Toxoplasmic encephalitis in a free-ranging Rocky Mountain bighorn sheep from Washington

A 4-mo-old free-ranging Rocky Mountain bighorn sheep (Ovis canadensis canad ensis) from the Hells Canyon area (Washington, USA) was diagnosed with ence phalitis associated with Toxoplasma gondii infection. The sheep had concurr ent pneumonic pastuerellosis and resided in a geographic area with endemic Pastuerella-associated pneumonia and mortality in bighorn sheep. The brain had multifocal necrotizing and nonsuppurative encephalitis with intralesion al protozoa. The protozoa were identified as T. gondii by immunohistochemis try. To our knowledge, this is the first report of T. gondii infection in a Rocky Mountain bighorn sheep.