The objectives of this study were to determine lateral transmission patterns of PEDv in the US.
For objective 1, evaluation of harvest plants as points or nodes of PEDv transmission. To accomplish this, samples were taken from each trailer before and after unloading pigs at 6 harvest plants. Other information was also collected of activities that could be implicated in transmission such as truck drivers stepping on the dock and plant personnel entering the trailer and the times and docks used were tracked.

This study found 6.6% of trucks contaminated before unloading over all plants and 5.2% of trucks that were negative upon arrival became contaminated in the unloading process. This indicates that the contaminated trucks pulling up to the harvest plant contaminate about one more truck that was clean prior to docking and indicates a point of spread within the industry that needs to be attempted to be controlled to avoid further transmission.

Also, harvest plant staff may have had a role as clean trailer became contaminated. Following the results of these findings, there is a need to ensure that biosecurity protocols between trucking and harvest plant staff is followed or perhaps that more precautions are put in place.
For objective 2, various possible transmission methods were evaluated in Oklahoma and North Carolina. To accomplish this, data were collected identifying spatial location of all sites as well as any PEDv outbreak dates for both areas of the US. There were also a number of biosecurity questionnaires filled out by herd veterinarians and managers at randomly-selected positive herds as well as randomly selected matched negative herds.
Spatial data and intrinsic farm data were used to evaluate potential transmission risk of herds of different production type and capacity, and herds in areas with higher and lower farm density. This aspect of the study found that sites with sows on the premises and sites greater than 2,000 head may be at increased risk likely due to increased transportation and more frequent input/output of resources at the site. Spatial analysis also found that increased swine density in a region, as well as the site’s proximity to nearest infected neighbor, are also associated with increased infection. Though, this is more of a confirmation of the pathogen’s lateral transmission capability, it is important to be able to identify more at-risk herds and regions using this information. Perhaps at-risk herds can attempt to re-double their biosecurity efforts and avoid infection from their neighbors.
Biosecurity questionnaires were used to identify any association between infection and any specific areas lacking in biosecurity measures. These questionnaires yielded results showing greater odds of infection after rendering service visits and after observation of wildlife such as birds, rats, mice, and raccoons in the pig buildings. These identify two likely methods of transmission of the virus in these regions. Herds should ensure that their biosecurity protocols for incoming trucks such as rendering services are thorough by incorporating off-site locations for vehicle meetings, Danish entry systems for drivers of services that require the driver to walk on the premises, and extra disinfection methods for incoming vehicles/equipment such as chemical disinfection, heating, drying, and downtime. Herds should also ensure that their methods of pest control are in place and effective including regular maintenance of traps or bait boxes, patching any holes in the buildings, maintaining bird netting, and upkeep of the grounds to avoid attraction of rodents and other pests.
Contact info:
o Bob Morrison, University of Minnesota
o Dane Goede, University of Minnesota
Department of Veterinary Population Medicine
University of Minnesota
385 Animal Science, VMC
1988 Fitch Ave
St Paul, MN 55108