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VIRAL GASTROENTERITISVIRAL GASTROENTERITIS
Dr. Amin Aqel, PhD. Molecular Microbiology Dr. Amin Aqel, PhD. Molecular Microbiology
Faculty of medicine, Mu’tah universityFaculty of medicine, Mu’tah university
GIT module, 2GIT module, 2ndnd year medical students year medical students
VIRAL GASTROENTERITISVIRAL GASTROENTERITIS
ROTAVIRUS ADENOVIRUS CALICIVIRUS ASTROVIRUS
ROTAVIRUSESROTAVIRUSES
ROTAVIRUSESROTAVIRUSES
DISEASESDISEASES Gastroenteritis Gastroenteritis
(diarrhea), especially (diarrhea), especially in in young childrenyoung children
PROPERTIESPROPERTIES
Member of the Reovirus family Member of the Reovirus family Non-enveloped, dsRNA viruses with Non-enveloped, dsRNA viruses with
icosahedral symmetryicosahedral symmetry 11 segments RNA11 segments RNA RNA-dependent RNA polymerase RNA-dependent RNA polymerase The capsid has double shellThe capsid has double shell 7 serotypes (A-G)7 serotypes (A-G)
Rotavirus EpidemiologyRotavirus Epidemiology
Max. incidence of Max. incidence of illness: illness: 6 - 24 months6 - 24 months
Re-infection common Re-infection common throughout lifethroughout life
Infections at < 6 months Infections at < 6 months and > 5 years of age and > 5 years of age often often asymptomaticasymptomatic or or mildmild
sporadicsporadic
Rotavirus Clinical IllnessRotavirus Clinical Illness
Characteristic clinical triadCharacteristic clinical triad:: feverfever vomitingvomiting diarrheadiarrhea
Frequent coryza and coughFrequent coryza and cough Dehydration is leading complicationDehydration is leading complication
CLINICAL FINDINGSCLINICAL FINDINGS
Babies under 2 years are the main victims.Babies under 2 years are the main victims. Incubation period: 1 - 3 daysIncubation period: 1 - 3 days Duration: 3 - 8 daysDuration: 3 - 8 days Nausea, vomiting some time projectile and Nausea, vomiting some time projectile and
watery, non-bloody diarrheawatery, non-bloody diarrhea Dehydration is the main complicationDehydration is the main complication
TRANSMISSIONTRANSMISSION
Fecal-oral routeFecal-oral route Season: winterSeason: winter By age of 6 years, the majority of children By age of 6 years, the majority of children
have antibodies to at least one serotype.have antibodies to at least one serotype.
PATHOGENESISPATHOGENESIS
Rotavirus replicates in the mucosal Rotavirus replicates in the mucosal cells of the small intestine, damaging cells of the small intestine, damaging the transport mechanisms with the transport mechanisms with consequent loss of fluids and consequent loss of fluids and electrolytes.electrolytes.
No inflammation occurs and the No inflammation occurs and the diarrhea is non-bloody.diarrhea is non-bloody.
ADENOVIRUSES
Adenoviruses
• Family Adenoviridae• dsDNA, non-enveloped; 70 - 75 nm• icosahedral capsid• Adenovirus is the only virus with a fiber
protruding from each of the 12 vertices of the capsid.
• The fiber is the organ of attachment and is a hemagglutinin.
• There are 41 known antigenic serotypes• Types 40 and 41 cause infantile gastroenteritis.
Adenovirus 40/41 Epidemiology
• Second leading cause of cases (5-20%) and hospitalizations in infants
• Occurs year around; no seasonal peak• Predominates in late fall and winter• Asymptomatic or mild illness in older
children, adults• Transmission: person-to-person
Adenovirus 40/41 Clinical Illness
• Incubation: 7-8 days• Duration: 8-12 days• Diarrhea predominates• Nausea / Vomiting• Cramping abdominal pain
– Due to excessive fluid– Increased peristalsis
• Absence of blood and fecal Leukocytes– Key to differential with
bacterial infections
Physical Signs
• Voluminous, non-bloody Stools• Dehydration
– Decreased urination– Mental status changes– Dry mucous membranes– Lethargy
Clinical appearance of dehydration
Photo Credit: Dr. D. Mahalanabis, World Health Organization
CalicivirusesNOROVIRUS
CalicivirusesNOROVIRUS
CalicivirusesCaliciviruses
Family CaliciviridaeFamily Caliciviridae genus norovirusgenus norovirus Naked icosahedral capsidNaked icosahedral capsid +ssRNA, linear, non-segmented+ssRNA, linear, non-segmented 4 “genogroups”4 “genogroups”
Norovirus EpidemiologyNorovirus Epidemiology
Occurs year aroundOccurs year around ““Winter vomiting disease”Winter vomiting disease” Causes epidemic viral gastroenteritisCauses epidemic viral gastroenteritis
Milder illnessMilder illness Usually self-limitingUsually self-limiting Affects both children and adultsAffects both children and adults Community outbreaksCommunity outbreaks
Norovirus Clinical IllnessNorovirus Clinical Illness
Incubation: 1-2 daysIncubation: 1-2 days Duration: 2-3 daysDuration: 2-3 days Abrupt onsetAbrupt onset of of nausea nausea and and vomitingvomiting
with prostration and malaisewith prostration and malaise Vomitus infectiousVomitus infectious Highly transmissible Highly transmissible Environmentally stableEnvironmentally stable
Norovirus CharacteristicsNorovirus Characteristics
Transmission:Transmission: fecal-oral, sewage-polluted fecal-oral, sewage-polluted water supply, shellfish taken from water supply, shellfish taken from contaminated water.contaminated water.
ASTROVIRUSASTROVIRUS
ASTROVIRUSASTROVIRUS
Linear, positive sense Linear, positive sense ssRNA non-enveloped ssRNA non-enveloped virusvirus
The surface of the The surface of the icosahedral capsid has five icosahedral capsid has five or six-pointed star or six-pointed star appearance.appearance.
Astrovirus EpidemiologyAstrovirus Epidemiology
Community impact uncertainCommunity impact uncertain Most common in < 3 years of age; often Most common in < 3 years of age; often
asymptomaticasymptomatic Mild illness in adultsMild illness in adults Winter peakWinter peak in temperate climates in temperate climates Transmission: person-to-person; water/food?Transmission: person-to-person; water/food? Causes outbreaks of diarrhea in children under Causes outbreaks of diarrhea in children under
5 years5 years Mild gastroenteritis, fecal-oral transmissionMild gastroenteritis, fecal-oral transmission
Outbreaks of AstrovirusOutbreaks of AstrovirusSource- http://www.ozestuaries.org/indicators/shellfish_closures.jsp
Outbreaks of AstrovirusOutbreaks of AstrovirusSource- http://www.ozestuaries.org/indicators/shellfish_closures.jsp
Astrovirus Clinical IllnessAstrovirus Clinical Illness
Incubation:Incubation: 3-4 days 3-4 days Duration:Duration: < 5 days < 5 days IllnessIllness milder milder than than
RotavirusRotavirus Diarrhea and low grade Diarrhea and low grade
fever predominatefever predominate
GASTROENTERITIS VIRUSESGASTROENTERITIS VIRUSES
Guidelines for Specimen Collection
Guidelines for Specimen Collection
Collect stool within 48 hours after onsetCollect stool within 48 hours after onset Bulk sample; no preservatives; rectal Bulk sample; no preservatives; rectal
swabs of little valueswabs of little value Refrigerate at 4°C; Refrigerate at 4°C; do notdo not freeze freeze
Laboratory Testing AvailableLaboratory Testing Available
Rotavirus: EIA*, EM, RT-PCRRotavirus: EIA*, EM, RT-PCR Adenovirus 40/41: EIA*Adenovirus 40/41: EIA* Norovirus: RT-PCR*, EMNorovirus: RT-PCR*, EM Astrovirus: RT-PCR*, EMAstrovirus: RT-PCR*, EM
* Method of Choice* Method of Choice
ManagementManagement
Self limiting courseSelf limiting course Replace fluids and electrolytesReplace fluids and electrolytes
Oral Rehydration (ORT)Oral Rehydration (ORT) Mild to moderate dehydrationMild to moderate dehydration
ManagementManagement
Severe DehydrationSevere Dehydration ORT can be successfulORT can be successful
IV fluids IV fluids ShockShock UremiaUremia IleusIleus Fluid loss > 10 ml/kg/hrFluid loss > 10 ml/kg/hr
VIRAL GASTROENTERITIS
VIRAL GASTROENTERITIS
PreventionPrevention Hand washing; hygiene; dealing with infantsHand washing; hygiene; dealing with infants Vaccination like Rotavirus vaccine (RotaShield) Vaccination like Rotavirus vaccine (RotaShield)
contains four serotypes of live, attenuated virus. contains four serotypes of live, attenuated virus. In 1999, a hold was placed on the vaccine because In 1999, a hold was placed on the vaccine because of the risk of intussusception.of the risk of intussusception.
Rotarix ????Rotarix ????
References for all lecturesReferences for all lectures
SherrisSherris, Medical Microbiology: an , Medical Microbiology: an introduction to infectious diseases, by introduction to infectious diseases, by Ryan and Ray, fourth edition, Mc Ryan and Ray, fourth edition, Mc Graw Hill, 2004Graw Hill, 2004
Medical Microbiology, by Mims, Medical Microbiology, by Mims, second edition, Mosby, 1998second edition, Mosby, 1998