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Chlamydia psittaci Was Detected in 20.6% of Brno Feral Pigeon Dropping Samples

Feral pigeon on Freedom Square in Brno, Czech Republic
Research · Disease, parasites & microbiology

Chlamydia psittaci was detected in 20.6% of pooled dropping samples collected from feral pigeons in Brno, Czech Republic, in a study published online on 30 March 2026. The bacterium can cause psittacosis in people. Feral pigeons are the domestic-derived urban form of rock dove (Columba livia), and the researchers examined their droppings for several pathogens of relevance to animal and human health.

Sampling took place from September to November 2024 at 35 localities covering most municipal districts in Brno. The researchers collected 175 pooled faecal samples representing 875 individual droppings across three urban zones. No birds were captured or handled.

Four target organisms were detected

Two multiplex real-time PCR assays were used to test the samples. C. psittaci was the most frequently detected target, occurring in 20.6% of the pooled samples. Trichomonas gallinae was detected in 9.7%, Salmonella enterica in 4.0%, and Mycobacterium avium subsp. hominissuis in 1.1%. M. avium subsp. avium was not detected.

The authors included T. gallinae because it is a re-emerging pathogen of passerine birds, but explicitly note that it is not considered zoonotic. The other targets were selected because of their relevance to zoonotic disease and urban public-health assessment.

Chlamydia-positive flocks occurred in geographic clusters

The geographic analysis showed that flocks with C. psittaci-positive samples were clustered rather than randomly distributed across the city, with positive findings concentrated more closely together than expected from the locations of all sampled flocks.

The researchers describe feral pigeons as potential carriers of zoonotic pathogens, particularly C. psittaci, and emphasise monitoring of urban pigeon excretions as a basis for local risk assessment. The study was initiated in cooperation with public authorities seeking epidemiological information for urban bird management and public-health planning.

Sources and image credit

  1. Dziedzinska, R., Kralik, P., Zeman, T., Šerý, O., Kamler, J., Homolka, M., Plhal, R., & Drimaj, J. (2026). Feral pigeons as reservoirs of zoonotic pathogens in the urban environment: Spatial clustering and molecular evidence. Veterinary Microbiology, 317, 111008. https://doi.org/10.1016/j.vetmic.2026.111008Primary peer-reviewed article published online 30 March 2026. Researchers analysed 175 pooled faecal samples representing 875 individual droppings from 35 locations in Brno; Chlamydia psittaci was detected in 20.6% and positive flocks showed significant spatial clustering.

Image: Pavel Ševela / Wikimedia Commons — feral pigeon on Freedom Square in Brno, Czech Republic; city- and species-relevant representative image, not one of the sampled pigeons. · CC BY-SA 3.0 · Source

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