In-Vitro Experiments on the Radiosensitivity of Foot-and-Mouth Disease Virus and other Animal Viruses to the Direct Effect of X-Irradiation

Various in-vitro techniques have been used to observe the direct X-ray inactivation of foot-and-mouth disease virus, vesicular stomatitis virus and the virus of Teschen disease. All these methods were intended to eliminate the indirect effects of the irradiation, and for each virus an upper limit to the radioresistance was observed, which was assumed to correspond to inactivation by the direct effect. Further confirmation of the absence of indirect effects was obtained by observing the dose-rate and the concentration-independent survival curves, and by direct observation of the inactivated virus in the electron microscope. Virus suffering only direct inactivation retained its morphological integrity at a much higher radiation dose level (relative to loss of infectivity) than virus which was exposed to some residual indirect effects. These results are of value since the radio resistances observed represent the upper limits which may have to be taken into account in, for example, the elimination of foot-and-mouth disease virus from frozen meat. (author)