Longitudinal and cross-sectional study of Chlamydia serpentis in captive snakes: Insights from two successive outbreaks in a zoological institution.

Among the Chlamydia species known to infect snakes, C. serpentis is a recently described pathogen. A first outbreak of C. serpentis in the snake collection of a zoological institution was documented in 2018. In 2023, a wild-caught asp viper (Vipera aspis) tested positive by PCR for C. serpentis, following introduction with two snakes of the same species that had tested positive in 2018. Real-time PCR analysis was used to detect the presence of C. serpentis in oral/cloacal swabs and tissue samples from snakes, and environmental samples from the terrariums of confirmed infected individuals. A sequential screening of 29 snakes was performed based on disease-risk analysis, with 5/29 (17.2 %) testing positive, including the three asp vipers and two co-housed European long-nosed vipers (Vipera ammodytes), all belonging to the same epidemiological unit. All three snakes treated with 5 mg/kg marbofloxacin intramuscularly daily tested PCR negative following treatment. Comparison of the ompA sequences and MLST profiles of the strains involved in the 2018 and 2023 outbreaks suggests a single source of contamination and unique circulating strain. As in 2018, the origin of the infection remains unknown, but potential sources include persistent infection and/or intermittent shedding among infected snakes from the 2018 outbreak, environmental persistence, or introduction via the newly acquired wild-caught viper. These successive outbreaks provide insights into the epidemiology and dynamics of C. serpentis infections in captive snakes, further supporting the need for integrated management strategies combining medical treatment, environmental decontamination, and epidemiological unit management to minimize cross-contamination and prevent pathogen transmission.