BIOASSAY OF FOWL LEUKOSIS VIRUS IN CHICKENS BY THE INOCULATION OF 11-DAY-OLD EMBRYOS.

Abstract Comparative assays of leukosis strains RPL 12, RPL 25, RPL 26, and RPL 29 were conducted by the intravenous inoculation of 11-day-old embryos and 14-day-old chickens. Most of the inoculated embryos hatched were held for a postinoculation period of 46 days. Chickens inoculated at 14 days were held to 77 days postinoculation. The primary specific neoplasm induced was erythroblastosis. Some of the chickens inoculated as embryos also developed fibrosarcomas, endotheliomas, nephromas, and hemorrhages. Quantal responses in terms of probits were related directly to the dose of virus, a straight line most nearly fitting the data. Equivalent responses were higher in the embryo inoculations than in the chicken inoculations by 2.0 log 10 dilution for three strains and 0.7 log 10 dilution for one strain. Thus when embryos are inoculated, lower levels of virus will cause a significant incidence of erythroblastosis than when chicks are inoculated.