Ocular Halicephalobus (syn. Micronema) deletrix in a horse.

The research explored a case where a horse developed severe eye infection caused by a parasite, Halicephalobus deletrix, which also spread to the brain leading to the animal’s death. This is the first instance documenting eye parasitism by H. deletrix, suggesting possible spreading of infection from the eye to other body parts.

Summary of the Research:

The study revolves around a case of a horse suffering from severe unilateral uveitis (inflammation of middle layer of the eye) for four weeks. The infected eye was subjected to histopathologic analysis which revealed:

• Unilateral granulomatous chorioretinitis: This indicates the inflammation of the choroid and retina of the horse’s eye caused by granulomas, which are inflammatory masses generally produced in response to foreign substances or infections.
• Presence of Halicephalobus deletrix: This is a parasitic nematode (roundworm) that typically inhabits soil and decaying organic matter but can cause serious infections in horses and rarely, humans.

The horse showed worsening neurological symptoms a few days after surgery to remove the affected ocular content and to implant a prosthesis, and consequently, had to be euthanized.

Post-Mortem Findings:

Autopsy of the horse revealed:

• Severe multifocal granulomatous encephalitis: Inflammation of the brain with multiple granulomatous spots.
• Presence of H. deletrix specifically in the optic chiasm (where the optic-nerve fibers cross), thalamus (relay station for sensory information), and brain stem.
• The non-affected eye remained disease-free, suggesting the infection predilected the originally affected side.

This is the first documented case of ocular parasitism by H. deletrix which resulted in systemic dissemination from a primary ocular site to the brain. The research highlights H. deletrix’s potential to cause systemic infection with lethal consequences, expanding its clinical significance beyond its known parasitic behavior.