Hepatitis B Virus and Plasmodium falciparum Co-Infection Among Pregnant Women in Gabon: Prevalence, Biochemical Impact, and Antagonistic Replication Dynamics

<b>Background:</b> Hepatitis B virus (HBV) and <i>Plasmodium falciparum</i> infections remain major public health concerns in sub-Saharan Africa, especially among pregnant women, who are particularly vulnerable due to physiological immunomodulation. While mono-infections are well documented, the burden and biological consequences of HBV-<i>P. falciparum</i> co-infection during pregnancy remain under-investigated in Gabon. <b>Aim:</b> To determine the prevalence, clinical relevance, and biochemical impact of HBV-<i>P. falciparum</i> co-infection among pregnant women in Libreville, Gabon, and to explore the interaction between viral and parasitic replication. <b>Methods:</b> A prospective cross-sectional study was conducted between May 2022 and May 2023 at the CHUME-FJE Laboratory in Libreville. Serum samples were tested for HBsAg using rapid diagnostic tests and ELISA confirmation; HBV surface antigen (HBsAg) levels were quantified by electrochemiluminescence (ECLIA). Parasitemia was assessed by rapid diagnostic test, microscopy, and the Lambaréné thick blood film method. Liver function parameters (ALT, AST, ALP, and GGT) were evaluated using an automated biochemistry analyzer. Statistical analysis included Mann-Whitney U tests, chi-square tests and Spearman's rank correlation coefficient with significance set at <i>p</i> < 0.05. <b>Results:</b> Of the 222 pregnant women enrolled, HBV infection was detected in 9 cases (4.05%). Among these, 6 (2.7% of the study population) were mono-infected with HBV, while 3 (1.35%) were co-infected with <i>Plasmodium falciparum</i>. <i>P. falciparum</i> parasitemia was detected in 58 cases (26.1%). Biochemical profiles revealed elevated transaminases (AST) in HBV mono-infected women, while liver enzymes remained within normal ranges in co-infected individuals. Quantitative analyses demonstrated an inverse relationship between HBV surface antigen levels and <i>P. falciparum</i> parasitemia. This observation could suggest an antagonistic replication dynamic. However, the relationship was not statistically significant (Spearman's ρ = -0.5, <i>p</i> = 0.67). <b>Conclusions:</b> HBV and <i>P. falciparum</i> co-infection occurs in a small but clinically relevant proportion of pregnant women in Gabon. The observed inverse replication pattern suggests a potential biological antagonism that may modulate disease severity. These findings although preliminary, could highlight the need for integrated screening and management strategies during pregnancy to improve maternal and fetal outcomes.