Relative rates of Aujeszky's disease virus attenuation, as assessed in mice.
Field strains of Aujeszky's disease virus (ADV) were attenuated by heat treatment and serial passage at sub-optimal growth temperatures in chicken embryo fibroblasts (CEF). At chosen passage levels, virus was titrated in cell culture and in mice. For each strain, the pathogenicity was expressed as a mouse lethal index (MLI), defined as the inverse of the log10 (CCID50:LD50). MLIs determined for field strains displayed a wide range of comparatively high values. The attenuation of field strains was accompanied by a rapid fall in MLI values, particularly in the initial stages. Heat-treated ADV attenuated faster than untreated ADV, when passaged at 30 degrees C. Passage at 27 degrees C resulted in considerably accelerated attenuation compared to passage at 30 degrees C, in the case of both untreated and heat-treated ADV. MLIs were determined for attenuated ADV strains that had been tested in 6-day-old piglets. Low MLI values were found to correlate with low virulence in piglets and high MLI values with virulence.
Chong
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YC
Central Veterinary Laboratory, Republic of Singapore.
Förster
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U
D000818:Animals; D002642:Chick Embryo; D005260:Female; D005347:Fibroblasts; D011558:Herpesvirus 1, Suid / Q000254:growth & development / Q000472:pathogenicity*; D006358:Hot Temperature; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011557:Pseudorabies / Q000382:microbiology*; D013552:Swine; D013696:Temperature; D014774:Virulence