Prevalence, socio-demographic features and risk factors of Hepatitis B virus infection among pregnant women in Southwestern Nigeria

Introduction Hepatitis B virus is responsible for 50%-80% of Hepatocellular carcinoma cases worldwide. In Nigeria, vertical transmission remains a major route of Hepatitis B virus infection. Primary (vaccines and post-exposure prophylaxis) and secondary prevention of HBV transmission by appropriate sexual and sanitary practices are not yet optimal in the country yet measures for early detection (serological, molecular) and treatment of infected pregnant women is not a practice. This study aimed at identifying the prevalence and risk factors for Hepatitis B virus infection among pregnant women in Ibadan, Southwestern Nigeria. Methods A cross-sectional study was done at the Ante-natal clinic of the University College Hospital Ibadan. One hundred and eighty pregnant women were recruited from March to August 2013, and tested for Hepatitis B surface antigen (BIORAD FRANCE) using third generation ELISA, as well as HIV-1 and 2 using Uni-Gold Recombigen and ALERE determine (a rapid immunoassay designed to detect antibodies to HIV 1 and/or 2). Positive HBsAg samples were tested for Hepatitis B envelope antigen, antibody and Hepatitis B core antibody (DIAPRO Italy) while serum HBV DNA was detected using PCR. Data were obtained using questionnaires to establish and analysis was performed using SPSS version 20. Results The seroprevalence of HBsAg was 8.3% out of which 26.7% were positive for HBeAg, 53.3% had HBeAb, 20% had neither HBeAg nor HBeAb, 100% had total HBcAb and 86.7% had HBV DNA in their serum. The mean age was 32.1years, the highest HBV infection rate occurred in 25-29 year age group. Multiple sexual partners (OR- 3.987, P- value=0.026) and early age at sexual debut (OR 11.996, P- value=0.022) were independent risk factors for HBV infection. Conclusion Hepatitis B virus infection is of high endemicity in Nigeria thus early detection, treatment of infected pregnant women, immunoprophylaxis for exposed newborns and surveillance for those with chronic infection is essential. Health education programs on prevention and control measures must be instituted.


Introduction
Hepatitis B virus is a major cause of Chronic Hepatitis, cirrhosis and Hepatocellular cancer (HCC). About 2 billion people worldwide have been infected with HBV, an estimated 360 million remain chronically infected of whom almost one million people die annually of HBVrelated liver disease [1,2]. Of the estimated 360 million chronically infected individuals, about 50% acquired their infections either perinatally or in early childhood [2]. This is seen in sub-Saharan Africa and other HBV endemic regions, where high rates of HBeAgpositive infections in women of child-bearing age are found [2], and is considered a major contributing factor to the high prevalence of HBV infection in these regions [3]. Despite advent of anti-viral therapies that can suppress HBV and delay progression of liver disease, most people with chronic HBV infection reside in developing countries where these drugs are neither affordable nor accessible [4]. The incidence of HBV-related HCC cases is projected to increase for at least two decades due to the high prevalence of chronic HBV infection throughout the world [4]. Regional studies in Nigeria have shown varied sero-prevalence rates, ranging from 4.7% to 15.8% [5,6]. Till date there has been no national study on the sero-prevalence of HBV in the Nigerian population as well as the pregnant women. Most regional studies done were solely on seroprevalence of HbsAg, a few studies analyzed other serological parameters of HBV infection but no molecular study on HBV infection among pregnant women has been reported so far. In developed countries, the increased awareness, identification of mothers who are Hepatitis B surface antigen (HBsAg) and HBV DNA positive as well as adequate prophylaxis among exposed newborns was found to reduce the overall prevalence of HBV infection [7]. This must be emulated in Nigeria to ensure Prevention of perinatal transmission and hence decrease the burden of chronic HBV infection in Nigeria. In Nigeria, primary (vaccines and post-exposure prophylaxis) and secondary prevention of HBV transmission (  About 500μl of HBC wash buffer was added, sample centrifuged at 13,000 rpm for 1 minute and filtrate discarded, after which 700μl of DNA wash buffer was added and centrifuged at 13,000 rpm for 1 minute, this was done twice and the flow through discarded. About 100 μl of preheated elution buffer was added, and centrifuged at 13,000 rpm for 1 minute, this was done twice to elute the DNA.  year age group and majority of the women presented in 2nd and 3rd trimester for first antenatal care.  to the capsid viral antigen and elimination of infected hepatocytes in the infected newborn is therefore impossible without intervention [24]. All the HBsAg sero-positive pregnant women tested positive for total HBcAb hence were chronically infected and had HBV DNA identified in 86.7% of them, majority (73.33%) of whom presented in their second and third trimester. In the absence of early detection and treatment in these pregnant women, the risk of transmitting HBV to their newborns at birth is nearly 100% [24]. In our study, a high frequency of HBV infection was found among women older than 29 years. This may be due to increased risk of exposure to HBV with each pregnancy, the cumulative years of sexual exposure and risky sexual behaviour. This finding though in contrast to some other studies [6,16], was consistent with a similar study done in the same region [25], all within Nigeria. Most of HBsAg-positive women were of low educational status (60%) and increasing level of education was noted to be inversely related with HBV infection, this finding was in agreement with similar studies in Nigeria [6,10,11,16], and this indicates the positive influence of education and public awareness on the carrier rate of HBV infection.

Seroprevalence and its risk factors
About (73.34%) of the HBsAg positive women were multi-gravida, this finding concurs with the observation that pregnant women are considered at a higher risk of HBV infection due to increased exposure to risk factors (such as blood transfusion, intravenous drugs or surgical procedures) [26]. None of the participants with previous history of blood transfusion had HBV infection, this is similar to studies done in Southern Nigeria [5,6,25], and in contrast to some published studies in Northern Nigeria [10,13,27]. This reflects the strengthening of the national regulatory policy on universal screening of blood and blood product especially in Southern Nigeria and calls for further strengthening in the Northern part. In the index study women with multiple sexual partners were four times more likely to acquire hepatitis B virus infection than women with one sexual partner; this finding corroborates the high prevalence of HBV infection among commercial sex workers as reported in some studies [9]. It was also observed that women who had their sexual debut less than fifteen years of age were twelve times more at risk of HBV infection than those who were above fifteen years at their first sexual experience. Sexual contact with known HBV positive persons was also significantly associated with Hepatitis B virus infection among these women. Likewise, there was an increased prevalence of HBV infection among women in polygamous family setting, those whose husbands had other sexual partners and those whose husbands were unable to come home every day due to the nature of their job, thus reflecting the increased likelihood of their partners engaging in risky sexual behavior. This concurs with reports among pregnant women in Afghanistan [22], and buttresses findings in literature ascribing sexual activity as a major risk factor for HBV infection [9,28]. HBV

Co-infection with human immunodeficiency virus (HIV) increases the
rate of transmission of viral hepatitis substantially. It also increases the risk for hepatotoxicity of HAART and likelihood of onset of an AIDS-defining illness [28,29]. The HIV/HBV co-infection rate in this study was 26.67%, this is similar to a study done in Tanzania [17] and Nigeria [29], but quite high when compared with similar studies in Nigeria [6], and the literature [28,30]. This study also highlighted that some of the respondents did not fall into any of the recognized high risk groups for HBV infection as was also reported by other authors [10,14,18]. This is not an uncommon finding as other for healthcare resources and society will be substantial.

Competing interests
The authors declare no competing interests.

Authors' contributions
This work was carried out in collaboration with all authors. Authors CGA, AF and RAB were involved in the research conceptualization and development. Author CGA coordinated specimen and data collection. Authors CGA and CEO performed specimen analysis.
Author CGA analyzed data and prepared the manuscript. All authors read and approved the final manuscript for publication. All authors have read and agreed to the final version of this manuscript and have equally contributed to its content and to the management of the case.

Acknowledgments
We wish to appreciate the Head of Department and Staff of the Antenatal Clinic of University College Hospital Ibadan, Oyo State, for their co-operation and support during the study.