Activation of lymphoid leucosis in chicks by irradiation.

Abstract

Two strains of commercially bred chicks (White Leghorn and Babcock), and one strain of “leucosis‐free” chicks (White Leghorn‐SPAFAS) were treated with whole‐body irradiation. This treatment enhanced the incidence of lymphoid leucosis in the commercially bred animals; with the highest dose of irradiation employed (300 rad × 4), 20 per cent of the Babcock chicks developed lymphoid leucosis after a latent period of 161–357 days, whereas none of the irradiated SPAFAS chicks which were kept in strict isolation during the whole experimental period developed leucosis. One out of eight SPAFAS chicks kept in contact with “leucosis‐carrying” chicks developed lymphoid leucosis. The disease was transmissible to other non‐irradiated chicks with cell‐free material. The whole‐body irradiation is considered to have a complex effect with possible activation of latent avian tumour virus. The possibility of induction of virus production in “leucosis‐free” chicks is discussed.