sentences:  The virus initially replicates in the lymphatic tissue of the respiratory tract.The virus then enters the blood stream and infects the respiratory, gastrointestinal, urogenital, epithelial, and central nervous systems, and optic nerves.Therefore, the typical pathologic features of canine distemper include lymphoid depletion (causing immunosuppression and leading to secondary infections), interstitial pneumonia, encephalitis with demyelination, and hyperkeratosis of the nose and foot pads.