Ll. Timms et al., HISTOLOGIC FEATURES AND RESULTS OF VIRUS ISOLATION TESTS OF TISSUES OBTAINED FROM TEAT LESIONS THAT DEVELOPED IN DAIRY-CATTLE DURING WINTER, Journal of the American Veterinary Medical Association, 213(6), 1998, pp. 862
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.