZIKA VIRUS
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BUNYAVIRIDAE FAMILY:
LA CROSSE ENCEPHALITIS VIRUS (LACV)
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CALIFORNIA ENCEPHALITIS VIRUS (CEV)
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REOVIRIDAE FAMILY:
COLORADO TICK FEVER VIRUS
other prevention for arbovirus ?
prevention is important to consider in endemic regions and include vector control, personal protective measures, and vaccination
approach for travelers includes avoiding infected areas, reducing exposure to vectors by wearing long clothing and using insect repellant, and considering vaccine
dd of arbovirus encephalitis ?
Aseptic meningitis
Autoimmune encephalitis
Bacterial meningitis
Herpes simplex virus (HSV) encephalitis
