L11- GI Infections IV (non-inflam. diarrhea, viral) Flashcards
Rotavirus:
- (1) family
- (2) genome
- (3) size, shape
- (4) relevant genotypes
- requires (large/small) inoculation dose
1- reoviridae (REO = respiratory enteric orphan)
2- 11 segments dsRNA, non-enveloped
3- wheel-shape, double capsid, 70nm diameter
4- G1, G2, G3, G4
5- small (~100 particles)
Rotavirus:
- serogroups are based on (1) Ag
- attachment is controlled by (2) Ag
- these proteins are also important to (3) in terms of incidences
1- VP7, G Ag = glycoprotein
2- VP4, P Ag = protease
3- defining serotype and therefore vaccine development
(1) rotavirus is the most common cause of infantile gastroenteritis in USA, its (2) in china, usually in (3) age group. It adults, they present with (4) symptoms.
(5) Briefly describe the other serogroups.
1- group A
2- group B (+ pigs)
3- (6 mos to) <2 y/o [immunity by 4-5y/o]
4- milder diarrhea
5- C found worldwide, D/E/F not found in humans
serotyping in rotavirus mainly refers to….
group A (USA strain) rotavirus
describe rotavirus preferred season by location
Temperate // High Income: mainly winter, spring
Tropical // Low Income: year round
Rotavirus pathogenesis:
- (1) transmission
- (2) incubation period
- (3) sxs
1- fecal-oral, water-borne
2- <48 hrs / 1-3 days
3- watery diarrhea for 3-8 days
Rotavirus pathogenesis:
- (1) location of replication –> causes (2) structural changes in those areas
- (3) is the main physiological effect
- viral shedding via lasts (4)
1- villous epithelium in SI
2- columnar epithelium replaced by irregular cuboidal, crypt-like cells
3- multiple defects in fluid and electrolyte regulation (in affected intestinal mucosa)
4- 10 days, peaks at day 8
briefly describe rotavirus pathogenesis
1) ingestion
2) infects epithelial cells (VP4, P, protease Ag) of SI
3) shortening / atrophy of villi of SI
4) dec production of brush border digestive enzymes, e.g. disaccharidases
5) watery diarrhea, help from NSP4 protein acting as toxin
______ part of rotavirus acts in a toxin-like manner to inc net fluid excretion
NSP4 protein
Rotavirus Dx
Stool (peak day 3-4):
- latex agglutination
- EIA for characterization (enzyme immunoassays)
- electron microscopy (labor intensive, insensitive)
- electrophoresis of RNA segments
______ are at biggest risk of getting rotavirus gastroenteritis, especially in outbreaks
- young children (daycare adults)
- adults in congregrate living centers
Norovirus:
- (1) family
- (2) genome
- (3) shape, size
- (4) transmission
1- calciviridae
2- (+) ssRNA, non-enveloped
3- icosahedral nucleocapsid, small 27nm diameter
4- many: food, water, people, manufacturing, environment contamination, animals, shellfish
Norovirus:
- (1) predominant location
- (2) affected age group
- requires a (large/small) inoculation dose
- (4) predominant season
1- worldwide
2- older children, adults (not children <5y/o)
3- very small, 18 particles
4- winter (aka, winter vomiting disease)
brief pathogenesis of Norovirus
1) ingestion –> multiplication in SI
2) transient lesions of mucosa (microvilli shortened + widened intercellular spaces are noted on EM)
3) no colon involvement = NO fecal leukocytes
4) shed in feces
Diagnosis criteria of epidemiological Norovirus gastroenteritis
1) mean/median illness duration of 12-60hrs
2) mean/median incubation 24-48hrs
3) >50% patients with vomiting
4) Sxs last 48-72hrs, rapid recovery
5) no bacterial agent previously found
describe Norovirus infection clinical diagnosis
(not routinely screened) Virus is found in stool (peak day 2 out 5):
- difficult to culture
- RT-qPCR (highly sensitive), RT-PCR (genotyping), EIA (not sensitive)
(T/F) for the following statements:
- (1) rotovirus has a vaccine
- (2) norovirus has a vaccine
1- T (childhood)
2- F, in clinical trials
Astrovirus:
- (1) family
- (2) genome
- (3) shape, size
1- astroviridae
2- non-enveloped, (+) ssRNA
3- small, 27-30nm diameter, icosahedral symetry, smooth/slightly indented outer shell
Astrovirus:
- mostly infects (1) age group
- (2) peak season
- resembles (3), so (4) assumption is made
1- infants
2- winter (some throughout)
3- rotavirus (but milder)
4- assume rotavirus infection unless vaccination status in known (or viral nuclear make-up is known)
Astrovirus pathogenesis:
- (1) architectural changes in (2) segment
- end result of decreased (3) secretion
- (4) is the resulting symptom
1- small intestinal villus shortening
2- SI
3- intestinal brush border enzymes
4- osmotic diarrhea
Adenovirus:
- (1) family
- (2) genome
- (3) shape, size
- (4) main infectious serotype
1- adenoviridae
2- dsDNA (protein core)
3- small 70-100nm diameter, icosahedral protein shell
4- 40-42 of group F
Adenovirus pathogenesis:
- (1) main target tissue
- (2) secondary target tissues
- may replicate in (3)
- (4) main GI symptoms
1- respiratory tract
2- epithelial cells in pharynx, conjunctiva, SI (occasionally others)
3- intestines –> present in stool
4- diarrhea, w/ or w/o vomiting
Cryptosporidium spp.:
- (1) affecting species
- (2) location
- (3) common transmission
1- parasite: C. parvum, C. hominis
2- worldwide
3- contaminated water (drinking or recreational) OR person-to-person
Cryptosporidium spp.:
- (1) typical presentation
- (2) presentation in endemic countries described as (3)
- (4) common in presentation in at-risk populations
1- Self-limiting diarrhea: stomach cramps / pain, dehydration, n/v, fever, weight loss
2- persistent diarrhea in children
3- developing tropical, sub-tropical countries
4- chronic diarrhea in immuno-compromised patients (AIDS- CD4 count <100 per uL)
Cryptosporidium spp.:
- (1) unique feature in terms of spread
- requires (large/small) dose
- mostly affects (3) populations
1- oocysts are infectious, last in environment up to 1 yr due to disinfecant / chlorination resistance
2- low dose (water sources)
3- immuno-compromised (weak against immune system): AIDS, children
Cryptosporium spp. lifecycle:
- (1- include types) form excreted in feces
- after ingestion –> attachment to (2)
- within (2), conversion to (3)
- (4) will recur to release (5) which eventually progress to (6) and then (7)
- Note- (7) reforms (1)
1- *Oocysts: thick-walled (commonly excreted) OR thin-walled (autoinfection)
2- brush border epithelium
3- (parasitophorous vacuole –>) enlarges into *Trophozoites
4- asexual multiplication
5- type I meronts / motile merozoites
6- sexual multiplication / type II meronts / micro-/macro-gamonts
7- (microgamete + macrogamere ==>) *zygote –> oocysts
Cryptosporidium spp. Dx
(not routine)
-stool microscopic investigation: multple, wet mounts, thick walled oocysts
- Differential stain: modified Ziehl-Neelson
- Immunofluorescent assay
- Ag-detection assays
