Neospora caninum pneumonia in an adult dog.

Neospora caninum was identified in a lung aspirate specimen from an adult dog with severe pneumonia. Neosporosis was tentatively diagnosed by cytologic examination of a Wright-Giemsa-stained smear of the aspirate specimen, using light microscopy. The infection was confirmed by immunohistochemical examination of a section of lung tissue obtained at necropsy. Neosporosis is usually a fatal ascending neurologic disease of dogs less than 1 year of age. Neospora caninum infections are uncommon in adult dogs and do not have a consistent clinical course. The disease in the dog of this report was unique because the dog had clinical respiratory tract disease and because preliminary diagnosis was made by cytologic examination.