Our study was carried out at a mining facility located in Moanda, in the Haut-Ogooué province of Gabon. It is a manganese mining and processing company operating open-cast mines.

This is a retrospective, cross-sectional, descriptive and analytical study based on a review of workers’ medical records held by the company’s occupational health service during the period from 1st October to 31st December 2023.

The study population consisted of all the records of employees of the mining company who visited the occupational health service during the study period. The study included all records of employees at the mining company found in the company’s occupational health department during the study period, provided that the employees had been with the company for at least one year, were permanent staff, and had undergone hepatitis B serology testing. Incomplete records and those of employees who were absent during the study period were excluded. Of the 2002 employees, we recorded 1504 workers who attended their medical check-ups, giving a participation rate of 75.12%, all of whom underwent the HBsAg test.

The dependent variable was a positive result for hepatitis B virus infection. The independent variables were: sociodemographic factors (age, gender, length of service, occupation, marital status).

Serological tests were carried out in a clinical laboratory. The biological parameter analysed was the HBs antigen using the Accu-tell® rapid test. Positive results were confirmed using the Vidas automated analyser; in cases of doubt, a PCR test was performed. The kit components and samples were brought to room temperature (15˚C - 30˚C). A 100 µL sample of plasma or serum was placed in the sample well. Results were interpreted after 15 to 30 minutes. The test was considered positive when a coloured band appeared on the control line (C) and another on the test line (T). All data were collected from the occupational health service (OHS) records.

In addition, telephone calls were essential for obtaining further information (marital status). The data were entered into Excel for Windows 2010 and analysed using R version 4.4.1. For the descriptive results, the data were expressed as counts and percentages for the qualitative variables. Quantitative variables were expressed by calculating the mean, standard deviation and extreme values (minimum and maximum). The tables and graphs were produced using Microsoft Office Excel. Bivariate analysis was used to highlight the relationships between the variables, with a significance level set at 5% (p = 0.05). The statistical tests used were Pearson’s chi-square test and Fisher’s exact test for qualitative variables where the conditions for the chi-square test were not met. The Wilcoxon-Mann-Whitney test was used to compare distributions between groups for quantitative variables. To investigate an association between the dependent variable (HBsAg) and a presumed risk factor, logistic regression was performed. In the multivariate analysis, the covariates were considered at a significance threshold of p < 0.20. The reference method took into account the fact that a significant number of HBsAg-positive individuals were found among this group of single people.

In the study, any worker who tested positive in the qualitative HBsAg test was considered to be a carrier of the hepatitis B virus (HBV).

The confidentiality and anonymity of the study participants were guaranteed. The study had been approved by the company’s management.

A total of 1504 workers were included out of a workforce of 2002 at the time of the study, representing a participation rate of 75.12%. The average age was 42 ± 7.13 years, with ages ranging from 22 to 60. The 30 - 40 and 41 - 50 age groups accounted for 42.3% of the sample respectively. Men were in the majority, with a male-to-female ratio of 7.9. Married workers numbered 345 out of 1504, or 22.9%.

In our study, 186 out of 1504 tested positive for HBsAg, representing a prevalence of viral hepatitis B of 12.4%.

Table 1 shows the socio-demographic and biological characteristics of the workers.

Table 1. General characteristics.

HBsAg-positive cases were more common among men (181/186, 97%) than among women (5/186, 2.7%); this difference is statistically significant (p = 0.001). Men are 5.62 times more likely to be exposed to hepatitis B than women (OR = 5.62 [2.53 - 16]). Unmarried individuals were more affected, with 135/186 (72.6%), than married workers. However, there was no statistical correlation based on marital status. Manual workers were the socio-occupational group most likely to test positive for HBsAg, although this showed no statistical correlation. Table 2 summarises the results of the bivariate analysis according to socio-demographic characteristics. Table 3summarises the results of the multivariate analysis.

Table 2. Results of the bivariate analysis of the AgHBs test and the participants’ socio-occupational characteristics.

Fisher’s exact test; Pearson’s Chi-squared test.

Table 3. Results of the multivariate analysis of the HBsAg test and the participants’ socio-occupational characteristics.

OR = rapport de côtes, IC = intervalle de confiance.

Our study revealed a prevalence of 12.4%. Similar prevalence rates have been reported by Sawadogo A etal. [10] in Bobo-Dioulasso, Pietra V etal. [11] in Nanoro, Agbenu E etal. [12] in Togo, Noubiap JJN etal. [13] in Cameroon, and Kadidj NJIMOGNA in Mali [14], who found prevalence rates of 11.2%, 12.1%, 10.87%, 10.1% and 13.6%, respectively. As for Sbai A etal. [15] in Morocco and Zayet S etal. [16] in Tunisia, they found low prevalences of hepatitis B, at 1.66% and 2% respectively. The difference between our results and those of Sbai A etal. and Zayet S etal. could be explained by the fact that our study region is an area of high prevalence [15]. Men are statistically significantly more exposed to HBsAg (97%) than women (2.7%) (p = 0.001). These findings are consistent with those observed in the general population of Gabon, where men were more affected (8.9%) compared with 5.4% for women. Other studies have reported similar results; for example, Dao S etal. found a prevalence of 63.3% among men in Mali, compared with 36.7% among women [17]. Finally, Tao I etal. [18], Camara Toumin et al [19] and Sbai etal. reported, respectively, a higher prevalence of HBsAg carriage among men than women: 18.58% versus 11.60%; 71% versus 29%; and 2.16% versus 0.90%. In our study, men are at greater risk of infection with viral hepatitis B, probably because the population engages in risk behaviours associated with transmission of this virus to a greater extent than women (alcohol, tobacco, risky sexual behaviour). However, Ouédraogo HG etal. [20], also in Burkina Faso, found a higher prevalence of viral hepatitis B among women than men: 59.8% compared with 40.2%.

The age group most affected was between 33 and 42 years (43%); however, we found no correlation between age and hepatitis B infection. Traoré et al. in Bobo-Dioulasso [7] and Agbenu etal. in Togo [12] found that the age group of workers most affected was between 40 and 50 years old, at 42.86% and 22.73% respectively. However, these various results show that the most affected workers are under 50 years of age and that this is a young and strong workforce. This could, in the long term, have negative socio-economic effects on both the workers and the company. The majority of workers were carriers of HBsAg 140/186 (75%). However, there was no statistical link between HBsAg carriage and occupational category. The high prevalence of hepatitis B among manual workers in our study could be explained by the fact that this group has a relatively low level of education and is less aware of the dangers of the virus compared to managerial staff. Traoré etal. reported the same trend, with a prevalence of hepatitis B among skilled workers who tested positive for HBsAg, who constituted the majority compared to supervisors and managers at 42.86%, 35.71% and 21.43% respectively [7]. However, Pietra V etal. [11] reported findings contrary to our own, with a higher prevalence of HBsAg positivity among supervisory and managerial staff compared with skilled workers—13.3% versus 9.1% respectively—with no statistical association between HBsAg positivity and staff category.

The limitations of the study included the fact that certain employee details in medical records had not been updated and that some workers could not be reached by telephone. The study included only one of the three companies operating in the region. Another limitation is the non-random selection of participants and the cross-sectional nature of the study. The lack of information regarding participants’ hepatitis B vaccination status and behavioural risk factors. The sex ratio was skewed towards men in our study, as we are in an industrial environment where the work involves considerable physical exertion.