Bovine herpes mammillitis in two New York dairy herds.

Bovine herpes mammillitis was diagnosed in 2 New York dairy herds. Lesions ranged from vesiculation and ulceration of large (up to 10 cm wide) areas of udder and teat skin to single small (2-3 cm wide) plaques of edema. Some lesions resembled "umbilicated pocks" characteristic of cowpox virus infections. Recently freshened heifers were the most severely affected; older cows and heifers with less turgid udders had milder lesions. In 2 cows, incurable mastitis developed. In other cows, the lesions healed by centripetal growth of epidermis into the lesions. Diagnosis was made by isolation of bovid herpesvirus 2 from lesions in both herds and by serum-neutralization testing. Virus isolated from a cow in 1 herd was injected into 9 members of the same herd and may have been responsible for the absence of lesions on these animals; all other members of the herd were affected.