viral gastroentitis Flashcards
Which fmaily is rota virus in
Reoviridae
epidemiology of rotaviruses
o Rotaviruses are major cause of
diarrheal illness in children (3-5years) /neonates
o peak age = 4 - 23 months
o Adults too can get infected.
o Young animals also infected
which animal host does rotavirus have
Young animals,calves,piglets
what factor plays a role in rotavirus infection
poor hygiene - esp in underdeveloped countries
structure of rotavirus
- non-enveloped
- icosahedral
- triple shelled
- genome = 11 segments of dsRNA ( has genetic reassortment)
how many structural & nonstructural proteins does RNA of rotaviruse encode for?
structural = 6
non-structural = 5
how is rotavirus transmitted
- fecal-oral route (water/food)
is rotavirus highly infectious and how can tell?
- High numbers of viral particles
are shed in diarrheal stools
(1010/gm) - highly infectious
whats the incubation period of rotavirus
1-3 days
clinical symptoms of rotavirus
- for some adults may aymptomatic
- for young children & some other adults after IP = leading to :
- watery Diarrhea
- abdominal pain
- Vomiting
- Dehydration
- Shock
- Death
how many days does it take for people with milder rotavirus infection recover
3-8 days
which cells does rotavirus infect
enterocytes - aid in digestion & absorb nutrients
what happens when those enterocyte cells infected
it causes diarrhoea & less absorption of nutrients
pathogenesis of rotavirus
oThe virus infect villi of SI : destroys the mature enterocytes in the villus epithelium
o They multiply in the enterocytes and damage their transport mechanisms
o The RV particle NSP4 is a viral enterotoxin & induces secretion by triggering a calcium - dependent signal transduction pathway
o Damaged cell may slough into lumen of the intestinal and release large quantities of virus which appear in the stool.
o Viral excretion usually lasts for 2–12days in healthy patients
Why Diarrhea in Rota-viral Infections
1.secretory diarrhea by reducing villous epithelium + increasing secretory crypt cells
(impared Na & glucose absorption as damaged cell on villi are replaced by non absorbing immarture crypt cell )
2.osmotic diarrhea = by reducing brush border enzymes causing accumulation of unmetabolized disaccharides
how to detect infants are suffering from rotavirus
- child is vomiting and diarrhoeing
- eye sunkened
- child crying w no tears
- sunken fontanelle
- dry mouth /tongue
- decreased skin tugor - (normally - more tight - but is now loose)
- sunken abdomen
immunity of rotavirus
o By age 3years , 90% of the children have
serum antibodies to one or more types.
o Young children suffer up to five reinfections
by 2years ofage.
o Secretary IgA or Interferon are important in protection against Rota viral infections.
how is rotavirus diagnosed in lab
can be detected in the stool via
o ELISA
o Latex agglutination - looking for antigen to rotavirus
o PCR
human rotavirus does not grow readily in cell culture
treatment of rotavirus
o Treatment of Gastroenteritis is supportive.
o Correction of Loss of water and electrolytes
- Failure for prompt correction of
dehydration lead to Acidosis Shock Death.
o Correction Electrolyte remain the goal treatment in Rota viral infections.
o replacement of fluid & restoration of electrolyte balance
prevention & control
-
waste water management, safe water
supplies and sanitation ,education - Vaccine – In 2006 an Oral Bovine based
Rotaviral vaccine was licensed inUSA.
differentiate between Endemic & epidemic viral gastroenteritis
Endemic = cause of GE among infants & young children
Epidemic(outbreak) - cause of GE in all ages
which type of adenovirus cause gastroenteritis
Adenovirus 40 & 41
strucutre of adenoviruse 40&41
naked
DNA virus
edidemiology
usually causes GE in young children & neonated
which subfamily is rota-virus in
sedoreovirinae ( appears more smooth - lacking large surface glycoproteins)
how many species are there of rotaviruses & which ones infect humans
A-H
infect humans = A,B,C
Classify group b & C of Rotavirus
Group B - causes adult diarrhoea
Group C - causes pediatric gastroenteritis
how many serotypes are identified in group A of rotavirus & which are common?
10 G
But 5 types common (G1-G4 & G9)
what are some examples of rotaviruses known to cause specific types of diarrhea in various species
- human infantile diaarhea
- nebraska claf diarrhea
- epizootic diarrhea of infant mice
- SA11 virus of monkety
which structural protein can be used for immunoassay & grouping rotaviruses
VP-6 major structurla protein - (target for commercial immunoassay & determines group specificity of rotaviruses)
role of the VP4 & VP7 structual proteins of rotavirus
VP4 & VP7 = carry epitopes for neutralizing activity
VP7 = predominant antigen
what are the main causes of secretory diarrhea by rotavirus
- reducing villous epithelium & incresaing crypt cells
- enterotoin (NSP4) - which alters epithelial cell function & permeability
3.Activation of enteric nervous system in intestinal wall
What family & genera is norwalk viruses in
Family: calicivirdae
Genus : norovirus
the norwalk virus can be cultured true/false
false
Antigen property of norovirus
- undergoes antigenic drift over time - in reposnse to population immunity
What is the recepetor for norwalk-like viruses
histocompatibility blood group antigens expressed on the mucosal epithelia of digestive tract
calciviruses
- Small RNA viruses, characteristic surface morphology
consisting of hollows. particles 35 nm in diameter. - Associated mainly with epidemic outbreaks of
gastroenteritis, although occasionally responsible for
endemic cases. - Like Norwalk type viruses, vomiting is the prominent
feature of disease. - Majority of children have antibodies against caliciviruses
by the age of three. - Diagnosed by electron microscopy only, often difficult
to diagnose because of small size.
incubation period of norwalk viral gastroenteritis
24-48hrs
epidemiology of norwalk viruses
- causes mild gE in community and affect all age groups
- are major causes of epidemic of GE
- survives 10ppm chlorine & heating of 60 degress - can maintain viabikity in steamed oysters
clinical presentation of norwalk virus
onset is rapid & clinical course is brief (12-60hrs)
symptoms
- diarrhea - MC in adults
- nausea
- vomiting - MC in children
- lowgrade fevr
- abdominal cramps
- headache
- malaise
Pathogenesis of norwalk viruses
1.attached on carbo of duodenal epithelium of individula w secretor phenotype
2.reversible lesion in upper jejunum e.g broadening & blunting of villi , shortening of microvilli
3.malabsorption of carbohydrates & fats & decreased brush border enzyme
4.Gastric motor function is delayed
diagnosis of norwalk viruses
1.PCR - detection of virus in stool & vomitus
2.EIA (Enzyme immunoassay) - detection of virus in stool & 3.serologic responce to specific viral antigen
how are norwalk viruses spread
aerosolization , contact w contaminated fomites , person to person contact
immunity to norwalk viruses
antibody is acquried later in life than the roatavirus
treatment & control
- effective handwashing
- care taken in disposal of stoll
-containment & disinfection of soiled areas & bedding - careful procesisng of food & educate food handles
- purification of drinking water , swimming pool
NO VACCINE
