Prevalence of hepatitis B among pregnant women in Libreville, Gabon

Background Hepatitis B virus (HBV) infection is one of the major public health problems worldwide. In pregnant women, there is a risk of mother‑to‑child transmission (vertical transmission) of the infection. The contaminated new‑ born will most often remain a chronic carrier. Gabon is part of the highly endemic area for hepatitis B. This study aims to determine the prevalence of hepatitis B in pregnant women at the Estuaire Regional Hospital of Melen, Libreville, Gabon. Material and methods The study was carried out at the Laboratory of the Center Hospitalier Régionale Estuaire Melen (CHREM), over a period of 5 years, from January 2018 to December 2022. It was a retrospective and pro‑ spective study ranging from January 2018 to December 2022. For the prospective study, the data was collected in the CHREM Laboratory library, by using registers and filing cabinets. For the prospective study, blood samples were taken and analyzed using Abbott Determine ® HBsAg kits and the BioMérieux mini Vidas system. The variables studied were age, HBs status, profession, level of study, and residence. The data collected was entered into an Excel file (Microsoft Office 2016) and analyzed using XLSTAT 2016.4.01 and Epi Info ™ 7.2.5 software and expressed as means and percentages. Results A total of 1615 pregnant women seen in the CHREM laboratory department were included in the study. Of which, 315 were diagnosed as HBsAg carriers, representing a prevalence of 8.36%. Depending on the year, the high‑ est prevalence was observed in 2019 with 20 positive cases out of 267 women screened, i.e., 9.38%. Depending on the districts, the highest prevalence was found in the Essassa and Plein Ciel districts with 16.43% and 18.18%, respectively. According to the age groups, the highest prevalence was observed in the age group 26–30 with 10.16% ( p = 0.075) out of 492 patients screened. Depending on the profession, the prevalence was higher among female stu‑ dents with 21.97% ( p = 0.020). According to marital status, unmarried had the highest prevalence with 8.8% ( p = 0.064). And according to nationality, women of Gabonese nationality had a higher prevalence with 9.52%. Conclusion Antenatal transmission of HBV is high in Libreville. The inaccessibility of antiviral therapy for viral hepatitis B makes the immunization of mothers and children a priority in Gabon.


Background
Hepatitis B virus (HBV) infection is one of the main public health problems in the world [1], more than two billion people have been or are infected with this virus.The WHO also estimates that 296 million people were living with chronic hepatitis B in 2019 and counts 1.5 million new infections each year.In 2019, hepatitis B caused approximately 820,000 deaths, mainly from cirrhosis or hepatocellular carcinoma [2].In Africa, the prevalence of HBV is high with disparities between countries, regions, and depending on rural or urban living environments.More than 8% of HBV surface antigen (HBsAg) prevalence is estimated in sub-Saharan Africa, one of the most endemic regions [3].Mother-to-child transmission of the hepatitis B virus is the main cause of chronic HBsAg carriage [4].
Children with chronic hepatitis B develop liver damage in two-thirds of cases, these lesions can progress to cirrhosis or and hepatocellular carcinoma, and those regardless of the presence or absence of cirrhosis [5].Hepatitis B serology is compulsory for all pregnant women because of the major risk of materno-fetal transmission during childbirth [6].
When the search for HBsAg is positive in the mother, the newborn must receive from birth, by intramuscular route, a first injection of vaccine and an infection of anti-HBs immunoglobulins [4].
Stopping vertical transmission of HBV is a central pillar of the global Triple Elimination Initiative which aims to eliminate mother-to-child transmission of three common infections in low-and middle-income countries: HIV, syphilis, and hepatitis B virus [2].The management of this infection in our regions faces numerous socio-economic and cultural difficulties.
In Gabon, a country in Central Africa, the prevalence of hepatitis B surface antigen in the general population is above 8%, but nothing is known about the diversity of HBV in pregnant women [7].Gabon is part of the highly endemic zone for hepatitis B. This is why this study set itself the objective of determining the prevalence of hepatitis B among pregnant women consulting at the Center Hospitalier Régionale Estuaire de Melen.

Study population
This study was carried out at the Laboratory of the Center Hospitalier Régionale Estuaire Melen (CHREM), over a period of 5 years, from January 2018 to December 2022.It is a retrospective and prospective study from January 2018 to December 2022, aimed at screening for possible HBV infection.The study concerned all pregnant women who came for a consultation at CHREM.

Inclusion and non-inclusion criteria
Included in this study was any pregnant woman seen in the CHREM laboratory for HBV screening and who gave their informed consent to participate in our study.On the other hand, all examinations other than that due to HBV infection were not selected.

Data collection and sampling
For the prospective study, the data were collected at the CHREM Laboratory library, by using registers and binders from January 2018 to November 2022.The registers made it possible to have the sociodemographic data of the patient, i.e., the name, first name, age, with the anonymity code, the medical prescriber.The binders, for their part, provided information on the type of examination requested and the reports of the HVB serology.All HBV serologies requested were recorded during this period, and were classified by frequency according to the years, according to the prevalence of hepatitis B infection.
The study involved pregnant women.Candidates for systematic HBsAg screening at CHREM over the period studied.
Informed consent was signed by each patient after an explanation of the study.After obtaining consent, samples were taken from the bend of the elbow in a dry tube or a tube containing lithium heparin.

HBV serodiagnosis using the Abbott Determine ® HBsAg test
The blood samples obtained after collection were subjected to centrifugation at 3500 rpm for 10 min.The serum obtained was used for direct diagnosis using Abbott Determine ® and Mini Vidas BioMérieux reagents.Briefly, 50 µl of serum was dispensed onto the sample deposit area (symbol: arrow) using a micropipette.After a minimum of 15 min (maximum: 60 min), the result has been read.The result was considered positive if two red bars appeared, one in the control window (labeled "control"), and the other in the patient window (labeled "patient") on the strip.On the other hand, the test was considered negative if only one bar appeared in the control window.Furthermore, the result was considered invalid if a red bar appeared in the/patient window and did not appear in the control window, but also if no bar appeared after depositing the serum on the strip.All invalid tests have been redone.

Assay on the BioMérieux mini Vidas system
For the mini Vidas assays, the reagents were brought to room temperature 30 min before use.The standard identified by "S1, " was used in duplicate.The positive control was identified as C1, and the negative control was identified as C2.The standard, controls, and samples were homogenized using a vortex mixer.The volume recommended by the manufacturer for the standard, the sample, or the control was distributed into the sample well of the cartridges depending on the analysis.Then the cones and the cartridges were placed in the automaton.The concordance of the codes (colors and letters) between the cone and the cartridge has been checked.The analysis was then started.All the steps were managed automatically by the PLC.Results were obtained after 90 min for total HBc II antibody and HBe antigen.At the end of the analysis, the used tips and cartridges were removed into an appropriate container.
For HBCT: i < 1: Presence of anti-HBc antibodies; 1 < i < 1.4: Equivocal result; i > 1.4: Absence of anti-HBc antibodies.Any equivocal result must be confirmed on a second sample.

Statistical analysis
The data collected was entered into an Excel file (Microsoft Office 2016) for statistical analysis.The data was divided into qualitative and quantitative variables.The results of the qualitative (nominal) variables are given in counts (n) and percentages (%).As for the quantitative variables, the data were expressed as a mean and analyzed using XLSTAT 2016.4.01 and Epi Info ™ 7.2.5 software and expressed as means and percentage.

Distribution according to age groups
The results in Table 1 indicate that the highest prevalence was observed in the age group 26-30 with 10.16% (p = 0.075) out of 492 patients screened.The average age was 27 years with the extremes ranging from 15 to 40 years.

Classification according to social status
The data in Table 2 show that the prevalence among female students was the highest with 21.97% (p = 0.020) out of a number of detected cases of 132.It indicates that unmarried were the most represented and had the highest seroprevalence with 8.8% (p = 0.064).In addition, it also indicates that the highest seroprevalence was found among women of Gabonese nationality with 9.52% (p = 0.15).

Classification of prevalence according to years
The classification of prevalences according to the years indicates that the highest prevalence was observed in pregnant women in 2019 where there were 20 positive cases out of 267 women screened, i.e., 9.38% (p = 0.68).Then come the prevalences for the years 2020 and 2022 with 8.39% and 8.81%, respectively (Table 3).

Classification of prevalence by neighborhood
The results of the classification of prevalences according to neighborhoods are recorded in Table 4 and show that the highest prevalences were found in the Essassa and Plein Ciel neighborhoods with respectively 16.43% (p = 0.045) and 18.18% (p = 0.032) out of a respective number of screened cases of 97 and 11.

Discussion
Hepatitis B is a viral infection that damages the liver and can lead to acute infection or chronic infection of this organ.It is a disease caused by a DNA virus, the hepatitis B virus [2].Hepatitis B is a global public health problem that can infect anyone regardless of gender and age.The purpose of this study was to assess the prevalence of hepatitis B in pregnant women, and this assessment was made at the Center Hospitalier Régional Estuaire de Melen with the Abbott Determine ® HBsAg test, which is a qualitative immunological test in visually read vitro for the detection of HBsAg in human serum, plasma, or whole blood.The search for total anti-HBc antibodies and HBe antigen was carried out systematically in all HBsAg-positive patients using the MiniVIDAS BioMérieux, which uses the ELFA (enzyme-linked fluorescent assay) technique to perform immunoenzymological assays by inhibition (HBCT) and sandwich (HBE) with final fluorescence detection.
From this evaluation, it appears that the overall prevalence of hepatitis B within the study population is 8.36%.This prevalence is similar to that reported in 2018 by Ousmane et al. (8.4%) in a study of pregnant women and their newborns in Niamey, Niger [8].A similar prevalence (8.2%) was also found in Nigeria in urban areas by Ajuwon et al. [9].and Congo (7.2%) in 2023 [10].But these results are lower than those reported in a study carried out in Benin (14.02%), [10], Cameroon (18.4%) in 2022 [11], and Mali (14%) in 2022 [12].However, our prevalence is higher than that reported by Kpossou et al. in 2020 (6%) in Benin [13].This prevalence does not necessarily reflect the reality of HBV in pregnant women consulting at the Center Hospitalier Régionale Estuaire de Melen and could be higher given the non-systematic performance of the HBsAg assay by pregnant women followed in this Center.
The overall prevalence is consistent with that of the WHO, which classifies Gabon among the countries of high endemicity, that is to say with a prevalence greater than 8%.
By distributing the seroprevalence by year, it appears that the year 2019 had the highest seroprevalence, i.e., 9.38%.A similar prevalence (9.08%) was reported in Benin by Kodjo in 2015 [14].
In a study carried out in Cameroon, a similar prevalence (9.7%) was also found [15]; however, the prevalence in this study is lower than that reported by Khaidjatou et al. in 2019 on the factors associated with viral hepatitis B among pregnant women in Benin which was 14.02% [16].But it is higher than the 7.3% reported by Adegbesan et al. in 2015 among pregnant women at the antenatal clinic of a tertiary hospital in Lagos [17].
The classification of infection according to neighborhood shows that the Essassa and Plein ciel neighborhoods have the highest seroprevalence.This could be explained by the precarious living conditions of the inhabitants in these neighborhoods and by the sexual depravity of young people in these neighborhoods.This could also be explained by the fact that these neighborhoods are areas where there is a high risk of contamination through promiscuity.A similar prevalence (18.4%) was reported in the Far North Cameroon by Abdoul Rahamane Njigou Mawouma et al. in 2022 [11].By ordering the seroprevalence according to age groups, we see that patients over 25 years old have the highest prevalence.This was not the case in our sample, but this result suggests a higher prevalence according to age.In the present study, the 26-30-year-old age group had the highest seroprevalence; this age group corresponds to a period of sexual activity often without protection, which would be favorable to the transmission of HBV.
The distribution of seroprevalence of HBV infection according to nationality shows a higher prevalence among Gabonese women than among non-Gabonese women.This could be due to the fact that the study was carried out in Gabon, justifying a greater representation of Gabonese women.
The arrangement of seroprevalence according to occupation of pregnant women allows us to observe that students are the most affected with a seroprevalence of 21.97%.The prevalence found in this population is higher than that noted in a random sample of Senegalese soldiers which was 10% [18].
The distribution of infection according to marital status shows that the seroprevalence of hepatitis B virus infection was high among unmarried women.This could be due to the difficult living conditions encountered in these patients, because the financial difficulties would push the unmarried to the multitude of sexual partners often to be able to get by financially.

Conclusion
Gabon is located among the countries with high endemicity by the WHO for viral hepatitis B. According to the present study, the seroprevalence of HBV among pregnant women was 8.36%.This result is of great importance for measuring the effectiveness of prevention strategies, hence the need to strengthen information, education, and communication programs regarding HBV and all sexually transmitted infections.Screening for hepatitis B must be systematic in pregnant women and those at risk.This approach is important for determining chronic carriers of HBV which will make it possible to detect the disease at an early stage, thus increasing the chances of cure or stabilization.

Table 1
Distribution of the study sample according to age group

Table 2
Distribution according to profession, marital status and nationality of pregnant women

Table 3
HBs antigen seroprevalence by year

Table 4
Seroprevalence of HBV infection according to neighborhood