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Gastrointestinal infectious virus Gastrointestinal infectious virus • a group of viruses that parasitize the enteric tract and cause diseases. • fecal-oral route Gastrointestinal infectious virus • belong to picornaviridae: 6 genera – Enterovirus – Rhinovirus – Hepatovirus – Par-echovirus – Aphthovirus: foot-and-mouth disease viruses – Cardiovirus: encephalomyocarditis Enteroviruses Virus family Serotypes Polio 1-3 Coxsackie A 1-22, 24 Coxsackie B 1-6 Echovirus Enteric, cytopathic, human, orphan 1-9, 11-27, 29-34 Hepatitis A Enterovirus 72 Other Enteroviruses 68-71 Common biological properties • • • • • • 24-30nm spherical naked, icosahedral +ssRNA multiply in the cytoplasm Resistance – resistant -- ether, acid (tolerate pH3-5) – sensitive -- drying, heat and UV – survive for a long period in water and sewage Pathogenicity – Portal of entry – Viremia – Target tissue – Different enteroviruses bind to different target cells Pathogenicity-clinical • Neurologic infection – aseptic meningitis, paralysis, encephalitis • Cardiac and muscular infection – myocarditis, pericarditis • Infection of skin and mucosa – hand- foot-and- mouth disease • Resoiratory infection: common colds • Alimentary infection: diarrhea in children. POLIOVIRUS paralytic poliomyelitis Biological properties • • • • 30nm Naked icosahedral capsid +ssRNA Synthesis of +ssRNA containing viruses Pathogenesis • Poliovirus infections • 3 types (type 1, 2, 3) – type 1 causes most epidemics • Progression of poliovirus infection – Types of illness • • • • Asymptomatic illness Abortive poliomyelitis Nonparalytic poliomyelitis Paralytic poliomyelitis Poliovirus→throat→regional lymphatic nodes → blood Peyer’s patches the small intestine 1-2% ↓ 90%↓ CNS (motor neurons) unapparent infection mild↙ ↘serious 0.1-0.2% no Flaccid paralysis ↙ ↓special syndrome a few days↓ headache progressive post-poliomyelitis muscle atrophy complete recovery ← stiff and pain ↓rare medulla paralysis ↓eventually death ← respiratory and heart failure Prevention • Poliovirus vaccines 1960 • Sabin (live attenuated virus) vaccine OPV Albert Sabin • Salk (killed virus) vaccine IPV Jonas Salk Property Safety Efficiency Sabin vaccine Satisfactory 3 doses at 6-8 weeks interval, Salk vaccine Satisfactory Primary vaccination: 2-3 doses at 4-6 weeks intervals, boosters doses oral every 3-5 years; injection Cost More Less Nature of immunity Induce both local and systemic immunity Systemic Ab, no local immunity Duration of immunity lifelong May need to be maintained by booster doses periodically Spread of vaccine Spread naturally to unvaccinated individuals No spread by fecal-oral spread Stability Less stable and more difficult for Stable; preservation and transportation are convenient Preservation and transport in tropic area Coxsackie viruses • Name of the town of Coxsakie, NY • Classification based on pathogenicity in mice • Group A – widespread myositis. flaccid paralysis – fatal • Group B – generalized. heart - CNS- focal myositis – myocarditis, hepatitis,and encephalitis Diseases • Herpangina – coxsackie A virus • Hand-foot-and-mouth disease – coxsackievirus A16 and enterovirus 71 • Pleurodynia – coxsackie B virus • Myocardial and pericardial infections – coxsackie B virus. (B3) • Viral meningitis – coxsackievirus or echovirus Hand, foot and mouth disease • This is an exanthem (a rash) caused by Coxsackie A16. • Symptoms include fever and blisters on the hands, palate and feet. Human diseases caused by enteroviruses Coxsackie A virus Coxsackie B virus Echovirus Enterovirus (other) Asymptomatic infection yes yes yes yes Meningitis Paralysis yes yes yes yes yes yes yes no Febrile exanthems yes yes yes yes Acute respiratory disease yes yes yes yes Myocarditis Orchitis yes no yes yes yes yes no no 睾丸炎 Chapter 28 Acute Gastroenteritis Viruses Acute gastroenteritis viruses • Rotavirus • Norwalk virus/small round structured virus (SRSV) • “Classic” calicivirus • Enteric adenovirus • Astrovirus • These viruses cause acute gastroenteritis with the similar symptoms, such as diarrhea and vomiting. Human Rotavirus (HRV) • reoviridae • the name reovirus • respiratory enteric orphan virus • in 1959 • Albert Sabin • the Latin word “rota”, meaning “wheel” Electron micrograph of rotavirus Biologicalproperties • 60-80nm • icosahedral • naked – Capsid: Possess two concentric capsid shells, icosahedral – Core: Possess a double-stranded segmented RNA genome Classification – HRV 7 groups (A~G) – Groups A~C: human and animal diarrhea • Group A: infantile acute gastroenteritis • Group B: outbreaks in adults • Group C: only sporadic diarrhea – Group D-G: animal diarrhea Pathogenesis • Rotavirus • one of the most common causes of infantile diarrhea worldwide. – High risk people: • children 6 months - 2 years old – Route of transmission: fecal-oral route Pathogenesis • Virus infects columnar epithelial cells covering the villi of the small intestine • multiply in the cytoplasm • causes cell lysis and abnormal function • damage their transport mechanisms to interrupt sodium and water absorption Pathogenesis • infection prevents the absorption of water • causing a net secretion of water and loss of ions, which together results in a watery diarrhea and vomiting→ dehydration, acidosis, shock and death • Diarrhea – watery (no blood or leukocytes), – lasting 3-9 days Pathogenesis • Many cases and outbreaks are nosocomial • Incubation period 1-4 days • Contagious Period - Before onset of diarrhea to a few days after end of diarrhea • Spread via fecal - oral route through fomites Diagnosis • Rapid diagnosis – antigen detection in stool by ELISA • Electron microscopy Treatment • Supportive - rehydration (oral / intravenous) – Antiviral agents not known to be effective • Prevention of spread – Handwashing with good technique – Disinfection of surfaces, toilets, toys • Vaccine – Rotashield was first licensed for use in infants in 1998. Acute gastroenteritis virus Virus Shape and Size NA Routes of Transmission Season of Disease Clinical feature Rotavirus Spherical, 60-80 dsRNA Fecal-oral Late autumn, winter Enteric Spherical, 70-90 Adenovirus Fecal-oral Whole year, summer SRSV dsDNA Spherical, 27nm +ssRNA Fecal-oral, respiratory tract Winter Classic Spherical, 31-38 +ssRNA calicivirus Fecal-oral Whole year Astrovirus Spherical, 28-30 +ssRNA Fecal-oral Winter Infant(<2Y), Watery diarrhea Infantile diarrhea Any age Infantile watery diarrhea Infant(<5Y) diarrhea