Experimental Induction of Nocardioform Placentitis in Mares

Nocardioform placentitis (i.e., infection caused by Amycolatopsis spp, and/or Crossielaequi (C. equi) or other actinomycetes) is associated with abortion and premature delivery in mares. However, the pathogenesis is unknown, and development of an experimental model for the disease is necessary. We hypothesized that inoculation of mares with C. equi can inducenocardioform placentitis. The study objectives were to determine whether inoculation of C. equi: intrauterine (IU) at 24 h post-breeding, or intravenous (IV), oral (PO), nasopharyngeal (NP) inoculation or intracervical (IC) administration between 180 and 240 d of gestation would result in nocardioform placentitis. Twenty mares received IU inoculation with 104 cfu of C.equi 24 h post-breeding with fresh extended semen without antibiotics. Endometrial samples were obtained 24 h after inoculation for PCR detection of C. equi DNA. Mares were monitored for placental disease by transrectal ultrasonography (15, 25, 35, 60, 90, and 120 d of gestation), and thereafter monthly by transabdominal ultrasonography until foaling. In addition, 15 pregnant mares were inoculated with 109 cfu of C.equi through NP (n=5), PO (n=4), IV (n=4) or IC (n = 2) routes from 180 to 240 d of gestation. [...]