Effect of antimicrobial-containing semen extender on risk of dissemination of contagious equine metritis.

The research investigates the effect of antimicrobial-containing semen extender on the spread of a sexually transmitted disease, contagious equine metritis (CEM), in horses. The study finds that the use of this extender significantly reduces the growth of the disease-causing bacteria and lowers the risk of dissemination.

Research Objective

• The study aimed to identify the impact of using a semen extender containing antimicrobials on the growth of Taylorella equigenitalis, the bacterium behind contagious equine metritis (CEM), in semen.
• The researchers also wanted to ascertain how the disease develops after artificial insemination with semen containing the bacteria and extended with the antimicrobial extender.

Methods and Participants

• There was a prospective study with 21 mature mares without CEM. They also used semen from one stallion that had been experimentally infected with CEM, and from another stallion naturally infected with this disease.
• CEM-positive semen was grown in a semen extender both with and without antimicrobials (amikacin [final concentration, 1 g/L] and penicillin G potassium [0.63 g/L]). Thereafter, the number of colony-forming units of T equigenitalis was determined.
• The mares were inseminated with raw, extended, or cryopreserved semen found to be culture-positive for T equigenitalis. The researchers then watched for clinical signs of CEM.
• Bacterial culture samples were taken from the uterus, clitoral sinuses, and clitoral fossa of the mares 7, 14, and 21 days after artificial insemination.

Findings

• Antimicrobial-containing semen extender significantly reduced the number of colony-forming units of T equigenitalis in the CEM-positive semen.
• Artificial insemination using raw CEM-positive semen resulted in visible signs of CEM, whereas insemination with extended or cryopreserved CEM-positive semen didn’t lead to any evidence of CEM.
• Therefore, the semen extender containing antimicrobials significantly diminished the risk of CEM dissemination.

Conclusion

• By integrating amikacin (1 g/L) and penicillin G potassium (0.63 g/L) into extended semen, the spread of CEM from stallions to mares during artificial insemination could be reduced. This could bring about changes in how the disease is disseminated.