RESUMO
OBJECTIVE: To determine the effects of transfusion of Rhodococcus equi hyperimmune plasma (REHIP) on serum concentrations of complement component 1q (C1q) and to examine the association of serum C1q and anti-rhodococcal antibodies of newborn foals with subsequent development of rhodococcal pneumonia. ANIMALS/SAMPLES: Foals (n = 205) from 2 Thoroughbred breeding farms in New York transfused with REHIP between January 1, 2022, and December 1, 2022. PROCEDURES: Blood was collected immediately before transfusion with REHIP and again from the contralateral vein immediately after transfusion. Foals were followed through weaning for clinical and ultrasonographic evidence of rhodococcal pneumonia. Serum samples were tested by ELISA for concentrations of C1q and for activity of IgG1 and IgG4/7 recognizing the virulence-associated protein A (VapA) of R equi. Logistic regression analysis was used to determine the association between rhodococcal pneumonia and levels of C1q and anti-VapA IgG1 and IgG4/7. RESULTS: REHIP significantly decreased C1q concentrations immediately after transfusion. Accounting for effects of farm and birth month, estimated odds of pneumonia were 2.1-fold (P = .0330) higher for foals with pretransfusion C1q concentrations less than or equal to the population median and 3.3-fold (P = .0051) higher for foals with posttransfusion IgG1 activity in the lower quartile. CLINICAL RELEVANCE: Both C1q and IgG appear to contribute to protection against R equi, and IgG1 appears to be especially important. Increasing IgG1 concentrations targeting rhodococcal proteins in REHIP or serum of foals might improve protection against R equi foal pneumonia.
RESUMO
Persistent endometritis in the mare is associated with hypersecretion of mucus by endometrial epithelium and migration of neutrophils into the uterine lumen. This study examines the relationships between N-acetylcysteine (NAC), a mucolytic agent with anti-inflammatory properties, and endometrial architecture, serum neutrophil function, post-breeding therapy, and reproductive performance of NAC-treated mares in a clinical setting. In study 1, endometrial biopsies from mares receiving intrauterine saline (fertile-control, n = 6) or 3.3% NAC (fertile-treatment, n = 6; barren-treatment, n = 10) were evaluated by histology and image analysis. In study 2, phagocytic activity of serum-derived neutrophils was measured after adding 0.5% or 3% NAC. In study 3, pregnancy rates of repeat breeders (n = 44) receiving an intrauterine infusion of 3.3% NAC 24-36 hours before mating (group 1) was recorded, as was first cycle of the season pregnancy rates of reproductively normal mares (group 2, n = 85), and mares treated for bacterial endometritis the cycle before mating (group 3, n = 25). Intrauterine NAC did not adversely affect endometrial histology. Extracellular mucus thickness and staining intensity were reduced in fertile-treatment mares (P < 0.03). Neutrophil function was inhibited by 3% NAC solution, but not by 0.5% NAC (P < 0.05). In study 3, for groups 1, 2, and 3, respectively, the first-cycle pregnancy rates were 77%, 74%, and 56%, and early embryonic death rates were 15%, 13%, and 7%. In group 2 mares treated with uterine lavage and oxytocin post-mating, the pregnancy rate was 89% (39/44), whereas in mares treated with uterine lavage and 1 g ceftiofur, it was 60% (24/40). Of the oxytocin-treated mares, 18% (8/44) had ≥ 1 cm of intrauterine fluid or marked uterine edema, whereas 80% (32/40) of the antibiotic-treated mares did. In conclusion, intrauterine infusion of a 3.3% solution of NAC was not irritating and inhibited the oxidative burst of neutrophils. Repeat breeder mares, with evidence of mucus hypersecretion, but no uterine pathogens, when treated with NAC followed by post-mating uterine lavage and oxytocin (and in some cases intrauterine antibiotics), achieved a pregnancy rate of 77%.
