In the eighth annual report to the Swine Health Information Center (SHIC), which provides the primary funding for its work, Morrison Swine Health Monitoring Project (MSHMP) leader Cesar Corzo of the University of Minnesota detailed project outcomes for its three primary objectives. MSHMP monitors trends in pathogens incidence and prevalence, conducts prospective monitoring of PRRSV sequence evolution and impact, and expands participation of producers to increase relevance and deliverables to the swine industry.
Swine pathogens PRRSV, PEDV, PDCoV, SVA, and central nervous system associated viruses are routinely monitored and compared to historical trends. Additional investigations were undertaken to evaluate pathogen patterns, epidemiology and herd stabilization post-infection. MSHMP investigated the relationship of the PRRS RT-PCR positivity rate between breeding and growing pigs during 2015 to 2020 from MSHMP participants. A correlation was identified in the time lapse between positive submissions from nursery/finisher samples and adult/farrowing samples. The correlation found that adult/farrowing positivity follows the same trend as the nursery/finisher positivity with a one-week lag. However, the data was interpreted with caution as no account for spatial distribution or PRRS virus sequence information was included. Consequently, MSHMP was unable to conclude that the increase in PRRS positive rate in breeding herds is due to an increase in positivity rate in growing pigs.
In another investigation, MSHMP assessed the frequency of PRRS outbreaks in breeding herds managing mortality either through composting, incineration, or rendering. The goal of the investigation was to identify associations between carcass disposal methods and PRRS occurrence. Results of the study include analysis of 133 breeding sites from eight production systems to date. One finding included a higher numerical rate of ≥1 PRRS outbreaks on sites using compost (29.7%) compared to sites using rendering (21.1%). However, when accounting for variables such as production system, average inventory, air filtration status, and state, composting was not associated with a higher number of PRRS outbreaks when compared to rendering (p = 0.67). Further assessment of data is warranted once additional data is received from participating systems and the study is evaluated over an extended time frame.
Regarding PEDV, MSHMP quantified the time that positive herds required for stabilization across both the epidemic phase (May 1, 2013 – December 31, 2014) and the endemic phase (January 1, 2015 – June 30, 2023). Results concluded that those infected during the epidemic phase of the disease in the US took nine weeks longer to reach stability than those infected during the endemic phase, reflecting industry progress in PEDV control. Being able to estimate time to stability can assist producers and their veterinarians develop an effective herd plan for PEDV management and potential elimination.