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.

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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