Viral Hepatitis

Cards (31)

What are all the different functions of the liver?
Carbohydrate, fat and protein metabolism

Synthesis of coagulation factors

Bile secretion- digestion

Endocrine- Insulin like GF, angiotensin

Cholesterol synthesis and homeostasis

Detoxification and urea synthesis

Iron and vitamin stores

Drug metabolism- benzodiazepines
What is the significance of hepatitis & liver failure in dentistry?
Damage to the liver can result in reduced function & so patients with liver failure can show:
Haemorrhagic tendenciesImpaired drug metabolismCutaneous manifestations (purpura, telangiectasia, finger clubbing)SialadenosisSjögren's syndrome (in primary biliary cirrhosis)Transmission of viral hepatitis is also a concern
Purpura: small blood vessels leads under skinTelangiectasia: Small red/purple clusters due to dilation of capillaries.Finger clubbing:enlarged fingers
What are the common liver diseases?
Alcoholic cirrhosis
Non alcoholic fatty liver- obesity
Viral hepatitis
Drug toxicity
Liver cancer
Autoimmune liver disease (primary biliary cirrhosis)
Can be damaged secondary to bile duct obstruction/gallstones
How do hepatocytes respond to damage?
They can demonstrate reversible changes, such as accumulation of fat.

However if the injury is too great, they will die-either by necrosis or by apoptosis.
Can the liver generally respond well to damage?
Response is limited because you get loss of hepatocytes and fibrosis 'cirrhosis (scar tissue)' (stellate cells convert to fibroblasts).

Therefore, hepatocytes are eventually replaced by fibrosis & the liver fails
Is liver failure acute or chronic? 
It is usually chronic but can result from massive necrosis of hepatocytes
What are some signs of liver failure?
Jaundice

Encephalopathy - spectrum of Neurological features

Bleeding tendency

Portal hypertension- ascites (collection of fluid within abdomen), hepatomegaly, arteriovenous shunts

Secondary renal failure

Anorexia, weight loss, weakness

Pruritis - itchy skin
What is hepatitis A and how can you get it?
It's a common form of infectious hepatitis and is only an acute infection which is acquired from contaminated food or water via faeco-oral route
Where is hepatitis A endemic?
Endemic in developing & hot countries

Although in developed countries, consumption of shellfish from contaminated water can give you it
What is the incubation period for hepatitis A?
2-6 weeks
What is the prognosis for hepatitis A?
Spontaneous recovery in 3 mths is very common

There's rarely any complications, it's only fatal 0.2% of the time

Vaccine is available for hep A
Describe the transmission & prevalence of hepatitis E.
Similar to A,acute infection onlyand is also acquired from contaminated food or water via faeco-oral route
It's very common in India and is spread from animal reservoirs
What's the incubation period for hepatitis E?
4-6 weeks
What is the prognosis like for hepatitis E?
It has a 20% mortality rate in pregnant women, but otherwise is similar to hep A
what does HBV look like?
HBsAG= Hepatitis B surface antigen
What is the life cycle of hepatitis B?
Binds sodium/bile acid cotransporting peptide

Endocytosed, membranes fuse, core released

DNA travels to nucleus, transcribes RNA

Viral proteins synthesised

Virus assembly in cytoplasm

RNA to DNA reverse transcription

Reinfection of cell and release of virus and
incomplete viral particles

Released as an 'enveloped' virus like C & D
Why is hepatitis B so transmissible?
Because minute traces of body fluids can transmit infection since the virus can survive well outside the body for a week at least, possible one month

Also the virus is relatively resistant to disinfection
How high is the risk of getting hepatitis B as a healthcare worker?
Up to 30% of needlestick injuries from an infected patient can lead to transmission of it to unvaccinated healthcare workers

Even in vaccinated individuals, the vaccine is not 100% effective

There is also a 0.1% chance of getting it from mucocutaneous exposure

The saliva can also be infectious (through the blood content in saliva)
How much more infectious is hepatitis B in comparison to hepatitis C & HIV?
10x more infectious than hep C
100x more infectious than HIV
Who is infectious with hepatitis? 
Everyone incubating (2-6 months) or with acute infection
All those with chronic hepatitis
Often asymptomatic individuals
0.3% of UK population
Only 1 in 4 carriers give a positive history
Particularly those with circulating e-antigen
What is the e-antigen?
Hepatitis B envelope antigen which lies inside the outer lipid membrane but outside of the protein core containing viral DNA

E-antigen is secreted into the blood (unlike the core antigen which stays within the host cell & due to this secretion, it can be used as a marker of infectivity and its level is proportional to the viral load within the individual
What happens in terms of the e-antigen as the infection resolves?
The host will make antibodies to this e-antigen which will appear as the infection resolves and will these antidotes will persist for several years
What are some examples of high risk individuals for hepatitis B? 
Intravenous drug users and their partners

Men who have sex with men

Those with frequent changes of sexual partners

Babies, family and partners of those infected

Anyone with chronic liver or renal disease

Those who need regular blood transfusions

Male and female sex workers

Travellers to endemic areas

Prison staff and prisoners

Healthcare staff, including dentists

Families adopting children from endemic areas

Patients and staff of institutions for the handicapped

Immunosuppressed patients

Patients who have had acupuncture or tattooing, especially in tropical countries
What are the universal infection control precautions for hepatitis B?
Vaccination:

-3 injections into deltoid muscle
-6 months required for adequate protection
-side effects are mild & rare
-if obese, may need to repeat course
-antibody levels no longer tested
-no booster injections
-protection is >95% but still incomplete
What is hepatitis D also known as?
Delta hepatitis
What is hepatitis D?
A unique defective RNA virus, related to plant viruses, & it can only infect in the presence of HBsAg which means it's dependent on hep B virus for its life cycle, so it's transmitted with hep B (co-infection)

This also means the hep B vaccine helps protect against hep D infection
Where is hepatitis D endemic to?
Middle East, Africa, & parts of South America
In UK, it only really occurs in IV drug users or from overseas transfusions
What is the mortality rate for hepatitis D?
Hepatitis rarely resolves, so it has a high mortality

Especially when it has occurred via co-infection with hep B, the mortality can be up to 20%
How serious is hepatitis C and what is it?
It's a major cause of liver disease & a severe infection; often fatal

It's an RNA virus with an incubation period of ~9 weeks

There is currently no vaccine for hep C as well

Hep C is worse than B and A
What is the prognosis like for hepatitis C?
15% develop acute hepatitis, 20% clear infection

85% of patients develop chronic hepatitis, cirrhosis and risk of liver failure

It's usually diagnosed LATE
How is hepatitis C transmitted?
By blood, commonly by:

•Needle sharing by IVDU or tattooing
•Overseas blood transfusions
It's rare in UK; 2% in USA ; 3% in worldwide
High in japan, Mongolia, parts of Africa and South America.
It's common in HIV positive patients
There is a lower risk of transmission than Hep B on sharps injury