Experimentally induced teat stenosis in dairy ewes: clinical, pathological and ultrasonographic features

A strain of Staphylococcus chromogenes was introduced into the teat cistern of five ewes, teat inflammation and stenosis being the primary consequences. Initially, the inoculated teats were swollen and warm; later, a hard structure was palpated running lengthwise inside the teat, with a thick ring above the tip of the teat, which interfered with expression of milk. Mastitis, confirmed by clinical, cytological, bacteriological and histological findings, was evident 4 days after infection. Ultrasonographically, a hyperechoic line under the mucosa of the teat cistern was observed. At necropsy, the duct wall of the inoculated teats was found to be thickened. Histopathological features included leucocytic infiltration, especially under the mucosa of the teat, and extensive fibrosis in the subcutaneous tissues. S. chromogenes was recovered from scrapings from the duct and the cistern of the inoculated teats.