#05-023

Complete

Date Full Report Received

11/01/2006

Date Abstract Report Received

07/21/2008

Bovine viral diarrhea virus (BVDV) is a virus usually found in domestic and wild ruminants. However, a BVDV was recently isolated from a case of severe mortality (about 55%) in finishing swine. This finding raised a question about what role this virus might have played in the field case. In addition to the BVDV, others agents were detected in affected pigs from this case. One of these was a bacteria that is not commonly found in pigs, Haemophilus parasuis serotype 13. Although different serotypes of H. parasuis can cause significant illness and death in pigs, the bacteria are not typically associated with severe mortality as in the field case. One idea to explain the high mortality observed in this case is that there was an interaction between the BVDV and the H. parasuis resulting in the high mortality.
A series of studies were conducted to 1) characterize the BVDV isolate, 2) test the clinical effects of the BVDV on pigs, and 3) test the potential interaction between the BVDV and the H. parasuis isolates from this field case. At the genetic level the BVDV isolate is most similar to the cattle BVDV type 1b strains. In contrast to type 1b strains, the swine BVDV isolate grows very well in porcine cell lines suggesting it has adapted to swine. Experimental infection of pigs with the BVDV isolate had no negative clinical effect. Experimental infection of pigs with the H. parasuis isolate made them very sick and 4 of the 12 pigs were euthanized for humane reasons. Pigs infected with the BVDV and H. parasuis isolate responded similarly. Collectively, the results of these studies suggest the BVDV isolate did not have a direct role in the high mortality field case, and a significant amount of the mortality could be attributed to infection with this serotype 13 H. parasuis