Pigeons as overlooked vectors: investigating Campylobacter carriage across different management systems

BACKGROUND: Campylobacter spp. are among the leading bacterial pathogens responsible for foodborne illness worldwide, yet the role of pigeons as reservoirs remains insufficiently investigated compared with poultry and livestock. RESULTS: In this study, we examined 450 pigeons from three distinct groups-backyard, racing, and ornamental flocks-to assess the prevalence, virulence gene repertoire, genotypic diversity, and antimicrobial resistance (AMR) of Campylobacter isolates. The overall prevalence reached 29.1%, with the highest rates observed in backyard pigeons (37.3%), followed by racing (28.7%) and ornamental (21.3%) birds. Species identification revealed that C. jejuni predominated (85.5%), while C. coli accounted for 14.5% of isolates. Virulence genes were widely distributed, with universal presence of flaA, high frequencies of adhesion and invasion markers (cadF, ciaB), and the complete cdtABC cluster in 72.5% of isolates, whereas GBS-associated genes were less frequent. Sequencing of the flaA-SVR region revealed 48 alleles, several of which were previously associated with wild birds, livestock, or poultry, demonstrating genetic overlap across ecological compartments. Antimicrobial resistance was widespread, with tetracycline (64.1%) and fluoroquinolone resistance (ciprofloxacin 54.2%, erythromycin 49.6%) being most common, and gentamicin resistance remaining less frequent (14.5%). Multidrug resistance (MDR) was detected in 22.1% of isolates, with backyard pigeons harbouring the greatest proportion of MDR strains. CONCLUSIONS: These findings indicate that pigeons maintain genetically diverse and virulent Campylobacter populations with relevant AMR profiles. The high prevalence of these pathogens in pigeons, often exceeding that reported in wild birds, combined with pigeons' close contact with humans and domestic animals, underscores their role as an important yet underappreciated reservoir in the epidemiology of campylobacteriosis.