Mastitis associated with ovine progressive pneumonia virus infection in sheep.

Eighteen ewes were experimentally infected with ovine progressive pneumonia virus and their mammary glands were examined for lesions and virus at 2.5 to 10 years postinoculation. Lesions were seen in 14 of 18 sheep; virus was isolated from 4 of 8 sheep. Lesion consisted of an interstitial accumulation of lymphocytes with periductal lymphoid nodules, and epithelial vacuolation and necrosis at the site of the lymphoid nodules.