from The American Heritage® Dictionary of the English Language, 5th Edition.
- adjective Not virulent.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- adjective Not
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adjective not virulent; unable to produce disease
Sorry, no etymologies found.
In the same way, those human bacilli which had become avirulent to cattle through long-continued culture in the laboratory can act again with considerable virulence in cattle if they are first used to infect goats and then, after the death of the animals, are cultivated from the carcases.
In my own experiments with tubercle bacilli of human origin which were avirulent to cattle, cultures were always used which had been cultivated for years in the laboratory.
Further investigations, however, disclosed that besides existing in their typical virulent, infectious state, many viruses are capable of adapting themselves so successfully to their hosts that they may live within the host cells in an avirulent, symbiotic or latent condition from which, under appropriate conditions, they may be released after long periods of time.
Asibi virus to the relatively avirulent French strain.
This proved of great value, for as strains of virus avirulent for monkeys were developed, the mouse was the only animal by which the presence and amount could be readily determined.
However, the intracerebral pathogenicity index of APMV-5 strain Kunitachi in one-day-old chicks was found to be zero, indicating that the virus is avirulent for chickens despite the presence of a polybasic F cleavage site.
In contrast, the cleavage site sequences of avirulent NDV strains characteristically have one or a few basic residues immediately upstream of the cleavage site that do not create a furin cleavage site.
The presence of a non-furin cleavage site as in avirulent NDV strains restricts viral replication to the respiratory and enteric tracts, where secretory proteases necessary for F cleavage are present.
Pfu/ml of APMV-5 via the amniotic sac did not cause embryo death even after 5 days post-infection, suggesting that the virus is avirulent in chickens.
However, it is interesting that this same virus was completely avirulent in chicken eggs.