SEROPREVALENCE OF HEPATITIS B SURFACE ANTIGEN AMONG APPARENTLY HEALTHY PRIMARY SCHOOL PUPILS AGED 5-12 YEARS IN BATAGARAWA LOCAL GOVERNMENT AREA OF KATSINA STATE, NIGERIA

Abstract

In man, the general term viral hepatitis refers to infections caused by at least six different viruses: hepatitis A, B,C, D, E and the non-A/non-B hepatitis.4 Hepatitis B is an infectious illness caused by hepatitis B virus which infects the liver of hominoidae, including humans, and causes an inflammation called hepatitis.5 Debilitating and deadly hepatitis has plagued humankind since the beginning of recorded history.6 The course of this disease was irrevocably changed with the accidental discovery of the Australian antigen and its link with the hepatitis B virus.6This discovery has led to a revolution in blood screening and the development of a highly effective hepatitis vaccine.6
More than one third of the world’s population is estimated to have been infected with hepatitis B virus.7 Most of the subjects have recovered, but there are about 350 million chronic carriers of the virus, which constitute about 5% of the world’s population.8 About a quarter of these carriers will develop serious liver disease, including chronic hepatitis, cirrhosis, and primary hepatocellular carcinoma.8,9 The World Health Organization estimates that hepatitis B infection results in more than one million deaths every year worldwide.8 , 9
Hepatitis B virus infection is a disease of global distribution. Majority of the estimated 200 million carriers of hepatitis B surface antigen (HBsAg) are located in tropical Africa and Asia.8,9 Nigeria is classified among the group of countries that are highly endemic for HBV infection with 19 million Nigerians already infected. The virus is the second most important cause of cancer in the country.10,11,12 About 75% of the Nigerian population is reportedly likely to have been exposed to HBV at one time or the other in their life time.12 The reported prevalence of HBsAg in the Nigerian population ranges from 2.7 to 13.3%.13 A preliminary survey of HBV infection in children and adults in northern Nigeria reported that the exposure rate ( i.e. the frequency of both HBsAg and anti-Hbs in the population) to HBV ranged from 59% in children aged <5years to 72.5% in adults aged >30years, while the frequency of HBsAg (which indicates the presence of HBV infection – acute or chronic) alone was 40% and 10%, respectively.14
Both the incidence of chronic HBV infection and the predominant route (s) of transmission of HBV infection in a particular region vary according to endemicity of the particular region and age of the infected individuals at the time of infection.5,6,9,16 In hyper-endemic regions of the world, most cases of HBV infections occur in infancy or early childhood through the vertical and/or the horizontal route whereas in the low endemic countries majority of HBV infections occur during young adulthood by sexual activity and injecting drugs use.5,6.9,15.16 Globally over 25% of persons who acquire infection as children often remain asymptomatic and unrecognized for up to 2 – 3 decades only to develop cirrhosis and hepatocellular carcinoma as adults.6,9 For this reason, HBV infection is sometimes regarded as a “silent killer”. HBV infection is a “vaccine-preventable” disease and Hep B vaccine has been available for decades in developed countries. It has just recently been incorporated into the NPI schedule of immunization in Nigeria (2004) as part of the Government’s efforts aimed to control the infection.10,16 HepB3 (third dose of recombinant hepatitis B vaccine) coverage in Nigeria was 27% as of 2005.4 The seroprevalence of HBsAg among children serves as a proxy for chronic HBV infection.17
Northern Nigeria has one of the lowest rates of immunization coverage in the world.18 Information on the prevalence of HBV infection, the commonest cause of hepatitis in Nigeria,10 in certain parts of Northern Nigeria such is scarce;10,19 hence, sero-epidemiological studies of this infection become necessary. The aim of this study was to determine the seroprevalence of HBV infection among apparently healthy primary school pupils aged 5 – 12 years in Batagarawa Local Government Area of Katsina state, Nigeria. This will generate information that could be used to monitor the trend and possible control of the disease in the area.

SEROPREVALENCE OF HEPATITIS B SURFACE ANTIGEN AMONG APPARENTLY HEALTHY PRIMARY SCHOOL PUPILS AGED 5-12 YEARS IN BATAGARAWA LOCAL GOVERNMENT AREA OF KATSINA STATE, NIGERIA