SHIC Wean-to-Harvest Biosecurity: Transport Trailer Cleanliness Study Using Bioluminescence Final Report

Livestock trailer cleanliness is typically determined by visual evaluation, assessing if it is free of organic material and suitable to return to a farm. However, visual inspection is insufficient to ensure cleanliness and eliminate disease transmission risk due to microscopic viruses and bacteria. In a Swine Health Information Center Wean-to-Harvest Biosecurity Program study conducted by Dustin Boler, Carthage Innovative Swine Solutions, and Bailey Harsh, University of Illinois, the suitability of bioluminescence for evaluating trailer cleanliness was assessed and confirmed as a prospective testing method. 

SHIC’s Wean-to-Harvest Biosecurity Research Program, funded with the Foundation for Food & Agriculture Research (FFAR) and the Pork Checkoff, addresses biosecurity gaps in the pork industry such as quantifying trailer cleanliness. Boler and Harsh’s research evaluated the performance of two adenosine triphosphate instruments to estimate cleanliness of livestock trailers. Results of the ATP instruments were compared to aerobic plate counts (quantity of bacterial contamination) to determine if ATP bioluminescence could be used as an indicator of trailer cleanliness and as an objective substitute for visual inspection that usually occurs after the cost to dry a truck with propane has been incurred. 

ATP is a source of cellular energy present among living organisms. ATP bioluminescence uses a chemical reaction where a swab is used to detect the quantity of ATP. The more ATP that is present, the greater the chemical reaction. This technology uses the same chemical process a firefly uses to illuminate. When ATP is exposed to the enzyme, a light is produced relative to the ATP quantity: the more ATP present, the brighter the light. The intensity (brightness) is measured in relative light units. A greater RLU indicates more ATP and can represent a reduction in overall cleanliness. In this case, the brighter the swab glows, the more ATP is present, the more potential microbial contamination is present.  

The goals of this project were to determine 1) the areas of the trailer with the greatest surface contamination, 2) the correlation between microbial counts and RLUs, and 3) the number of sample locations that are needed to accurately determine surface cleanliness.  

Livestock trailers at two commercial washes were evaluated in this study. One of those locations included trailers known to transport livestock from a PRRSV or PEDV positive site. In total, 100 livestock trailers were tested using bioluminometers to quantify the amount of ATP remaining after a commercial trailer wash. Due to protocols preventing people from entering a livestock trailer after it has been cleaned to prevent post-wash contamination, samples were collected from locations inside the trailer that were accessible from outside the trailer. Sample location access was a critical consideration for this technology to be adopted into practice. This trial evaluated the back door flush gate, rear drivers side access door, the belly flush gate, belly side access door, and nose side access door. 

Study results indicated the areas of highest concern sampled in this study were the nose access door and the back door flush gate as detected by both ATP bioluminescence and aerobic plate counts. A key finding of this research was that the nose access door was the area least likely to be adequately cleaned, but only a few trailers actually had nose access doors. Nearly all of the trailers evaluated had a back door flush gate, making it a logical place to swab a livestock trailer as a representation of the overall cleanliness.  

The ability of ATP to be used as an indicator of trailer cleanliness was associated with the instrument used, with the 3M machine being most closely correlated with bacterial contamination. Swabs were also collected to determine the presence of PEDV, but all swabs were PCR negative. These data suggest that ATP bioluminometers can be used in livestock trailers to quickly and objectively determine the general cleanliness of the trailer. Bacterial swabs to determine aerobic plate count levels can also be used to determine the effectiveness of the cleaning protocol. 

SHIC, FFAR and Pork Checkoff launched the two-year Wean-to-Harvest Biosecurity Research Program in the fall of 2022. The first call for research proposals was announced in October 2022 with the goal of investigating cost-effective, innovative technologies, protocols or ideas to enhance biosecurity during the wean-to-harvest phases of swine production. Round one projects, launched in March 2023, received approximately $1 million. Round two proposals were due April 2023 and began summer 2023. Approximately $2.3 million is available for the entire program.