Abstract: Bovine chlamydiosis caused by Chlamydia abortus is a local infectious disease. The main symptoms include fever, reproductive failure, pneumonia, enteritis, polyarthritis, encephalomyelitis and so on. Chlamydia abortus is an important zoonotic pathogen which infect sheep and human. 765 serum samples from 12 collected areas in Huzhu County of Qinghai province were used for antibody detection of Chlamydia infection by indirect hemagglutination test（IHA）. The results showed that the total positive rate was 26.1%（200/765）, while yak serum positive rate was 32.3%（20/62）, and cow serum positive rate was 25.6%（180/703）. The results of the survey in the areas of dairy cattle and yak farms have different degree of Chlamydia infection, thus providing reference data for the prevention and control of the bovine chlamydiosis.

Key words: bovine chlamydia, serological investigation, indirect hemagglutination test