Feral pigeons as reservoirs of zoonotic pathogens in the urban environment: Spatial clustering and molecular evidence

Abstract

Feral pigeons ( Columba livia f. domestica ) are common inhabitants of cities and often come into close contact with humans. This study aimed to investigate the prevalence and spatial distribution of zoonotic pathogens in feral pigeons, with emphasis on Chlamydia psittaci , Mycobacterium avium complex and Salmonella enterica . Given its emergence in passerine birds, Trichomonas gallinae was included, although it is not considered a zoonotic species. A total of 175 pooled faecal samples representing 875 individual droppings were collected from 35 localities across three urban zones. Two multiplex real-time PCR (qPCR) assays were developed and validated to detect the presence of target organisms. Spatial clustering of positive findings was analysed using hierarchical clustering based on geographic distances. C. psittaci was the most prevalent pathogen, found in 20.6% of faecal samples. T. gallinae was detected in 9.7%, S. enterica in 4.0%, and M. avium subsp. hominissuis in 1.1%. M. avium subsp. avium was not detected. Based on average pairwise geographic distances, statistically significant spatial clustering of C. psittaci -positive flock was shown, suggesting non-random distribution of infection. The study highlights urban feral pigeons as potential carriers of zoonotic pathogens, particularly C. psittaci , which shows spatial clustering in densely populated urban areas. The results support the need for monitoring potential zoonotic risks associated with urban pigeon excretions to human health. These findings provide essential baseline data for public health authorities and contribute to risk assessment and urban wildlife management strategies in Central European cities.