Migration of a spiruroid nematode through the brain of a horse.

This research investigated an unusual case where a spiruroid nematode migrated through a horse’s brain, causing significant neurological problems. Despite initial treatment for a protozoal brain infection, the mare’s condition worsened leading to euthanasia, and after death, nematode tracts were discovered in the brain.

Initial Presentation and Diagnostic Attempts

• The subject of the study was a pregnant, 10-year-old Paint mare that developed acute neurological problems.
• Physical examination pointed to a broad and uneven brain stem disease.
• The blood test, serum chemical panel, and lumbar spinal fluid analysis all came back normal, ruling out many common equine neurologic diseases.
• The main diagnosis considered was equine protozoal myeloencephalitis, a type of infection in the horse’s spinal cord and brain caused by a protozoan parasite.
• The horse was treated with trimethoprim-sulfadiazine, a common antibiotic therapy for this suspected condition.

Treatment and Subsequent Deterioration

• The mare initially showed signs of improvement during five weeks of treatment.
• However, the neurological symptoms eventually worsened, leading to the decision to euthanize the horse for humane reasons.

Necropsy Findings and Final Diagnosis

• Post-mortem examination revealed the presence of large damaged (malacic) tracts in the brain stem and cerebral cortex.
• Microscopic examination further identified cross-sections of a nematode within these tracts.
• The nematode was identified as a gravid female Draschia megastoma, a type of spiruroid nematode.
• This unexpected finding suggests that the neurologic disease was due to this parasitic infestation, not the initially suspected protozoal infection.