It has been estimated that on any given day about 1 million pigs are being transported in the United States. To move that many hogs, it also has been estimated that approximately 3,000 trucks are zig-zagging across the country. Hogs aren’t the only things carried by these trucks and trailers, as it has been widely recognized that transportation is a significant risk for transmission of swine diseases.
The presence of porcine epidemic diarrhea virus has reinforced the importance of ensuring that transport trailers are properly washed, disinfected and inspected for organic debris and microbial contamination prior to use. Most of the time, producers and haulers rely on visual inspection of equipment to confirm cleanliness after washing, cleaning, disinfection and drying. Occasionally, microbiological testing via culture method has been used.
Reliability of visual inspections has been questioned, and the traditional microbiological culture method can cause significant downtime for trailer operations and delay the implementation of corrective actions while waiting for test results.
With that in mind, researchers Bernardo Predicala and Alvin Alvarado with the Prairie Swine Centre in Saskatoon, Saskatchewan, and Jingjing Cabahug from the University of Saskatchewan sought to find a rapid, reliable and easy-to-use way of monitoring surface cleanliness of swine transport trailers.
In this study, they looked at the feasibility of using adenosine triphosphate (ATP) bioluminescence as a rapid and effective assessment tool to determine trailer cleanliness.
Sixteen commercial swine transport trailers were assessed for surface cleanliness after washing and disinfection using two methods: ATP bioluminescence method and microbiological culture method using two formulations of contact agar plates (MacConkey and R2A). Samples were taken from newly cleaned, dry trailers using an ATP swab by swabbing an area of 10 centimeters by 10 centimeters and were tested for microbial contamination level using an ATP bioluminescence meter. The results obtained from ATP testing were compared to the co-located samples taken using standard microbiological techniques.
Sampling locations were identified for each trailer: lower deck floor and wall, upper deck floor and wall, loading ramp and partition panels, and trailer exterior. At each sampling location, five pairs/sets of co-located samples, one for each method, were gathered.
More than 500 samples for each method were collected from 16 commercial swine transport trailers across Saskatchewan.
A significant correlation (r = 0.206; p=0.001) was found between the ATP bioluminescence method and the standard microbiological technique using R2A agar plates. Lower correlation (r = 0.154; p=0.002) was observed between ATP method and MacConkey agar plate counts. Unlike R2A that detects a wider group of bacteria, MacConkey agar supports only the growth of selected gram-negative bacteria while ATP bioluminescence detects ATP from both microbial and organic sources.
Assessing the effectiveness of swine transport trailer cleaning protocol using ATP bioluminescence method, threshold values were established with readings of less than 430 relative light unit (RLU) per 100 cm2 as a “pass” while higher than 850 RLU per 100 cm2 was a “fail” or has high risk of disease propagation. With these assessment criteria, ATP bioluminescence method can be used as a supplementary tool for monitoring surface cleanliness of transport trailers in a rapid, simple, inexpensive and reliable way, to complement the procedures specified in Canadian Swine Health Board guidelines.
Using the threshold values for ATP bioluminescence method established in this study, contamination level of the different sampling locations in a trailer washed at different truck wash facilities was determined.
Figure 2 shows the plot of contamination levels in different locations in trailers washed from four different truck wash facilities (A, B, C and D). For trailers in truck washes A and D, floors have exceeded the RLU pass threshold values and thus, careful cleaning and disinfection should be observed in these areas.
All sampling locations in trailers in truck washes B and C have exceeded the suggested “pass” threshold level, indicating a high risk of disease propagation and corrective actions should be implemented.
Regardless of the truck wash facility, microbial contamination was found concentrated on trailer floors. Aside from corrugations on floors, which make cleaning relatively challenging, accumulation of water on floor surfaces before complete drying may have contributed to this observation.
ATP bioluminescence method can be used as a tool for rapid assessment of surface cleanliness of swine transport trailers, complementing the procedures specified by the Canadian Swine Health Board. Dirty areas in trailers can be rapidly identified using the ATP method; hence, corrective actions on the current washing/disinfection protocol can be made. Regardless of the method of assessment, trailer floors posed the highest risk of microbial contamination among all the six critical areas tested.
Enhanced monitoring and detection will significantly reduce the potential for disease outbreak within individual production operations. While a specific cost benefit is difficult to assess, one must only look at the losses that can easily exceed $250 per sow place when individual sites or production operations break with PEDV or porcine reproductive and respiratory syndrome.
Researchers acknowledge the financial support for this project provided by the ADOPT Program by the Saskatchewan Ministry of Agriculture. They would also like to acknowledge the strategic program funding provided by Sask Pork, Alberta Pork, Ontario Pork, the Manitoba Pork Council and the Saskatchewan Agriculture Development Fund.