Diversity Of Chlamydia Species In Chinese Holstein Cows

The obligate intracellular bacteria of the genus Chlamydia has unique life cycle that contains elementary body and reticulate body. The infectious elementary body with 0.2-0.4 μm diameter can not replicate, while the non-infectious reticulate body with 0.9-1.0 μm diameter can replicate. The family Chlamydiaceae currently contains the single genus Chlamydia, which includes 11 recognized species, namely C. pneumoniae, C. trachomatis, C. psittaci, C. suis, C. muridarum, C. abortus, C. caviae, C. felis, C. pecorum, and two recently established species, C. avium and C. gallinacea. Most Chlamydia species with the widened host rang can cause disease in wild and domestic birds, mammals and humans. C. pneumoniae infection in human and mammals cause respiratory disease, while C. trachomatis mainly lead to urogenital disease also with the trachoma, conjunctivitis, pneumoniae. C. psittaci in humans give rise to symptoms like influenza and pneumoniae, with conjunctivitis and gastrointestinal disease and the interstitial pneumoniae will result in death.The international research had identified a spectrum of chlamydial agents occurring in cattle including C. pecorum, C. abortus, C. psittaci and C. suis, as the first three species in dairy cattle. These researches also indicated that Chlamydia in cows have been associated with milk production and quality that causing enormous economic loss. In China, the method used to investigate Chlamydia in cattle always concentrated on serology, and some results still deem that bovine chlamydiosis caused by C. psittaci. To investigate the prevalence and diversity of Chlamydia in Chinese Holstein cows, whole blood from Chinese Holstein cows (n=1,450) and beef cattle (n=553) in 11 provinces of China and vaginal swabs, blood, feces, milk samples from cows (n=108) in a Jiangsu dairy farm were examined using generic and species-specific FRET-qPCR.The results from 11 provinces indicate that 2.4%(48/2,003) of whole-blood samples were positive for Chlamydia species. In Chinese Holstein cows,2.4%(35/1,450) were positive and four Chlamydia species were identified, as C. gallinacea, C. psittaci, C. pecorum, C. pneumoniae and also some mixed infection about C. psittaci and C. pecorum. In Chinese beef cattle,2.4%(13/533) were positive and detected two Chlamydia species C. pneumoniae (84.7%, 11/13) and C. gallinacea (15.3%,2/13).In a further study on a Jiangsu dairy farm,64.8%(70/108) of the cows were positive for Chlamydia spp., four Chlamydias pecies were identified, the most common chlamydial species was C. pecorum (75.7%,53/70), followed by C. gallinacea (47.1%,32/70), C. psittaci (10.0%, 7/70) and C. pneumoniae (4.3%,3/70). Among the 70 Chlamydia-positive cows in this selected herd,68.6%(48/70) carried a single Chlamydia spp. while 28.5%(20/70) carried two different chlamydial species and 2.9%(2/70) harbored three different chlamydial species. In four kinds of samples, Chlamydia spp. was most commonly found in feces (72.9%,51/70), with 94.1%(48/51) for C. pecorum, also some mixed infection with C. psittaci (5.9%,3/51); in vaginal swabs,38.6% (27/70) were positive for Chlamydia species, including C. gallinacea (88.9%,24/27), C. pneumoniae (7.4%,2/27) and C. pecorum (3.7%,1/27); in milk samples,11.4%(8/70) were positive with for Chlamydia species C. gallinacea (62.5%,5/8) and C. psittaci (37.5%,3/8), and in blood,8.6%(6/70), including 66.7%(4/6) for C. gallinacea,16.7%(1/6) for C. pneumoniae, C. pecorum and C. psittaci. In addition, to investigate the polymorphism of Chlamydia species, the species-specific PCR methods were designed based on ompA gene. In a Jiangsu dairy farm, the sequencing results demonstrated the multiple in-herd C. pecorum with 7 ompA variants and only 2 of these 7 full ompA sequences showed identical sequences; in contrast, a single C. gallinacea and C. psittaci serovar which were identical with those of poultry from Yangzhou.In conclusion, the research on Chlamydia prevalence and diversity demonstrate that the positivity in 11 provinces is much lower than the results from a Jiangsu dairy farm. In this study, four kinds of Chlamydia species were detected, including C. gallinacea, C. psittaci, C. pecorum, C. pneumoniae, and this is the first report of C. gallinacea as the new avian agent and C. pneumoniae as the human species in cattle, which widen the host range of these two Chlamydia species. The polymorphism of Chlamydia species on ompA gene showed that C. gallinacea and C. psittaci in cattle are from poultry. A systematic study is required to address the prevalence of Chlamydia in cattle and their potential pathogenic effect on health and production of cattle.