Experimental "Runde" virus infections in embryonated eggs and chickens.

Three-day-old chicks and 11-12 day embryonated eggs were inoculated with 100 BMLD50 (baby mouse lethal doses) of Runde virus. Chicks were infected subcutaneously and eggs in the allantoic or amniotic cavities, in the yolk sac, or on the chorioallantoic membrane. "Runde" virus produced viraemia and antibody responses in 3-day-old chicks. The virus multiplied only in the amniotic cavity of the embryonated eggs and was detected in the brains of the embryos from day 5-9 p.i. Out of five eggs left to hatch, two hatched on time, while in three unhatched eggs the chicks were alive but extremely weak. Virus was detected in the brains of all five chicks, and high antibody titres were found in the two which hatched. These two chicks had "epilepsy-like" attacks. The results suggested that one passage in chicks or eggs reduced the mouse pathogenicity of "Runde" virus. No antigenic difference between chick- and mouse-passaged virus could be demonstrated by gel precipitation.