Treatment efficacy of trimethoprim sulfamethoxazole, pentoxifylline and altrenogest in experimentally induced equine placentitis.

This study explores how long-term treatment with trimethoprim sulfamethoxazole (an antimicrobial), pentoxifylline (an anti-inflammatory), and altrenogest (a synthetic progestin) could potentially improve the pregnancy outcomes in mares with artificially induced placentitis. The results suggest that this treatment combination may enhance the viability of foals born to mares with placentitis.

Experiment Overview

• Seventeen healthy, pregnant pony mares, between 280 to 295 days into their pregnancy, were included in the study. Placentitis, an inflammation of the placenta, was intentionally induced in all mares by injecting them with Streptococcus equi subsp. zooepidemicus (10^7 CFU).
• These mares were divided into two groups: the UNTREAT group consisted of five mares that were infected but not treated, functioning as control animals. The other twelve formed the TREAT group, which were not only infected but also treated with trimethoprim sulfamethoxazole, pentoxifylline, and altrenogest from the onset of clinical signs until delivery.

Procedures and Treatments

• The dosage for each of the three drugs given to the TREAT group were as follows:
  • Trimethoprim sulfamethoxazole – 30 mg/kg, orally every 12 hours
  • Pentoxifylline – 8.5 mg/kg, orally every 12 hours
  • Altrenogest – 0.088 mg/kg, orally every 24 hours
• Blood samples were collected from all the foals at delivery and fetal stomach and thoracic contents were also obtained from dead fetuses.

Results and Conclusion

• The results showed a significant difference in the viability of foals between the two groups. In the TREAT group, ten out of twelve mares delivered viable foals (83%), whereas in the UNTREAT group, none of the mares delivered a viable foal (0%).
• Negative blood cultures at birth were found in 10 out of 12 foals (83%) in the TREAT group. On the other hand, all foals in the UNTREAT group had positive cultures from one or more samples (blood, stomach contents, thoracic fluid).
• Bacteria were found in uterine culture samples in both groups, with Streptococcus equi subsp. zooepidemicus being the most common organism.
• The authors concluded that the administration of trimethoprim sulfamethoxazole, pentoxifylline, and altrenogest might improve the viability of foals from mares with artificially induced placentitis.