Summary Whole blood and serum were collected from foals to determine the prevalence of Equine herpesvirus type 2 (EHV2) infection in foals, age at which infection can first be identified and serological responses to infection. Equine herpesvirus type 2 was isolated from peripheral blood mononuclear cells (PBMC) from 68 of 69 foals, 1–8‐months‐old, sampled once. Virus isolation was performed twice at intervals of 2–7 months on PBMCs from 33 foals and EHV2 was isolated on both occasions in all but one foal (negative, then positive). Regression analysis of log2‐transformed reciprocal serum EHV2 virus neutralising (VN) titres revealed that in foals age 1–7 months, EHV2 VN antibody titre was positively correlated with age (r = 0.94). Paired serum samples were obtained from 58 foals, with the first samples collected age 1–6 months and the second samples collected 2–4 months later. There were significant (P<0.05) increases in mean VN titres to EHV2 in foals sampled initially at age 1–4. Eight foals had blood sampled prior to sucking and at age 7, 20, 30 and 45 days. Each foal was negative for EHV2 in PBMC and each foal had a negative serum EHV2 VN titre immediately after birth. Each foal was positive for EHV2 in PBMC by age 45 days, with the earliest isolation at 25 days. Tracheal aspirate fluid and peripheral blood were collected from 20 foals without clinical signs of respiratory disease and from 30 foals with clinical signs of lower respiratory disease. In 20 foals without clinical signs of respiratory disease, EHV2 was isolated from tracheal aspirates (1/20 foals) and PBMC (20/20 foals) and in 30 foals with such clinical signs, from trachea aspirates (20/30 foals: P<0.01) and from PBMC (30/30 foals). In one 6‐month‐old foal, EHV1, but not EHV2, was isolated from the tracheal aspirate, 3 months after EHV2 had been isolated from a tracheal aspirate. These results demonstrate a greater prevalence of EHV2 in lower respiratory secretions in foals with clinically apparent lower respiratory disease, but a cause and effect relationship between the virus and lower respiratory disease remains to be elucidated. It is noteworthy, however, that of virus isolations performed on 50 tracheal aspirates, a virus (EHV1) other than EHV2 was isolated only once.

Sympathetic denervation in a 20-year-old, gray, Thoroughbred-Percheron gelding was manifested by cutaneous hyperthermia and sweating over the right side of the body, demarcated by a line from the withers to the elbow and extending cranially. There was cutaneous hyperthermia over the right side of the head, but other signs of Horner's syndrome (sweating, ptosis, miosis, enophthalmos) were not present. The pattern of cutaneous hyperthermia and sweating was consistent with sympathetic denervation localized to the cervicothoracic ganglion, and thoracic radiographs 20-year-old, gray, Thoroughbred-Percheron gelding A was examined because of increased heat in the distal right front limb but no associated lameness. The owner also reported that the right front hoof had grown more than the left front hoof during the previous month. The horse had been examined frequently at the hospital during the previous 3 years for a chronic gastric ulcer problem, and this new problem had never been reported to or noted by the attending clinician. The horse was maintained in a 4-acre field with 2 other horses and was used for occasional light riding.Examination revealed the horse to be bright and in good body condition. Temperature, pulse rate, and respiratory rate were within normal limits. The skin over the right front limb from the carpus down felt warmer than the skin over the left front limb. Also the skin over the right side ofthe neck felt slightly warmer than that on the left side. There was no evidence of pain with hoof testers, on flexion of the front limbs, or at a trot. Radiographs of the distal right front limb had been taken by the referring veterinarian and no lesions had been detected.Nuclear scintigraphy was performed to determine whether there was an underlying lesion in the distal right front limb that might coincide with the increased skin temperature. Scintigraphy was performed using 200 mCi technetium 99m monodiphosphonate. Soft tissue phase imaging was performed 10 minutes after administration of the radiopharmaceutical, and bone phase imaging was performed 180 minutes after its administration. The soft tissue phase imaging revealed moderate, focal uptake of radiopharmaceutical over the palmar aspect of the right coronary band, compared to the left limb. The bone-phase imaging revealed diffuse increased uptake in both front third phalangeal bones, with greater uptake in the right front compared to the left front third phalanx. These findings were nonspecific and were not interpreted to be associated with the increased skin temperature over the right front limb.The next week the owner indicated that the horse had developed a sinall focal area of intermittent sweating over the right scapula. This occurred in February, and sweating was not visible over any other area of the horse. A neurologic examination was performed and no abnormalities were noted. Another lameness evaluation revealed mild sensitivity to palpation of both front iuspensory ligaments, and ultraso- nography revealed a mild lesion in the right front s...