Viruses Affecting the GIT - PDF

Viruses Affecting the GIT Dr. Sara Lotfy Asser Associate Professor of Medical Microbiology and Immunology  Responsible for up to 75% of all infectious diarrheal diseases VIRUSES Second most common viral illness after upper respiratory tract infection Maj...

Viruses Affecting the GIT Dr. Sara Lotfy Asser Associate Professor of Medical Microbiology and Immunology  Responsible for up to 75% of all infectious diarrheal diseases VIRUSES Second most common viral illness after upper respiratory tract infection Major killer of infants who are undernourished Transmitted through the feco-oral and direct contact routes and affect immunocompetent as well as immunocompromised host Many different 1. Local infection: types of viruses causing inflammation and irritation of the lining of the stomach and intestines are found in the Example: Rotavirus, Adenovirus, Norovirus gut 2. Infection of the glands and organs related to the GIT: As Mumps virus infects the salivary glands Hepatitis A virus infects the liver 3. Invasion of the host To produce systemic illness in other organs and not associated with gastroenteritis Example: Enterovirus, poliovirus  Viral Gastroenteritis 1. ROTAVIRUS ROTAVIRUS ROTAVIRUS The name rotavirus is derived from the Latin word rota, meaning “wheel” which refers to the triple- layered virion appearance in electron micrographs  ROTAVIRUS: Structure Reoviridae Family Icosahedral symmetry Double stranded RNA Segmented (11 segments) Resistant to environmental conditions Activated by mild proteolysis increasing their infectivity. Inner capsid contains a complete transcription system, including RNA-dependent RNA polymerase  ROTAVIRUS The genome encode : 6 structural proteins (VP) VP6 is the mid-layer and its 6 non-structural proteins (NSP) epitopes classify rotavirus into 8 groups (A-H) VP7 and VP4 (the spike protein) Group A rotaviruses are the compose the outer structural most frequent pathogens of layer humans. ROTAVIRUS: Epidemiology Worldwide with 95% of children infected by 3 to 5 years Maximal shedding of the virus occurs 2 to 5 days after the start of diarrhea Virus survives well on fomites and on hands because it can withstand drying. Outbreaks occur in preschools and day-care centers and among hospitalized infants. Infection predominates during winter and early spring seasons. ROTAVIRUS: Pathogenesis Enterotoxin Enterocytes lysis NSP4 Blunting of Calcium influx microvilli into enterocytes Excretion of large Disrupt tight quantities of viruses junction Prevent water and electrolyte Leakage absorption watery diarrhea Watery diarrhea  ROTAVIRUS: Clinical picture Incubation period is 48 hours. The major clinical findings are vomiting, diarrhea, fever, and dehydration. Neither fecal leukocytes nor blood occurs in stool for this form of diarrhea. Rotavirus gastroenteritis is a self-limited disease, and recovery is generally complete and without sequelae. However, it may be fatal in malnourished and dehydrated infants. ROTAVIRUS: Lab diagnosis Direct detection: ELISA EM and IEM  ROTAVIRUS: Management No specific antiviral therapy is available for rotavirus infection. Morbidity & mortality result from dehydration and electrolyte imbalance. Rehydration therapy is necessary to replace fluids so that blood volume and electrolyte and acid–base imbalances are corrected. ROTAVIRUS: Vaccination Two human rotavirus vaccines are available and effective: LIVE ATTENUATED Rotarix (RV1) is a monovalent human rotavirus vaccine, given in 2 doses at ages 2 months and 4 months. Rotateq (RV5) is a pentavalent human- bovine reassortant rotavirus vaccine, given in 3 doses at ages 2 months, 4 months, and 6 months.  Viral Gastroenteritis 2. CALICIVIRUS 3. ADENOVIRUS 4. ASTROVIRUS  FAMILY STRUCTURE TRANSMISSION CLINICAL AGE GROUP VACCINE Triple Severe Available: ROTAVIRUS Reoviridae layered Feco-oral watery Infants Live DS RNA diarrhea attenuated Segmented Enterotoxin Rotateq Group A and rotarix Severe ADENOVIRUS Adenoviridae DS DNA Feco-oral watery Children Non Naked diarrhea and adults Epidemics: Serotype 40,41 SS -ve RNA Outbreaks NOROVIRUS Caliciviridae Naked Feco-oral in groups as Adults Non Surface ships and calyx camps SS –ve RNA Watery ASTROVIRUS Astroviridae Naked Feco-oral diarrhea Adults Non Star-like Sporadic and outbreaks MUMPS  Acute Contagious Benign Non-suppurative parotitis (painful swelling of the salivary glands) Acquired through inhalation of droplet aerosols Incidence dropped due to vaccination  HN (Haemagglutinin- neuraminidase) surface spikes F protein are also spike proteins are the viral attachment that promotes fusion of the viral proteins that bind to sialic acid envelope with plasma membrane cell surface receptors and RBC’s Neuraminidase activity cleave sialic acid on viral and cellular surface to facilitate release of the virus and prevent large virions that consist of a aggregation of its particles negative-sense RNA genome in a helical nucleocapsid surrounded by an envelope. Paramyxoviruses can produce cell-cell fusion creating multinucleated giant cells (syncitia).  v Mumps is a very communicable disease v Only one serotype, and it infects only humans, hence immunity is permanent. v The virus spreads by direct person-to- person contact and respiratory droplets. v The virus is released in respiratory secretions 7 days before symptoms and even from those who are asymptomatic. v Incidence of infection is greatest during the winter and spring. MUMPS PATHOGENESIS  CLINICAL PICTURE v 1/3 of cases asymptomatic v Acute onset v Low grade fever, malaise, anorexia v Painful enlargement of parotid gland v As well as other salivary glands v CNS involvement is common v Mumps meningitis and meningoencephalitis is usually self- limited v 20-50% of males may develop oophoritis which is painful due to enlargement. Pressure atrophy may rarely lead to sterility v 5% mumps oophoritis v 4% pancreatitis  LAB DIAGNOSIS Ag/ IgM ELISA Monkey kidney cell lines for isolation RT-PCR PREVENTION LIVE ATTENUATED MONOVALENT: Adults and children over 1 year of age TRIVALENT MMR: Children > 15 months of age