GROWTH CYCLE OF FOWLPOX VIRUS AND CHANGE IN PLAQUE MORPHOLOGY AND CYTOPATHOLOGY BY CONTAMINATING MYCOPLASMA

Studies of the multiplication of fowlpox virus (FP) in chick embryo (CE) monolayers indicate that the eclipse period in this system extends for 24-36 hours and the increase of infectious virus is exponential from 36 to 72 hours with a decline in titer by 120 hours. Most of the virus remains cell-associated throughout this period. The kinetics of the in vitro growth curve in cultures dually infected with FP and Mycoplasma gallisepticum are very similar to pure FP infection, but the in vivo infectivity is markedly decreased. Whereas the pock count of FP alone was approximately 1 log lower than the plaque titer, the pock count of the FP-Mycoplasma mixture was at least 5-6 logs lower. The mechanism of this effect of Mycoplasma on the in vivo infectivity of FP has not been elucidated. © 1969.