Infection, Haemorrhage and Death of Chick Embryos after inoculation of Herpes Simplex Virus Type 2 on to the Chorioallantoic Membrane

SUMMARY When the chorioallantoic membrane of the embryonated hen’s egg was inoculated with herpes simplex virus type 2 strains, an infection resulted which spread rapidly throughout the egg. Haemorrhage and death occurred in the embryo, and haemorrhage was also observed in the chorioallantoic membrane. Virus was recovered from the infected chorioallantoic membrane, allantoic fluid, amniotic fluid and selected organs of the embryo. In contrast, similar inoculation of herpes simplex virus type 1 strains gave no haemorrhage in chorioallantoic membrane or embryos, embryos did not die and virus was recovered only from the inoculated chorioallantoic membrane. Inoculation of either type into the allantoic cavity did not result in spread of virus to the embryo. Prolonged adaptation of herpes simplex viruses to growth in eggs eventually resulted in spread of type 1 virus from the chorioallantoic membrane to other regions of the egg and there were also marginal increases in virulence of type 2 virus.