155 EMBRYO TRANSFER SUCCESS DURING CONCURRENT CONTAGIOUS EQUINE METRITIS INFECTION

Abstract

Contagious Equine Metritis (CEM) is an equine venereal disease caused by the bacterium Taylorella equigenitalis. CEM reduces fertility by causing acute vaginitis and endometritis in mares bred by infected stallions. Stallions are asymptomatic carriers and mares can pass the bacteria back to stallions. This disease caused massive financial losses in the thoroughbred breeding industry of the United Kingdom and United States in 1977 and 1978. CEM is considered a foreign animal disease in the United States. Fresh or chilled semen from three stallions, unknowingly CEM positive, was used for AI as part of an embryo transfer (ET) program. Positive diagnosis for T. equigenitalis was by culture. Cultures were on carried out on chocolate agar under 5–10% CO₂. Test mare breeding per the U.S. Code of Federal Regulations (2006 9 CFR) was performed, and stallions did infect these mares. Real-time PCR was used to distinguish between T. equigenitalis and T. asinigenitalis, with a 97% homology for T. equigenitalis. Kirby-Bauer antibiotic sensitivity testing was performed. Of note, the bacterium was sensitive to gentamicin. Semen was collected using a Minitube artificial vagina (Minitube of America, Inc., Verona, WI, USA), analyzed using CASA (SpermVision^™, Minitube), and prepared according to published guidelines. Semen was extended using Minitube EquiPRO^® CellGuard^™ extender with amikacin and penicillin. Six mares were used for breeding. Donor and recipient mares were examined using transrectal palpation and ultrasound to confirm estrus, follicular size, and ovulation synchrony. Mares were examined for signs of vaginitis, cervicitis, or endometritis. Embryo recovery was performed using EquiPRO recovery media on Day 7. Recovered embryos were washed twice in EquiPRO holding medium at dilution rate of 5 µL recovery media to 3 mL holding media. Media contained gentamicin and kanamycin. No mares were treated with systemic antibiotics. Recovered embryos were transferred to recipients for the purpose of producing live foals. Seventeen embryos were recovered in 19 attempts, yielding an 89% embryo recovery rate. Fourteen of the embryos were transferred to recipient mares. Three embryos were vitrified. Ten of 14 (78%) transfers yielded pregnancies by Day 14 of gestation. Seven live foals were born. After CEM diagnosis in the stallions, the donor and recipient mares were tested. Testing was performed per 2006 9 CFR. The clitoral fossa and sinuses and, in addition, the cervix were cultured. Culture methods were as previously described. No mare sample returned a positive culture. To our knowledge, this is the first report in the United States demonstrating transfer of genetics of CEM-infected stallions without transfer of disease or reduction of fertility since eradication. The use of AI with extended semen is likely the greatest contributor to this success. It is felt that ART (Assisted Reproductive Technology(s)) may be a beneficial tool for propagating genetics of animals confronted with pathogen presence; however, further controlled studies are necessary.