Improvement of monitoring and surveillance systems for porcine reproductive and respiratory syndrome virus in the United States swine industry

Abstract

Porcine reproductive and respiratory syndrome (PRRS) is the most economically significant disease affecting swine production in the United States (US). The etiologic agent of PRRS is an RNA virus named as PRRS virus (PRRSV). Substantial economic losses attributed to PRRS are due to reduced reproductive performance in sows and reduced growth rate and increased mortality in growing animals. In the US, PRRSV activity is routinely monitored by production systems and/or veterinary clinics. A group of swine production systems in the US voluntarily share their PRRSV breeding herd incidence to a program that gathers, aggregates, and reports the weekly incidence and prevalence among participants. As of February of 2020, most of the participants are from large production systems that represented 2.8 million sows. Currently, there is no information on PRRSV detection in the broader industry which totals of 6.46 million sows. Additionally, American Association of Swine Veterinarians (AASV) guidelines for PRRSV monitoring (from 2011) was based on the use of serum samples. However, there is a recent description of processing fluid as a population-based sample type to monitor PRRSV herd status more efficiently. The validation of this new sample type raises the need to better understand the practical applications of this sample type to monitor PRRSV. Considering (a) the high economic importance of PRRS to the US swine industry, (b) the current gap of information about PRRSV activity in most breeding herds, and in growing animals, and the (c) gap in knowledge about applications of processing fluids to monitor and surveil PRRSV, there is the critical need to develop additional tools for improvement in the monitoring and surveillance systems for PRRSV in the US swine industry. Therefore, the overall objectives of this dissertation were: a) to develop a capability to reliably and consistently track PRRSV detection over time, age group, geographical space, and specimen in the US swine industry; and b) to develop monitoring and surveillance systems to enable veterinarians to make science-driven decisions to support disease prevention, detection, and control strategies. To that end, a capability to monitor and report the detection of PRRSV RNA by RT-PCR at the four major US swine-centric veterinary diagnostic laboratories was built. A procedure to receive data, a process to compile to the same format, aggregate, report, and a capability for continuous automated updates was developed. This information was used to describe the macroepidemiological aspects of PRRSV RNA detection by RT-PCR in the US