Disinfection of foreign animal disease viruses on surfaces relevant to the Pork Packing Industry

The overall purpose of this research was to test the efficacy of commercial chemical disinfectants against foreign animal disease (FAD) viruses dried in swine products and on surfaces relevant to the Pork Packing industry. While packing plants have robust sanitization procedures in place, these are designed to limit bacterial contamination, so it is unknown if the disinfectants used are capable of effectively disinfecting the plant in the case of an introduction of FAD virus-infected animals. A further objective was to begin exploring a less pathogenic domestic virus as potential surrogates to replace foot-and-mouth disease virus (FMDV) in disinfection assays and enable disinfection testing outside high containment laboratories.

Using methodology we had previously developed (Krug et al, 2012) two commercial disinfectants currently used in the industry; CD631 (acid quaternary ammonium based) and XY12 (sodium hypochlorite based) were tested against 3 FAD viruses. The three viruses tested were foot-and mouth disease virus (FMDV), classical swine fever virus (CSFV) and African swine fever virus (ASFV). Viruses were tested in contaminated swine products (blood, meat juice, feces) dried onto surfaces (stainless steel, plastic, concrete) relevant to the pork packing industry.

Both commercial disinfectants were highly effective when the FAD viruses were dried without organic material (i.e. blood, meat juice or feces) on steel and plastic surfaces. However, drying the FAD viruses in meat juice and blood made disinfection less effective by both commercial disinfectants. Swine feces contaminated with FAD viruses and dried on various surfaces could be rapidly disinfected with CD631 and citric acid, however feces strongly inhibited XY12 (sodium hypochlorite-based) disinfectant and bleach.

Concrete disinfection assays were difficult to standardize due to interference with the disinfection assay by untreated concrete. After extensive testing of various methods; it was found that sealing the concrete with a commercial sealer allowed FAD virus disinfection assays. Viruses dried on sealed concrete were inactivated with similar profiles to the plastic and steel surfaces.

A potential FMDV surrogate, the Equine Rhinitis A virus (ERAV) compared favorably with FMDV in respect to disinfection with CD631 and citric acid disinfectants. However ERAV was found to be more sensitive to disinfection by XY12 and bleach products than FMDV and therefore is not a good surrogate. More studies are necessary to find a better surrogates.

Our findings indicate that acid-based commercial disinfectants such as CD631, used under manufacturer’s instructions, are appropriate for disinfection during a FAD virus outbreak. However, surface pre-cleaning steps as recommended by the manufacturers, prior to disinfection are necessary when blood products or meat juices are present since these products inhibit disinfection on dried surfaces. The hypochlorite-based product XY12 tested was ineffective in inactivating FADs in the presence of organic material.

Recommendations:
a. Disinfection of pork packing plants should be done with acid-based disinfectants (such as CD631) following manufacturer’s instructions particularly regarding pre-washing procedures.
b. Hypochlorite based disinfectants such as XY12 and bleach should be avoided when organic load (e.g. blood, feces) is high.
c. Concrete surfaces should be sealed to render them nonporous in order to allow appropriate disinfection.
d. Finally, ERAV should not be used as a suitable surrogate virus for FMDV disinfection with hypochlorite-based products and alternate surrogates for FMDV and other FAD viruses should be investigated.