Immunological insights into the occurrence of in horses from southern Brazil using flow cytometry.

BACKGROUND AND AIM

is an obligatory intracellular bacterium associated with equine proliferative enteropathy (EPE), which significantly impacts equine health. Despite its clinical relevance, epidemiological and diagnostic approaches for this infection in horses have remained underexplored. This study aimed to evaluate the humoral immune response in horses immunized with an experimental vaccine for and to determine the occurrence of anti- antibodies in horses from southern Brazil using the flow cytometry antibody test (FCAT).

MATERIALS AND METHODS

A total of 12 horses were immunized with an experimental vaccine containing inactivated and adjuvants. Blood samples were collected on day 0 (D0) and every 7 days until day 35 (D35) to monitor the antibody response using FCAT. In addition, serum samples from 79 horses from the North and Northwest regions of Rio Grande do Sul were tested to determine the occurrence of anti- antibodies. The FCAT protocol was optimized for equine samples, and a cut-off fluorescence threshold was determined using Receiver Operating Characteristic curve analysis.

RESULTS

FCAT demonstrated high accuracy, with a sensitivity of 100% and specificity of 92% at a fluorescence cut-off of ≥15%. Immunization triggered a robust humoral response, with a significant increase in fluorescence from day 7 to day 35. In the occurrence analysis, 26% of the horses tested positive for anti- antibodies. The highest occurrence was observed in females (35.8%) and horses aged 16-22 years (50%).

CONCLUSION

This study provided evidence that infection is relatively common among horses in southern Brazil. FCAT was a sensitive and specific diagnostic tool for detecting anti- antibodies in horses. The findings highlight the need for better diagnostic and preventive measures to control EPE in equine populations.