Platelet aggregation responses and virus isolation from platelets in calves experimentally infected with type 1 or type II bovine viral diarrhea virus

Altered platelet function has been reported in calves experimentally infect ed with type II bovine viral diarrhea virus (BVDV). The purpose of the pres ent study was to further evaluate the ability of BVDV isolates to alter pla telet function and to examine for the presence of a virus-platelet interact ion during BVDV infection. Colostrum-deprived Holstein calves were obtained immediately after birth, housed in isolation, and assigned to 1 of 4 group s (1 control and 3 treatment groups). Control calves (n = 4) were sham inoc ulated, while calves in the infected groups (n = 4 for each group) were ino culated by intranasal instillation with 10(7) TCID50 of either BVDV 890 (ty pe II), BVDV 7937 (type II), or BVDV TGAN (type I). Whole blood was collect ed prior to inoculation (day 0) and on days 4, 6, 8, 10, and 12 after inocu lation for platelet function testing by optical aggregometry by using adeno sine diphosphate and platelet activating factor. The maximum percentage agg regation and the slope of the aggregation curve decreased over time in BVDV -infected calves; however, statistically significant differences (Freidman repeated measures ANOVA on ranks, P < 0.05) were only observed in calves in fected with the type II BVDV isolates. Bovine viral diarrhea virus was not isolated from control calves, but was isolated from all calves infected wit h both type II BVDV isolates from days 4 through 12 after inoculation. In c alves infected with type I BVDV, virus was isolated from 1 of 4 calves on d ays 4 and 12 after inoculation and from all calves on days 6 and 8 after in oculation. Altered platelet function was observed in calves infected with b oth type II BVDV isolates, but was not observed in calves infected with typ e I BVDV. Altered platelet function may be important as a difference in vir ulence between type I and type II BVDV infection.