A 19-mo-old female captive white-tailed deer in a public wild animal park i
n Richmond (Virginia, USA) was necropsied and evaluated histologically foll
owing spontaneous death after a 1 wk period of lethargy in a captive herd o
f 22 deer. An acute necrotizing pneumonia was associated with intraendothel
ial protozoal schizonts that were identified immunohistochemically as Sarco
cystis spp. This is the first confirmed report of acute sarcocystosis in a
wild ruminant.