Salt inactivation kinetics of six porcine viruses in a 3D collagen model, simulating natural sausage casings

Natural sausage casings are derived from intestines of regularly slaughtered pigs, bovines and small ruminants. Although casings are derived only from healthy animals after mandatory veterinary inspection, some slaughtered animals may originate from areas where contagious animal viral diseases are endemic. A validated 3D collagen model was used to establish inactivation kinetics of bovine viral diarrhoea virus (BVDV), porcine epidemic diarrhoea virus (PEDV), porcine reproductive and respiratory syndrome virus (PRRSV), pseudorabies virus (PrV), swine vesicular disease virus (SVDV) and transmissible gastroenteritis virus (TGEV) following treatment with saturated sodium chloride (NaCl) brine in line with the common production process of natural casings and alternatively a phosphate supplemented sodium chloride (P-salt). Decimal reduction values (D-values), representing time needed to reduce the initial viral load by 1 log₁₀ (or 90 %), were determined at 4°C, 12°C and 20°C. For PRRSV and PrV, NaCl treatment at 12°C and 20°C was effective in lowering D-values significantly, while opposite results were found for BVDV, PEDV, SVDV and TGEV. Compared to the non-treatment, P-salt significantly decreased D-values for each virus at all temperatures, except for PrV and SVDV at 4°C. Despite clear thermal inactivation, no consistent correlation was found between salt inactivation and virus characteristics, like enveloped versus non-enveloped, DNA versus RNA viruses, and virion sizes. However, for individual viruses, the presented D-values can be used for future quantitative microbial risk assessment (QMRA) and to support emergency protocols and precautionary measures for sourcing of natural casings in cases of an acute outbreak of viral disease in endemic areas.