Polio Flashcards
Polio is a (segmented, nonsegmented) (ss, ds) (+,-)(DNA, RNA) virus
Nonsegmented ss RNA (+)
To what genus does poliovirus belong? What does this tell you about the virus?
Enterovirus
Replicates in GI tract and spread via fecal-oral route
How did the Amish in MN get polio in 2005?
Introduced by outsider via vaccine shedding
What countries continue to have endemic polio?
Afghanistan, India, Pakistan, Nigeria
Describe the disease process of polio
Contracted via fecal-oral route
Initial replication in lymphoid tissue of pharynx and gut
Secondary viremia spread to CNS
Directly lysis motor neuron cells
What would you collect to check for polio in a suspected infected individual?
Throat or rectal swab and feces collection (initially replicates in pharynx and gut)
CSF
Incubation time for polio?
1-2 weeks
___% of polio is asymptomatic
90%
Three diseases caused by polio
Abortive polio
Aseptic meningitis (non-paralytic)
Paralytic polio
Your Nigerian patient is making a decent recovery 7 months after being struck with paralytic polio. He asks if he will regain function in his legs, which are paralyzed. You tell him:
No; any paralysis after 6 months is permanent
Describe the immune response to polio
IgM then IgG + secretory IgA from gut mucosa
(T/F): After being infected with the natural virus, one has life-long immunity to polio
True - IgG response
What function does secretory IgA serve during a polio infection?
Neutralizes polio before it’s shed in feces
What is abortive polio?
Does not involve CNS
What is post-polio syndrome?
Progressive weakness of muscles that were involved during polio illness later on in life
What occurs a few days before paralysis in paralytic polio?
Fever decreases
How can you confirm polio infection? Tell vaccine from wild strains?
Neutralization assays confirm polio
Antibody assays distinguish wild from vaccine strains
Which can kill polio: Alcohol and detergents or formaldehyde and chlorine
Formaldehyde and chlorine
Which vaccine do we use in the US?
Inactivated polio vaccine = Salk IPV
What are the advantages of the IPV?
Formalin inactivation means it cannot revert to virulence
What are the disadvantages of the IPV?
Since it’s given subQ, we don’t mount an IgA response, so we don’t neutralize polio before it’s shed in the feces = we’re protected if we contract wild virus but we can still pass it to others
Contraindications of IPV?
Allergy to neomycin, polymyxin B, streptomycin
used in prep of IPV
What are the advantages of the OPV?
Cheap, oral, IgA response, no spread of wild virus
What are the disadvantages of the OPV?
1:3 million revert during prep and 1:500,000 revert during shedding
