الملخص

Chlamydia psittaci, the causative agent of avian chlamydiosis, is a well-recognized zoonotic pathogen with pigeons (Columba livia domestica) serving as a primary natural reservoir. Despite its significance, C. psittaci remains a neglected public health threat in many regions, including Iraq. This study aimed to determine the prevalence and molecular characterization of C. psittaci in oropharyngeal samples from domestic pigeons and nasal swabs from their human handlers in Baghdad, Iraq, using a combination of rapid antigen testing and conventional PCR techniques.

From October 2023 to April 2024, a total of 150 pigeon oropharyngeal swabs and 20 nasal swabs from pigeon breeders were collected. Initial screening for the C. psittaci major outer membrane protein (MOMP) antigen using a rapid diagnostic cassette test revealed a 40% positivity rate (60/150) among the pigeon samples. These positive samples were subsequently inoculated into embryonated chicken eggs for pathogen propagation. DNA extracted from the cultured material was subjected to PCR amplification targeting the 16S rRNA and ompA genes specific to C. psittaci.

PCR analysis confirmed C. psittaci DNA in 8.3% (5/60) of the antigen-positive pigeon samples and in 5% (1/20) of the human samples. Furthermore, all six PCR-positive samples harbored antibiotic resistance-associated genes, including rpID (azithromycin resistance) and rpIV (spectinomycin resistance), indicating 100% resistance gene detection. Phylogenetic analysis of the ompA gene sequences revealed that all avian isolates belonged to genotype B. To our knowledge, this study represents the first molecular detection and genotypic characterization of C. psittaci in Iraq.

These findings highlight the zoonotic risk posed by domestic pigeons and underscore the urgent need for targeted surveillance, public education, and biosecurity measures to mitigate the risk of pigeon-to-human transmission of chlamydial pathogens in urban environments.