Inactivation of Foot-and-Mouth Disease Virus by pH and Temperature Changes and by Formaldehyde

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Abstract
Rates of inactivation of tissue-culture-derived, foot-and-mouth disease virus, type A, were determined in the pH range 2 to 10 at 4[degree]C. Below pH 4 the virus was totally destroyed within a few seconds; at pH 5 and 6 infectivity was lost at a rate of 90% per second and minute, respectively, until a one-millionth part of the virus possessing much greater stability remained; at pH 6.5 and 10, 90% of the infectivity was lost every 14 hours; at pH 7 and 7.5, it was completely stable for at least 5 weeks; and at pH 8 and 9, a 90% reduction of infectivity occurred within a 3- and a 1-week period, respectively. Rates of thermal inactivation were determined for the range 4[degree] to 61 [degree]C at pH 7.5. The time intervals required for inactivation of 90% of the infectivity existing at any time were as follows: 18 weeks at 4[degree]; 11 days at 20[degree]; 21 hours at 37[degree]; 7 hours at 43[degree]; 1 hour at 49[degree]; 20 seconds at 55[degree] to a survival of 0.001, 7 minutes thereafter; and 3 seconds at 61 [degree]C to a survival of 0.00001, 11 minutes thereafter. Activation energies calculated for loss of infectivity below and above 43[degree]C were 27,200 and 120,600 calories per mole of virus, respectively. Virus treated with 0.009% formaldehyde at 4[degree]C was inactivated initially at a rate of 90% per day.

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