Transmissible Gastroenteritis Virus in Neonatal Pigs Bovine Viral Diarrhea Virus Isolated from Fetal Calf Serum Enhances Pathogenicity of Attenuated

Abstract. A bovine viral diarrhea virus (BVDV-C) was isolated from swine tissue culture cells used toattenuate the transmissible gastroenteritis virus (TGEV) after 68 passes. Piglets given a pure culture of BVDV-C developed clinical signs similar to those of a mild TGEV infection and recovered by 10 days postexposure.Villous blunting and fusion was observed in the small intestine, and a lymphocyte depletion was observed inPeyer’s patches in the ileum. Piglets given a combination of BVDV-C and attenuated TGEV developed clinicalsigns similar to those of a virulent TGEV infection and were euthanized. The combined infection induced ageneralized lymphocyte depletion throughout the lymphatic system and villous atrophy in the intestinal tract.Piglets exposed to a another type I strain of BVDV (NY-1) either alone or in combination with the attenuatedTGEV had mild clinical signs similar to those of a TGEV infection. Moderate villous atrophy in the ileum anda lymphocyte depletion in the mesenteric lymph node were observed in these piglets postmortem. The dataindicate a potential problem for diagnostic laboratories in relation to a diagnosis of virulent TGEV infectionsand in the field for young piglets exposed to a BVDV-contaminated TGEV vaccine.The transmissible gastroenteritis virus (TGEV) is amember of the Coronaviridae family of viruses. Co-ronaviruses are pleomorphic enveloped viruses with anonsegmented positive-stranded RNA genome.