Introduction to Hepadnaviridae

Hepadnaviridae includes one virus that is pathogenic to man: Hepatitis B virus (HBV). All of the known hepadnaviruses are hepatotropic, infecting liver cells, and all can cause hepatitis in their known host. Hepatitis is the syndrome characterized by inflammation of the liver. It can be caused by hepatitis viruses, other viruses and non-infectious agents such as alcohol.

The hepadnaviurses include three viruses of mammals and two viruses of birds. Members of the Hepadna family include:

1) Genus Orthohepadnavirus

Virus Member-Natural Host-Disease

Hepatitis B (HBV)-Humans, Chimps, Gibbons, Monkeys-Hepatitis

Ground Squirrel Hepatitis B-Ground Squirrels, Woodchucks, Chipmunks-Hepatitis

Woodchuck Hepatitis B-Woodchucks-Hepatitis

2) Genus Avihepadnavirus

Virus Member-Natural Host-Disease

Duck Hepatitis B-Ducks, Geese-Hepatitis

Heron Hepatitis B-Herons-Hepatitis

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http://health.howstuffworks.com/immunizations-in-depth.htm/printable

HBV Basics

Genome: partial ds DNA, circular, monopartite, smallest at 3.2kb in length

Morphology: roughly spherical, icosahedral nucleocapsid.
Replication: Violates Central Dogma-DNA->RNA->DNA

Clinical Symptoms: Jaundice, fatigue, abdominal pain, nausea

Transmission: Blood-borne, sexual

Prevention: Recombinant HBV surface antigen vaccine or HBV immunoglobulin post-exposure prophylaxis.

Related Viruses: Duck Hepatits B, Ground Squirrel Hepatitis Virus, Wooley Monkey Hepatitis Virus, Woodchuck Hepatitis Virus


Pathogenesis

Hepatitis B virus is dangerous because it attacks the liver, thus inhibiting the functions of this vital organ. The virus causes persistent infection, chronic hepatitis and immune complex disease.

The younger a person is when she becomes infected with HBV, the more likely she is to be asymptomatic and become a chronic carrier of the disease. Babies born to infected mothers are at very high risk of to becoming carriers and developing liver pathology. Only about 5% to 10% of Immuno-competent adults infected with HBV develop chronic hepatitis B. Many people die mostly due to cirrhosis and liver cancers that develop in people with the chronic form of this disease.


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http://biology.kenyon.edu/slonc/bio38/scuderi/parti.html

Symptoms of Acute Infection

Symptoms usually activate 6 weeks to 6 months afterwards acknowledgment to the virus. In adults, aboriginal affection can cover abhorrence, loss of appetite, vomiting, fatigue, and belly cramps and jaundice. Persons can accept all or alone a few of the aloft signs and symptoms. 50% of adults with a new infection accept no affection. Over 90% of infants, 50% of children, and 5% of adults with astute hepatitis B will advance abiding or abiding infection. Abiding hepatitis B may advance to alarmist ache including cirrhosis and alarmist cancer.

Symptoms of Chronic Infection

Most patients do not undergo any symptoms. Abiding hepatitis B may advance to alarmist ache including cirrhosis and liver cancer.

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http://www.flickr.com/photos/cooljerk/1485764926/

Lab Diagnosis

Diagnosis of HBV infection is usually through serological and virological markers. Hepatitis B surface antigen (HBsAg) is the hallmark of HBV infection and is the first serological marker to appear in acute hepatitis B, and persistence of HBsAg for more than 6 months suggests chronic HBV infection.

Hepatitis B e antigen (HBeAg) usually indicates active HBV replication and risk of transmission of infection. Occult HBV infection is recognized as the absence of circulating HBsAg in individuals positive for serum or tissue HBV DNA, irrespective of other HBV serological markers.

Monitoring the serum HBV DNA level is valuable for assessing liver disease activity, differentiating other etiologies of hepatitis activity in HBV carriers. In conclusion, it is particularly important for physicians to screen for HBV infection in HBV-endemic areas and to monitor liver disease progression in HBV carriers by using both serological and virological markers, so that effective treatment can be initiated early before the development of advanced liver disease.

Inflammation of Liver

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http://www.med.unsw.edu.au/medweb.nsf/page/Infection%20Immunity%20and%20Inflammation

Transmission

Parenteral Transmission- One of the major modes of transmission for HBV this occurs through blood transfusions or blood products. A blood-borne virus, HBV surface antigens as well as the viral DNA can use blood as a vehicle for spread.

Perinatal and Postnatal Transmisson- This type of transmission includes bodily fluids such as breast milk and maternal saliva. It also includes mothers who pass the virus on to their children in or during pregnancy (perinatal transmission), resulting in a 90% of HBV carriers transmitting the chronic disease to their infants.

Contact-Associated- High sexual activity, working in an environment with high levels of HBV, and sharing dirty syringes can all increase ones chances of contracting HBV. Thus sexually promiscuous people, IV drug users, and health care workers are at high risk.

Prevention

Vaccines against hepatitis B were introduced in the early 80s and babies were all vaccinated.

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http://www.flickr.com/photos/moonypics/3022530281/


References

http://www.wrongdiagnosis.com/medical/herpesviridae.htm

http://www.virology.net/Big_Virology/BVDNAherpes.html