Detection and Genotyping of Chlamydia abortus by qPCR in Aborted Dairy Cows in Algeria: Epidemiological Insights and Risk Factor Assessment.

Chlamydiaceae are Gram-negative obligate intracellular bacteria responsible for reproductive disorders in ruminants, notably Chlamydia abortus, the aetiological agent of enzootic abortion. Despite its veterinary importance, chlamydiosis remains poorly documented in Algeria. This study aimed to detect and genotype Chlamydia spp. in placental tissues from aborted and normally calving dairy cows using quantitative PCR (qPCR), and to identify associated risk factors. A total of 98 placental samples (84 aborted, 14 normally calving) were collected from four Algerian provinces between 2022 and 2024. qPCR targeting the 23S rRNA gene revealed 11 positive samples (11.22%), all from aborted cows. Sequencing of amplified fragments showed 97.22% similarity to Chlamydia abortus strain NL2335-4C, confirming its presence in Algerian herds. Statistical analysis identified the occurrence of abortion, the spring season, poor hygiene, and tick infestation as significant risk factors for Chlamydia positivity (p < 0.05). These findings demonstrate the active circulation of C. abortus in Algerian dairy cattle and underline the importance of improving herd hygiene, biosecurity, and tick control to reduce infection pressure. Further molecular surveillance and sero-epidemiological studies are warranted to assess better the zoonotic potential of chlamydial infections in Algeria.