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ID Ex 2 > Arbovirus > Flashcards

Arbovirus Flashcards

1
Q

Major arboviruses

- Globally and in US

A

Globally:

  1. Yellow fever (YFV)
  2. Japanese encephalitis
  3. Dengue viruses
  4. West nile virus
  5. Zika virus
  6. Chikungunya virus

In us:
West nile virus

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2
Q

Taxonomy and genome structure of arbovirus

A

RNA genome

Taxonomic family:

  1. Bunyaviridae
  2. Flaviviridae
  3. Togaviridae
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3
Q

Arboviruses are maintained in nature how?

  1. Arthropod vectors
  2. Vertebrate hosts
A
  1. Arthropod
    - mosquitos, ticks, flies
  2. Vertebrate hosts
    (hu are dead end)

*presence of high titer serum viremia of long enough duration to infect adequate number of vectors

  • exceptions:
    1. dengue virus
    2. yellow fever
    3. zika virus
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4
Q

Hus role in arbovirus

A

Hu are dead end host for most arbovirus

- no sig role in :maintenance of virus in nature, and amplification during outbreaks/epidemics

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5
Q

Role of mosquitos in arbovirus transmission

A
  1. female mosquito ingests blood from viremic vertebrate
  2. virus replication in the mosquito midgut
  3. systemic spread in mosquito
  4. virus replicates and accumulates in salivary glands
  5. Mosquito injects saliva/virus into skin during next blood meal
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6
Q

After biting an infected vertebrate host, is a mosquitoimmediate infectious for hu?

A

no
- virus must first rep. in mosquito and accumulate in saliva
. . .

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7
Q

How often are arboviruses asymptomatic

A

Dengue virus/WNV 80%

Chukungunya virus: 10-15%

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8
Q

When arboviruses are not asymptomatic, what symptoms do you see?

A
  1. Febrile illness
  2. Neurologic disease
    - encephalitis, meningitis
  3. Arthtitis
  4. Hemorrhagic fever
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9
Q

Extrinsic incubation period

A

Mosquitos “ripened” for 12 days prior to inoculation

*occurs after the initial 3 days of attack: having High titer serum viremia

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10
Q

Dengue viruses causes 2 syndromes:

A
  1. Dengue Fever (milder)

2. Dengue hemorrhagic fever/dengue shock syndrome

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11
Q

Dengue hemorrhagic fever/Dengue shock syndrome

A
  1. Characterized by thrombocytopenia
  2. capillary leakage
  3. Damage to liver
  4. fluid loss in tissue space –> hypovolemic shock and death
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12
Q

Increased risk of getting Dengue viruses

A
  1. High temp and ppt
    - tropical/subtropical countries
  2. Proximity to low income urban centers
    ______
    Risk factors for developing DHF/DSS:
  3. A second dengue infxn by a diff serotype
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13
Q

How many serotypes of dengue fever?

A

4 - all 4 are found cocirculating in subtropical areas

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14
Q

Mosquitos that are vectors for Arboviruses

A
  1. Ae. aegypti

2. Ae. albopictus

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15
Q

Members of flavivirus genus of flaviviridae

A
  1. Hepaciviruses
    - HCV
  2. Pestiviruses
    - Bovine viral diarrhea virus
    - Classical swine fever virus
  3. Flaviviruses
    - Dengue virus
    - Yellow fever
    - Jap encephalitis
    - WNV
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16
Q

Hypothesis: Antibody-dependent enhancement (ADE) of disease severity

A

1st infxn

  • Ab response to 1st infnx
    1. Protects from 2nd infxn w/ homologous DENV serotype
  • strongly neutralizing ab against DENV serotype responsible for 1st infxn
    2. Due to cross-rxn, initially protects from second infxn w/ a diff DENV serotype
  • over time, these cross-reactive antibodies DECLINE to a subneutralizing level

2nd infxn with DIFFERENT serotype:

  1. Cross-reactive subneutralizing ab generated during the 1st infxn mediate enhanced infxn of specific cells
  2. Leads to increased viral replication and immune activation

*Abs increase disease severity

17
Q

Chikungunya virus

A

“that which bends up”

3 clinical stages

  1. Acute: sudden fever, arthalgia, arthritis, rash
  2. Post-acute: perisistent joint pain, arthritis, tenosynovitis
  3. Chronic
    - musculoskeletal disorder

*hu-mosquitos-hu transmission fuels epidemic spread

18
Q

Zika virus

A

80% asymptomatic
20%
Fever, muscle/joint pain (arthralgia), conjunctivitis

19
Q

WNV sx

A

80% asymptomatic

  1. Abrupt onset of fever, HA, Fatigue
  2. In elderly or poor immune syste: Altered mental status, neck stiffness
    (encephalitis, meningitis, acute flaccid paralysis)
20
Q

WNV directly infects _____

A

neurons

Virus replicates locally at site of inoculation –>
Infected cells migrated to lynph nodes –>
Seeds primary viremia –>
Virus gains acess to CNS –>
neuronal injury

21
Q

Ways to acquire WNV

A
  1. Mosquitos
  2. SOlid organ transplantation
  3. Blood transfusion
    (screen with RT-PCR)
22
Q

Which arboviral disease have a vaccine?

A

Yellow fever: Live attenuated

JEV: inactivated vaccine

TIck born encephalitis (TBEV): Inactivated vaccine

23
Q

Sx associated with each:

  1. Yellow fever (YFV)
  2. Japanese encephalitis
  3. Dengue viruses
  4. West nile virus
  5. Zika virus
  6. Chikungunya virus
A
  1. Yellow fever (YFV) - Hemorrhagic fever
  2. Japanese encephalitis
    - encephalitis
  3. Dengue viruses
    - Hemorrhagic fever
  4. West nile virus
    - Encephalitis
    (severe neurologic disease)
  5. Chikungunya virus
    - acute and chronic arthritis
24
Q

Risk factors for developing DHF/DSS:

A

Risk factors for developing DHF/DSS:

  1. A second dengue infxn by a diff serotype
    - antibody dependent enhancement (ADE) of disease
25
Q

Most common cause of arboviral diseases in US

A

WNV

- vector isthe culex mosquitos

26
Q

Host and vector for WNV

A

host: birds
Vector: culex mosquitos

Hu are dead end hosts

ID Ex 2 (18 decks)

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