A flock of 8-month-old feeder lambs presented to the Cornell University Ambulatory Service on August 22, 2018 with a one-month history of hind-end ataxia progressing to paralysis and complete recumbency. The 1079 animals were purchased from Nevada on June 1st. On arrival, they were treated with levamisole and albendazole and then placed on pasture. On presentation, several animals were ataxic or recumbent, but lacked visual impairment or cranial nerve deficits and had normal mentation. Results of forage analysis and listeriosis culture were evaluated to rule out nutritional causes. Six representative animals were submitted to the Cornell Anatomic Pathology department for gross and histologic examination. Necropsy revealed histologic changes in the spinal cord most compatible with Parelaphostrongylus tenuis infection. Select animals were treated with high-dose dexamethasone with no clinical resolution. Since presentation, 19% of the group has been lost. This report will discuss etiology, presentation, diagnosis and treatment options for Parelaphostrongylus tenuis infection in small ruminants.