Polio

Question 1

Polio is a (segmented, nonsegmented) (ss, ds) (+,-)(DNA, RNA) virus

Answer 1

Nonsegmented ss RNA (+)

Question 2

To what genus does poliovirus belong? What does this tell you about the virus?

Answer 2

Enterovirus

Replicates in GI tract and spread via fecal-oral route

Question 3

How did the Amish in MN get polio in 2005?

Answer 3

Introduced by outsider via vaccine shedding

Question 4

What countries continue to have endemic polio?

Answer 4

Afghanistan, India, Pakistan, Nigeria

Question 5

Describe the disease process of polio

Answer 5

Contracted via fecal-oral route
Initial replication in lymphoid tissue of pharynx and gut
Secondary viremia spread to CNS
Directly lysis motor neuron cells

Question 6

What would you collect to check for polio in a suspected infected individual?

Answer 6

Throat or rectal swab and feces collection (initially replicates in pharynx and gut)
CSF

Question 7

Incubation time for polio?

Answer 7

1-2 weeks

Question 8

___% of polio is asymptomatic

Answer 8

90%

Question 9

Three diseases caused by polio

Answer 9

Abortive polio
Aseptic meningitis (non-paralytic)
Paralytic polio

Question 10

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:

Answer 10

No; any paralysis after 6 months is permanent

Question 11

Describe the immune response to polio

Answer 11

IgM then IgG + secretory IgA from gut mucosa

Question 12

(T/F): After being infected with the natural virus, one has life-long immunity to polio

Answer 12

True - IgG response

Question 13

What function does secretory IgA serve during a polio infection?

Answer 13

Neutralizes polio before it’s shed in feces

Question 14

What is abortive polio?

Answer 14

Does not involve CNS

Question 15

What is post-polio syndrome?

Answer 15

Progressive weakness of muscles that were involved during polio illness later on in life

Question 16

What occurs a few days before paralysis in paralytic polio?

Answer 16

Fever decreases

Question 17

How can you confirm polio infection? Tell vaccine from wild strains?

Answer 17

Neutralization assays confirm polio

Antibody assays distinguish wild from vaccine strains

Question 18

Which can kill polio: Alcohol and detergents or formaldehyde and chlorine

Answer 18

Formaldehyde and chlorine

Question 19

Which vaccine do we use in the US?

Answer 19

Inactivated polio vaccine = Salk IPV

Question 20

What are the advantages of the IPV?

Answer 20

Formalin inactivation means it cannot revert to virulence

Question 21

What are the disadvantages of the IPV?

Answer 21

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

Question 22

Contraindications of IPV?

Answer 22

Allergy to neomycin, polymyxin B, streptomycin

used in prep of IPV

Question 23

What are the advantages of the OPV?

Answer 23

Cheap, oral, IgA response, no spread of wild virus

Question 24

What are the disadvantages of the OPV?

Answer 24

1:3 million revert during prep and 1:500,000 revert during shedding

Question 25

What is the problem with the WHO’s polio eradication plan?

Answer 25

The last round of kids to receive OPV will shed virus and 1:500,000 will revert so non-vaccinated people will catch it