
18-month-old cattle had the highest incidence. The disease seems less severe in animals which are on pasture than those in feedlotsg. Polioencephalomalacia affects sheep of all ages from 10-day-old lambs to adults, a greater incidence being reported in pregnant ewe@. The disease has been described in a 2-year-old goat which was on a clean pasturelz.
No report describing this disease in deer (Odocoilez4.r spp.) was found in the literature. TOURNUT et a1.20 reported polioencephalomalacia in a 6-month-old female antelope of unspecified variety. However, the basis for this diagnosis was the animal's response to thiamine therapy and polioencephalomalacia was not confirmed by post mortem examination.
The purpose of this paper is to describe a spontaneous case of polioencephalomalacia in a white-tailed deer which was also infested with Pneumostrongylus tenuis.
Case History
On March 5, 1969, a southern Minnesota farmer found an adult female white-tailed deer (Odocoileus virginianus borealis), apparently blind and exhibiting no fear of humans, wandering aimlessly in circles. The deer was confined in a barn and provided feed and water. Reportedly, it drank considerable amounts of water but ate nothing while in confinement. The deer became comatose on March 7, 1969 . Blood samples were taken by one of us (P.D.K.) before the deer was transported to the College of Veterinary Medicine, University of Minnesota. The hemogram was normal for white-tailed deer and blood analysis for lead was negative. The tentative clinical diagnosis was cerebrospinal nematodiasis. 
Necropsy Findings
The deer was killed with pentobarbital sodium intravenously and necropsied immediately. The deer was in excellent nutritional condition with abundant subcutaneous and abdominal adipose tissue. The rumen was full of grain, the major portion being ground corn. The deer was pregnant with twin fetuses in the 3rd trimester of development.
Except for nonspecific bilateral hypopyon and suppurative conjunctivitis, the only lesions were in the central nervous system. Bacterial culture was not obtained from any organ.
Eight adult nematodes (P. fenuir) were in the subdural space over the cerebrum and in the area of the optic chiasma. Some nematodes were imbedded in the dura, which was brownish and roughened in the area around parasites. There was no parasite in the subdural space of the spinal cord, which had normal meninges.
The brain was sectioned transversely after the central nervous system was fixed in 10% neutral formalin. O n cut surface the cerebral cortex had a yellow discoloration and there were petechial hemorrhages and softening in the lingula, nodulus, and uvula of the cerebellum. There were bilaterally symmetrical hemorrhage and softening in the geniculate bodies, oculomotor nuclei, thalamus, vestibular nuclei, and the posterior colliculi ( Fig. 1 ). Numerous histologic sections were taken through various levels of the spinal cord.
Histopathology
There was no lesion in the spinal cord although its leptomeninges contained a few small granulomas. No histologic evidence of verminous migration was found in the brain, but P. tenuis (ova, larvae, and adults) had elicited a granulomatous meningitis.
In areas of the brain with acute necrosis, the neurons were pykngtic and their cytoplasm was hyaline and markedly eosinophilic (Fig. 2) . There was vacuolation in the perineuronal areas and beginning lysis of the neuropil. Neither extensive microgliosis nor infiltration by lipophages was evident in the areas of acute necrosis, or elsewhere ; however, there was proliferation and swelling of capillary endothelial cells in the necrotic areas.
Extensive cerebrocortical necrosis existed in all areas of cerebrum. Laminae 4 through 6 were most consistently involved but in some sections all layers of the cerebral cortex were necrotic. Lines of cleavage between the gray and white matter were lacking. Necrosis was less severe in the depths of the sulci than in the gyri. The white matter was edematous but glial cells were not activated in these areas.
The cerebellum had petechial hemorrhages in the granular layer and in the white matter. In the lingula, nodulus, and uvula there was acute necrosis of the Purkinje cells; this necrosis extended through the granular layer into the white matter. There were bilateral necrosis and hemorrhage in the vestibular nuclei.
A few acute inflammatory cells were in the leptomeninges adjacent to the necrotic areas in the lingula.
There were bilateral necrosis and hemorrhage in the caudal colliculi (Fig. 3) . The neuropil was vacuolated by edematous fluid and many axons were swollen and eosinophilic. There were a few lipophages in these necrotic areas (Fig. 4) .
A slight microgliosis existed and some microglia were karyorrhexic. Gemistocytes were at the periphery of the necrotic areas and a few plasma cells and siderocytes were in the perivascular spaces.
In the midbrain the oculomotor nuclei were necrotic and hemorrhagic. There were vacuolated neurons but no neuronal necrosis in the nucleus ruber. Bilaterally symmetrical necrosis occurred in the lateral geniculate nuclei. The nuclei of the medial dorsal thalamus had selective neuronal necrosis and a few swollen axons. There was no degenerative change in the hippocampus, caudate nuclei, or pituitary.
Discussion
Reports's 2 have described meningeal infestation of white-tailed deer by P. tenuis, but polioencephalomalacia has not been reported in this species. No apparent association existed between the parasitic infestation and the polioencephalomalacia in this deer.
The lesions of polioencephalomalacia and their distribution were similar to those described in other ruminants affected with this diseases, * , 9 , 1 5 + 18,1*, 21. There was acute ischemic-type neuronal necrosis with a laminar distribution in the cerebrocortex. Acute necrosis and hemorrhage occurred in the cerebellar vermis, caudal colliculi, oculomotor nudei, lateral geniculate nuclei, and nuclei in the medial dorsal thalamus. In these necrotic areas the capillaries were hyperplastic and their endothelial cells were swollen. There was a slight microgliosis and a few lipophages in the vacuolated neuropil. The lesions would indicate a duration of approximately 72 h.
The ruminal contents indicated that this deer was eating a diet similar to that of feedlot animals. The etiology of this disease is unknown but investigators believe it to be a toxicosis or thiamine deficiency's. Some animals with polioencephalomalacia respond clinically to thiamine therapy but the possibility exists that the beneficial effect of thiamine be nonspecific, No attempt was made to treat this deer with thiamine.
Szimmay
In an aduIt white-tailed deer affected by polioencephalornalacia the lesions were acute ischemic-type necrosis, malacia, and hemorrhage in 'the cerebral cortex, vestibular nuclei, caudal colliculi, oculomotor nuclei, geniculate nuclei, thalamus, and ventral portion of the cerebellar vermis. The deer also had granulomas associated with Pneumostrongyfus tenuis in the spinal leptomeninges.
Zzi.ramnzenfa.rszing
Bei einem erwachsenen an Polioenzephalomalazie erkrankten weisschwanzigen Hirsch waren die Veranderungen vom Typ der akuten ischamischen Nekrose ; Malazie und Hamorrhagien in der Grosshirnrinde, im Vestibularis Kern, den kaudalen Vierhiigeln, dem Okulomotorius Kern, Nukleus geniculatus, Thalamus und ventralen Anteil des Kleinhirnwurmes. Der Hirsch hatte ausserdem Granulome in Verbindung mit einer Pneumostrongyfus tennis Infektion der spinalen Leptomeningen.

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