A series of embryonated eggs incubated from 6 to 18 days have been successfully infected by yolk sac inoculation with a strain of group A Coxsackie virus. The resulting pathologic changes are here described. The principal lesion consisted of widespread acute necrosis of striated muscle, apparently essentially identical in type and development with that characteristically produced by the virus in suckling mice. The infection was not itself lethal; some embryos with virtually complete destruction of skeletal muscle were found alive. The older the embryo at the time of inoculation, the less the severity and extent of the lesions; but susceptibility was sometimes not entirely lost in embryos 18 days old. Two embryos inoculated at this time hatched and lived for 4 and 11 days respectively. One showed minimal specific muscle lesions, and the other only some irregularity in muscle fiber size. The lessening of severity of the lesions was especially marked and abrupt in embryos inoculated on the 10th and the 12th day of incubation.
In addition to the muscle lesions characteristic of infection with group A Coxsackie virus, there were regularly present in the more immature embryos extensive necrosis of epidermis and feathers and degeneration of feather follicles, believed to be probably a direct dermotropic effect of the virus infection. Other visceral lesions, chiefly liver necrosis, were occasionally observed but seemed not to have been due to direct virus action.
As in suckling mice infected with group A Coxsackie virus, no lesions were observed in the central or peripheral nervous system nor in the heart muscle. No lesions deemed specific were seen in the few specimens of chorioallantoic membranes examined.