1、Gastrointestinal Gastrointestinal VirusesViruses急性胃肠炎病毒eViral Gastroenteritis It is thought that viruses are responsible for up to 3/4 of all infective diarrhoeas.Viral gastroenteritis is the second most common viral illness after upper respiratory tract infection.In developing countries,viral gastr
2、oenteritis is a major killer of infants who are undernourished.Rotaviruses are responsible for half a million deaths a year.Many different types of viruses are found in the gut but only some are associated with gastroenteritis.急性胃肠炎病毒eAssociated with gastroenteritis Rotaviruses Adenoviruses 40 41 Ca
3、liciviruses嵌杯病毒 Norwalk like viruses or SRSV(Small Round Structured Viruses)Astroviruses SRV(Small Round Viruses)Coronaviruses Toroviruses急性胃肠炎病毒eFound in the gut,not normally associated with gastroenteritis Polio Coxsackie A Coxsackie B Echo Enteroviruses 68-71 Hepatitis A Hepatitis E Adenoviruses
4、1-39 Reoviruses急性胃肠炎病毒eFound in the gut as opportunistic infection CMV HSV VZV HIV急性胃肠炎病毒eGastrointestinal VirusesGastrointestinal VirusesVirusGenomeTypical diseaseincubationDuration Rotaviruses:Group A,B,Cds-segmented RNA Major cause of diarrhea in children1-3 days24-56 h5-8 days3-7 daysCalicivirus
5、esNorwalk agentsssRNAInfects adults and childrenEpidemic viral gastroenteritis1-3 days18-24 h1-3 days12-48 hEAd 40,41Linear dsRNA diarrhea in children 7-8 days 8-12 d Astrovirus+ssRNAInfects mainly children and elderly1-4 days1-4 d急性胃肠炎病毒eGastrointestinal VirusesGastrointestinal Viruses Infants:Rota
6、virus A;Adenovirus 40,41;Coxsackie A24 virus Infants,children,and adults Norwalk virus;Calicivirus嵌杯病毒;astrovirus;Rotavirus B;Reovirus.急性胃肠炎病毒eHuman RotavirusHuman Rotavirus急性胃肠炎病毒eImportant Characteristics70 nm round,double shelleddouble shelled,enclosing a genome of 11 11 segments of segments of d
7、ouble stranded double stranded RNARNA.急性胃肠炎病毒e急性胃肠炎病毒eGroups of Rotaviruses Group AGroup A subtypes 1,2,3,4(main human pathogens)(Further 7 subtypes)also infect animals(monkey,calf,mouse)Group BGroup B Infects pigs and ratsFound to cause extensive outbreaks in China in past decade Group CGroup C Inf
8、ects Pigs(Occasionally Man)Group DGroup D Infects birds Group EGroup E Infects pigs 急性胃肠炎病毒e急性胃肠炎病毒ePathogenesisPathogenesis Essentially an ingestion disease(faecal-oral route)Incubation is short:1 to 3 daysIllness:Sudden onset watery diarrhoea,with or without vomiting.May last up to 6 days(or longe
9、r if immunocompromised).The disease is self limiting.Complications:Dehydration may result,this can be severe and life threatening in young children.急性胃肠炎病毒ePathogenesisGroup A:Main pathogen of infantile diarrheaGroup B:Cause epidemic adult diarrheaGroup C:Cause human or animal sporadic diarrhea急性胃肠炎
10、病毒e急性胃肠炎病毒eImmunityImmunity:sIgALab.DiagnosisLab.DiagnosisIEM,Cell culture,PAGE of RNA segments,PCRLatex agglutination ELISA 急性胃肠炎病毒eTreatment treatment of dehydrationtreatment of dehydration by oral and/or intravenous fluids and electrolytes急性胃肠炎病毒ePreventionNon specific factors:improved hygiene,ed
11、ucation,clean waterSpecific-Breast feeding helps to provide passive immunity in the newborn(from maternal antibodies),Vaccination is still experimental.急性胃肠炎病毒eEnteric Adenoviruses Naked DNA viruses,75 nm in diameter.Fastidious enteric adenovirus types 40 and 41 are associated with gastroenteritis.A
12、ssociated with cases of endemic gastroenteritis,usually in young children and neonates.Can cause occasional outbreaks.Possibly the second most common viral cause of gastroenteritis(7-15%of all endemic cases).Similar disease to rotaviruses Most people have antibodies against enteric adenoviruses by t
13、he age of three.Diagnosed by electron microscopy or by the detection of adenovirus antigens in faeces by ELISA or other assays.急性胃肠炎病毒eAstroviruses Small RNA viruses,named because of star-shaped surface morphology,28 nm in diameter.Associated with cases of endemic gastroenteritis,usually in young ch
14、ildren and neonates.Can cause occasional outbreaks.R e s p o n s i b l e f o r u p t o 1 0%o f c a s e s o f gastroenteritis.Similar disease to rota and adenoviruses.Most people have antibodies by the age of three.Diagnosed by electron microscopy only,often very difficult because of small size.急性胃肠炎
15、病毒eCaliciviruses 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 disea
16、se.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.急性胃肠炎病毒eNorwalk-like Viruses Small RNA viruses,with ragged surface,35 nm in diameter,now classified as caliciviruses.Always associ
17、ated with epidemic outbreaks of gastroenteritis,adults more commonly affected than children.Associated with consumption of shellfish and other contaminated foods.Aerosol spread possible as well as faecal-oral spread.Also named winter vomiting disease,with vomiting being the prominent symptom,diarrho
18、ea usually mild.Antibodies acquired later in life,in the US,only 50%of adults are seropositive by the age of 50.Diagnosis is made by electron microscopy and by PCR.急性胃肠炎病毒e急性胃肠炎病毒eOther Possible Diarrhoeal VirusesCoronaviruses RNA viruses with a crown-like appearance Not convincing associated with g
19、astroenteritis at presentSmall Round Viruses Small virus-like particles with a smooth surface,22-28nm in diameter May possibly be parvoviruses,enteroviruses,or cubic bacteriophages Occasionally seen in the faeces of endemic or epidemic cases of gastroenteritis急性胃肠炎病毒eGastrointestinal VirusesGastroin
20、testinal VirusesVirusGenomeTypical diseaseincubationDuration Rotaviruses:Group A,B,Cds-segmented RNA Major cause of diarrhea in children1-3 days24-56 h5-8 days3-7 daysCalicivirusesNorwalk agentsssRNAInfects adults and childrenEpidemic viral gastroenteritis1-3 days18-24 h1-3 days12-48 hEAd 40,41Linear dsRNA diarrhea in children 7-8 days 8-12 d Astrovirus+ssRNAInfects mainly children and elderly1-4 days1-4 d急性胃肠炎病毒e
