Myxoviruses - Bacteriology - Lecture Slides, Slides of Bacteriology

Download Myxoviruses - Bacteriology - Lecture Slides and more Slides Bacteriology in PDF only on Docsity! Myxoviruses Docsity.com Influenza Viruses • Replicate in mucus membranes • Target tissue: upper & lower respiratory tract • Cause influenza: acute respiratory disease that may occur in epidemics or even pandemics Docsity.com Haemagglutinin  Binds to host cell surface receptor  The target of neutralizing Abs  Haemagglutinates RBCs from various animal species Neuraminidase  Cleaves neuraminic acid to release virus progeny from infected cells  Degrades the protective layer of mucin in the respiratory tract  Plays a min role in immunity to influenza Docsity.com Types of Influenza virus I- Type A virus:  Infects humans as well as animals Undergoes continuous Agic variations Many animal species have their own influenza A virus Pigs & birds are important animal reservoirs playing a role in occurrence of influenza epidemics Docsity.com II- Type B virus:  causes milder disease  Infects human only Undergoes Agic variation but only Agic shift III- Type C virus: Of doubtful pathogenicity Agically stable Docsity.com Agic shift occurs only in infuenza A because it has a wide host range, giving influenza A the opportunity for a major reorganization of its genome & hence its surface Ags Pigs are susceptible to avian, human & swine influenza viruses and they potentially may be infected with influenza viruses from different species. If this happens, it is possible for the genes of these viruses to mix and create a new virus Docsity.com Antigenic Variation 2- antigenic drift • It is spontaneous point mutation of known strains of influenza causing minor change of an amino acid sequence of HA or NA. • Occurs in influenza A & B Docsity.com Mode of transmission • Highly contagious disease with person to person transmission • Three modes of transmission Droplet Contact Air- Borne Direct Indirect Docsity.com Laboratory Diagnosis Specimen: nasal washings, gargles, throat swabs 1- Direct Virus Demonstration: a) Direct Immunofluorescence: for rapid Ag detection in nasal aspirates, not very sensitive b) RT-PCR: for detection of viral RNA Docsity.com 2- Viral Isolation: specimens are inoculated into emberyonated eggs or primary monkey tissue culture Cell culture are tested for the virus by Haemagglutination Docsity.com Prophylaxis I-vaccines II- chemoprophylaxis - Inactivated - Live attenuated -Amantadine& Rimantadine -Zanamavir & Osteomavir Docsity.com 2) Live attenuated  Recently approved only for healthy individuals  Prepared from temperature- sensitive mutants that can replicate in cooler nasal passages (33C) but not in warm lower respiratory tract Given by nasal spray thus could provide mucosal, humoral & cell-mediated immunity Docsity.com II- Chemoprophylaxis 1)Amantadine & Rimantadipne:  Prevent penetration & uncoating of the virus  Treat & prevent influenza A only  Given to high risk groups 2) Zanamavir & Oseltamivir (tamiflu)  They are neuraminidase inhibitors, inhibiting the release of virus from infected cells  This limits the infection by reducing the spread of virus from one cell to another  For treatment not prevention  Effective against influenza A &B Docsity.com