Large-scale serosurvey of Chlamydia abortus in zoo ungulates in Spain.

Chlamydia abortus is a zoonotic bacterium worldwide distributed, which mainly leads to reproductive disorders in different domestic and wild species. Although C. abortus infection has been widely reported in free-ranging ungulates, information regarding this pathogen in captive wild ungulates remains limited. The aims of the present study were to assess C. abortus exposure in zoo ungulates in Spain and to determine the dynamics of seropositivity in animals sampled longitudinally throughout the study period. Between 2007 and 2023, serum samples from 483 ungulates representing 65 species were collected across 11 zoos from Spain. Additionally, 42 of the 483 animals were longitudinally sampled. Anti-C. abortus antibodies were detected in ten individuals (2.1 %; 95 %CI: 0.8-3.3) using a commercial indirect multi-species ELISA. Seropositivity was found in 9.2 % (6/65) of the species analyzed and in 45.5 % (5/11) of the zoos sampled. Seroprevalence was significantly higher during the period 2019-2020 compared to 2007-2014, 2015-2018 and 2021-2023 (P = 0.013). Three of the 42 longitudinally surveyed animals presented seropositivity throughout the study period. This is the first large-scale serosurvey of C. abortus conducted in zoo ungulates, also describing for the first time exposure to C. abortus in four species, which could expand the host range of this zoonotic bacterium. Our results suggest a limited but widespread circulation of C. abortus in wild ungulates housed in zoos in Spain. Zoo ungulates should be included in surveillance programs for C. abortus to enhance our understanding of the epidemiology of this zoonotic pathogen in anthropized environments under a One Health framework.