Onchocercosis of an intervertebral joint capsule causing cervical vertebral stenotic myelopathy in a horse

Department of Biomedical Sciences and Veterinary Public Health, Division of Pathology, Pharmacology and Toxicology, Swedish University of Agricultural Sciences, Box 7028, 750 07 Uppsala, Sweden.

A novel case where onchocercosis was identified as a cause of cervical myelopathy in the horse is described. A 15-year-old Connemara mare was euthanized due to progressive locomotion disturbance. Postmortem examination revealed soft-tissue swelling in the intervertebral joint capsule of C6-7 with narrowing of the vertebral canal. On light microscopy, axonopathy was pronounced in the corresponding segment of the spinal cord. Fibrous tissue and eosinophilic granulomas were found in the joint capsule, together with parasites identified histologically as Onchocerca sp.