Lec 38 Vector-borne and zoonotic viral disease Flashcards
(54 cards)
What are viral properties of arboviruses of alphaviruses? examples?
single strand pos sense RNA
examples: EEE, WEE, VEE
What are viral properties of flaviviruses? examples?
single strand pos sense RNA
examples: DENV, WNV, YF, SLE
What are viral propertiers of bunyaviruses? examples?
single strand neg sense RNA
examples: La Crosse, Hantaviruses
What is pathogenesis of alpha and flaviviruses?
- 2-3 days : mild or asymptomatic
- 3-7 days: prodrome viremia: mild systemic disease, fever, aches, chills, may infect macrophages, liver, spleen, lymph nodes
- after that: viremia: sever or life threatening – encephalitis, yellow fever, hepatitis, hemorrhagic fever –> DHF/DSS [dengue]
Where is dengue virus [DV] normally found?
mainly in tropical and subtropical
What is the main vector of dengue?
aedes aegypti mosquito
What is the aedes aegypti mosquito? what does it look like? importance?
- most common epidemic vector of dengue and yellow fever
- has white bands or scale patterns on legs and thorax
What is the importance of culex sp mosquito?
associated with transmission of WNV [west nile], SLE [st louis encephalisit], EEE [eastern equine], WEE [western equine], VEE [venezuelen equine]
How is dengue virus transmitted?
- aedes aegypti mosquito [major vector]
- aedes albopictus mosquito
- no human to human transmission
How do the 4 serotypes of denV differ? is there cross immunity?
- each serotype gives specific lifetime immunity and short-term cross immunity
- all lead to severe and fatal disease
- all types genetically distinct
What are markers present in serum with dengue infection?
- see high levels of NS1 antigen during dengue infection
- first antibody produced is IgM
- if you get secondary infection of same virus type will get IgG
How do you detect dengue?
- detect anti-DENV IgM in serum
- PCR to detect DenV genome in serum/mosquitoes/tissue
- detect NS1 with elisa
What are signs of dengue fever?
- fever, muscle pain, rash, hepatitis, cytopenias
- biphasic course
what are signs of DHF [dengue hemorrhagic fever] and dengue shock syndrome [DSS]?
- increased vascular permeability and plasma leakage, bleeding diathesis [from eyes, ears, etc]
- develops during 2nd phase of illness
- associated with 2ndary infection w/ different serotype
Who primarily gets DHF/DSS?
children, normally develops during second phase of biphasic DF and happens in secondary infection
What is antibody mediated immune enhancement [ADE]?
- cross-reactive antibodies allow uptake of virus by macrophages/monocytes that have Fc receptor –> virus infects these cells and replicates = massive superinfection with increased viral load
- get lots of cytokine release –> DHf/DSS
big problem = disease is caused by our own immune system
How do you prevent DENV?
- minimize reduction of human-vector contact
- 3 vaccine trials ongoing
How do you control dengue vector?
- eliminate egg-laying habitat [water/waste store/remove]
- insecticides/barriers
- sterilize male mosquitos [population control]
- intriduce wolbachia pipientis into A aeypti = bacteria that blocks denv transmission
What are the concerns about DENV vaccines?
- need to give protection against all 4 serotypes
- need to be safe in already dengue immune pop
- need protective antibody response and T cell immunity
- need to be accessible and affordable
What happens with CYD vaccine?
- only 30% efficacy, didn’t work against DENV-2
- need to go back to drawing board
Where is yellow fever endemic?
parts of south america and subsaharan africa
What is natural reservoir for yellow fever?
monkeys [humans can also act as source of infection]
What is vector for yellow fever to humans?
aedes aegypti
What are symptoms of yellow fever?
stage 1: fever, headache, leukopenia, can be asymptomatic
some people progress to stage 2: hepatitis, hemorrhagic diasthesis, multiorgan failure, mortality 50%
