Microbiology Immunology Lecture #8 PDF

VIRUSES - Part 2 Viruses Causing Glandular Enlargement • MUMPS – Childhood disease; bilateral inflammation of parotid glands; many inapparent infections – Complications: meningitis, orchitis (can lead to sterility), ovaritis – Epidemiology: spread by salivary and respiratory...

VIRUSES - Part 2 Viruses Causing Glandular Enlargement • MUMPS – Childhood disease; bilateral inflammation of parotid glands; many inapparent infections – Complications: meningitis, orchitis (can lead to sterility), ovaritis – Epidemiology: spread by salivary and respiratory secretions; incubation 18 -21 days – Prevention: MMR vaccine (live, attenuated) Infectious Mononucleosis (Epstein -Barr Virus) • Belongs to Herpes virus family • Mild disease; children and young adults; can be prolonged and debilitating • Transmission by saliva (kissing disease) • Symptoms: lymphadenopathy, fever, sore throat, atypical lymphocytes, enlargement of liver and spleen • Latent virus – Chronic disease (rare) or asymptomatic shedding (common) for lifetime of host • Diagnosis: blood picture ( in atypical lymphocytes) Monospot Test (detects RBC agglutination) Presence of EBV antigens • NO VACCINE Cytomegalovirus (CMV) • Herpes family, infection usually asymptomatic and latent BUT dangerous for – Pregnant women: neonatal infection with jaundice, enlarged liver and spleen, intellectual deficiency and motor disorders – Transplant patients: disseminated infection can cause transplant rejection – AIDS and other immunocompromised patients: frequent infection, GI tract ulceration and retinitis C M V • Diagnosis: – Isolation of virus from urine, blood, organ biopsies (slow process, but accurate) – CMV antigen detection, DNA hybridization and PCR in leucocytes much faster – Serology screening for donors and recipients before transplant • Treatment: antivirals • Prevention (immunocompromised): – Match CMV immune status between donor and recipient in transplants – Preventative administration of antivirals – Universal precautions to prevent transmission – NO VACCINE Hepatitis Viruses • Hepatitis = Inflammation of the liver – Malaise, fatigue, nausea, loss of appetite and jaundice • Hep A, B most common and well characterized – Hep C, E, G less common • * Other viruses and bacteria can cause hepatitis as a complication of infection * • Diagnosis: serological Hepatitis A • Mainly children and young adults • Sporadic cases and small epidemics • Epidemiology: – Transmission by fecal -oral route – Incubation 15 -50 days – Stools infectious 2 -3 weeks before onset – Mild or inapparent infection in children – No chronic hepatitis – Life -long immunity Hepatitis A • Diagnosis: – Suspected clinical cases: detection of IgM – Immunity: detection of IgG (before travel) • Prevention: – Vaccine for high risk populations – Commercial γ -globulin for prevention after exposure Hepatitis B • Sporadic cases; all ages • Epidemiology: – Contaminated blood/blood products; saliva, urine, semen – Avg. incubation 90 days – Infective serum 30 -60 days before onset of symptoms – Carriers • Clinical – More severe than HepA – Chronic hepatitis and chronic carrier -state Hepatitis B • Diagnosis: – Blood test for HepB surface antigen (HBsAg) – Antibodies are produced several months after onset of symptoms • Used as markers of infection and immunity Hepatitis B • Prevention – Universal precautions for blood and body fluids – Proper handling of needles – Screening – Vaccination – HepB immunglobulins after exposure – HepB carriers He p at i t i s C • Epidemiology: – Blood and sexual transmission – Initially mild disease but can cause chronic hepatitis • Diagnosis: – Serological • Prevention: – Same as HepB – Treatment/cure? • Epclusa (sofosbuvir -velpatasvir)  Hepatitis Delta Agent • Epidemiology: – Blood and sexual transmission – “Viroid” -relies on HepB presence for replication in cells – Increases severity of HepB infection • Diagnosis: – Serological • Prevention: – Vaccination against HepB Hepatitis E • Transmission via fecal - oral route • Incubation 15 - 50 days • Symptoms similar to HepA BUT 20% mortality in pregnant women • Endemic in India, Pakistan, Nepal, Burma, North Africa and Mexico Hepatitis G • Epidemiology: – Blood and sexual transmission – Incubation 14 -180 days – Initially mild and no jaundice, can cause chronic hepatitis • Diagnosis: – Detection of viral DNA by PCR or other molecular methods • Prevention: – NO VACCINE Yellow Fever Virus • Haemorrhagic fever with hepatitis • Endemic in Africa, South America and Caribbean • Mortality rates as high as 50% • Transmitted by mosquito • Travellers to endemic countries receive live attenuated vaccine Viruses affecting the CNS • Clinical Manifestations – Aseptic meningitis – Encephalitis – Meningo -encephalitis – Poliomyelitis – Slow progressive, persistant infections CNS Viruses • General Diagnosis * Always first exclude possibility of bacterial or fungal infection * – Lumbar puncture X4 – Other specimens • Blood, urine, aspirates, • throat swabs • stools, sera CNS Viruses with a Human Resevoir • Usually an extension of a primary infection in another part of the body – Mumps -aseptic meningitis in children – Enteroviruses -aseptic meningitis in infants and children – HSV1 -RARE cause of herpetic encephalitis in young adults – HSV 1 or 2 -RARE cause of meningo -encephalitis in neonate or young adult – Vaccination for mumps, measles and polio (entero) CNS Viruses with an Animal Reservoir • RARE: Humans are accidental or dead -end hosts – Arbovirus: • over 200 different types • Tropical rainforest areas • Encephalitis • Eg. West Nile – Rabies virus • Fatal, acute encephalitis • Infects mammals, transmitted via saliva • Long incubation (30 -60 days) • Combined active and passive immunization • Prevention by vaccination of wildlife and pets HIV and AIDS • Severe immunosuppressive condition; often fatal; predisposition to opportunistic infections and cancers • HIV causes depletion in helper T - cells making the host very susceptible to other infections • Frequent antigenic changes HIV • Inactivation – Virus often protected by living inside cells, protect it from disinfecting action • Transmission – Sexual, blood/blood products, congenital, organ transplants, sperm donation – Lengthy asymptomatic period increases spread of disease • Pathogenesis – Virus is cytocidal to helper T4 cells – AIDS develops from decreasing immune status HIV HIV • Clinical – Incubation 6 months -several yrs – AIDS -related Complex disease, progress to AIDS – Terminal stage patients develop dementias, other neurological problems, many opportunistic infections • Lab Diagnosis – Serology based; seropositivity can take months to occur – Isolation of virus from blood, plasma, semen, cervical, vaginal secretions HIV • Prevention – Universal precautions for healthcare personnel – Screen blood, organ and semen donors – Heat inactivation of plasma for haemophilia patients – Sexual education – Education of drug users – Testing pregnant women at risk – NO VACCINE yet, but is a key focus of current research HIV • Treatment – MANY forms of treatment – Most effective is cocktail of treatments • HAART – Protease inhibitor (stops viral maturation) – Reverse transcriptase (stops viral replication) – Bad side -effects – Expensive – Treatment and Prevention in developing countries very difficult