On a weekly basis, hundreds of thousands of hogs are hauled from different finishing pig farms with different health statuses to harvest plants making these facilities the ultimate concentration point for our industry. Therefore, trailer cross-contamination is imminent, yet today the risk is poorly understood. The University of Minnesota and the Swine Health Information Center partnered to better understand the risk of contamination with pathogens often found in U.S. pigs.
Market hog trailers are farms on wheels: Without proper sanitation they can contribute to virus spread
At a single, large, Midwestern harvest plant, samples were collected from 389 trailers on arrival but before unloading pigs. The samples were tested for the presence of four common pig viruses -PRRSV, PEDV, PDCoV and SVA. If the sample tested positive for any virus, we considered the trailer to be contaminated. Overall, 71% (275 out of 389) of the trailers arrived at the lairage area of the harvest plant already contaminated with at least one virus; only 29% (114 out of 389) of arriving trailers were negative for all four viruses. Detecting viruses on these trailers indicate that either the pigs being hauled are actively shedding virus or the trailer being used to haul those pigs had not gone through a proper sanitation process. Regardless of the reason, the chances are very high that pigs are carrying viruses to the plant, contributing to environmental contamination of the dock area, and exposing income trailers to the risk of contamination.
Trailers are becoming contaminated during unloading
The same trailers that were tested on arrival and before unloading pigs were tested after unloading using the same procedures. A shocking 75% (85 out of 114) of the virus-negative at arrival trailers were virus-positive after unloading, which clearly highlights that contamination is occurring at some point during the unloading process. Contamination occurs because the dock (the hard-surface area where all pigs walk immediately after unloaded from the trailer) is heavily contaminated. Over half of the environmental samples collected from the dock during the same study also tested positive for at least one of the four viruses.
When breaking down the results for each individual virus, we found that approximately 35% of trailers arrived at harvest plants contaminated with PRRSV. More concerning, the proportion of positive trailers increased to almost 45% as the trailers left the plant. A similar pattern was observed for other pathogens. For example, approximately 41% of trailers arrived positive for PDCoV, but that number increased to approximately 62% after unloading. In the case of PEDv, the proportion of positive trailers increased from 27.3% to 51%, which is concerning given the current industry plan to eliminate this virus. Senecavirus results were similar, with 22% of the trailer arriving contaminated and 39% positive after unloading. No sample tested positive for TGE.
Trailer washing and disinfection doesn’t happen very often
Data on trailer sanitation before and after unloading was gathered from all 389 loads. While it is commonly accepted that improved trailer sanitation decreases the risk of disease spread, this study revealed that 20% of the trailers being unloaded at the plant had not been sanitized prior to loading the hogs. Furthermore, 14% of the trailers were not heading to the truck wash and all of these tested positive for at least one virus. Instead, they were in route to another farm to load more pigs. There were two main reasons given for not washing, 1) no one asked them to wash; and 2) they did not have the extra time and money to do the washing.
The fewer pigs shedding pathogens, the lower the risk for the pork industry. So, what can the industry do?
Hog farms, pig producers, swine veterinarians, pork production companies and meat processors all need to recognize that trailer sanitation should be a shared responsibility and a necessary step towards reducing virus spread. The more the industry invests in this area, the better prepared all will be when the next pig disease crisis arrives.
To that end, producers and veterinarians should consider the following as they begin working towards trailer sanitation and biosecurity excellence.
Owners and upper management should work towards fine tuning livestock transportation logistics to ensure that every trailer backing up to their loading chutes does not represent risk. Otherwise, questions related to “where has the trailer been”, “when was it washed” and “what way was it washed” will become a source of uncertainty when investigating disease outbreaks:
- Where has it been?
- When was it washed?
- What way was it washed?
Producers need to make sanitation expectations clear. Washing trailers between loads is an important way to protect every herd. Washing should be a “must have” instead of a “nice to have” rule for all trailers.
All need to understand that the harvest plant is not the problem. The real problem comes from the populations of pigs being hauled to the plant. Once the industry begins hauling virus-free pigs to the plant, both the level of environmental contamination in the lairage area and the chance of cross contamination will decrease. People responsible for transportation need support. Drivers need training and retraining about disease risks and biosecurity. Increasing awareness and understanding will ensure that transportation sanitation is a crucial part of the overall biosecurity program of each farm and company.
The U.S. pork industry invests a lot of time and resources to protect our herds from diseases that make pigs sick, cost money to treat and reduce profits. We control people movement, incoming animals, equipment, feed and other possible pathways of infection. The market-hog trailer deserves the same attention.
If the U.S. pork industry wants to slow down or stop viruses from spreading from farm to farm, state to state, and region to region when sending pigs to market, we all need to make sure that viruses do not get a free ride on the way home.
This article was written by Lucas Ferreira, Marie Culhane, Mark Schwartz and Cesar A. Corzo of the University of Minnesota for the National Hog Farmer.