Epidemiological and molecular aspects of hepatitis B infection in Kenya
Abstract
Kenya is one of the areas of the world with a high
prevalence of hepatitis B virus infection. Although much is
known about the virus, the modes of transmission in such
endemic areas are not fully determined. The aim of this
work was to investigate some aspects of hepatitis B virus
infection including the relationship of hepatitis B to
hepatocellular carcinoma and the possible means whereby
infection may be prevented.
For this purpose, a laboratory was established in
Nairobi and personnel trained to facilitate the routine
testing of sera for markers of hepatitis B infection using,
in the main, an assay system based on monoclonal antibodies.
Once the local availability of modern diagnostic techniques
had been established, various epidemiological studies were
commenced.
The results showed that although perinatal infection
with hepatitis B virus was uncommon, probably due to low
levels of circulating hepatitis B viral DNA in the maternal
plasma, infection with hepatitis B virus was frequent,
commencing around 3 years and increasing linearly with age
to peak around 30-40 years. Over 80% of urban Kenyan adults
showed some markers of hepatitis B infection with around 8%
having hepatitis B surface antigenaemia.
As the vast majority of Kenyan adults have immunity to
both the hepatitis A virus and the hepatitis B virus it was
of interest to determine the aetiology of acute hepatitis in
this group. Markers for acute hepatitis A virus, hepatitis
B virus and other hepatitic viruses were examined in the
sera of 94 adult patients presenting with acute hepatitis.
Hepatitis B virus was responsible for 70% of cases and the
hepatitis A virus for only 12%. In the majority of cases
known risk factors for hepatitis B infection, including
tribal scarification and circumcision, were absent.
A national epidemiological survey of the prevalence of
hepatitis B infection and delta virus infection was
undertaken. The distribution of both hepatitis B virus and
delta virus was very variable. In certain tribes of
pastoral nomads the prevalence of hepatitis B surface
antigenaemia was found to be over 25%, with delta antibody
present in 60%.
A study conducted at the Kenyatta National Hospital
confirmed the close relationship of cirrhosis and
hepatocellular carcinoma with the presence of hepatitis B
surface antigen in the serum. A Southern blot analysis of
DNA extracted from liver tissue of patients with
hepatocellular carcinoma showed that integrated HBV-DNA
sequences could be detected in 41% of cases and episomal
HBV-DNA in 18%. This gives further support to the
epidemiological evidence implicating the hepatitis B virus
in the aetiology of hepatocellular carcinoma.
These studies have emphasized the importance of active
intervention against hepatitis B infection taking place at
an early age. Unfortunately the cost of vaccination for
countries like Kenya is prohibitive. An attempt was
therefore made to try and lower the cost of vaccination by
reducing the dosage. It was found that one-fifth of the
conventional dose of vaccine given intradermally to neonates
achieved a 90% seroconversion. However the antibody titres
were much lower than those resulting from the administration
of the conventional dose and this may adversely affect the
long term protection against hepatitis B infection.
Citation
Doctor of medicine,University of Newcastle,1985.Publisher
University of Newcastle medicine