enteroviruses and polio
TRANSCRIPT
LEARNING OBJECTIVES
At the end of the session students will be able to:
• Describe the family of Picornavirus
• Enumerate the members of enteroviruses
• Give a brief descriptions on enterovirus and the diseases:
– Coxsackie virus
– Polio virus
– Rota virus
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Brief classification of enterovirus
PICORNA VIRIDIAE FAMILY
ENTEROVIRUS RHINOVIRUS
Coxsakie virus Polio virus Rota virus Adenovirus
HEPATOVIRUS PARECHOVIRUS CARDIOVIRUS
Hepatitis A virus
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Important properties of enteroviruses
• Virion: Icosahedral
• Genome: ssRNA, positive sense
• Viral proteins: Four , VP1-VP4 (VP: Viral proteins)
• Envelope: None
• Site of replication: Cytoplasm
• Diseases: Ranges from poliomyelitis to aseptic meningitis to common cold (Rhinovirus only)
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Medically important enteroviruses and Type
Syndrome Poliovirus Coxsackie Enterovirus
Aseptic meningitis √ (type 1-3) √ (A+B) √ ( type 71)
Paralysis √ (type 1-3) √ (A+B) √ (type 70,71)
Encephalitis √ (A+B) √ (type 70,71)
Herpangina √ (Group A) √ ( type 71)
Hand-foot and mouth disease √ (Group A) √ ( type 71)
Pleurodyna √ (Group B)
Carditis √ (Group B)
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Coxsackie virus
• A large subgroup of enterovirus
• Two antigenic types: Coxsackie A and Coxsackie B virus
• 24 serotype of Coxsackie A
• 6 serotypes of Coxsackie B
• Group A virus produce: Myositis and Flaccid paralysis
• Group B virus produce: Lesion in heart, pancreas, CNS
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Pathogenesis and pathology of Coxsackie virus
• Initial replication in oropharynx and gastrointestinal tract
• Spread to blood (viremia)
• Type A attacks the mucus membrane
• Type B attacks heart, pleura, pancreas, liver
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Clinical features
Herpangina : Hand foot mouth disease: Tender vesicle in oropharynx Vesicular lesion on hand-foot-mouth
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Pleurodynia: Pericarditis: Severe pleuritic type chest pain Inflammatory cells in pericardium
Clinical features
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Hemorrhagic conjunctivitis Generalized disease of infants involving many organs caused by Coxsackie B
Clinical features
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Laboratory diagnosis
• SAMPLES: – Throat washing, Stool, Nasal secretion, CSF, Conjunctival swab
• VIRUS ISOLATION – Monkey kidney cell line, human embryonic lung fibroblast cell
• NUCLEIC ACID DETECTION – Reverse transcriptase PCR
• SEROLOGY – Neutralizing antibody appears early in life
– Immunofluorescence test is done with antibody against infected cell culture
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Immunity and management
• Neutralizing antibodies are transferred from mother to fetus
• Immunity is type specific, life long and mediated by IgG
• TREATMENT – There is no antivirals
• PREVENTION – No vaccines
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Polio virus
• RNA non envelope virus
• Belongs to picorna virus family
• Infective hosts limited to primates
• Three serologic types
• Transmission: Fecal- oral route
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Immunopathogenesis of poliomyelitis
• Virus preferentially replicates in the anterior horn cells of motor neuron result in death of these cells and paralysis of muscle(Flaccid type paralysis)
• Immune response generates both IgA and IgG
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Poliomyelitis: Clinical features
• Asymptomatic
• Abortive poliomyelitis: – Mild fever, headache ,sore throat, nausea, vomiting
• Non paralytic poliomyelitis: Aseptic meningitis
– Fever, headache, neck stiffness
• Paralytic poliomyelitis: – Flaccid paralysis
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Poliomyelitis: Laboratory diagnosis
• Sample: Stool, throat swab, CSF
• Culture: Isolation and identification
• Serology: Rising antibody titer against the virus
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Poliomyelitis: Management
• Treatment: Symptomatic
– Respiratory support
– Physiotherapy
• Prevention: By vaccination
• Two types of vaccines:
– Live attenuated vaccine(Sabin, OPV))
– Killed vaccine(Salk vaccine, IPV)
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Rota virus
Belongs to Reoviridae family Double stranded RNA genome Genome is segmented (11 segments) Non envelope Replicates in cytoplasm Common cause of infantile diarrhea Cart-wheel appearance in EM Five serotypes have been identified Group A is the main human pathogen
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Transmission and pathogenesis
• TRANSMISSION: Fecal-oral route
• PATHOGENESIS: 1. Virus infects the enterocytes lining villi of small intestine and causes
damage and sloughing of cells
2. Rotavirus encoded protein also acts as an enterotoxin
• In both cases there is impaired absorption of sodium and glucose and increase excretion of water and electrolytes leading to watery diarrhea.
• Sloughing enterocytes contain virus and infectious for 2-12 days in otherwise healthy patient.
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Clinical features and complications
• CLINICAL FEATURES
• Commonly affects infants
• Incubation period: 1-3 days
• Watery diarrhea, fever, abdominal pain and vomiting leading to dehydration.
• Adult can be infected by children, but disease milder
• COMPLICATIONS
• Water and electrolyte imbalance
• Hypovolumic shock
• Acidosis
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Laboratory diagnosis
• SAMPLES: Stool
• Detection of viral antigen: ELISA
• Detection of viral antibody: ELISA
• Detection of virus: EIA, IEM (Immunoelectron Microscopy)
• Detection of nucleic acid: PCR
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Treatment and Prevention
• TREATMENT
• Fluid replacement and correction of electrolyte by oral or intravenous rehydration therapy.
• Correction of acidosis.
• PREVETION
• Transmission control: Improvement of water supply and sanitation.
• New live attenuated oral vaccines is safe.
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Reference
• Review of Medical Microbiology and Immunology. Warren Levinson, 12th May 2012. Mc Graw-Hill (Lange)
• Jawetz, Melnick and Adelberg’s Medical Microbiology
George F. Brooks, Karen C. Carroll, Janet S. Butel,
25th Mar 2010. Mc Graw-Hill (Lange)
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