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GI Week 4 - WLB > Viral Gastroenteritis - Diebel > Flashcards

Viral Gastroenteritis - Diebel Flashcards

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1
Q

What are the most common viral pathogens that cause gastroenteritis?

A
  • Major Causes:
    • Rotavirus
    • Norovirus (Norwalk Virus)
  • Minor Causes:
    • Adenovirus
    • Astrovirus
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2
Q

What is the route of infection for viruses that cause gastroenteritis?

A

Fecal to oral

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3
Q

What transmission characteristics of Rotavirus allow it to cause gastroenteritis?

A
  • After ingestion → travels to GI tract
    • virus particle is stable within the low pH of the GI system
  • Infects the villus cells of proximal small intestine
  • Virus replicates within villus cells
  • Virus causes cell lysis
    • causes impaired absorption of carbohydrates and other nutrients
    • leads to vomiting followed by watery diarrhea
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4
Q

How is gastroenteritis caused by Rotavirus diagnosed?

A
  • Stool specimen
  • Serology for the virus ⇒ ELISA
    • Serotypes are based off of the VP4 and VP7 genes → your body will make antibodies against these → can be tested by ELISA studies
  • Latex agglutination assay of stool samples possible.

(Electron microscopy/RT-PCR also possible)

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5
Q

What is the treatment for gastroenteritis caused by Rotavirus?

A

Supportive!

  • Rehydration
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6
Q

Is there a vaccine for Rotavirus?

A

Yes!

  • live oral attenuated vaccine
    • Rotarix = single strain of a human-infecting rotavirus
    • Rotateq = reasortants
      • 10 cow rotavirus genes + 1/5 human rotavirus genes
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7
Q

Rotavirus

RNA/DNA

Genome

Shape

Envelope

Unique characteristics

A
  • RNA virus
  • Icosahedral Nucleocapsid
  • Nonenveloped
  • DS, Segmented Genome (Class III)
  • Reoviridae
  • Unique characteristics:
    • DOUBLE-PACKAGED → double capsid
    • Stable in the environment.
    • Digestive enzymes actually enhance infectivity.
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8
Q

What is the tropism of Rotavirus (where do they infect, grow, replicate)?

A
  • Rotaviruses infect the mature absorptive villous epithelium of the upper two thirds of the small intestine.
  • After replication in the upper small intestine, infectious particles are released into the intestinal lumen
    • undergo further replication in the distal areas of the small intestine
  • Infection is generally confined to the intestinal mucosa.
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9
Q

When is Rotavirus most contagious?

A
  • Large amounts of virus are released during the diarrheal phase.
  • Maximal virus shedding 2 to 5 days after the start of the diarrhea phase → CONTAGIOUS!!!
    • Incubation period is about 48 hours.
  • Outbreaks most common in day care centers, preschools, and among hospitalized infants.
  • Higher incidence of cases in the autumn, winter, and spring.
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10
Q

What age group does Rotavirus primarily affect?

A
  • Disease is most serious in individuals under the age of 2.
  • By age 3, almost every individual worldwide (~95%) has been infected and develops lifelong immunity.
  • Infection before 6 months of age is uncommon due to passive IgA immunity from the mother’s colostrum.
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11
Q

What are the symptoms of gastroenterities caused by Rotavirus?

A
  • Secretory diarrhea
    • caused by the infection and damage to the proximal small bowel.
    • Stool does NOT contain leukocytes or RBCs.
  • Nausea/vomiting
  • abdominal pain
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12
Q

What is the most common cause of foodborne disease outbreaks in the United States?

A

Norovirus Virus

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13
Q

How are Noroviruses transmitted?

A

fecal-oral route in contaminated water and food

(group-related or institutional diarrhea common)

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14
Q

Norwalk Virus

DNA/RNA

Shape

Envelope

Genome

A
  • RNA virus
  • Icosahedral Nucleocapsid
    • ragged outlined capsid
  • Nonenveloped
  • SS (+) Nonsegmented Genome (Class IV)
  • Caliciviridae
  • Calicivirus (also includes astroviruses)
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15
Q

What is the tropism of Norovirus?

A

intestinal epithelium

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16
Q

How does Norovirus cause gastroenteritis?

A
  • Only takes 10 virions to initiate infection.
  • The virus infects and damages the small intestine
    • cytolytic damage and inflammation
    • prevents proper absorption of water and nutrients
    • causes a watery diarrhea
  • Gastric emptying may be delayed, causing vomiting.
  • Shedding of the virus may continue for 2 weeks after symptoms have ceased.
17
Q

What are the symptoms of gastroenteritis caused by Norovirus?

A
  • 24-hour incubation period, symptoms start after
    • Diarrhea
    • Nausea/vomiting
      • more severe than Rotavirus
    • Abdominal cramps
    • Fever is typically no higher than 101°F
    • Headache
    • Anorexia and malaise
  • Disease resolves after 48 hours, without serious consequences
18
Q

Why are Norovirus infections the leading cause of gastroenteritis in the US?

A

Norovirus can mutate quickly (causing drift).

  • Results in new strains every few years.
  • Immunity is generally short lived at best and may not be protective.
    • The large number of strains and high rate of mutation allows reinfection despite antibodies from a previous exposure.
19
Q

How is gastroenteritis caused by Norovirus diagnosed?

A
  • Not typically diagnosed!
  • When it is done:
    • visualization of the virus in stool specimens
    • RT-PCR
    • Serology of stool and/or vomit specimens
    • Electron microscopy
    • Enzyme-linked assays
20
Q

What is the treatment for gastroenteritis caused by Norovirus?

A
  • Usually not required → self-limiting infection
  • Supportive if necessary
    • rehydration
21
Q

Adenovirus

DNA/RNA

Shape

Envelope

Genome

A
  • DNA virus
  • Icosahedral Nucleocapsid
  • Nonenveloped
  • DS DNA Linear (Class I)
  • Adenoviridae
  • Mastadenovirus (Adenovirus)
22
Q

What serotypes of Adenovirus are enteric and are a major cause of acute infantile gastroenteritis?

A

Serotypes 40, 41, and 42

23
Q

How is gastroenteritis caused by Adenovirus diagnosed?

A
  • Direct analysis of the clinical sample without virus isolation is possible.
  • Rarely used except for epidemiological purposes.
    • Immunoassays (either fluorescent antibody or ELISA)
    • PCR detection of the viral genome within a stool sample
    • DNA probe analysis
    • Above approaches required for serotypes 40 – 42
24
Q

What is involved in the treatment, prevention, and control of Adenovirus?

A
  • Careful handwashing
  • Chlorination of swimming pools
  • No approved treatments.
    • Supportive care.
    • Self-limiting infection in immunocompetent individuals
  • Live oral vaccines for types 4 and 7 (military personal only)

GI Week 4 - WLB (8 decks)

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