Stability of Bovine viral diarrhea virus antigen in ear punch samples collected from bovine fetuses.

Fourteen first-calf heifers were tested free of antibodies against Bovine viral diarrhea viruses (BVDV) by serum neutralization and free of BVDV by polymerase chain reaction. Twelve were exposed to BVDV-1b strain CA0401186a at 84-86 days of gestation, and 2 were exposed to mock inoculum and served as negative controls. Fetuses were harvested by cesarean section at 115-117 days of gestation. The 12 fetuses removed from the BVDV-exposed heifers were BVDV positive based on virus isolation from kidney, thymus, cerebellum, and spleen. It can be assumed that these fetuses would have developed into persistently infected calves had they been allowed to go to term. Virus was not isolated from the fetuses of control animals. Ear punch samples were collected from all fetuses at time of harvest. Antigen capture enzyme-linked immunosorbent assay (ACE), using a commercial kit, was performed on ear punch samples that were frozen within 5 hr of collection and stored at -20 degrees C until tested, tested after storage for 7 days at room temperature (18-25 degrees C), or tested after storage for 7 days at 37 degrees C. Samples stored for 7 days at room temperature or 37 degrees C lost an average of 34% of their starting weight. All samples from BVDV isolation-positive fetuses tested positive by ACE, whereas samples from nonexposed fetuses tested negative, regardless of storage conditions. These results suggest that ACE testing of skin samples collected from aborted fetuses and stillborn calves found in the field may represent a practical surveillance method for BVDV-induced reproductive disease.