Opisthotonos and unilateral internal hydrocephalus associated with aberrant migration of Serratospiculum sp. or Serratospiculoides sp. in a prairie falcon.

A juvenile, wild-caught prairie falcon ( Falco mexicanus) kept for falconry was presented to a veterinary hospital for intermittent opisthotonos and torticollis. Clinical examination, complete blood count, serum biochemistry panel, and fecal analysis were unremarkable. Clinical signs did not resolve, and the bird was euthanized 6 mo after the appearance of clinical signs. Autopsy revealed a mild, unilateral hydrocephalus and nematodes within the thoracic air sac. Histopathology demonstrated mild, unilateral hydrocephalus; scattered glial nodules; meningeal nematode sections; and meningeal and intraventricular embryonated eggs. Morphology and molecular characterization were consistent with the air sac nematode Serratospiculum or Serratospiculoides spp. Air sac nematode infection can be associated with air sacculitis or pneumonia in falcons. Aberrant migration of air sac filariid nematodes Serratospiculum or Serratospiculoides spp. into the nervous system resulting in clinical disease is rare, but should be included in the differential diagnosis of neurologic diseases in falcons.