Seroepidemiological study of Chlamydia abortus in domestic and wild ruminants in Spanish Mediterranean ecosystems

Chlamydia abortus is a worldwide bacterium that can affect a wide range of mammal species, being considered an occupational zoonotic pathogen. In small domestic ruminants, C. abortus infection causes ovine enzootic abortion, a major cause of reproductive disorders. Different wild ruminant species have also been suggested as potential reservoirs of this bacterium. Nevertheless, data on the epidemiology of C. abortus in both domestic and wild ruminants in Spain, which hosts the largest population of small domestic ruminants in the European Union and a high density of wild ruminants, are still very limited. A cross-sectional study was conducted to assess the seroprevalence, spatial distribution, and risk factors associated with C. abortus exposure in small ruminant flocks and wild ruminant populations in southern Spain. Sera from 780 small ruminants (390 sheep and 390 goats) from 52 flocks, and 605 free-ranging wild ruminants (390 red deer (Cervus elaphus), 110 mouflon (Ovis aries musimon) and 105 Iberian ibex (Capra pyrenaica)) from 32 hunting estates were analysed using a commercial indirect ELISA. Anti-C. abortus antibodies were detected in 222 (28.5 %; CI_95 %: 25.4–31.7) of the 780 small ruminants. Seroprevalence was higher in goats (34.1 %; CI_95 %: 29.5–38.9) than in sheep (22.8 %; CI_95 %: 18.9–27.2). Seropositivity was detected in 76.9 % (CI_95 %: 57.9–88.9) of the sampled flocks. The final generalised estimating equations (GEE) model identified management system (intensive and semi-intensive), and larger farm size (≥492 animals) as significant risk factors associated with C. abortus seropositivity in domestic small ruminants. In wild ruminants, the overall seroprevalence was 2.6 % (16/605; CI_95 %: 1.6–4.3). Anti-C. abortus antibodies were found in 1.8 % of red deer, 3.8 % of Iberian ibex and 4.6 % of mouflon. The high exposure of small ruminants to C. abortus is of animal and public health concerns. Nevertheless, the low seroprevalence values observed in sympatric wild ruminant populations indicate that these species seem to play a limited role in the epidemiology of C. abortus in southern Spain, suggesting independent epidemiological cycles of this pathogen in domestic and wild ruminant populations in this European region. Control measures should be implemented in small ruminant farms to minimize the risk of C. abortus transmission to other sympatric species, including humans.