Meningoencephalitis Caused by Halicephalobus gingivalis in a Thoroughbred Gelding

A 6-year-old Thoroughbred gelding was euthanized after a 2-month period of abnormal neurological signs, such as circling left in his pen and hitting his head and body against the wall. After the horse was euthanized on the farm, a half of the brain and whole blood were submitted for diagnostic tests. Histopathological examination of the brain revealed granulomatous and eosinophilic meningoencephalitis with numerous intralesional nematodes, predominantly affecting the cerebrum. Multifocal malacic foci were scattered in the brain parenchyma. The intralesional parasites were identified as Halicephalobus gingivalis by morphological features and PCR testing. To the best of our knowledge, this is the first report of meningoencephalitis caused by H. gingivalis in the horse in Korea.