An estimated one million pigs are transported daily from one location to another in the United States. This includes genetic stock, weaners, feeders, harvest pigs and cull sows. With pig movement common at all phases of production, transportation biosecurity is a critical control point for bioexclusion and biocontainment. Pathogens are commonly spread through oral/fecal or nasal droplet contact, making transportation a common route of contamination to pig populations and facilities if not properly managed. Swine enteric corona viruses, including porcine epidemic diarrhea virus (PEDV) and porcine delta corona virus (PDCoV) are the most recent viruses of concern that are transferred via fecal and oral contact.
When the washing and drying of transporters is limited, it is important to set up a hierarchical system to reduce transportation risk. The risk matrix is based on both incoming risk and outgoing risk in order of priority genetic animals, weaners, cull sows, feeder pigs and harvest animals. All herds should manage incoming risk through isolation, quarantine, diagnostic monitoring and ongoing communication with suppliers, in addition to transport biosecurity. Because of the frequency (one to five times per week) and the potential contact with down-stream delivery risk, weaned pig exits require that all transportation be clean, disinfected and dried.
Removal of cull sows is a lower frequency, and thus a lower risk, but has a high risk of downstream contamination unless there is a dedicated transfer point. Producers frequently do not wash transporters that remove animals to harvest from an all-out site. This reasoning is logical, but should only apply to all-out barns and sites. First-cut or lightweight pigs for the early harvest market should always be transported on a trailer that has been washed, disinfected and dried.
Recognizing that a primary route of contamination is through contaminated transport, washing, disinfecting and drying transport trailers is an obvious process to reduce biocontamination. Even though the value of washing, disinfecting and drying of transport has long been recognized, the industry has a tremendous shortage of facilities and/or inadequate truck washes and drying facilities.
Challenges associated with washing, disinfecting and drying are compounded by time and frequency since the transport is not uniformly distributed through the week or day of the week. Given these constraints, it raises the question: Are there procedures and processes that the industry could undertake at the processing plant that would minimize the frequency of harvest transport contamination, allowing the industry to focus on 100% washing, disinfecting and drying of the transportation vehicles used to haul genetic stock, wean pig, cull sow, feeder pig and first-cut removal animals?
A study completed by Lowe, et al. in 2013, demonstrates that plants with similar rates for PEDV-positive trucks at arrival vastly differed in their contamination rates of outgoing trailers, demonstrating that internal plant and transporter biosecurity practices can have a positive influence with disease transmission. Another study is proposed to evaluate the practical application of plant processes.
Transport washes are highly valuable for biocontainment and bioexclusion of emerging and resident pathogens. These facilities have to be well-designed and managed, and the processes audited. There is inherent contamination risk because trailers are contaminated with feces and bedding. Environments within the washes are also conducive to pathogen survival and cross-contamination. Moisture is high, and temperatures fluctuate because of the process of entering and exiting facilities.
Design of the truck wash should take steps to minimize this contamination between trailers, transporters, facility staff and cleaning staff. A design layout is included in Figure 4.
Truck washes should contain the following components.
- Separate dirty entry and clean exit.
- Elevation to facilitate external water drainage away from the facility.
- Internal elevations to facilitate contained water drainage from the transporter.
- Method of bedding and feces removal, containment and disposal.
- Procedures to optimize containment of feces and bedding.
- Disposal location for disposal of boots, coveralls, gloves.
- No cross-over traffic between incoming transporters (dirty) and outgoing transporters (clean).
- Detailed procedures for washing, cleaning and disinfecting transporter. There are test strips available to ensure disinfectant concentrate is utilized at the labeled rate.
- Internal yard tractors to move transporters unless there is a dedicated tractor for the transporter.
- Visual inspection still remains the most practical control method. Cleanliness can be objectively assessed through swabbing of cleaned trailers; however, sensitivity of this testing is low.
- Inspection of trailer prior to disinfection via third party. Figure 1 shows a chart measuring passed vs. failed inspections conducted at a transport center.
- Laundry facilities for staff and transporters.
- Drying bay that achieves targeted temperature and duration.
- Automated recording that links washing/drying and transporters to allow quality control (see charts).Examples of data capture from a transport center are shown in the figures.
Washing times vary from 30 to 120 minutes depending on category of animals transported, amount of bedding used and season (See Figure 2). Figure 3 illustrates differences in drying time. Drying can occur over time in a room-temperature building, with studies suggesting that trailers would require one week of drying post-washing and disinfection at room temperature of 70 degrees F to inactivate PEDV.
A study funded by the National Pork Board (NPB) and conducted at the University of Minnesota identified that PEDV requires a higher temperature and longer duration time for inactivation (160 degrees F for 10 minutes) compared to 150 degrees F for five minutes for porcine reproductive and respiratory syndrome virus (Nitikanchana S., 2014). To turn transporters around more rapidly, a high temperature automated system is necessary.
NPB identified areas of risk and procedures and/or processes that would minimize these risks at collection points from transportation. Transportation of live animals is done by dedicated drivers committed to minimizing pathogen transfer.
Dee SA, Deen J, Rossow KD, Mahlum C, Otake S, Joo HS, and Pijoan C. Mechanical transmission of porcine reproductive and respiratory syndrome virus throughout a coordinated sequence of events during warm weather. Can J Vet Res (Accepted for publication).
Dee SA, Deen J, Rossow KD, Mahlum C, Otake S, Joo HS, and Pijoan C. Mechanical transmission of porcine reproductive and respiratory syndrome virus throughout a coordinated sequence of events during cold weather. Can J Vet Res (Accepted for publication).
Dee SA, Corey MM. The survival of Streptococcus suis on farm and veterinary equipment. Swine Health Prod. 1993; 1(1): 120.
Fussing V, Barfod K, Nielsen R, Moller K, Nielsen JP, Wegerner HC, Bisgaard M. Evaluation and application of ribotyping for epidemiological studies of Actinobacillus pleuropneumoniae in Denmark. Vet Microbiol. 1998; 62:145-162.
Lowe J, Connor J, Lower A, et al. (2013). Transport risks for PEDV transmission.
Nitikanchana S. (2014). Potential alternatives to reduce porcine epidemic diarrhea virus (PEDV) contamination in feed ingredients. University of Minnesota.
Thompson RW. Transmission of pathogens via transportation vehicles. Proceeding of the AD Leman Swine Conference 2001 Minneapolis, pp 37-42.