Experiment Station Record, Volume 92, January-June, 1945 Page: 112

                                
112                   EXPERIMENT STATION RECORD                      IVol. 92
air-borne contagion of tuberculosis in rabbits. When the radiant energy is of low
intensity it reduces considerably the incidence of tuberculosis. It completely protects
rabbits of high natural resistance from acquiring demonstrable disease though they
become tuberculin sensitive. It fails to protect a small proportion of rabbits of
low natural resistance from fatal tuberculosis.
"When the radiant energy is of high intensity all rabbits, whether of high or of
low natural resistance, are almost completely protected from a contagion so severe
that it is fatal to the great majority of rabbits of the same genetic constitution not
protected by these rays. The protected rabbits do not develop tuberculin sensitivity.
"The contagion of tuberculosis in these studies is air-borne, and the radiant
energy exercises its protective influence by its bactericidal properties. It is probable
that ultraviolet irradiation may control air-borne contagion of human tuberculosis."
Experimental epidemiology of tuberculosis: Hereditary resistance to attack
by tuberculosis and to the ensuing disease and the effect of the concentration of
tubercle bacilli upon these two phases of resistance, M. B. LURIE (Jour. Expt.
Mled., 79 (1944), No. 6, pp. 573-589, illus. 2). Studies carried on with two families
of rabbits, one of high inherited resistance to tuberculosis and one of low inherited
resistance, indicated that hereditary resistance to attack by air-borne tubercle bacilli
is distinct from resistance to the ensuing disease. Increasing concentrations of
tubercle bacilli in the environment of the family of high genetic resistance to the
disease increase the incidence of infection, accelerate the onset of the disease, and
affect its essential character in proportion to the concentration of the micro-organism.
tp to a certain concentration of tubercle bacilli in the environment of the
families of low genetic resistance to the disease, increasing concentrations of the
infectious agent also increase the incidence of the disease and accelerate its onset,
although its anatomical character is always of a uniform rapidly progressive type.
Beyond this concentration further increment of the infectious agent exercises no
effect.
The tuberculin test in guinea-pigs and cattle: The allergic response of animals
to tuberculin and to extracts of non-pathogenic acid-fast bacteria, A. S. CANHAM
(Onderstepoort Jour. Vet. Sci. and Anim. Indus., 19 (1944), No. 1-2, pp. 29-70).From
this comprehensive investigation the following conclusions are drawn:
"In guinea pigs a sufficient degree of infection with the organism of tuberculosis
can be set up by artificial means so that reactions with tuberculin are given within
from 24 to 30 days. This means that the period of 6-8 weeks usually elapsing
before subjects injected with suspected tubercular material are killed for diagnosis
can be shortened by testing the subject and a control with tuberculin in from 24
to 30 days, thus expediting results of tests.
"Animals infected with Br[ucella] aborts may give strongly suspicious reactions
when tested with tuberculin. Reactions strongly suspicious of positive tuberculin
reactions have been observed in cattle that were pregnant and close to the time of
parturition. A similar case was observed in a control guinea pig. Guinea pigs
infected with strains of nonpathogenic acid-fast organisms gave reactions in some
cases when tested with tuberculin in a dilution of 1 : 100. More marked reactions
to tuberculin were obtained when lower dilutions were used, viz, 1 : 10 to 1 : 40
dilutions.
"Extracts prepared from nonpathogenic acid-fast organisms, in the same way
as tuberculin is prepared, appear to contain some antigenic factor common to all
members of this group that gives rise to reactions when inoculated into small animals
artificially infected with separate members of this group. Extracts prepared
on the lines of L'anaexo-Tuberculin may contain products that are specific for each
member of the acid-fast group of organisms.