Comparison of type I and type II bovine viral diarrhea virus infection in swine

Some isolates of type II bovine viral diarrhea virus (BVDV) are capable of causing severe clinical disease in cattle. Bovine viral diarrhea virus infe ction has been reported in pigs, but the ability of these more virulent iso lates of type II BVDV to induce severe clinical disease in pigs is unknown. It was our objective to compare clinical, virologic, and pathologic findin gs between type I and type II BVDV infection in pigs, Noninfected control a nd BVDV-infected 2-month-old pigs were used. A noncytopathic type I and a n oncytopathic type II BVDV isolate were chosen for evaluation in feeder age swine based upon preliminary in vitro and in vivo experiments. A dose titra tion study was performed using 4 groups of 4 pigs for each viral isolate. T he groups were inoculated intranasally with either sham (control), 10(3), 1 0(5), or 10(7) TCID50 of virus. The pigs were examined daily and clinical f indings were recorded. Antemortem and postmortem samples were collected for virus isolation. Neither the type I nor type II BVDV isolates resulted in clinical signs of disease in pigs, Bovine viral diarrhea virus was isolated from antemortem and postmortem samples from groups of pigs receiving the 1 0(5) and the 10(7) TCID50 dose of the type I BVDV isolate. In contrast, BVD V was only isolated from postmortem samples in the group of pigs receiving the 10(7) TCID50 dose of the type II BVDV isolate. Type I BVDV was able to establish infection in pigs at lower doses by intranasal instillation than type II BVDV, Infection of pigs with a type II isolate of BVDV known to cau se severe disease in calves did not result in clinically apparent disease i n pigs.