Microassay for measuring thermal inactivation of H5N1 high pathogenicity avian influenza virus in naturally infected chicken meat.

A precise, reproducible microassay was developed to measure thermal inactivation of high pathogenicity avian influenza (HPAI) virus in chicken meat. Small pieces of breast or thigh meat (0.05 g) from chickens infected with A/chicken/Pennsylvania/1370/1983 (H5N2) (PA/83) or A/chicken/Korea/ES/2003 (H5N1) (Korea/03) HPAI viruses were tested for inactivation in the heating block of a thermocycler. Korea/03 infected thigh and breast meat had higher virus concentrations (10(6.8) and 10(5.6) mean embryo infectious doses [EID(50)]/g, respectively) compared to PA/83 infected thigh and breast meat (10(2.8) and 10(2.3) EID(50)/g, respectively). The samples were ran through a ramp-up cycle from 25 to 70 degrees C, and meat samples were removed and examined for virus infectivity at 30, 40, 50, 60 and 70 degrees C, and after treatment for 1, 5, 10, 30 and 60 s at 70 degrees C. The reduction in virus infectivity titers was dependent on virus concentration and no HPAI virus was isolated after 1 s of treatment at 70 degrees C. A change in coloration from pink-tan to white was associated with a loss in recovery of infectious virus. The microassay provided a predictable and reproducible method to measure thermal inactivation of HPAI virus in chicken meat.