HISTOLOGIC FEATURES AND RESULTS OF VIRUS ISOLATION TESTS OF TISSUES OBTAINED FROM TEAT LESIONS THAT DEVELOPED IN DAIRY-CATTLE DURING WINTER

Objective-To determine microscopic features and involvement of viruses in teat-end lesions (TEL) of dairy cows during winter. Sample Populat ion-Teats with TEL on lactating Holstein cows and from udders of carca sses. Procedure-Tissues obtained from TEL of 10 teats from 7 cows on 2 research farms during the winter of 1994 to 1995 and 13 teats with TE L excised from udders of carcasses at an abattoir during February 1995 were submitted for virus isolation. During the winter of 1995 to 1996 , an increased prevalence of TEL was observed in a research herd. Afte r a decrease in ambient temperature, TEL were identified, and a full-t hickness section of epidermis was removed from skin surrounding teat o rifices. Tissues were examined by use of light and electron transmissi on microscopy. Results-Viruses were not isolated from TEL tissues. Les ions ranged from mild elevations of the epidermis to thickened oval re gions that encircled the teat orifice. The most severe lesions were da rk and had thick crusts. Histologically. IEL were composed of thickene d regions of epidermis most notably caused by hyperplasia of cells wit hin the stratum spinosum. Excess production of keratinocytes was also evident, and the keratinocyte layer often contained bacteria. Ultrastr ucturally, squamous cells contained large amounts of keratin, but viri ons were not detected. Evidence of a viral etiologic agent for IEL was not detected. Clinical Implications-Development of TEL may be associa ted with decreases in ambient temperature. Numerous bacteria were evid ent in the keratin of TEL. Lesions and associated bacteria may predisp ose cows to mastitis.