| Summary: | This study surveyed the prevalence of chlamydial infection among farms in the mid-northeastern provincial cluster of Thailand by PCR and phylogenetic analyses of the sequences. Samples from 94 crocodiles were collected from 17 farms in five provinces together with farm management data. Chlamydiaceae was found in 48.94% of the samples (46/94). Of the 17 pooled samples analyzed using 16S rRNA sequencing, four samples exhibited 99.3 to 99.5% nucleotide identity with Chlamydia psittaci, three samples exhibited 99.1 to 99.3% nucleotide identity with C. crocodili, and one sample exhibited similarity to both species. The risk factors related to chlamydial infection included the source of young crocodiles and the frequency of water changes. Chlamydial infection was higher in nonclinical crocodiles than in clinical or dead crocodiles (P=0.003). Pharyngitis, fibrinous pharyngitis, hepatitis, pneumonia, and hydropericardium were commonly found in chlamydial-positive cases of ill or dead crocodiles. C. psittaci and C. crocodili were found in both clinical and nonclinical crocodiles. C. psittaci is a well-known zoonotic pathogen. C. crocodili is a new species found in Siamese crocodiles in Thailand. In conclusion, the source of young crocodiles and frequency of water changes were identified as risk factors for chlamydial infection in crocodile farms. C. crocodili should be further investigated to better understand its implications for crocodile heath.
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