An outbreak of respiratory disease in horses associated with Mycoplasma felis infection.

The study examines an outbreak of lower respiratory tract disease in racehorses, finding a connection between the disease and infection by Mycoplasma felis bacteria.

Objective of the Research

• The primary goal of the research was to investigate the cause of a lower respiratory tract disease that occurred in a group of training racehorses aged between two and six years old. The disease was noticed in 22 out of the 25 horses whose full health records were available.

Findings from the Study

• Upon testing, 19 out of the 22 horses showed a seroconversion (change in the antibodies level in the blood indicating an immune response) to Mycoplasma felis using a test named indirect haemagglutination assay.
• The remaining three horses that did not initially show a seroconversion displayed high titres indicating a significant amount of antibodies in their blood during their recovery period, which also suggested an infection by M. felis.
• Also, out of the 22 horses, two showed seroconversions to equine herpesvirus-4, suggesting a possible viral infection restricted to these two horses.
• Tracheal wash samples, a diagnostic procedure, were taken from four horses that showed visibly increased tracheal mucous. The samples showed over 10,000 colony-forming units/ml of M. felis and high numbers of neutrophils, a type of immune cell, indicating an infection.

Significance of the Study

• This research is significant as it provides the first description of an outbreak of lower respiratory tract disease among racehorses in training, linked to an infection by M. felis. It thus brings attention to the potential threat that this bacterium poses to horses’ health, particularly those in training.