Hepatitis B Virus Surface Antigen Carriage Among Blood Donors in Ziguinchor, Senegal: Prevalence and Associated Factors

Introduction: Hepatitis B virus is endemic in Senegal, West Africa, however the prevalence of hepatitis B virus surface antigen (HBsAg) carriage in Ziguinchor, Senegal is unknown. This study was conducted in order to determine the prevalence of HBsAg carriage among blood donors in Ziguinchor and to identify factors associated with HBsAg carriage. Methodology: A retrospective study was conducted in the blood donation unit of the Ziguinchor Regional Hospital in 2013. Screening for HBsAg was performed with kits from Rapid Signal TM HBsAg Serum/Plasma Dipstrip (Orgenics ltd Israel). Results: A total of 2122 donors were included in this study, of which 1715 (80.8%) were male and 407 (19.2%) were female. The overall prevalence of HBsAg carriage among all donors was 12.1% (n=256). Carriage was higher among male donors, (n=223, 13%) compared to female donors (n=33, 8.1%) (p=0.04). Carriage was lower among regular voluntary donors (n=24, 5.8%) compared to new voluntary donors (n=101, 14.1%) and replacement donors (n=131, 13.2%) (p<0.001). Conclusion: This is the first study to report the prevalence of HBsAg carriage in Ziguinchor, Senegal. HBsAg carriage is highly prevalent among blood donors in Ziguinchor, especially among males and new voluntary or replacement donors.


Introduction
Hepatitis B is a major public health problem in developing countries of sub-Saharan Africa. The World Health Organization (WHO) estimates that more than 2 billion people have been infected with hepatitis B virus (HBV) worldwide and 350 million (5%) are chronic carriers, of which one million die each year from complications such as cirrhosis and hepatocellular carcinoma [1,2]. The prevalence of chronic HBV carriage is between 8% and 20% in Africa and Asia [3]. Hepatitis B virus can be transmitted by blood transfusion. According to WHO recommendations, donated blood must be screened for HBV, in addition to human immunodeficiency virus (HIV), hepatitis C virus (HCV) and syphilis, prior to use [1]. The prevalence of HBV in Ziguinchor is not well known. However, blood donor screening for HBV can be used as an indicator of the prevalence of hepatitis B in the general population. This study was conducted in order to determine the prevalence of HBsAg carriage among blood donors in Ziguinchor and to identify factors associated with HBsAg carriage.

Material and Methods
Ziguinchor is located in the southern region of Senegal. It is separated from the rest of the country by the Gambia to the north, Guinea-Bissau to the South, and the Atlantic Ocean to the west. It is an isolated and remote area with unique sanitary conditions and epidemiological characteristics. Our study was conducted in the laboratory of the Ziguinchor Regional Hospital which has a small blood transfusion unit. Donations are made daily at the unit or during campaigns organized outside the hospital. We conducted a retrospective study using data from all blood donations received in this unit from the January 1 st to December 31 st , 2013. Individuals who were <16 or >60 years of age, those with diabetes or recent high-risk sexual activity, and women who were pregnant, breast-feeding, or menstruating were not eligible to donate blood. For all donors, information regarding age, sex and the type of donor was collected.
We distinguished between three types of donors, "regular voluntary donors" who regularly donate blood and have a blood donor card, "new voluntary donors" who donated blood for the first time, and "replacement donors" who were parents or relatives of a patient in need of a blood transfusion.
We used the RapidSignalTM HBsAg Serum / Plasma Dipstrip (Orgenics ltd ISRAEL) provided by the National Blood Transfusion

Journal of Infectious Diseases and Therapy
Center. This is a qualitative rapid test used for the detection of HBsAg in whole blood, serum or plasma. The membrane is pre-coated with anti-HBs antibodies (anti-HBsAb) on the test line (T) region of the strip. During testing, serum or plasma containing HBsAg reacts with the particle coated with anti-HBsAb and generates a colored line. A control line (C) confirms the validity of the test. Results are available within 15-30 minutes. This test has a higher sensitivity (99.8% [98.6% -100%]) and specificity (99.2% [98.1-99.7%]) compared to a reference test as HBsAg Enzyme ImmunoAssay (HBsAg EIA). The sensitivity and specificity of HBsAg EIA are 97.8% and 97.9% respectively [4]. The manufacturer notes that the limitations of the test are that it is qualitative rather than quantitative and very low HBsAg concentrations (<1 ng/mL) cannot be detected.
Data were entered and analyzed with EPI Info 3.3.5 software. Chisquare or Fisher tests were used where appropriate and a p-value <0.05 was considered significant.

Results
A total of 2,122 blood donors were included, of which 1715 (80.8%) were male and 407 (19.2%) were female. HBsAg carriage was identified in 256 donors, resulting in a prevalence of 12.1%.
The characteristics of HBsAg carriers are summarized in Table 1. HBsAg carriers were predominantly male (87.1%) with a sex-ratio of 6.7. The majority (82%) were 20-39 years of age. More than half (51.2%) were replacement donors, 39.4% were new voluntary donors, and 9.4% were regular voluntary donors. The majority (60.5%) weighed 60-74 kg. The most common blood group was O+ (53.4%).  There was no association between age and HBsAg carriage.

Discussion
HBsAg carriage is highly prevalent among blood donors in Ziguinchor, with a prevalence of 12 Compared to neighboring countries in the region, the prevalence of HBsAg carriage in our study is comparable to the prevalence reported in the Ivory Coast (11-12.5%) [9], but lower than the prevalence reported in Mauritania (20.3%) [10]. The fact that HBV is highly endemic in this region necessitates more rigorous screening of blood donors and the use of highly sensitive tests. The use of other HBV markers such as Anti HBc and viral DNA would improve screening and reduce the risk of transmission [11]. In a recent study among blood donors in Nigeria, the prevalence of occult hepatitis B as determined by DNA testing was 17% [12]. Our findings demonstrate that high sensitivity screening of donated blood, including screening for occult HBV, is indicated in our population. This is of particular importance for individuals in need of repeated transfusions, such as those with sickle cell disease or renal insufficiency, who are at greater risk of transfusion related transmission.

Distribution of carriers by sex
In our study the rate of HBsAg carriage was higher among men (13%) compared to women (8.1%). A higher prevalence of carriage among men has been noted in other studies in the sub-region [9,10,13]. The male predominance may be the result of high risk exposures during recreational or professional activities.

Distribution of carriers by type of donor
We found that the prevalence of HBsAg carriage was significantly lower among regular voluntary donors compared to new voluntary donors and replacement donors. This finding is of particular importance in resource-limited settings and suggests that when blood supply is limited, blood from regular voluntary donors may pose the lowest risk. Our findings are in line with the WHO statement that regular voluntary donors are safer [14]. However, our findings differ from a recent study in Ghana which suggested that replacement donors may provide a low-risk blood supply when resources are scarce [15]. The observed positive results among regular voluntary donors in our study could indicate acute infection. This finding suggest that immunization against HBV should be consider for all non-HBsAg carriers regular blood donors who are not protected.

Conclusion
This is the first study to report the prevalence of HBsAg carriage in Ziguinchor, Senegal. We found a high prevalence of HBsAg carriage in our population of blood donors, especially among male donors, new voluntary donors, and replacement donors. Future studies are needed to provide a greater understanding of additional factors associated with HBsAg carriage in this region. Our blood banks need greater resources to provide high-quality donor screening and ensure access to a safe and sufficient blood supply for our region. The utilization of new markers such as anti-HBc Ab and viral DNA will enhance the detection of hepatitis B in donors. Furthermore, enhanced advocacy is needed to encourage regular blood donation within the community and the general population.