From flyways to foci: a systematic review and meta-analysis on the role of birds in the maintenance and global dispersal of ticks and tick-borne pathogens.

Abstract

BACKGROUND: Birds (Aves) are considered to play important roles in the dissemination of ticks and tick-borne pathogens, yet the global extent of their contribution to vector maintenance and long-distance dispersal remains poorly quantified. This study provides a comprehensive global synthesis of bird-associated ticks (BATs) and bird-associated tick-borne pathogens (BATBPs) to characterize the epidemiological roles of birds and assess the resulting public health and biosecurity risks. METHODS: We systematically searched multiple bibliographic databases and GenBank up to February 2025 in accordance with Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Field-based studies reporting bird-tick-pathogen associations were included. Thematic maps showing the geographical distributions of birds, BATs, and BATBPs were produced in ArcGIS, and pooled infestation prevalence was estimated via logit-transformed random-effects meta-analysis with the Hartung-Knapp adjustment. RESULTS: Our synthesis of 772 studies and 86 molecular records identified 185 BAT species and 102 BATBPs across 34 avian orders, representing 77.3% of all global orders. Within the BATBP spectrum, 53.9% are zoonotic, and 99 tick species have documented records of human-biting. Passeriformes (songbirds) hosted the greatest tick diversity (129 species), while Galliformes exhibited the highest pooled infestation prevalence (17.6%; n = 29 studies, m = 18,746 birds). Globally, allochthonous tick records showed relatively high spatial overlap with the Black Sea-Mediterranean and East Atlantic flyways. Critically, we identified a profound surveillance imbalance in Asia, which accounts for only 6.5% of sampling coordinates (26/397 sites) despite exhibiting a high diversity of emerging pathogens. CONCLUSIONS: Birds serve as important contributors to global tick-borne disease epidemiology through local vector maintenance and intercontinental bio-dispersal. They support tick feeding and life-cycle completion and may disperse ticks during migration, facilitating population establishment in new areas. Molecular evidence indicates that birds carry a broad spectrum of tick-borne pathogens; however, the available evidence is largely observational, and experimental validation is required to clarify reservoir competence and transmission. Strengthening integrated One Health surveillance of high-risk hubs, particularly in data-deficient regions such as Asia, is essential to mitigate spillover risk at shifting ecological and migratory interfaces.