Heat lability of five strains of infectious bursal disease virus

Abstract

An extensive world trade environment has created a need for many nations to protect their food animal industries against the importation of pathogenic microorganisms. We initiated studies to determine how cooking conditions would affect the viability of different infectious bursal disease virus (IBDV) strains. Five different viral strains were tested. The strains included two serotype 1 variant viruses, Del-A and MD; two serotype 1 classic viruses, STC and D78; and a serotype 2 virus, OH. A 100-microL aliquot of each viral stain in Dulbecco's Modified Eagle Medium with 2% fetal calf serum was heated to 37,65, 71, 74,77, 82, or 100 C for 1 min. Following heat treatment, the virus titers were determined in a BGM-70 cell culture. Virus titers declined following each incubation, and there were no appreciable differences among the five viral strains tested. The greatest decline in titer occurred at temperatures above 65 C. After 1 min at 65, 71, and 100 C, reduction of viable viruses were > or =90, > or =99, and >99.9%, respectively, compared to nonheated controls. A viral reduction curve similar to the first heating trial was observed when viruses were heated at 71 or 74 C for 6 min. Drumsticks and boneless chicken patties were seeded with the virus at a mean value of 10(5.5) TCID50/25 microL of IBDV and were cooked to internal temperatures of 71 and 74 C, respectively. All samples were quickly cooled after achieving target temperatures. Viable virus was recovered from both products following cooking.