Effects of firocoxib, trimethoprim sulfamethoxazole and altrenogest on inflammation and foal survival after administration to mares with experimentally induced placentitis

Abstract

Bacterial placentitis is a leading cause of pregnancy loss in mares. Infection, inflammation and prostaglandin production induce preterm delivery leading to poor foal survival. Treatment strategies for placentitis that control infection and inhibit inflammation are vital. The goals of this study were: 1. Assess the anti-inflammatory effects of firocoxib, trimethoprim sulfamethoxazole (TMS) and altrenogest administered to mares with placentitis; 2. Determine the efficacy of firocoxib, TMS and altrenogest for improving foal outcome in mares with placentitis. We hypothesized that this treatment would significantly decrease pro-inflammatory mediators in fetal fluids and tissues when compared to untreated, infected mares and would also improve foal survival. Placentitis was induced in 13 pregnant mares (270-300 days gestation; via intracervical inoculum of Streptococcus zooepidemicus). Mares were randomly assigned to: infected/untreated (UNTREATED; n=6); or infected/treated groups (TREATED; n=7; administered firocoxib, TMS, and altrenogest from the onset of clinical signs of placentitis until abortion/delivery). Fetal fluids, membranes and tissue samples were obtained at abortion/delivery for quantification of TNF-α, IL-1β, IL-10, IL-6, IL-8, PGE2, PGF2α, and matrix metalloproteinases (MMP) -1, -3, -9 using ELISA (fluids) and real-time PCR (tissues). P < 0.05 was considered significant. Gestation length and foal survival were significantly higher in TREATED (mean days post-infection = 40; 7/7 live foals) than UNTREATED (mean days post-infection = 14; 2/6 live foals). Administration of firocoxib, TMS andaltrenogest resulted in significantly lower amniotic fluid concentrations of IL-1β, IL-6, PGE2 and PGF2α in TREATED than UNTREATED. Amniotic fluid IL-10 concentration tended (P < 0.1) to be lower in TREATED than UNTREATED. Cytokine and prostaglandin concentrations in allantoic fluid were not different between groups except PGE2 which tended (P < 0.1) to be lower in TREATED than UNTREATED. The relative quantity of cytokine and MMP mRNA expression in fetal membranes and foal tissues (non-survivors) was log-transformed and estimated marginal means determined. Fetal membranes from TREATED had significantly lower mRNA expression for IL-8 and TNFα compared to membranes from UNTREATED. mRNA expression of IL-1β, IL-6 and MMP3 tended (P < 0.1) to be lower in membranes from TREATED than UNTREATED. mRNA expression of IL-1β, IL-8, IL-10, TNFα, MMP1, 3 and 9 were significantly different between fetal membrane sites. In non-surviving foals, IL-8 mRNA expression was significantly lower in liver than lung while MMP3 expression was significantly higher in liver than lung or spleen. These data provide physiologic evidence that administration of firocoxib, TMS and altrenogest to mares with placentitis has broad anti-inflammatory effects and may improve foal survival. Research funding: Grayson Jockey Club Research Foundation; Merial Animal Health; Kentucky Thoroughbred Breeders Association, University of Florida, University of Georgia.