The effect of temperature and urea on virulent and attenuated strains of pseudoabies virus.

Out of 10 virulent strains of pseudorabies virus (PRV), 9 proved to be resistant and 3 out of 4 attenuated strains were sensitive to the temperature of 53 degrees C. No differences were found between attenuated and virulent strains of PRV in their rate of inactivation of 2 M urea; its inactivating effect was enhanced by increasing the temperature. The t (effect of temperature) and u (effect of urea) markers proved unsuitable for a sufficient characterization of PRV strains.