Lecture 55 Enteroviruses & LCMV

Question 1

Polio presentation and diagnosis

Answer 1

Fever and asymmetric flaccid paralysis
RT-PCR needed to confirm
Isolation of virus from fecal matter or respiratory secretions is suggestive but not definitive

Question 2

Polio virus characteristics

Answer 2

Picorna virus
Single strand RNA
Non enveloped
Acid stable

Question 3

Polio hosts

Answer 3

Humans are only natural host for polio

Question 4

How is someone infected with Polio?

Answer 4

Direct or indirect fecal-oral, or direct contact with respiratory secretions
Swimming is a common cause

Question 5

Pathogenesis of Polio

Answer 5

Enters through GI, multiplies in pharynx and small intestine
Seeds many sites and spreads to CNS
Infects anterior horn cells, brain stem, and sometimes motor cortex

Question 6

How does Polio enter the CNS

Answer 6

Direct transfer from the blood, or retrograde axonal flow

Question 7

Describe polio genome and replication

Answer 7

(+) sense RNA, translated into one giant polypeptide that is then cut to individual pieces

Question 8

What is IRES?

Answer 8

IRES is: internal ribosomal entry site

Nucleotide sequence that allows swift entry into the ribosome for translation

Question 9

Clinical syndromes of Polio

Answer 9

1) Inapparent infection
2) Abortive illness: fever, malaise, headache, drowsiness, N/V, spontaneous recovery
3) Non-paralytic poliomyelitis: fever, malaise, headache, drowsiness, N/V, stiff neck and back, spontaneous recovery
4) Paralytic Poliomyelitis: Flaccid paralysis from lower motor neuron damage, some recovery over time through muscle hypertrophy and compensating motor neurons, peak dysfunction after 2-3 days
5) Post Polio Syndrome: gradual clinical course, drop-out of motor neurons decades later in paralyzed patients

Question 10

Polio bulbar paralysis

Answer 10

Cranial nerve involvement=> motor dysfunction in the face including difficulty swallowing, facial movements, speech, eye movements

Respiratory center depression=> respiratory paralysis

Question 11

Polio prevention

Answer 11

Vaccine:
-IPV: Inactivated Polio Vaccine, stops paralysis but not infection or spread, less effective than OPV

-OPV: Oral, live attenuated, grown in human or monkey cells, puts virus in the community, and can mutate and cause neurovirulence

Question 12

Properties of Polio that make it possible to eradicate

Answer 12

Humans only reservoir
Doesn’t persist well in environment
Vaccine => life-long immunity

Question 13

SV 40

Answer 13

Not a picorna virus, came from monkey cells used to grow the Polio virus for vaccines
Causes malignant malformation => brain malignancies in kids
Causes lysis of oligodendrocytes => opportunistic PML (Progressive Multifocal Leukoencephalopathy) which is a disease of the aged and immunosuppressed

Question 14

What are the 2 genera of human picorna viruses?

Answer 14

Enteroviruses

Rhinoviruses

Question 15

Name the non-polio enteroviruses discussed

Answer 15

Echo

Coxsackie

Question 16

General characteristics of enteroviruses

Answer 16

Typically assoc. with intestinal infections
Broad tissue tropism
Possible eventual neurologic disease
Most kids infected at least once by age 2
Newborns and immunocompromised at greatest risk
Same translation pattern as polio into large polyprotein
Nonenveloped

Question 17

Echo Virus

Answer 17

Accidentally discovered in feces while looking for polio

Question 18

Coxsackie Viruses

Answer 18

Two groups:

1) Causes diffuse myositis with acute inflammation and necrosis
2) Focal areas of degeneration of brain and skeletal muscle

Question 19

Clinical manifestations of Echo/Coxsackie

Answer 19

Newborn:
Sudden onset, fever, vomiting, anorexia, rash, meningeal infection, Bulging of Anterior Fontanelle
Death by hepatic failure in Echo, and myocarditis in coxsackie

Older kids and adults: Fever, headache, nuchal rigidity
(outside first 2 weeks of life not usually severe)

Question 20

Echo/Coxsackie diagnosis and treatment

Answer 20

Throat and fecal samples
Up to 30% will turn up negative
Caxsackie A will not grow in culture
Nonsymptomatic shedding common in summer/fall
RT-PCR useful
Body site for isolation matters:
-Feces: most sensitive, least specific
-Nasopharynx: better link to disease
-CSF, Blood: presence here indicates invasive disease (usually not found here?)

Question 21

Echo/Coxsackie epidemiology

Answer 21

Infections most common in summer/fall in temperate zones
Young children primarily
Disease probability and severity inversely proportional to age (opposite to polio)
Fecal-oral transmission

Question 22

Echo/Coxsackie prevention

Answer 22

Vaccines unlikely because of many serotypes

Careful handwashing and disinfection

Question 23

LCMV general characteristics

Answer 23

Arenavirus group
2 RNA strands: one (-), one ambisense
Enveloped, studded with ribosomes, large
Chronic infections of rodents

Question 24

LCMV clinical manifestations

Answer 24

Encephalitis rare
Flu-like usually
Meningitis uncommon

Question 25

LCMV diagnosis and treatment

Answer 25

Suspected in cases of aseptic meningitis
History of exposure to mice, hamsters or other rodents
No treatment

Question 26

LCMV epidemiology

Answer 26

Found anywhere mice are found
Infection through aerosols
Autumn-Winter predominance
All age groups
Prevent through rodent control