Active surveillance and impact of an intervention on PEDV occurrence in a large pig production system in the US

Today, we are sharing a recent publication from the MSHMP team led by Dr. Cesar Corzo in collaboration with a US pork producer. The full article is available in open access on the Porcine Health Management journal’s website. The objectives of this study were to actively monitor Porcine Epidemic Diarrhea in pigs during several stages of the finishing phase and to assess the impact of added biosecurity measures.


Active surveillance

The surveillance sampling protocol was designed to assess disease status as follows:

  • upon placement into the growing pig site by collecting an environmental sample
  • before shipping to the slaughter plant by collecting oral fluids
  • when diarrhea events occurred at the site by collecting an environmental sample

All samples were tested by RT-PCR and considered positive if the cycle threshold (Ct) was below 30.

Intervention strategy

The strategy revolved around three types of intervention:

  • System-wide segregation of farm equipment such as pig sorting boards, snares, screw drivers or dead haul trailers
  • Facility cleaning and disinfection processes improvement
  • Inclusion of a hydrogen peroxide-based disinfectant

Internal biosecurity protocols regarding personnel movement between sites were reviewed and emphasized with staff.


About a third of the sites (out of 274) had at least one PEDV introduction event pre-intervention. Overall, the farm-level PEDV incidence rate was 2.41 per 100 farm-weeks.

63% of these introductions were noticed due to PEDV-positive clinical signs following a negative placement sample. There was a large variability in time between negative placement samples and positive clinical samples, but a median of eight weeks interval was calculated in this study.

The overall PEDV incidence rate post-intervention was 0.37 per 100 farm-weeks. This represents an 84.65% reduction in the PEDV incidence rate. Western Kansas remained a high PEDV occurrence pre and post-intervention (see figure below).  

Kernel density map of PEDV introductions during the pre- A and the post-intervention B periods

Read the full article on the journal’s website.


Background: In 2013, PEDV was introduced in the United States (U.S.) and rapidly spread across the country. Here we describe the occurrence of PEDV in the growing pig herd of one large U.S. production system through an active surveillance set in place between October 2019 and November 2020 designed to assess disease status upon placement into the growing pig site, before shipping to the slaughter plant and when diarrhea events were present at the site. We also assessed the impact of preventive procedures implemented in PEDV incidence that comprised site-specific equipment segregation and biosecurity changes regarding personnel movement between sites.

Results: 36.50% (100/274) of the sites had at least one PEDV introduction event before preventive procedures were implemented, yielding an incidence rate of 2.41 per 100 farm-weeks. Most (63/100) of them occurred in sites where animals were placed negative and PEDV was detected in clinical samples in a median of 8 weeks post placement. After preventive procedures were implemented, the overall PEDV incidence rate dropped to 0.37 per 100 farm-weeks (84.65% reduction, p < 0.001).

Conclusion: These results highlight the importance of systematic surveillance to identify the burden of diseases, areas of improvement in prevention and control, and to allow the measurement of the impact of policy/protocol changes.

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