Brucellosis seroprevalence among high-risk occupational groups in Nigeria: a systematic review and meta-analysis (2001-2025)

Brucellosis is a neglected occupational zoonosis in Nigeria, driven by a large livestock sector and widespread exposure in high-risk settings. This systematic review and meta-analysis, conducted in accordance with the PRISMA 2020 guidelines, synthesizes evidence from 2001 to 2025 to estimate group-specific occupational seroprevalence of brucellosis in Nigeria. We systematically searched PubMed, Scopus, Medline, Web of Science, African Journals Online, Embase, and Google Scholar, using ResearchGate as a supplementary source of gray literature, for studies reporting laboratory-confirmed human seroprevalence among occupational and nonoccupational comparator groups. We computed pooled estimates with 95% confidence intervals (CIs) using a random-effects (DerSimonian–Laird, logit-transformed) meta-analysis. The final corrected dataset comprises 15 studies from 11 named Nigerian states and the Federal Capital Territory (FCT), spanning 5 of Nigeria's 6 geopolitical zones (North-Central, North-East, North-West, South-East, South-West); no eligible studies from South-South. Overall pooled seroprevalence was 12.8% (95% CI: 8.6–18.6%; I² = 94.0%; raw seroprevalence 13.6%, 508). Among nine occupational group studies, pooled seroprevalence was 13.7% (95% CI: 7.8–22.7%), with the highest among abattoir/slaughterhouse workers (27.2%, 95% CI: 21.3–34.1%), followed by livestock/cattle farmers (10.3%), nomadic herdsmen/pastoralists (10.0% and 0.7%, two divergent single- study estimates), and butchers (5.2%). Six non-occupational comparator studies pooled to 11.4% (95% CI: 6.6–20.5%), ranging from 0.7% among pastoralists to 28.7% among febrile/malaria patients in Enugu (South- East) and 19. 0% among women with miscarriage in Zaria. A high-quality-only sensitivity analysis (NOS ≥ 7/9) yielded 17.1% (95% CI: 11.0–25.7%). Key risk factors included handling aborted fetal tissue, raw dairy consumption, lack of personal protective equipment (PPE), and unregulated livestock migration. Abattoir workers remain the clearest, most robustly supported occupational risk group in the Nigerian evidence base and should be the priority target for mandatory PPE enforcement, targeted screening, and public health messaging.