Effects in calves of mixed infections with bovine viral diarrhea virus and several other bovine viruses

The objective of this study was to verify whether a mixed infection in calves with bovine viral diarrhea virus (BVDV) and other bovine viruses, such as bovid herpesvirus-4 (BHV-4), parainfluenza-3 (PI-3) and infectious bovine rhinotracheitis (IBR) virus, would influence the pathogenesis of the BVDV infection sufficiently to result in the typical form of mucosal disease being produced. Accordingly, two experiments were undertaken. In one experiment calves were first infected with BVDV and subsequently with BHV-4 and IBR virus, respectively. The second experiment consisted in a simultaneous infection of calves with BVDV and PI-3 virus or BVDV and IBR virus. From the first experiment it seems that BVDV infection can be reactivated in calves by BHV-4 and IBR virus. Evidence of this is that BVDV, at least the cytopathic (CP) strain, was recovered from calves following superinfection. Moreover, following such superinfection the calves showed signs which could most likely be ascribed to the pathogenetic activity of BVDV. Superinfection, especially by IBR virus, created a more severe clinical response in calves that were initially infected with CP BVDV, than in those previously given the non-cytopathic (NCP) biotype of the virus. Simultaneous infection with PI-3 virus did not seem to modify to any significant extent the pathogenesis of the experimentally induced BVDV infection whereas a severe clinical response was observed in calves when simultaneous infection was made with BVDV and IBR virus. L'objectif de cette étude était de vérifier si une infection mixte chez des veaux provoquée par le virus de la diarrhée bovine virale (BVDV) et d'autres virus bovins, tels que l'herpesvirus-4 du bovin (BHV-4), le virus parainfluenza-3 (PI-3) et de la rhinotrachéite bovine infectieuse (IBR), influenceraient assez la pathogénie de l'infection par BVDV pour en arriver à produire la forme typique de la maladie des muqueuses. Deux expériences ont été entreprises en ce sens. Dans l'une, les veaux ont tout d'abord été soumis à l'infection par BVDV, puis, respectivement, par BHV-4 et le virus IBR. La deuxiéme expérience consistait en une infection simultanée des veaux au moyen de BVDV et du virus PI-3 ou de BVDV et du virus IBR. D'aprés la première expérience, il semble que l'infection par BVDV puisse être réactivée chez les veaux par BHV-4 et le virus IBR. Une preuve en est que BVDV, ou tout au moins la souche cytopathique (CP), a été retrouvée chez les veaux suite à la superinfec