BVDV Type Research Articles

Genetic typing of bovine pestiviruses from England and Wales

Using RNA purified directly from stored clinical specimens, a collection of 62 pestiviruses were typed by RT-PCR and sequencing within the 5′-untranslated region of the genome. All the specimens had been obtained in 1966/1967 from diary cattle in England and Wales. Eight further pestiviruses, grown in cell culture, were characterised in the same way. Seven of these viruses were representatives of a panel of British isolates, obtained from cattle ten years before. The eighth was the virus used in a British bovine viral diarrhoea (BVD) vaccine. Most of the viruses were genetically unique and were of BVDV type Ia. One recent isolate was BVDV type Ib, two others were intermediate between Ia and Ib. No BVDV type II or border disease virus (BDV) isolates were found. There was no overall association between geographical and phylogenetic clustering, suggesting long-distance virus dispersal, presumably via trading of infected cattle. The sequences of the recently obtained cattle viruses were very similar or, in one case, identical to the older isolates in the region studied. Their close similarity to some previously characterised pestiviruses from British sheep suggests that a common pool of BVDV Ia is shared by these two livestock species, although another pestivirus — BVDV — is confined to sheep. The British cattle viruses were mostly distinct from continental European isolates, but more similar to type Ia isolates from North American cattle.

Genetic typing of pestiviruses from New Zealand

Aim. To investigate the genetic type of 20 pestiviruses collected from New Zealand over the period 1967–97. Methods. The pestiviruses were genetically typed by the sequencing of polymerase chain reaction (PCR) products. The primers selected were from the 5′-untranslated region (5′-UTR) of the pestivirus genome and consistently amplified a 288bp fragment from all samples tested. Results. Sequencing and phylogenetic analysis of PCR products revealed that all samples obtained from cattle represented bovine viral diarrhoea (BVDV) type I. Two sheep isolates were characterised as border disease virus (BDV). A pestivints isolated from foetal calf serum of USA origin was typed as BVDV type II. Conclusions. The findings show that the evolution of pestiviruses in New Zealand has been similar to Europe and North America, indicating the occurrence of a conservative phylogenetic branch of BVDV type I in cattle and the presence of BDV in the sheep population.

Induction of procoagulant activity in virus infected bovine alveolar macrophages and the effect of lipopolysaccharide

Three viruses known to be associated with the bovine respiratory disease complex were evaluated in vitro for potential impact upon the procoagulant activity (PCA) of bovine alveolar macrophages (bAM). Cultures of bAM were inoculated with bovine parainfluenza virus Type 3 (PI-3), cytopathic bovine viral diarrhea virus (cpBVDV), non-cytopathic BVDV (ncpBVDV), or bovine herpes virus Type 1 (BHV-1) and incubated for several time periods (24, 48, 72, 96 h). BAM were then exposed to E. coli lipopolysaccharide (LPS), or LPS with bovine serum. The amount of PCA expressed was quantified using a chromogenic assay. Viral inoculation increased bAM expression of PCA ( P < 0.01). The increase in PCA expression was larger at higher rates of viral inoculation ( P < 0.01). LPS enhanced PCA expression by bAM at low rates of viral inoculation ( P < 0.01). The effect of LPS-serum treatment was greater than the LPS alone ( P < 0.01). At high rates of viral inoculation, LPS had no enhancing effect on PCA expression. The effect of LPS on virus inoculated bAM varied with virus type, rate of inoculation, and duration of virus exposure ( P < 0.01). The results suggest that these four viruses initiate the production of PCA by bAM independently of LPS. In the field situation, an initial viral infection may induce fibrin deposition in the pulmonary alveoli prior to the establishment of a secondary gram negatmtive bacterial infection.