Viral contamination of bovine foetal serum and cell cultures

THE presence of adventitious viruses in cell cultures is well recognised¹, and when the cultures are of primate origin there are serious hazards for the production of human viral vaccines². This is one reason for the increasing use of bovine cell cultures. These cultures, however, are not free from viral contamination³. We found that calf kidney (CK) and calf testis (CT) cells were often infected by non-cytopathic mucosal disease virus (MDV): the cells seemed morphologically healthy but nearly all showed fluorescence with MDV antiserum and rabbit-anti-bovine conjugate. We report here that both the cells and foetal calf serum, an essential growth factor of cell culture medium, are sources of the virus.