Microbiology - Endy - Arboviruses Flashcards
What is the reservoir and vector of Eastern Equine Encephalitis?
Bird reservoir
Mosquito vector
Horse and human - incidental (dead end) host
virus
What are the symptoms of EEE?
Clinical manifestations vary from an inapparent to influenza like illness to the syndrome of encephalitis.
fever, headache, mental status changes and neck stiffness;
CBC demonstrated a leukopenia.
CSF: WBC 120 (90% lymphocytes), Protein 100 (high), Glucose of 30 (low)
*same symptoms as Japanese encephalitis–travel history a must
Probability of developing encephalitis varies widely: highest for the EEE and lowest for VEE.
What kind of virus is EEE?
EEE is in the Togaviridae family in the genera alphavirus. Positive ssRNA enveloped viruses
Alphavirus genus contains 4 encephalitic viruses which produce encephalitis; EEE, WEE, VEE and Everglades.
Focal epidemics of EEE have occurred in the Eastern USA, WEE is endemic in the Western USA, VEE is endemic in South America and N. America.
What kind of virus is Japanese encephalitis?
Family Flaviviridiae, positive sense single-stranded RNA
JEV circulates as a single serotype (Vaccine efficacy ramifications)
What is the natural host of Japanese encephalitis?
Pig, some birds
Humans and horses are accidental hosts
What are the symptoms of Japanese encephalitis?
Incubation period 6 to 16 days
Spectrum: Febrile headache → Aseptic meningitis → Encephalitis (
What kind of adverse reactions have occurred with the yellow fever vaccine?
Yellow fever vaccine–associated viscerotropic disease (YEL-AVD)- febrile illness that begins 3–5 days after vaccination and clinically resembles naturally acquired yellow fever.
What virus causes yellow fever?
Family Flaviviridiae, genus Flavivirus
What are the clinical features of the acute period of yellow fever?
Incubation period ranges from 3 to 6 days.
The clinical spectrum can manifest as a mild, nonspecific, febrile illness to a fulminating, sometimes fatal hemorrhagic disease.
Severe YF begins acutely with fever, chills, severe headache, lumbosacral pain, generalized myalgia, anorexia, nausea and vomiting, and minor gingival hemorrhages or epistaxes.
Bradycardia may be present despite a rising temperature (Faget’s sign).
Symptoms may last for 3 days and period of viremia.
What are the clinical features of the hemorrhagic period of yellow fever?
Hemorrhagic phase is manifested by “coffee-ground” hematemesis (vomito negro), melena, metorrhagia, petechiae, and ecchymoses.
Volume depletion is secondary to vomiting and plasma leakage.
Renal failure is manifested by an increase in albuminuria and diminishing urine output.
Death (in 20% to 50% of severe cases) occurs on the 7th to 10th day of illness and is preceded by deepening jaundice, hemorrhages, rising pulse, hypotension, oliguria, and azotemia (elevated BUN).
Hypothermia, agitated delirium, intractable hiccups, hypoglycemia, stupor, and coma are terminal signs.
Laboratory findings: leukopenia, elevation of bilirubin, serum transaminase levels, thrombocytopenia, prolonged PT and PTT, and ST-T wave changes in the electrocardiogram.
What virus causes dengue fever?
Genus Flavivirus & Family Flaviviridae
Four serotypes
DEN-1, -2, -3, and -4
What are the symptoms of dengue fever?
After a 2- to 7-day incubation period, high fever, headache, retrobulbar pain, lumbosacral aching pain, conjunctival congestion, and facial flushing develops.
Fever lasts for 6 to 7 days with generalized myalgia, bone pain, anorexia, nausea, vomiting, weakness, and prostration.
A generalized macular rash may appear on the first or second day. Following defervescence (day 3 to 5) a secondary rash, maculopapular or morbilliform appears on the trunk and then spreads centripetally to the face and limbs but spares the soles and palms..
Fever may rise again, creating the second phase of the saddle-back course.
The peripheral WBC count is depressed with an absolute granulocytopenia, and the platelet count may fall to less than 100,000/mm3.
Secondary/hemorrhagic dengue is characterized by:
Hemorrhagic manifestations include petechiae, epistaxis, intestinal bleeding, menorrhagia, and a positive tourniquet test.
Myocarditis may occur and neurologic disorders (encephalopathy, peripheral mononeuropathy, polyneuritis, and Bell’s palsy). Reye’s syndrome has also been reported to follow dengue infection.
Prolonged convalescence may occur with generalized weakness, depression, bradycardia, and ventricular extrasystoles.
Petechiae in a person with viral symptoms would suggest what diagnosis?
Dengue hemorrhagic fever (DHF)
____ is the most common arbovirus causing human infection in the subtropical and tropical regions of the world.
Dengue is the most common arbovirus causing human infection in the subtropical and tropical regions of the world.
Arbovirsus cause 4 clinical syndromes. What are they?
- Systemic febrile illness (ie Chikungunya, O’nyong-nyong, Ross River, Dengue);
- Fever with arthritis (Chikungunya, Ross River, O’nyong-nyong
- Encephalitis (Japanese encephalitis, West Nile Virus, Venezualan EE, EEE, WEE, Murray Valley E)
- Hemorrhagic Fever (Yellow fever, Dengue, Rift Valley Fever, Chikungunya)
In what places is the incidence of Japanese Encephalitis increasing?
India and Nepal
high mortality and morbidity
What arbovirus has the highest incidence of developing encephalitis?
EEE
Lowest for Venezualen EE
64 year old white male who presents in August with fever, headache (worse hes had in his life), mental status changes (forgetfulness) and neck stiffness. No travel in the preceding year outside of NY State.
Lives in Cicero, NY with a house bordering on Cicero Swamp. CBC demonstrated a leukopenia.
CSF: WBC 120 (high) (90% lymphocytes), Protein 100 (high), Glucose of 30 (low).
What does he have?
West Nile Encephalitis St. Louis Encephalitis Powassan encephalitis Eastern equine encephalitis None of the above.
Eastern equine encephalitis - key is that EEE is endemic to Cicero swamp
Others could all be possible and share similar symptoms - Critical take away is that knowing the geography and history of travel is essential to identifying correct diagnosis
Not St. Louis powassan or West Nile b/c of location - but all present with similar symptoms
Powassan is tickborne other are mosquito vectors
What are the most rapidly lethal type of arboviruses?
Those that cause hemmoragic fever
Yellow fever
Dengue
Rift valley fever
Chikungunya
What is a dead end host?
An organism that once gets infection doesn’t propagate it
What type of viruses cause Eastern Equine Encephalitis , Western Equine Encephalitis, Venezuelan Equine Encephalitis, and Everglades Encephalitis?
Which is more likely to contract in US?
Wich have greater mortality?
What is Vector? Reservoir?
What is the treatment?
Alphaviruses: +ssRNA, enveloped
Likelyhood of contracting: EEE>WEE
Mortality: EEE>VEE>WEE
Most infections do not manifest in encephalitis (more common are flu-like symptoms) but still detectable from blood work
Mosquito - Culista melanura
Reservoir - Birds
Supportive care - No cure
What are signs of encephalitis?
fever
headache (worse in life)
mental status changes (forgetfulness)
neck stiffness
64 year old white male who presents in March with fever, headache, mental status changes and neck stiffness. Patient had traveled to Thailand 2 weeks before his illness. Lives in Cicero, NY with a house bordering on Cicero Swamp. WBC 120 (high) (90% lymphocytes), Protein 100 (high), Glucose of 30 (low).
What does he have?
West Nile Encephalitis Japanese Encephalitis Powassan encephalitis Eastern equine encephalitis None of the above.
Japanese Encephalitis - travel history
What type of virus causes Japanese encephalitis? What is the nucleic acid? What is the vector? Host? What is special about the host? When is the most likely time of day to become infected? What locations are high infections sites? What time of year can you be infected?
Flavivirus (type of arbovirus)
+ssRNS (Single serotype but 5 genotypes endemic to diff parts of SE Asia)
Mosquito - Culex
Natural host is Pig - can sustain high viral loads without becoming infected
Humans are accidental hosts
Night time because Culex is a night feeder
Rice fields, marshes
Year round transmission due to agricultural irrigation but rainy seasons have highest transmission rates
Why is JEV considered a preventable disease?
2 Vaccines available (single serotype virus makes it amenable to vaccination)
JE-Vax - discontinued production due to anaphylaxis reaction
IXIARO - contains purified and inactivated JEV virus - protamine sulfate clears DNA and contaminants - formaldyhyde inactivates virus
What are the two presentation of yellow fever?
Visotropic - high mortality >60% a febrile illness that begins 3–5 days after vaccination and clinically resembles naturally acquired yellow fever.
Neurotropic - encephalitis
How is Yellow fever transmitted?
nonhuman primates to mosquitoes to humans
Jungle cycle of monkey to mosquito to monkey is reservoir
What is Faget’s sign? What disease is it seen in?
Bradycardia despite high temp - acute phase of yellow fever
Where is yellow fever found?
Equitorial parts of south america and Africa
Can you get Dengee fever in the US?
Yes - Key west
Clinical presentation of Dengue
What is the most serious pathology?
Hemorrhagic disease!
Petechia on chest wall or subcutaneous hemorrhage or hemorrhage into stomach.
Can develop shock syndrome - intravascular volume depletion from plasma leakage into lung causing pleural effusion or from hemorrhagic blood loss - can lead to cardiovascular collapse
Hematocrit increase is indication of plasma leakage into lung because RBS become concentrated with less plasma
What is the most common arboviral infection in the subtropical and tropical regions of the world?
Dengue mother fucker!
- True or False: Arboviruses are viruses that are transmitted by rodents that breed in forests
(arboretum) and named from the combination of arboretum and virus (arbovirus).
- F
Which are the following clinical syndromes are produced by the arboviruses?
a. Systemic febrile illness.
b. Fever with arthritis.
c. Encephalitis.
d. Hemorrhagic fever.
e. All of the above.
- E
Which are the following statements are true about Japanese encephalitis virus?
a. It is a minor cause of encephalitis in Asia.
b. The life cycle involves birds, mosquitoes, pigs and humans are a dead-end host.
c. There is no licensed vaccine available for protection.
d. Infection in the brain is mild and not severe.
e. None of the above.
- B
Which are the following statements are true about Dengue virus?
a. It is a minor cause of infection in the world.
b. The life cycle involves birds, mosquitoes, pigs and humans are a dead-end host.
c. There is a licensed vaccine available for protection.
d. Infection can result in a febrile illness to a severe hemorrhagic form.
e. None of the above.
- D
