Understanding Bovine Viral Diarrhea Virus (BVDV) and BVD-PI Cattle. Article and photos courtesy of Central State Testing.  Bovine Viral Diarrhea Virus (BVDV) is a significant viral pathogen that affects cattle worldwide. Among the various strains of BVDV, cattle persistently infected with BVDV (BVD-PI) play...