Blood transfusion is a vital component of modern healthcare systems, providing life-saving support in trauma, surgery, obstetric emergencies, and the management of severe anemia and hematological disorders. However, in sub-Saharan Africa (SSA), ensuring the safety of transfused blood remains a persistent public health challenge. Despite notable improvements in blood screening infrastructure and donor recruitment practices, transfusion-transmissible infections (TTIs) including hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), and syphilis continue to contribute substantially to morbidity and mortality across the region [1][2]. These infections not only endanger recipients but also reflect broader systemic vulnerabilities in blood safety surveillance, laboratory capacity, and community health education.

In addition to these well-characterized viral and bacterial threats, parasitic infections such as filariasis remain endemic in many areas of Central and West Africa. Filarial parasites, primarily Wuchereriabancrofti and Loaloa, may circulate as microfilariae in peripheral blood and therefore pose an underrecognized risk for transfusion safety [3]. While transmission of microfilariae through transfusion is considered rare, the presence of these parasites in donor blood highlights ongoing gaps in pre-donation screening, particularly in regions where vector-borne diseases and TTIs co-occur. Yet, data quantifying the prevalence of microfilariae among blood donors remain extremely limited across much of Africa, including Gabon.

First-time blood donors are of particular epidemiological interest, as they often exhibit higher infection rates compared with repeat donors. This difference is attributed to the “healthy donor effect”, where regular donors undergo repeated health assessments, while first-time donors represent a more heterogeneous and less pre-screened population [4][5]. Surveillance among first-time donors therefore provides a crucial indicator of community-level infection patterns and the effectiveness of pre-donation screening protocols. In Gabon, evidence regarding microfilarial carriage among blood donors is scarce, with only a few recent reports documenting the persistence of filariasis despite ongoing control programs [6]. Anemia remains another major concern in donor health and transfusion safety. Its prevalence in SSA reflects a complex interplay of nutritional deficiencies, infectious diseases such as malaria, and chronic parasitic infections. Anemia not only leads to donor deferral but may also signal underlying systemic or parasitic disease burdens [7][8]. The association between anemia and filarial infection is biologically plausible, as chronic microfilaremia can induce inflammation and contribute to iron dysregulation and erythropoietic suppression [9][10]. However, this interaction remains poorly characterized in the context of blood donor populations.

Understanding the overlap between TTIs, anemia, and parasitic infections among blood donors is crucial for strengthening transfusion safety and informing national blood service policies. In endemic regions such as Gabon, where parasitic and viral infections coexist, comprehensive epidemiological data are essential to guide evidence-based screening strategies. To address this gap, the present study aimed to assess the prevalence and temporal trends of TTIs, microfilariae, and anemia among first-time blood donors in Lambaréné, Gabon, between 2018 and 2021, and to identify demographic and hematological factors associated with microfilaremia.

This study provides a comprehensive assessment of transfusion-transmissible infections (TTIs), anaemia and microfilariae carriage among new blood donors in Gabon. The results revealed a strong male predominance (89%) and a high proportion of young donors aged 17 to 29 years (45.7%), which is consistent with previously reported demographics in Gabon and throughout sub-Saharan Africa [6][11][12][13]. This trend likely reflects sociocultural norms and the higher frequency of exclusions among women due to iron deficiency anaemia [14]-[16]. Targeted strategies to promote donor retention and improve iron supplementation could help rebalance the donor demographic. The predominance of blood group O (64.9%) is consistent with previous studies conducted in Gabon and Central and West Africa, where the frequency of group O exceeds global averages [17]-[19]. Although blood group distribution does not directly influence transfusion safety, understanding it is essential for managing blood stocks and planning compatibility in resource-limited settings.

The prevalence rates of STIs observed in this study (HBsAg 4.3%, anti-HCV 2.5%, HIV 0.2% and syphilis 2.7%) are consistent with previous findings in Gabon and comparable African settings [2][20][21]. These results confirm that STIs remain a persistent barrier to transfusion safety in the region, despite improvements in donor screening and testing algorithms. Strengthening confirmatory testing capacities and integrating molecular tests for HBV and HCV could further improve detection accuracy.

The prevalence of microfilaremia (4.5%) observed in new donors is remarkable and highlights the need to recognise parasitic infections as an underestimated element of transfusion safety. Although a significant decline was observed between 2018 and 2021, this trend may reflect the cumulative effect of community control efforts, including mass administration of ivermectin and vector management initiatives, as reported in other endemic regions of Africa [22]. Marked heterogeneity was observed between donation sites, with a significantly higher prevalence of microfilaremia among CHRGRL donors compared to HAS donors (OR 0.16; p < 0.001). This disparity may reflect ecological and occupational differences between donor recruitment areas. Donors from the CHRGRL region, who often reside in forested environments, are more exposed to filarial vectors, while the HAS population, dominated by fishing and sand extraction communities, is located in lake areas less conducive to vector proliferation [23]. Variations in diagnostic practices or differences in donor recruitment strategies could also contribute to this disparity [24].

The fluctuations observed in the prevalence of anaemia, particularly the peak reached in 2020 (48.5%), likely reflect the indirect impact of the COVID-19 pandemic on health systems and population well-being. Disruptions to health services, reduced access to malaria prevention, and food insecurity during this period have been documented throughout sub-Saharan Africa and may have contributed to the increase in anaemia prevalence [25]-[28].

It is important to note that this study demonstrated a significant association between anaemia and microfilaremia (OR = 1.83; p < 0.01), corroborating previous findings reported in Gabon. Microfilariae have been described as potentially contributing to the development of anaemia by competing with host cells for nutrients essential to their growth and survival [6]. Several biological mechanisms could explain this relationship. Chronic filarial infection can lead to systemic inflammation and increased hepcidin expression, resulting in inflammatory anaemia [7][8]. In addition, splenic hypertrophy and hypersplenism associated with chronic helminthiasis may promote the sequestration and destruction of red blood cells [29]. Co-endemicity with malaria or intestinal helminths may further exacerbate the burden of anaemia [30]. Conversely, a study conducted in Congo found a strong association between Loa loa microfilarial density and anatomical hyposplenism, suggesting that regional and host-related factors may influence the haematological response to infection [31].

The results suggest that the current national blood donor eligibility algorithm based on systematic screening for HIV, hepatitis B and C viruses, and syphilis should be strengthened to include routine screening for Plasmodium species and microfilariae.

Several studies have identified these parasitic infections as risk factors for, or conditions associated with, anemia. However, the detection of anemia during donor screening constitutes grounds for rejection or temporary deferral of blood donation. The high prevalence of anemia among blood donors in Gabon highlights the challenges in maintaining an adequate and sustainable supply of high-quality blood products. Furthermore, these parasitic infections are recognized as transfusion-transmissible and have been implicated in the occurrence of per- and post-transfusion reactions [6][7][9].

Integrating systematic screening for parasitic infections into the current blood donor eligibility algorithm could help reduce the risk of such reactions. It would also facilitate the accurate identification of parasite-related anemia and support the implementation of appropriate, evidence-based corrective measures. Ultimately, this approach could expand the pool of eligible donors while minimizing the risk of transfusion-transmitted parasitic infections.

From a transfusion safety perspective, the coexistence of microfilariae and significant transfusion infections such as HBV, HCV, HIV or Treponema pallidum presents a potential risk, particularly for immunocompromised recipients. Although transfusion-transmitted filariasis is rare, documented cases confirm its plausibility [3][32]. Furthermore, helminth-induced immune modulation via Th2 polarisation and regulatory T cell activation could potentially alter recipients’ immune responses to co-transmitted pathogens [33][34]. This interaction warrants further immunohematological research in endemic regions.

This study has several limitations. Its retrospective and descriptive design does not allow us to establish a causal link between microfilaremia, anemia and other variables. The lack of detailed clinical and nutritional data (e.g. folate, vitamin B12, malaria, intestinal helminths) limits our understanding of the determinants of anemia in this population. Furthermore, reliance on rapid diagnostic tests (RDTs) for the screening of blood-borne infections may introduce bias by potentially underestimating their true prevalence. Compared with laboratory-based assays such as ELISA and PCR, RDTs generally have lower sensitivity, particularly during the early or latent (window) period of infection, when detectable levels of antigens or antibodies may not yet be present. The results cannot be extrapolated to the general population, as blood donors represent a selected subgroup. Finally, the COVID-19 pandemic may have influenced donor availability, demographic profile, and health status, complicating the interpretation of fluctuations in anemia.

In summary, this study highlights a noteworthy prevalence of microfilaremia (4.5%) among first-time blood donors in Gabon and demonstrates its significant association with anemia. While the prevalence of microfilaremia showed a steady decline between 2018 and 2021, anemia rates fluctuated, peaking during the COVID-19 pandemic. The predominance of young male donor’s mirrors trends observed throughout sub-Saharan Africa. These findings emphasize the need to integrate parasitic disease surveillance particularly filariasis into transfusion safety frameworks in endemic regions. Monitoring donor hemoglobin levels and strengthening pre-donation screening for both TTIs and parasitic infections are essential to safeguard both donor health and recipient safety. Continued investment in diagnostic standardization, community-level vector control, and donor education will be key to achieving sustainable improvements in blood transfusion safety in Gabon and across the region.

CB and SP conceived and designed the study; SP and RB acquired the data; SM analyzed and interpreted the data; SP and CB drafted the manuscript; BMN, CB and DI critically reviewed the manuscript for important intellectual content; all authors gave approval of the version to be submitted; all authors agree to be accountable for all aspects of the work.

All authors concur with the submission presented by the corresponding author.