Serological titers of equine monocytic ehrlichiosis associated with gastro-intestinal disorders and serological follow-up on two endemic farms

Abstract

The purpose of this work was to study the association of positive serological titers to Ehrlichia risticii, the causative agent of equine monocytic ehrlichiosis (EME) with gastro-intestinal disorders in hospitalized horses referred to The Ohio State University College of Veterinary Medicine Teaching Hospital (OSU VMTH). In addition, serological titers for E. risticii were monitored in two horse populations with endemic EME for one season to monitor temporal changes in titers. A statistically significant difference was found between the proportion of the total hospitalized horse population presented with a gastro-intestinal disorder during the study period, and study horses with IFA titers ≥1:80 with these signs ( P<0.05). No such difference was found between the proportion of the total hospital horse population presented with signs of gastro-intestinal disorder, and the study horses with IFA titers of 1:20–1:40 with these signs, suggesting that these titers may not have any clinical significance for EME ( P>0.05) Thirty-eight horses on two farms endemic for EME were tested approximately every 3 weeks, 33 of which were tested serially at least two times. Five of the 38 horses (13.2%) had IFA titers ≥1:80-two that were positive initially and three that seroconverted the study; 15 horses' titers fluctuated between negative (IFA titers <1:20) and exposed titers (1:20 through 1:40); and 18 horses remained negative throughout the study.