Genetic and antigenic analysis of Chlamydia pecorum strains isolated from calves with diarrhea

OHTANI, Akifumi; KUBO, Masahito; SHIMODA, Hiroshi; OHYA, Kenji; IRIBE, Tadashi; OHISHI, Daiki; ENDOH, Daiji; OMATSU, Tsutomu; MIZUTANI, Tetsuya; FUKUSHI, Hideto; MAEDA, Ken

Chlamydiaceae are obligate intracellular bacteria that have a unique developmental cycle which includes morphological changes. They cause a wide range of diseases in animals and humans [20, 21] . The most important mode of transmission is thought to be fecal shedding by carrier animals. Chlamydiae may be shed in vaginal, ocular and nasal discharges, uterine fluid, placental tissue, urine and semen. Chlamydial infection can be acquired by direct contact between animals or by indirect transmission, such as the fecal-oral route or via inhalation of contaminated air [18] . Clarkson et al. [4] reported that Chlamydia was isolated from lamb's feces on 26 farms in England and Wales, and the prevalence of infection varied from 5-50% on individual farms. Isolates were identified as enteric type rather than abortion type and thus were classified as Chlamydia pecorum rather than Chlamydia psittaci. In cattle, C. pecorum is known to cause encephalomyelitis, pneumonia and enteritis, but subclinical and persistent infections are more common [8] . DeGraves et al. [5] reported that low-level of C. psittaci and C. pecorum genital infections was detected in 53% of virgin heifers by quantitative PCR, suggesting predominantly extra-genital transmission of Chlamydia in cattle. Reinhold et al. [17] reported that natural infections with Chlamydia spp. in calves were associated with subclinical chronic effects on animal health. Recently, it was reported that asymptomatic endemic C. pecorum infections reduced growth rates in calves by up to 48% [16] . However, the pathogenesis of C. pecorum is still unclear. In Japan, there are only a few reports of C. pecorum strains isolated from affected cattle [6] [7] [8] .