Brucellosis in Portugal: A systematic review and meta-analysis of animal and human Brucella spp. infections (2001–2025)

Abstract

Brucellosis remains one of the most widespread zoonoses globally, yet its true burden in Portugal remains insufficiently characterised1,2,3,4. This study presents the first nationwide systematic review and meta-analysis of Brucella spp. infections across both animal and human populations in Portugal, following PRISMA and MOOSE guidelines. A total of 871 studies were screened, yielding 62 eligible reports published between 2001 and 2025, including 6,137,223 animals and 8,724 humans tested for Brucella spp. using various diagnostic methods (e.g., RSAT, ELISA, IFAT, qPCR). Meta-analytical estimates based on a random-effects model revealed a pooled prevalence of 2.42% (95% CI: 1.79–3.13%) in animals and 10.57% (95% CI: 8.80–12.47%) in humans, with high heterogeneity (I² > 84%). The overall pooled prevalence across species was 4.49% (95% CI: 3.77–5.27%), suggesting widespread and underdiagnosed exposure to Brucella spp., especially in occupationally exposed groups and livestock-rich regions. The asymmetry observed in the funnel plot, along with statistically significant results from Egger’s (p = 0.0004) and Begg’s (p = 0.0077) tests, suggests the presence of publication bias and small-study effects. These findings expose critical surveillance gaps and support the implementation of integrated One Health strategies, combining veterinary, medical, and environmental monitoring. The systematic synthesis of seroepidemiological data highlights the urgent need for harmonised diagnostic protocols, cross-sectoral data sharing, and improved awareness of Brucella spp. as a zoonotic threat in Portugal.