V1: Hepatitis Viruses Flashcards
1. List the viruses associated with hepatitis 2. Describe the main properties of Hepadnaviruses (including Hep B) and Picornaviruses (Hep A) 3. Summarise the diagnostic features of hepatitis A and B infections 4. Outline modes of transmission of different types of hepatitis viruses 5. Explain the principles of prevention of hepatitis 6. Summarise the significance of hepatitis B in dentistry 7. Recognise the significance of other hepatitis viruses
Define hepatitis
Inflammation of the liver without a pinpoint specific cause
What can hepatitis be caused by
- liver injury by toxin
- liver damage by interruption of the organ’s blood supply
- an attack of the immune system (autoimmunity)
- trauma to the abdomen in the area of the liver
What happens in acute infectious fevers compared to in hepatitis
The virus infects the kuppfer cells of the reticuloendothelial system and so liver damage is avoided
The main target of hepatitis viruses are the hepatocytes
How can people be hepatitis carriers
Carriers evolve from acute infections which are mild and anicteric and the patient may be asymptomatic but the infection is detectable on blood screening, they might also suffer long term sequelae of persistent infections
Features of HAV
RNA enterovirus transmitted
- faecal-orally (children, group homes, water/food contamination, shellfish)
- oral anal sexual activity
Incubates for 10-15 days and causes mild flue like signs and symptoms
Immune globulin within two weeks of exposure
What are the clinical features of HAV
Jaundice (more likely when the patient is >14)
Fulminant hepatitis
Cholestatic hepatitis
Relapsing hepatitis
It can cause prolonged illness for 6 months but it is typically short periods of illness which do not cause chronic liver disease
Outline the pathogenesis of HAV
Virus replicates in hepatocytes and passes through the bile duct into the intestine where it is shed in large quantities
Damage to liver function results in raised liver enzymes
How is the spread of HAV controlled
- Passive protection = human normal immunoglobulin
- Vaccination = one serotype, formalin inactivated vaccine prepared from HAV grown in human diploid cells
- Very high hygiene standards
Features of HBV
DNA virus which transmits through blood, skin/mucus membrane contamination with blood/serous fluid, semen and vaginal fluid
- IVDU (Parenteral)
- Sexual
- Perinatal (at/during birth)
Incubation = 48-180 days and typically affects young adults (20-39)
What complications can arise with HBV
Chronic hepatitis (chronic persistant/chronic active) Cirrhosis Liver cancer (hepatocellular carcinoma)
Outline the morphology and replication of HBV
It is a DNA virus (double stranded and circular) and DNA polymerase is involved in replication
- HBcAg = core antigen (not detectable)
- HBeAg = active virus antigen (Dane particles = infective virions)
- HBsAg = surface antigen
When replicating, HBV uses an RNA intermediate and reverse transcriptase. There is a high mutation rate, but the small genome prevents much genetic variability
What are the clinical features of HBV
Jaundice
Chronic infection
Can cause premature mortality from chronic liver disease
How is the spread of HBV controlled
Infection control: sterilisation and aseptic technique
PPE
Vaccination/ immunisation
Passive prophylaxis immunisation post exposure
Safe sex
What treatments are available for HBV
- Interferon (HBeAg+ve with chronic acute hepatitis)
- Lamivuidine (relapse on drug cessation)
- Adefovir (less likely to develop resistance)
- Entecavir (most powerful antiviral)
Features of HDV
Defective RNA virus which is seen with HBV in coinfection or superinfection and it has the same routes of transmission
Incubation = 14-56 days and the patient is usually asymptomatic
