Thermal Inactivation of Feline Calicivirus in Pet Food Processing

Extrusion is the most common manufacturing process used to produce heat-treated dry dog and cat food (pet food) for domestic use and international trade. Due to reoccurring outbreaks of notifiable terrestrial animal diseases and their impact on international trade, experiments were undertaken to demonstrate the effectiveness of heat-treated extruded pet food on virus inactivation. The impact of extrusion processing in a pet food matrix on virus inactivation has not been previously reported and very few inactivation studies have examined the thermal inactivation of viruses in complex food matrices. The feline calicivirus vaccine strain FCV F-9 was used as a surrogate model RNA virus pathogen. Small-scale heat inactivation experiments using animal-derived pet food raw materials showed that a > 4 log10 reduction (log10 R) in infectivity occurred at 70 °C prior to reaching the minimum extrusion manufacturing operating temperature of 100 °C. As anticipated, small-scale pressure studies at extrusion pressure (1.6 MPa) showed no apparent effect on FCV F-9 inactivation. Additionally, FCV F-9 was shown not to survive the acidic conditions used to produce pet food palatants of animal origin that are typically used as a coating after the extrusion process.