Development and Validation of an Objective Risk Scoring System for Assessing the Likelihood of Virus Introduction in Porcine Reproductive and Respiratory Syndrome Virus-Free Sow Farms in the US

Abstract

The lack of validated tools to predict how long sow farms will remain PRRS virus-free following successful elimination of the virus has deterred veterinarians and producers from attempting to eliminate the PRRS virus from sow farms. The aim of this study was to use the database of PRRS Risk Assessments for the Breeding Herd in PADRAP to develop and validate an objective risk scoring system for predicting the likelihood of virus introduction in PRRS virus-free sow farms in the US. To overcome the challenges of dealing with a large number of variables, group lasso for logistic regression (GLLR) was applied to a retrospective dataset of PRRS Risk Assessment for the Breeding Herd surveys completed for 704 farms to develop the risk scoring system. The validity of the GLLR risk scoring system was then evaluated by testing its predictive ability on a dataset from a long-term prospective study of 196 sow farms to assess risk factors associated with how long PRRS virus-free sow farms remained PRRS virus-free. Receiver operator characteristic(ROC) curves were estimated to compare the performance of the GLLR risk scoring system to the risk scoring system based on expert opinion (EO), currently used in the PRRS Risk Assessment for the Breeding Herd, for predicting whether herds remained PRRS virus-free for 130 weeks. The GLLR risk scoring system (AUC, 0.76; 95% CI, 0.67 -0.84) performed significantly better than the EO risk scoring system (AUC, 0.36; 95% CI, 0.27 -0.46) for predicting whether to sow farms in the prospective study survived for 130 weeks (p < 0.001). Dividing farms into 3 risk groups (low, medium and high) using a low and high cutoff values for the GLLR risk score was informative as the differences in the KM survival curves for the 3 groups were both clinically meaningful and statistically significant. The GLLR risk scoring system used in conjunction with the PRRS Risk Assessment for the Breeding Herd survey delivered through PADRAP appears to have the potential to help veterinarians predict the likelihood of virus introduction in PRRS virus-free sow farms in the US.

Biosecurity in pig farms: a review

“…Sasaki et al [ 138 ] developed a similar evaluation system named BioAsseT. Several scoring systems developed for specific pathogens (PRRS, Brachyspira hyodysenteriae, Mycoplasma hyopneumoniae) have been reported [ 139 – 142 ].…”

Development of a quantitative risk assessment of bovine viral diarrhea virus and bovine herpesvirus-1 introduction in dairy cattle herds to improve biosecurity

“…Consequently, these kinds of models have a higher degree of complexity and need quantitative data that are not always available. Most of the developed models that measure biosecurity at the farm level in cattle and other species have been based only on opinions and perceptions and do not provide an estimate of probability of disease introduction (Julio Pinto and Urcelay, 2003;Holtkamp et al, 2013;Laanen et al, 2013;Allepuz et al, 2018). Such models can be very useful as educational tools, for developing skills in risk-based prioritization, and increasing awareness (Sternberg-Lewerin et al, 2015), as well as to benchmark farms in relation to their biosecurity level (Dewulf and van Immerseel, 2018).…”