Success of different therapy concepts for bacterial endometritis in stud farm practice

Abstract

Bacterial endometritis is among the major problems in equine reproduction and is usually treated with antibiotics. Data on clinical success rates of antibiotic as well as non-antibiotic treatment is scarce. The study aimed to collect data of mares diagnosed with intrauterine growth of facultative pathogenic bacteria and compare the outcome of different therapies for bacterial endometritis in stud farm practice. Data on mares (different breeds) with positive uterine culture results was collected retrospectively in private veterinary practices (n=5) from 2018 to 2022. Information relating to 30 factors (mare, diagnostics, therapy and pregnancy rate) of cases with bacterial endometritis (Endometritis, n=1005) were recorded and analysed. Possible effects on treatment success (negative control swab or positive pregnancy result in the first heat after treatment) were tested by binomial logistic regression. For comparison of pregnancy rates, data on mares with negative uterine culture and without any treatment (Control; n=446) was also collected and compared with Endometritis group by chi square testing. In group Endometritis, uterine swabbing (technique: 72% double-guarded swab, 28% low-volume lavage) revealed presence of β-hemolytic streptococci in most cases (n=918). Pseudomonas aeruginosa (n=21), Klebsiella pneumoniae (n=15), Staphylococcus aureus (n=13) and Candida sp. (n=10) were observed less frequently. Results positive for E. coli were not included. In group Endometritis, treatment occurred regardless of the cycle stage either with trimethoprim-sulfonamides (n=532), procain-penicillium (n=277),marbofloxacin (n=71), other antibiotics (n=66) or without antibiotics (n=59) after susceptibility testing (performed in 549/1005 cases). Antibiotics were administered rather intrauterine (n=34) than systemically (n=911). Uterine lavage was reported in 46% of mares. Additional local treatment with different substances (e.g., n-acetylcysteine, dimethyl sulfoxide or Coca Cola) was performed in 164 mares. Uterotonic drugs were administered in 39.9% of mares. A control uterine culture was not obtained in most cases (n=677). Different breeding programs in this study included artificial insemination (AI) with chilled semen (n=667), AI with frozen semen (n=169), transfer of fresh (n=112) or cryopreserved (n=27) embryos and natural cover (n=27). In the control group, AI with chilled semen (n=230), AI with frozen semen (n=106), embryo transfer (fresh: n=49; cryopreserved: n=58) and natural cover (n=2) were used. After the first breeding after treatment, pregnancy rate was 47% in group Endometritis and 54% in the control group (p<0.05). End of season pregnancy rate was 72% in treated mares and 76% in the control group (p>0.05). Treatment success was affected significantly by duration of antibiotic treatment, usage of uterotonic drugs, veterinary practice, and mare's age, but neither by the chosen antibiotic drug nor administration route nor covering method. In conclusion, end of season pregnancy rate did not differ among mares treated for bacterial endometritis vs. mares with negative uterine cultures.