Influence of salts on foot-and-mouth disease virus.

The effect of sodium and magnesium chloride in 1 and 2 m concentration at temperatures of 37 and 50 C on type C, strain 149, foot-and-mouth disease virus during storage for 6 days was studied. The exclusively passaged cattle strain and its tissue culture-adapted line were compared. Preparations of the various chemicals and their concentrations were made directly in suspensions of the virus, which, together with untreated control virus suspensions, were stored at indicated temperatures and tested daily for concentration of virus present. Both 1 and 2 m concentrations of Mg markedly slowed the degradation of the bovine-passaged virus, as compared with untreated virus stored at 37 or 50 C. Such was not the case with 1 and 2 m concentrations of Na at 37 and 50 C, in which instance the treated virus was degraded faster than the untreated controls at 37 C, and but slightly influenced at 50 C. The tissue culture-adapted virus at the 25th passage was not stabilized by any concentration of chemical additive either at 37 or 50 C, except for 1 and 2 m concentrations of Na at 37 C, which partially retarded degradation of the virus. After 91 passages of the virus in tissue culture, only a suggestion of the influence of 1 and 2 m concentrations of Na at 37 C remained to show a stabilizing effect. These responses tend to separate the bovine-passaged virus from the tissue culture-adapted virus under the conditions of this study.