Systemic Bovine herpesvirus 1 infections in neonatal dairy calves.

During a 6-year period, 62 out of 2,980 calves examined (2.08%) between 1-30 days of age had lesions consistent with Bovine herpesvirus 1 infection. The mean and median age of affected calves was 14 days of age. Most cases of infection were in calves 12 and 15 days of age, with 34 calves (54.8%) affected; 14 calves (22.6%) were between 16-21 days of age; 11 calves (17.8%) were between 7-11 days of age; and 3 calves (4.8%) were between 22-30 days of age. In 29 of the calves, the adrenal gland was the only organ affected. In 25 calves, the adrenal gland and at least 1 other tissue had lesions consistent with herpes viral infection. Five animals had no adrenal lesions but had 1 or more additional tissue with lesions consistent with herpesvirus. Three animals had no adrenal gland present for examination but had lesions in other tissues. Organs and number of animals affected by Bovine herpesvirus 1 infection were adrenal gland (54), liver (18), lungs (15), kidney (8), small intestines (7), large intestines (7), rumen/omasum (7), trachea/larynx (3), abomasum (2), heart (1), esophagus (1), thymus (1), and lymph node (1).