Anosmia associated with canine distemper.

The sense of smell in dogs infected with canine distemper virus (CDV) was examined by use of EEG olfactometry, behavioral olfactometry, and electro-olfactography. Infection with CDV was confirmed by a direct immunofluorescence technique in 8 active cases and was suggested by clinical history compatible with canine distemper 10 to 26 weeks earlier in 6 cases. Pathologic alterations of the olfactory mucosa in 3 clinically affected dogs was examined by light microscopy. Infection with CDV was found to be associated with anosmia and lack of recorded responses on electro-olfactogram in 8 of 8 dogs with clinical signs of acute distemper from naturally acquired infections. Anosmia was found in 5 of 6 dogs that had recovered from acute distemper 10 to 26 weeks earlier. The sixth dog had hyposmia, with abnormalities on the electro-olfactogram. Histologic examination was not performed on the 6 dogs that had recovered. Histologic lesions observed at necropsy in 3 dogs that had had clinical signs of acute distemper were those of subacute purulent rhinitis and atrophy of the olfactory epithelium. Altered olfactory function could be explained by mucopurulent exudate blocking odors from olfactory receptors in the acutely affected dogs, but alteration of olfactory function in the dogs that had recovered without clinical evidence of rhinitis could not be explained.