[Detection of leptospira in the vitreous body of horses without ocular diseases and of horses with equine recurrent uveitis (ERU) using transmission-electron microscopy].

The research article investigates the presence of a bacteria named leptospira in the vitreous body (inner part of the eye) of horses, and its suspected role in causing Equine recurrent uveitis (ERU) – a recurring inflammatory eye disease in horses. This is studied through a comparative analysis of leptospira prevalence in eyes of healthy horses versus those suffering from ERU, using transmission-electron microscopy.

Methodology

• The study involves 38 vitreous body samples from 36 horses affected by ERU, and 10 samples from 5 horses not affected by any ocular disease (control group).
• The samples are collected during a surgical procedure called vitrectomy from ERU-affected horses, and directly from the healthy ones.
• To further establish the association of leptospira with the vitreous body, the researchers inject a suspension of leptospira culture into the vitreous body of 2 eyes from the horses belonging to the control group.

Results

• Leptospira detection is straightforward in the vitreous body samples that were artificially inoculated with the bacteria, confirming the ability of the method to identify the bacteria.
• However, in the vitreous body samples of horses spontaneously suffering from ERU, leptospira detection is only successful in a few cases (3 out of 38).
• These observations indicate that the bacteria may be changing or concealing its form in the eye, hence the term “bacterial masquerade.” This phenomenon could explain the difficulty in detecting leptospira in samples from naturally-occurring ERU cases.

Implications

• Although the detection of leptospira was uncommon in spontaneously affected horses, its presence in some ERU cases suggests it may play a role in ERU development.
• The observed “bacterial masquerade” suggests that the bacteria adapts or changes its presentation within the vitreous body, making it more challenging to detect and perhaps enabling it to evade the host’s immune response.
• These findings raise the need for further investigation into the mechanisms through which leptospira infects the vitreous body and potentially induces ERU.