Surveillance of amyloid A deposits in commercial beef liver and assessment of food hygiene risks.

Bovine amyloid A (AA) amyloidosis has been reported to be experimentally transmitted to mice, like prion disease. Although the prevalence of AA amyloidosis in cattle at slaughterhouses has been reported in several studies, how much bovine AA is distributed in retail stores remains unknown. In this study, to clarify the food hygienic risk of bovine AA, we collected beef livers from seven commercial retail stores in Japan to investigate the deposition rate and the transmissibility of bovine AA. Congo red staining and immunohistochemistry revealed bovine AA deposition in two of 185 commercial beef livers (1.08%). No differences were observed between the gross appearance of amyloid-laden and amyloid-free livers. Administration of bovine AA from commercial beef liver to mice, either intraperitoneally or into the spleen, did not promote the development of AA amyloidosis. This contrasts with previous studies demonstrating cross-species transmission of AA amyloidosis via intraperitoneal or even oral administration of bovine AA. Although the cause of this discrepancy is unknown, the low transmissibility may be related to the species-barrier. These results support that the actual food hygienic risk of AA amyloidosis associated with consuming commercial beef liver may not be significant.