Isolation of a Moraxella sp from horses with conjunctivitis.

The research article discusses a study conducted on horses affected with conjunctivitis, wherein a bacterium similar to Moraxella bovis, commonly seen in cattle with conjunctivitis, was isolated from horse eyes suffering from conjunctivitis.

Research Setting and Purpose

• The study was conducted on a set of eight Thoroughbreds on a stud that had contracted an odd case of bilateral conjunctivitis, showing symptoms such as oedema and excoriation around eyes, erosion of eyelid epithelium and mucopurulent discharge. These horses were kept in a single paddock on a farm.
• The purpose of the study was to isolate and identify the bacterium causing these symptoms, given that conjunctivitis is one of the most common conditions seen in horses, and that infectious agents’ role remains under-researched.

Methodology

• Conjunctival samples were taken from five affected horses and two unaffected horses for bacteriological examinations. Several of these horses had been introduced to the stud from New South Wales and New Zealand.
• A chloramphenicol ophthalmic ointment was then applied, resulting in early resolution of both conjunctivitis and eyelid margin erosion.
• Similar cases at a neighboring training stable were also treated with this ointment.
• Swabs were soaked into Amies transport medium and were inoculated onto defibrinated horse blood agar under various atmospheric and temperature conditions.

Results

• After overnight incubation, large numbers of bacteria were found on the agar plates. The bacteria exhibited properties of the Moraxella species, similar to M. bovis. They did not, however, haemolyse horse blood.
• The bacteria did not grow from the swabs of horses showing no clinical signs of the disease, suggesting a correlation between the bacteria and the condition.
• When the bacterial samples were introduced into a healthy crossbred mare, it developed symptoms of mild conjunctivitis over the following two to four days.

Discussion and Conclusion

• One of the notable aspects of this condition was erosion of the eyelid margin, which is notably seen in bovine eyes affected with M. bovis infection.
• It was observed that conjunctivitis outbreak was particular to a single group of horses in the stud, indicating a possible environmental or geographical component to the disease.
• The study’s results suggest the bacterium’s significant role in causing conjunctivitis in these horses, further strengthening the necessity for attention and research on infectious agents’ roles in equine conjunctivitis.