Teratogenetic and Lethal Effects of Influenza-A and Mumps Viruses on Early Chick Embryos

Abstract

Summary

Experimental evidence has been presented to show that influenza-A virus (PR8) has teratogenetic effects on the early chick embryo. It produces a specific syndrome, comprising microcephaly and micrencephaly, twist of the axis and impairment of the growth of the amnion. Furthermore, the virus is lethal for early embryos, within 3 days after infection. The mumps virus is likewise lethal for early embryos, within 5 days after infection. It does not produce specific abnormalities but seems to raise the incidence of malformations of the types which occur occasionally in uninfected chick embryos. These results place Influenza-A virus in line with rubella virus, as a teratogenetic agent. Furthermore, our observations on Influenza-A infections in chick embryos confirm the observations on rubella in humans in that only infections of early embryos result in abnormalities. Chick embryos of 4 days of incubation are killed by the influenza virus, but it seems that at this stage of development most organs have passed the critical period at which their morphogenesis can be directed into atypical channels. In this respect, it is of interest to find that the patterns of infectiousness are different for the embryo and for the fully developed structures. In the embryo, the brain tissues seem to be particularly susceptible to Influenza-A virus, whereas in the adult the respiratory mucous membranes are primarily affected. In mumps, the infection of the salivary glands is not infrequently combined with meningitis, but no effect on the brain was found macroscopically in embryos. The situation is the same as in rubella where the embryonic defects seem to have no obvious relations to the manifestations of rubella infections in older phases of life.