Detection and differentiation of bovine herpesvirus 1 and 5 using a multiplex real-time polymerase chain reaction.

A multiplex real-time PCR was developed for the detection and differentiation of two closely related bovine herpesviruses 1 (BoHV-1) and 5 (BoHV-5). The multiplex real-time PCR combines a duplex real-time PCR that targets the DNA polymerase gene of BoHV-1 and BoHV-5 and a real-time PCR targeting mitochondrial DNA, as a house-keeping gene, described previously by Cawthraw et al. (2009). The assay correctly identified 22 BoHV-1 and six BoHV-5 isolates from the Biosecurity Sciences Laboratory virus collection. BoHV-1 and BoHV-5 were also correctly identified when incorporated in spiked semen and brain tissue samples. The detection limits of the duplex assay were 10 copies of BoHV-1 and 45 copies of BoHV-5. The multiplex real-time PCR had reaction efficiencies of 1.04 for BoHV-1 and 1.08 for BoHV-5. Standard curves relating Ct value to template copy number had correlation coefficients of 0.989 for BoHV-1 and 0.978 for BoHV-5. The assay specificity was demonstrated by testing bacterial and viral DNA from pathogens commonly isolated from bovine respiratory and reproductive tracts. The validated multiplex real-time PCR was used to detect and differentiate BoHV-1 and BoHV-5 in bovine clinical samples with known histories.

Towards Ecologically Sustainable Management of the Torres Strait Prawn Fishery. CRC Torres Strait Task T1.5 – Final Report

This publication, which is the final report to the Torres Strait Cooperative Research Centre, provides an overview of all the research that was conducted as part of the Torres Strait CRC Task 1.5 - Towards Ecologically Sustainable Management of the Torres Strait Prawn Fishery The objectives of the task were: To develop cost-effective protocols to monitor and quantify the bycatch and environmental impacts of commercial prawn trawling. To monitor the status of target species using both fishery dependent and fishery independent data. To develop biological reference points for target species and undertake management strategy evaluation, in particular a risk assessment of fishing at various levels of fishing mortality. This report focuses on the second component of objective 1 and details a comparative analysis of bycatch samples collected from areas of the Torres Strait that were both closed and open to prawn trawl fishing. The report also reviews the research conducted in relation to objectives 2 and 3 which are detailed in a separate report, Stock Assessment of the Torres Strait Tiger Prawn Fishery (Penaeus esculentus).

Effects of exposure to Bovine viral diarrhoea virus 1 on risk of bovine respiratory disease in Australian feedlot cattle

Viruses play a key role in the complex aetiology of bovine respiratory disease (BRD). Bovine viral diarrhoea virus 1 (BVDV-1) is widespread in Australia and has been shown to contribute to BRD occurrence. As part of a prospective longitudinal study on BRD, effects of exposure to BVDV-1 on risk of BRD in Australian feedlot cattle were investigated. A total of 35,160 animals were enrolled at induction (when animals were identified and characteristics recorded), held in feedlot pens with other cattle (cohorts) and monitored for occurrence of BRD over the first 50 days following induction. Biological samples collected from all animals were tested to determine which animals were persistently infected (PI) with BVDV-1. Data obtained from the Australian National Livestock Identification System database were used to determine which groups of animals that were together at the farm of origin and at 28 days prior to induction (and were enrolled in the study) contained a PI animal and hence to identify animals that had probably been exposed to a PI animal prior to induction. Multi-level Bayesian logistic regression models were fitted to estimate the effects of exposure to BVDV-1 on the risk of occurrence of BRD.Although only a total of 85 study animals (0.24%) were identified as being PI with BVDV-1, BVDV-1 was detected on quantitative polymerase chain reaction in 59% of cohorts. The PI animals were at moderately increased risk of BRD (OR 1.9; 95% credible interval 1.0-3.2). Exposure to BVDV-1 in the cohort was also associated with a moderately increased risk of BRD (OR 1.7; 95% credible interval 1.1-2.5) regardless of whether or not a PI animal was identified within the cohort. Additional analyses indicated that a single quantitative real-time PCR test is useful for distinguishing PI animals from transiently infected animals.The results of the study suggest that removal of PI animals and/or vaccination, both before feedlot entry, would reduce the impact of BVDV-1 on BRD risk in cattle in Australian feedlots. Economic assessment of these strategies under Australian conditions is required. © 2016 Elsevier B.V.