Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 4, 2002
Publication Date: April 4, 2002
Technical Abstract: Differences in the distribution and spread of viral antigen, development of lesions and correlation between presence of viral antigen and lesions were compared between an avirulent and virulent strain of BVDV2. Two groups of 2-week- to 2-month-old colostrum-deprived calves were intranasally inoculated with the naturally occurring avirulent BVDV2 strain 28508-5 or the virulent strain 1373. To study the sequence of virus spread and lesion development, calves were necropsied at days 3, 6, 8/9 and 12 to 14 post inoculation (pi). Viral antigen was detected by the indirect immunoperoxidase method in cryostat sections and lesions were evaluated in H&E-stained paraffin sections. Clinical signs and changes in lymphocyte and thrombocyte numbers confirmed the difference in virulence between the two strains. The avirulent and virulent strain showed comparable initial infection and spread at day 3 pi. At day 6 pi, both strains were found widespread in lymphoid tissues and multifocally in intestinal mucosa. Lesions were very mild despite the large amount of antigen in the lymphoid tissues. After day 6 pi, differences between the avirulent and virulent strain became more prominent. The avirulent strain was cleared from the tissues, but there was a transient phase of depletion. The virulent strain continued to spread to different organs and there was severe depletion of lymphoid tissues without recovery.