A Meta-Analysis of Bovine Chlamydia Prevalence in Cattle in China from 1989 to 2020

Chlamydia bovis is a widespread infection disease caused by the mixed infection of Chlamydia psittaci, Chlamydia pecorum, Chlamydia abortus, and Chlamydia suis in cattle. Although many studies have investigated Chlamydia infection in cattle, there is no nationwide study on the prevalence of Chlamydia infection in cattle of China. We constructed the first meta-analysis to assess the infection rate and infection risk factors of Chlamydia in cattle in China, and we searched PubMed, ScienceDirect, Chinese Web of Knowledge, Wanfang, and VIP Chinese journal database for studies reporting Chlamydia infection in cattle from April 29, 2020. We collected a total of 563 publications from 1989 to 2019, and finally, 78 studies were eligible, which included 152,364 cattle from 27 provinces across the country. We estimated the pooled prevalence of Chlamydia in cattle was 14.2% (95% confidence interval [CI]: 12.2 to 16.4). The prevalence of bovine Chlamydia in China collected before 2000 (14.8%, 95% CI: 5.6 to 27.3) showed the highest prevalence rate. The highest prevalence was found in Central China (22.6%, 95% CI: 12.8 to 34.2). The prevalence of Chlamydia spp. between abortion cattle (39.1%, 95% CI: 24.6 to 54.6) and healthy cattle (8.3%, 95% CI: 3.1 to 15.2) showed significant variation (p < 0.05). In detection methods subgroup, enzyme-linked immunosorbent assay (30.5%, 95% CI: 21.5 to 40.3) showed the highest prevalence. In the age subgroup, the prevalence rate of age >1 year (16.6%, 95% CI: 12.6 to 20.9) was higher compared with age ≤1 year (9.8%, 95% CI: 6.7 to 13.3). Yaks (17.8%, 95% CI: 13.3 to 22.8) showed the highest Chlamydia prevalence among the varieties of bovine. We also estimated the potential risk factors such as feeding model, sample classification, sampling seasons, bovine gender, parity, and quality level of included studies. Our findings suggested that Chlamydia was prevalent in cattle in China. So we should pay attention to bovine Chlamydia and take necessary measures to prevent it.