BIOLOGICAL PROPERTIES OF 3 MEXICAN ISOLATES OF AUJESZKYS-DISEASE VIRUS

Four strains of Aujeszky's Disease virus (ADV) were included in this s tudy; three Mexican field isolates (215,145 and C-8) in conjunction wi th the Shope reference strain of ADV, which has known pathogenic chara cteristics. All four strains were included in each treatment, which co nsisted of heat treatment, trypsin treatment and passed ten times on c hicken embryo fibroblasts. Both virus titer and plaque size were deter mined on the first and tenth passage and on treated and untreated stra ins. On each of the treatments, the plaque size had significant differ ences (p=0.001) which had relation to the two factors studied, namely strain and passage level. There was no significant variation related t o the type of treatment between strains. With the strains under study, the authors also made rabbit pathogenicity tests, and it was found th at on passage one, the strains caused clear nervous symptoms and death , while on the tenth passage level, the Mexican strains produced sligh t pruritus, few nervous symptoms and allowed the rabbits to survive. T he mouse test revealed an increased median death time after the treatm ents, as well. as a large increase in standard deviations. These data are interpreted as an increased heterogeneity of the strains in all of the treatments to the strains of viruses.