Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/3/1998
Publication Date: N/A
Citation: Interpretive Summary: Controlling the swine disease transmissible gastroenteritis (TGE) on the farm is usually attempted through the use of commercial vaccines. These vaccines contain a TGE virus (TGEV) that has been altered by growing it in the laboratory. Sometimes the material in which the vaccine virus is grown also contains a second virus, namely bovine viral diarrhea virus (BVDV) that is found in the serum of cattle. The bovine virus generally does not produce a disease in swine, although it may produce clinical signs in cattle. When young piglets are given a laboratory modified TGEV, they may become sick, but usually recover without any ill effects. However, when litter mate piglets were given the same TGEV combined with a BVDV virus adapted to grow in the medium used to grow the TGEV, they developed clinical signs similar to a virulent TGEV infection. This study emphasizes the importance of screening TGEV vaccines for the presence of BVDV to prevent clinical illness following the use of such vaccine on the farm.
Technical Abstract: A bovine viral diarrhea virus (BVDV-C) was isolated from swine tissue culture cells used to attenuate the transmissible gastroenteritis virus (TGEV); 68 passes. Piglets given a pure culture of BVDV-C developed clinical signs similar to that of a mild TGEV infection and recovered by ten days post exposure. Villous blunting and fusion were observed in the small intestine and a lymphocyte depletion was observed in Peyer's patches in the ileum. Piglets given a combination of BVDV-C and attenuated TGEV developed clinical signs similar to a virulent TGEV infection and were euthanized. The combined infection induced a generalized lymphocyte depletion throughout the lymphatic system along with 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 attenuated TGEV had mild clinical signs similar to a TGEV infection. Moderate villous atrophy in the ileum and a lymphocyte depletion in the mesenteric lymph node were observed in these piglets at post-mortem. The data indicate a potential problem for diagnostic laboratories in relation to a diagnosis of virulent TGEV infections and in the field for young piglets exposed to a contaminated TGEV vaccine.