Influence of temperature on the growth in cell culture of malignant catarrhal fever virus.

The growth characteristics of malignant catarrhal fever (MCF) virus in bovine thyroid cultures were affected by incubation temperature. The cytopathic effect at 37 degrees C was predominantly syncytial and little or no cell-free virus could be detected. At 32 degrees to 34 degrees C foci of rounded refractile cells were observed, and this was accompanied by an increase in the amount of cell-free virus found in culture fluids. Growth curve studies with one low passage isolate of MCF virus showed that optimum yields of cell-free virus were obtained at 32 degrees to 34 degrees C and survival curves at 32 degrees and 37 degrees C indicated that this was a result of the relatively short half life of the virus at the higher temperature. A number of other benefits resulted from the use of lowered incubation temperature and these are discussed with reference to in vitro work with the virus.