Elevated serum amyloid A levels in cases of aborted equine fetuses due to fetal and placental infections

Determination of fetal serum amyloid A (SAA) concentrations in aborted fetuses can provide valuable information regarding the infectious and/or inflammatory process of abortion in horses. To investigate the relationship between fetal SAA levels and the infectious/inflammatory disease process in feto-placental tissues, a SAA ELISA was used to test heart serum samples of 89 equine fetuses that were necropsied and diagnosed in the following groups: a multiorgan disease process diagnosed with an identified microorganism (14 cases, group 1); only placentitis diagnosed with an identified microorganism (nine cases, group 2); only placentitis diagnosed with no microorganism identified (six cases, group 3); and no infectious or inflammatory disease process diagnosed (60 cases, group 4). Serum amyloid A concentrations in equine fetuses were elevated from 10.5 to ≥40 mg/L in 10 of 14 cases in group 1; and from less than 2.5 mg/L to greater than 40 mg/L in seven of nine cases in group 2. In group 3, SAA concentrations were found to be less than 2.5 mg/L in five of six cases. In group 4, SAA concentrations were less than 2.5 mg/L in 55 cases, whereas in five cases SAA concentrations were elevated. Statistical significant differences were found between the concentrations of SAA in fetal horse blood and the presence of infectious and/or inflammatory disease process in the feto-placental tissues when a causative microorganism was identified. These results suggest that testing SAA concentrations in fetal heart blood may aid in further understanding the causes of abortions in horses.