Comparison of polymerase chain reaction, direct immunofluorescence, cell culture and enzyme immunoassay for the detection of Chlamydia psittaci in bull semen.

The polymerase chain reaction (PCR), direct immunofluorescence (DIF; JMAGEN Chlamydia, DAKO Diagnostics, UK), cell culture (CC) and enzyme immunoassay (EIA; Syva Micro Trak) were evaluated for detection of Chlamydia psittaci in bull semen. Three specimens were collected from each of 47 bulls at 3-6 month intervals (134 samples). Judging by the number of samples tested (n = 134), PCR showed a sensitivity of 90.9%, DIF of 93.9%, CC of 72.7% and EIA of 81.8%. PCR, DIF, CC and EIA were 100% specific, respectively. Of the 47 bulls the maximum number of chlamydia-positive animals (n = 14) was revealed when repeated tests were made by PCR. PCR detected 21.4% more positives than DIF and CC and 35.7% more than EIA. Although CC was less sensitive judging by the number of samples tested, it was as sensitive as DIF (78.6%) when judged by the number of bulls investigated. All bulls found to be chlamydia-positive remained so throughout the investigation, which lasted 18 months.