Persistent infections after natural transmission of bovine viral diarrhoea virus from cattle to goats and among goats

Abstract

Bovine viral diarrhoea virus (BVDV) is an economically important pathogen of cattle worldwide. Infection of a pregnant animal may lead to persistent infection of the foetus and birth of a persistently infected (PI) calf that sheds the virus throughout its life. However, BVD viruses are not strictly species specific. BVDV has been isolated from many domesticated and wild ruminants. This is of practical importance as virus reservoirs in non-bovine hosts may hamper BVDV control in cattle. A goat given as a social companion to a BVDV PI calf gave birth to a PI goat kid. In order to test if goat to goat infections were possible, seronegative pregnant goats were exposed to the PI goat. In parallel, seronegative pregnant goats were kept together with the PI calf. Only the goat to goat transmission resulted in the birth of a next generation of BVDV PI kids whereas all goats kept together with the PI calf aborted. To our knowledge, this is the first report which shows that a PI goat cannot only transmit BVD virus to other goats but that such transmission may indeed lead to the birth of a second generation of PI goats. Genetic analyses indicated that establishment in the new host species may be associated with step-wise adaptations in the viral genome. Thus, goats have the potential to be a reservoir for BVDV. However, the PI goats showed growth retardation and anaemia and their survival under natural conditions remains questionable.

Figure 1

Immunohistochemistry of a skin biopsy of the initial PI goat. The immunohistological analysis of a snap frozen skin biopsy of the initial PI goat shows the presence of BVDV antigen (red staining) in epithelial cells of the hair root shaft as typically seen in PI cattle [48]. C16 antibody, 20× magnified.

Figure 2

Immunohistochemistry of the femur of PI goat B2_2. The immunohistological analysis of a paraffin-embedded femur section of the PI goat B2_2 shows the presence of BVDV antigen (red staining) in the cytoplasm of an osteoblast (top) and an osteoclast (bottom). 15c5 antibody, 40× magnified.

Figure 3

Deduced amino acid alignment of the BVDV E2 coding region. The coding region for the envelope glycoprotein E2 was determined (see Additional file 3) and the deduced amino acid sequences of viruses originating from cattle to goat and goat to goat infections were compared to the virus of the PI heifer. In addition, E2 amino acid sequences from viruses from the PI heifer and the initial PI goat (termed “PI goat”) that had been passaged in vitro in bovine turbinate (BT) and goat synovial membrane cells (GSM) are included. Dots represent identical amino acids. Positions of amino acid changes are highlighted by arrows. Numbering refers to the nucleotide positions as depicted in Additional file 3.