SHIC-Funded Study Finds Powder Disinfectant May Slightly Reduce Trailer Cross-Contamination with PRRS Virus at Harvest Facilities

A study funded by the Swine Health Information Center Wean-to-Harvest Biosecurity Research Program, in partnership with the Foundation for Food & Agriculture Research and Pork Checkoff, sought to examine whether preventing trailer cross-contamination during unloading at a commercial harvest facility may help reduce viral transmission from positive to negative herds. Dr. Noelle Noyes, of the University of Minnesota, led the study to evaluate the efficacy of a commercial powder disinfectant to reduce trailer cross-contamination in this setting. PRRSV contamination was observed among treated trailers compared with control trailers following unloading. These results suggest that the use of a commercial powder disinfectant may reduce trailer contamination with PRRSV.

Find the industry summary for SHIC project #24-095 here.

Harvest facilities remain an important biosecurity consideration

Transportation is a recognized pathway for the movement of swine pathogens between farms, and trailers serving multiple sites can provide opportunities for indirect transmission. Trailers at harvest facilities can serve as a contact point between different farms and a contamination source when trailers return to pig farms. Harvest facilities are of particular interest because trailers from different sources converge at a common location, while pigs, drivers, and plant personnel move through unloading areas.

Preventing trailer cross-contamination during unloading may play a role in reducing viral transmission from positive to negative herds. The primary objective of this research was to test the efficacy of a commercially available powder disinfectant as a practical intervention to reduce negative-to-positive cross-contamination events during unloading of pigs at a commercial harvest facility. The secondary objective was to provide estimates of PDCoV, PEDV, and PRRSV prevalence and qPCR-based viral load of both inbound and outbound trailers at a commercial harvest facility under normal operating procedures over a 12-month period.

Samples were collected once a month from February 2025 through January 2026, during normal plant operating conditions at a harvest facility with five unloading docks. Trailers were sampled over a 12-month period, and each month 10 trailers were enrolled for testing with a total of 120 trailers tested. For each sample, the following data points were collected: time of powder application, time of sample collection, and trailer organic load (on a scale of 1-5, with 1 being completely clean and 5 being completely covered with organic material).

Powder disinfectant was applied directly behind treated trailers prior to unloading, while control trailers did not receive an intervention. The rear trailer deck was swabbed immediately before and after unloading. Samples were tested for PRRSV, PEDV, and PDCoV using real-time RT-PCR. Powder was reapplied for each additional trailer enrolled in the treatment docks.

Contamination increased during unloading

Across the 12-month study, incoming trailers tested positive for PDCoV, PEDV, and PRRSV at unexpectedly high rates. Among trailers that initially tested negative, approximately one-quarter became positive for at least one of the viruses during unloading. Crude prevalence across all samples was 60.4%, 50.4%, and 27.1% for PDCoV, PEDV, and PRRSV, respectively. When researchers compared samples collected before and after unloading, the prevalence of all three viruses increased. The increases were statistically significant for PEDV and PDCoV. Overall, approximately 25% of trailers that arrived negative for PEDV or PDCoV became positive after unloading, while the corresponding figure for PRRSV was 17.5%. Crude prevalence varied by month across all three viruses.

The most meaningful treatment effect was observed with PRRSV. Among trailers that were negative before unloading, 20% of control trailers became PRRSV-positive after unloading, compared with 15% of trailers receiving the powder intervention. The difference was statistically significant.

The intervention did not produce a statistically significant reduction in contamination events for PEDV or PDCoV. The researchers caution, however, that the study had fewer virus-negative trailers available for comparison than expected because the incoming prevalence of PEDV and PDCoV was unusually high. This limited the ability to detect differences between treated and control groups and and suggests that additional research with larger sample sizes is needed.

A practical intervention—but not a stand-alone solution

One of the study’s important industry considerations is practicality. Unlike a full trailer wash and disinfection process, which can require significant infrastructure, time, and cost, the powder intervention was incorporated into normal harvest-facility operations. The researchers estimated the material cost at approximately $1.50 per trailer and noted that application was quick enough to fit within commercial unloading operations.

This makes the approach potentially attractive as an additional layer of biosecurity, particularly where complete trailer cleaning and disinfection between loads is difficult to implement consistently.

At the same time, the researchers emphasize that the five-percentage-point reduction in PRRSV contamination observed in this study may or may not translate into a meaningful reduction in farm-level or regional disease transmission. The ultimate impact will depend on how trailers move among farms and the broader disease dynamics within the industry. Multiple interventions throughout the pork production chain are likely necessary to achieve meaningful reductions in disease risk.

Implications of results

For producers, the findings reinforce an important biosecurity principle: the risk associated with a market trailer does not necessarily end when pigs leave the farm. The harvest facility itself can be another point where a trailer may acquire contamination before returning to a production site. The researchers noted that the movement of people, pigs, and contaminated material from the dock or lairage area back into the trailer may be an important contributor to this risk.

The study provides evidence that trailers arriving at harvest facilities often have virus contamination and that virus prevalence increases during unloading. The results suggest that use of a commercial powder disinfectant may reduce trailer contamination for PRRSV.  Future studies with larger sample sizes, particularly those enrolling sufficient numbers of initially virus-negative trailers, are warranted. For an industry challenged with PRRSV, PEDV, and PDCoV outbreaks, the addition of another biosecurity measure at a critical point in the transportation chain can be of value for potential reduction in disease transmission risks at the harvest plant. 

Foundation for Food & Agriculture Research

The Foundation for Food & Agriculture Research (FFAR) builds public-private partnerships to fund bold research addressing big food and agriculture challenges. FFAR was established in the 2014 Farm Bill to increase public agriculture research investments, fill knowledge gaps and complement US Department of Agriculture’s research agenda. FFAR’s model matches federal funding from Congress with private funding, delivering a powerful return on taxpayer investment. Through collaboration and partnerships, FFAR advances actionable science benefiting farmers, consumers and the environment. Connect: @FoundationFAR

Swine Health Information Center

The Swine Health Information Center, launched in 2015 with Pork Checkoff funding, protects and enhances the health of the US swine herd by minimizing the impact of emerging disease threats through preparedness, coordinated communications, global disease monitoring, analysis of swine health data, and targeted research investments. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Lisa Becton at [email protected].