03b: Viral, parasitic gastroenteritis

Question 1

T/F: Viral gastroenteritis is indistinguishable clinically from other types of gastroenteritis
(from bacteria, toxins, or protozoa).

Answer 1

True

Question 2

T/F: Enteric viral infections tend to disseminate (viremia).

Answer 2

False - usually remain localized in the intestinal tract

Question 3

T/F: Enteric viruses are different from enteroviruses.

Answer 3

True - enteroviruses are a group of viruses in Picornaviridae family

Question 4

T/F: Enteroviruses don’t cause gastroenteritis.

Answer 4

True

Question 5

Rotaviruses are in the (X) family of viruses. They’re (enveloped/non-enveloped) with (ss/ds)-(RNA/DNA) composed of 11 (separate/combined) segments.

Answer 5

X = reoviridae
Non-enveloped
dsRNA

Separate (genetic reassortment can occur)

Question 6

Rotaviruses are unusually stable to (X), but can be
inactivated by (Y).

Answer 6

X = heat, pH changes, lipid solvents
Y = EtOH, phenol, chlorine

Question 7

Rotavirus: you would expect to see inclusion bodies in (cytoplasm/nucleus), the site of replication.

Answer 7

Cytoplasm

Question 8

Rotavirus: does it carry its own polymerase?

Answer 8

Yes - RNA-dependent-RNA Pol

Question 9

Rotavirus:
(Symptomatic/asymptomatic) infections occur in children 6-24 months of age; (symptomatic/asymptomatic) infections are common in infants <6 months old.

Answer 9

Symptomatic; asymptomatic

Question 10

Most human rotavirus infections are caused by Group (X) serotypes.

Answer 10

X = A

Question 11

By age (X) years, (Y)% of children have serum Ab to one or more rotavirus serotypes.

Answer 11

X = 3
Y = 90

Question 12

Rotaviruses causes (watery/bloody) diarrhea. What’s the mechanism of action?

Answer 12

Watery;

Infects cells at tip of villi, blunting/shortening them and preventing water/ion absorption

Question 13

T/F: Immunity to rotavirus infection cannot be attained.

Answer 13

False - IgA in the lumen of the gut is required for some immunity to infection (can’t prevent reinfection, but lessens severity of disease)

Question 14

Major cause of viral diarrhea in children 6-24 months old.

Answer 14

Rotavirus

Question 15

Rotavirus treatment:

Answer 15

Supportive (fluids)

Question 16

Rotavirus vaccines

Answer 16

RotaTeq and Rotarix (live, attenuated given orally to infants)

Question 17

Norovirus: (Enveloped/non-enveloped), with (ss/ds) (RNA/DNA).

Answer 17

Non-enveloped

ssRNA (positive-sense)

Question 18

Norovirus: does it carry its own polymerase?

Answer 18

No, but encoded in genome - viral RNA directly translated by host machinery

Question 19

(X) the most common cause of severe acute gastroenteritis in children < 5 y.o. who seek healthcare.

Answer 19

X = norovirus

Question 20

Pathogenesis/pathology of norovirus infection is similar to that of (X) infection. Diarrhea is (watery/bloody).

Answer 20

X = rotavirus

Watery

Question 21

Treatment of norovirus infection:

Answer 21

Supportive (fluids)

Question 22

Norovirus vaccines

Answer 22

None

Question 23

All parasite subtypes (flagellates, amebae, and sporozoans) are transmitted via contaminated (X), except (Y) which is transmitted sexually.

Answer 23

X = water
Y = Trichomonas (a flagellate)

Question 24

Entamoeba histolytica is a(n) (X) form of parasite. List the forms it exists in and star the infective form.

Answer 24

X = amoeba

1. Cysts*
2. Trophozites

Question 25

T/F: Chlorine treatment in pools inactivates Entamoeba histolytica.

Answer 25

False - resistant to many things, including that

Question 26

Which form of (X) causes amebiasis (invasive disease)?

Answer 26

X = Entamoeba histolytica

Trophozite (active, replicating form)

Question 27

Entamoeba histolytica replicates via:

Answer 27

binary fission (asexually)

Question 28

T/F: There are commensal Entamoeba species found in the human GI tract that do not
cause disease.

Answer 28

True

Question 29

How many Entamoeba histolytica cysts required to cause disease?

Answer 29

One

Question 30

Entamoeba histolytica (cysts/trophozoites) penetrate the (X) layer of the colon. What does the organism do to cause damage?

Answer 30

Trophozoites;
X = mucosal epithelial

1. Adheres to cells via adhesin and multiply
2. Necrosis in colon by lysing colonic cells (epithelial, PMNs, lymphocytes, monocytes)

Question 31

(Full/partial/no) immunity against Entamoeba histolytica may occur. Antibodies are produced against (X).

Answer 31

Partial
X = adhesin (lectin)

Possible vaccine target

Question 32

Three possible outcomes of Entamoeba histolytica infection:

Answer 32

1. Asymptomatic carrier (90%)
2. Intestinal amebiasis
3. Extra-intestinal amebiasis

Question 33

Intestinal amebiasis range of symptoms.

Answer 33

Mild diarrhea to severe dysentery (diarrhea with blood and mucus in stools)

Question 34

Extra-intestinal amebiasis commonly involves (X) structure and presents with which symptoms?

Answer 34

X = liver (since filters out trophozoites)

Abscess formation (especially in right lobe), hepatomegaly, RUQ pain, systemic symptoms

Question 35

Laboratory diagnosis of Entamoeba histolytica is done via:

Answer 35

Stool/tissue sample examined microscopically for trophozoites and stool for cysts

Question 36

T/F: All E. histolytica infections, even asymptomatic, are treated.

Answer 36

True - to prevent invasive disease and transmission

Question 37

(X) used to treat amebiasis, killing E. histolytica (trophozoites/cysts). This is followed by (Y).

Answer 37

X = Metronidazole
Trophozoites
Y = iodoquinol (to eliminate intraluminal cysts)

Question 38

E. histolytica vaccine

Answer 38

None

Question 39

E. histolytica trophozoite appearance on microscopy

Answer 39

Single nucleus, motile, with potential ingested RBCs in cytoplasm

Question 40

E. histolytica cysts appearance on microscopy

Answer 40

Smaller than trophozoites and usually quadranucleated