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

This research examined whether there’s an association between positive test results to Ehrlichia risticii, a bacteria causing Equine Monocytic Ehrlichiosis (EME), and gastrointestinal issues in horses. The study also monitored these positive test results in endemic horse populations over a period of time to observe any changes.

Objective and Methodology of the Study

• This research aimed to investigate any potential association between positive serological titers (a measurement used in blood tests to evaluate the concentration of specific antibodies produced in response to an infection) to Ehrlichia risticii and gastrointestinal disorders in horses admitted to The Ohio State University College of Veterinary Medicine Teaching Hospital.
• Additionally, the researchers were interested in tracking any changes in these serological titers over time within two endemic horse populations. These were populations where EME, the illness caused by Ehrlichia risticii bacteria, was recurrent.

Key Findings

• The research found a significant difference when comparing the proportion of the total hospital horse population that displayed gastrointestinal issues during the research period with those horses that had positive IFA (Immunofluorescence Assay, a technique to visually identify the presence of specific antibodies) titers of 1:80 or more. This finding suggests an association between Ehrlichia risticii infection and gastro-intestinal disorders in horses.
• However, no notable difference was identified when comparing the proportion of the total hospital horse population with gastro-intestinal disorders and those horses which had IFA titers between 1:20 to 1:40. This indicates that titers in this range may not carry clinical significance towards EME.

Monitoring Endemic Horse Populations

• Two farms known for endemic EME were included to monitor E. risticii serological titers over one season. Thirty-eight horses were tested approximately every three weeks, with 33 of these tested at least twice.
• Among these, five horses (13.2%) had IFA titers of 1:80 or more, indicating a positive result. Two were positive right from the beginning, while three showed positive results during the study.
• Fifteen horses’ titers fluctuated between negative (< 1:20) and exposed titers (1:20 through 1:40). The remaining 18 horses maintained a negative status during the entire study.