Chlamydiae are diverse bacteria that have adapted to a large variety of animal hosts resulting in many different disease presentations. Accordingly, this study examined the host range and prevalence of chlamydiae in a variety of mammalian farm and companion animals. Previously optimized TaqMan1 real-time polymerase chain reaction (PCR) assays were used for the zoonotic Chlamydophila psittaci and Cp abortus agents. Species-specific real-time PCR assays for Cp pecorum, Cp felis, Cp caviae, and Chlamydia suis were developed and validated for use in this study. Both chlamydial and nonchlamydial bacterial strains were used. Diagnostic swab and fecal samples from cattle (n = 100), sheep (n = 38), goats (n = 4), pigs (n = 128), horses (n = 11), dogs (n = 5), cats (n = 138), guinea pigs (n = 12), and rabbits (n = 4) from 2004 to 2006 were submitted for chlamydial diagnosis, and an additional 159 previously positive samples from cats, dogs, guinea pigs, and rabbits were included from Vet Med Labor GmbH. DNA was extracted from all specimens and PCR was used for sequencing; the most frequently identified chlamydial pathogen in cattle, sheep, goats, pigs, and horses was Cp abortus, which was detected in 63.9% (n = 212) of all tested samples. Cp felis was primarily identified in cats (135/138 samples) and in dogs (4/5). Cp caviae was identified in guinea pigs (12/12), rabbits (4/4), and a single dog. Cp psittaci was identified in cattle (n = 11), pigs (n = 7), cats (n = 2) and goats (n = 1). DNA from 2 different chlamydial species was detected in 12.7% (56 of 440) of tested samples, demonstrating evidence of multispecies infection.

Commentary: This study highlighted the potential for mixed chlamydial infection in a variety of mammalian species with a broader host range than originally suspected. Future diagnostic tests and sequencing will allow a greater understanding of the molecular epidemiology of chlamydial species, and could provide clues to the natural history, pathogenicity, host range, and virulence characteristics of such species.—Indu Mani, DVM, DSc

Detection of all Chlamydophila and Chlamydia species of veterinary interest using species-specific real-time PCR assays. Pantcheva A, Sting R, Bauerfeind R, et al. COMP IMMUNOL MICROB 33:473-484, 2010.