Ulcerative keratitis caused by beta-hemolytic Streptococcus equi in 11 horses

Area of Science:

• Veterinary Ophthalmology
• Equine Infectious Diseases
• Microbiology

Background:

• Equine ulcerative keratitis is commonly associated with Gram-negative bacteria and fungi.
• Beta-hemolytic Streptococcus spp. are typically part of normal equine conjunctival flora but can cause severe infections.

Purpose of the Study:

• To document clinical cases of ulcerative keratitis in horses linked to beta-hemolytic Streptococcus equi.
• To analyze the clinical presentation, treatment, and outcomes of these specific equine eye infections.

Main Methods:

• Retrospective clinical study of 11 horses diagnosed with ulcerative keratitis.
• Bacteriological culture and antibiotic sensitivity testing of beta-hemolytic Streptococcus equi isolates.
• Review of clinical signs, treatment modalities, and patient outcomes.

Main Results:

• Beta-hemolytic Streptococcus equi (subspecies zooepidemicus in 10/11 cases) was identified as the causative agent.
• Severe keratomalacia, deep ulcers, descemetoceles, iris prolapse, and uveitis were common clinical signs.
• Treatment involved conjunctival flaps, corneal transplantation, and topical antibiotics; healing time averaged 44.7 days.

Conclusions:

• Beta-hemolytic Streptococcus spp. can cause severe, aggressive ulcerative keratitis in horses, distinct from typical equine ulcer pathogens.
• These bacteria demonstrate a capacity to degrade conjunctival graft tissue, complicating surgical management.
• Aggressive surgical intervention combined with intensive medical therapy, including topical antibiotics and protease inhibitors, is recommended.