Inactivation of infectious hepatitis E virus present in commercial pig livers sold in local grocery stores in the United States

Abstract

Hepatitis E virus (HEV) is a zoonotic pathogen and pigs are a known reservoir. Recently we showed that approximately 11% of commercial pig livers sold in local U.S. grocery stores for food consumptions are contaminated by infectious HEV. In this study, a swine bioassay was used to determine if the infectious HEV in contaminated commercial pig livers could be inactivated by traditional cooking methods. Group 1 pigs (n=5) were each inoculated intravenously (i.v.) with a HEV-negative liver homogenate as negative controls, group 2 pigs (n=5) were each inoculated i.v. with a pool of two HEV-positive pig liver homogenates as positive controls, groups 3, 4 and 5 pigs (n=5, each group) were each inoculated i.v. with a pool of homogenates of two HEV-positive livers incubated at 56 degrees C for 1 h, stir-fried at 191 degrees C (internal temperature of 71 degrees C) for 5 min or boiled in water for 5 min, respectively. As expected, the group 2 positive control pigs all became infected whereas the group 1 negative control pigs remained negative. Four of the five pigs inoculated with HEV-positive liver homogenates incubated at 56 degrees C for 1 h also became infected. However, pigs in groups 4 and 5 did not become infected. The results indicated that HEV in contaminated commercial pig livers can be effectively inactivated if cooked properly, although incubation at 56 degrees C for 1 h cannot inactivate the virus. Thus, to reduce the risk of food-borne HEV transmission, pig livers must be thoroughly cooked.

FIG. 1

Seroconversion to IgG anti-HEV in inoculated and control pigs. Panel A, pigs inoculated with a liver homogenate negative for HEV as negative controls (group 1); Panel B, pigs inoculated with a pool of two HEV-positive pig liver homogenate as positive controls (group 2); Panels C, D and E, each with a pool of two HEV-positive liver homogenates incubated at 56°C for 1 hr, stir-fried at 191°C for 5 min or boiled in water for 5 min (groups 3, 4 and 5, respectively). The ELISA cutoff OD value is 0.30.