Unloading docks at processing plants appear to be source of PRRSV

Unloading docks at processing plants may be one way that livestock trailers become contaminated with porcine reproductive and respiratory syndrome virus (PRRSV), indicates a recent study.¹

It’s known that transport vehicles can be a source of PRRSV transmission and that trailer hygiene isn’t always adequate, but less is known about the different ways that trailers become contaminated with the virus.

A previous study demonstrated trailers can become contaminated with porcine epidemic diarrhea virus when unloading, so researchers hypothesized that loading docks might also play a role in the transmission of PRRSV to trailers.

For their study, they developed an experimental model simulating indirect contact involving footwear between a PRRSV-contaminated unloading dock and pig transport vehicle.

In one experiment, they evaluated whether different temperatures affected the transmission of PRRSV to a model trailer for 60 minutes after contact with a contaminated dock. The temperatures were 4˚ C (39.2˚ F), 15˚ C (59˚ F) and 28˚ C (82.4˚ F).

In a second experiment, they determined whether PRRSV on the dock was affected by the temperatures 4° C (39.2˚ F) or 32° C (89.6 ˚ F), by ultraviolet light or by mechanical scraping, James Lowe, DVM, and colleagues of the University of Illinois explain in the January/February 2017 issue of the Journal of Swine Health and Production.

In the first experiment, temperature did not affect the amount of PRRSV RNA recovered. In addition, when PRRSV RNA was detected on the model dock, investigators said it was transferred and detected on the model trailer 80% of the time.

The most pertinent findings from the second experiment was that debulking — mechanical scraping of the dock — reduced the risk for PRRSV RNA transfer from the model dock to model trailer, say the researchers, from the University of Illinois and Carthage Innovative Swine Solutions.

They point out their research needs to be validated in the field, but conclude that mechanical removal of gross contamination of unloading docks may reduce the probability that PRRSV will be transmitted to trailers.

1. Lowe J, et al. Factors that influence mechanical transmission of porcine reproductive and respiratory syndrome virus at the time of unloading animals into slaughter plant lairage. J Swine Health Prod. 2017;25(1):19–23.