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VIRAL AGENTS CAUSING GASTROENTERITIS Dr. Osama AL Jiffri Viral gastroenteritis • Inflammation of stomach and small and large intestines • Infection caused by a variety of viruses that results in vomiting or diarrhea (stomach flu) VIRAL AGENTS CAUSING GASTROENTERITIS Major Viruses 1. Rotavirus 2. Enteric adenoviruses 3. Noroviruses : a. Norwalk-like viruses b. Calicivirus c. Astrovirus Noroviruses Norwalk-like viruses Caliciviruses Astroviruses other viruses Viruses associated with gastroenteritis (cont) : Other viruses (minor): • Coronaviruses • Parvoviruses • Pestiviruses • Toroviruses ROTAVIRUS Family Reoviridae Genus Rotavirus ROTAVIRUS • First isolated in 1973 from children with diarrhea • EM identification from duodenal biopsies • Human and animal strains Rotavirus- EM Structure ROTAVIRUS • 60-80nm in size • Non-enveloped virus • Double capsid • EM appearance of a wheel with radiating spokes • double stranded (ds) RNA in 11 segments (double – double) Rotavirus ROTAVIRUS- ultrastructure STRUCTURE • Double capsid (outer and inner capsid) • Core with genome ROTAVIRUS- 3D STRUCTURE Viral Structural Proteins (VP) • Outer structural proteins - VP7 and VP4 VP7=glycoprotein VP4=protease-cleaved, P protein, viral hemagglutinin, and forms spikes from the surface • Inner core structural proteins VP 1, 2, 3, 6 • VP6 is an important antigenic determinant Gene coding assignment • Genome is composed of 11 segments of double-stranded RNA, six structural coding for proteins five nonstructural Classification • Groups, subgoups, serotypes based on viral capsid proteins •Seven serological groups have been identified (A-G), three of which (groups A, B, and C) infect humans . • Group A is the most common and has 2 subgroups • 10 human serotypes based on G protein (VP 7) • 8 P protein serotypes Rotavirus - Properties • Virus is stable in the environment • Relatively resistant to handwashing agents • Susceptible to disinfection with 95% ethanol, ‘Lysol’, formalin Rotavirus Epidemiology • Leading cause of severe gastroenteritis in children aged <5 years worldwide • Millions are affected • 600,000-850,000 deaths/year • A major cause of diarrhea-associated hospitalizations • Seroprevalence studies show that antibody is present in most by age 3y. Estimated Global Distribution of The 800,000 Annual Deaths Caused By Rotavirus Diarrhea Epidemiology • Age- 4mo - 2 years Protection of younger infants through transplacental antibody transfer • Asymptomatic infections are common, especially in adults • Nosocomial infections • Outbreaks Epidemiology (contd.) • Seasonality Winter months (Nov. through May in US) Gradual spread W to E Year-round in the tropics • Incubation period - thought to be <4 days Epidemiology (transmission) • Mainly person to person via fecal-oral route • Fomites • Food and water-borne spread is possible • Spread via respiratory route is speculated EPIDEMIOLOGY Differences in Groups • Group A infections are most common • Group B has been associated with outbreaks in adults in China • Group C is responsible for sporadic cases of diarrhea in infants around the world Clinical Features • Incubation period - thought to be <4 days • Fever- can be high grade (>102F in 30%) • Vomiting, nausea precede diarrhea • Diarrhea - usually watery (no blood or leukocytes) - lasts 3-9 days • Dehydration is the main contributor to mortality • Recovery is usually complete. • However, severe diarrhea without fluid and electrolyte replacement may result in dehydration and death . Diagnosis • Antigen detection in stool by ELISA, Latex Agglutination (for Group A rotavirus) • EM- non-Group A viruses also • Culture- Group A rotaviruses can be cultured in monkey kidney cells • Serology for epidemiologic studies Treatment and Prevention • TreatmentSupportive - oral, IV rehydration • PreventionHandwashing and disinfection of surfaces Vaccine (old) • Live tetravalent rhesus-human reassortant vaccine (Rotashield) • Licensed for use in August 1998 • Removed from the market in October 1999 due to risk of intussusception • Cases were seen 3-20 days after vaccination • Approx. 15 cases/1.5 million doses Vaccine (New) • New licensed vaccine ( RotaTeq) • No elevated risk of intussusception • In U.S.A. recommendation made to routinely vaccinate all children at 2,4,6 months • Considered for routine immunization in many countries GASTROENTERITIS DUE TO ENTERIC ADENOVIRUS ADENOVIRUS • A nonenveloped double-stranded DNA virus • First isolated in the 1950s in adenoid tissue • Gastroenteritis, upper and lower respiratory tract infection, ocular infections GASTROENTERITIS DUE TO ADENOVIRUS • Types 40, 41 • Belong to serogroup F • Some cases due to types 31, 3, 7 Clinical features of Enteric Adenovirus gastroenteritis • Age <4 years • Incubation period 3 -10 days • Diarrhea lasts for 10 -14 days Laboratory Diagnosis • Isolation standard cell cultures of human neonatal kidney cells • ELISA for rapid detection is available • Complement fixation for antibody level HUMAN CALICIVIRUSES HUMAN CALICIVIRUSES (HuCV) • Belong to Family Caliciviridae • Non-enveloped RNA viruses with ss RNA • 27-35 nm in diameter • Contain a single capsid protein HUMAN CALICIVIRUSES •Genomic analysis divides it into 4 groups •Human caliciviruses belong to 2 genera CLASSIFICATION OF HuCV NLV (Norovirus) Norwalk virus Hawaii virus Snow Mountain virus Montgomery county virus Taunton (England) SLV (Sapovirus) Sapporo virus Manchester virus Houston/86 London/92 Morphology of HuCV- typical • Typical morphology •EM appearance of “Star of David” E.g.- Sapporo-like viruses HUMAN CALICIVIRUSES - SLV Morphology of HuCV- atypical • Atypical morphology • Smooth surface • Small Round Structured viruses E.g.- Norwalk-like viruses Diagnosis- Human Caliciviruses • Specimen- stool , vomitus, environmental swabs, [not yet on foods] • Immune EM • RT-PCR in state public health labs. • Serology for epidemiologic purposes SRSV- NORWALK VIRUS CLINICAL FEATURES • Epidemic in Adults and Children • Usual incubation Period is <24-48 hours (ranges from 12hrs. to 4 days) • Short duration of illness <3 days • Nausea, vomiting, fever, headache • Abdominal cramping • Watery diarrhea Epidemiology-Noroviruses • Worldwide distribution • >23 million cases/year in the U.S. • Outbreaks of foodborne, waterborne and shellfish • Most people have had infections by age 4 years (by seroprevalence studies) Spread of Norwalk virus A. Person-to-person Fecal-oral spread (stool/vomitus) B. Fecal contamination of food or water C. Spread through fomites? Epidemiology-Noroviruses • Asymptomatic infections- seroconversion but asymptomatic shedding of virus • Low infective dose • Viral excretion during recovery (up to 2 weeks) • Ability to survive in water chlorination at routine levels Epidemiology of Outbreaks • Cruise ships, schools, nursing homes, etc. • Can involve infants and school-age children • Source usually is contaminated food and water (seafood-oyster and shellfish etc.) HUMAN ASTROVIRUS ASTROVIRUS • Belong to family Astroviridae • 8 human serotypes are known • Described in relation to an outbreak of gastroenteritis in 1975 • Detected by EM • Immunologically distinct from Human Caliciviruses ASTROVIRUS- structure • Small ss RNA virus • Non-enveloped • 27-32nm in size • Round with an unbroken, smooth surface • EM appearance of a 5 or 6 pointed star within smooth edge • Contain 3 structural proteins ASTROVIRUS- EM STRUCTURE ASTROVIRUS - Epidemiology • Worldwide • Mainly in children <7 years of age. • Transmission person-to-person via fecal-oral route • Outbreaks due to fecal contamination of sea-food or water ASTROVIRUS - Clinical Features • Infants and children are most often affected • Short incubation period 1-4 days • Nausea, vomiting, abdominal cramping and watery diarrhea • Symptoms-fever, malaise, headache ASTROVIRUS - Diagnosis • EM (virus shed in stool in great numbers) • EIA • RT-PCR www.kau.edu.sa/ojiffri الملفات سيرة ذاتية FID 6370 6373 13534 13537 أخرى ● العنوان نماذج الوصف منشورات تاريخ اإلضافة Papilloma فيروسات viruses محاضرة رقم and ()1 Poxviruses Viral 11/7/200 Agents فيروسات محاضرة رقم 8 5:53:55 Causingتحميل الملف PM Gastroent ()2 eritis 12/26/20 BIOSAFE BIOSAFE 08 5:15:12 تحميل الملف TY-01 TY-01 PM 12/26/20 BIOSAFE BIOSAFE 08 5:39:23تحميل الملف TY-02 TY-02 PM 11/7/200 8 5:43:56تحميل الملف PM
