Effect of Stress by Crowding Prior to and Following Tuberculous Infection

¹ From the Department of Animal Behavior, American Museum of Natural History, and the Division of Tuberculosis, The Public Health Research Institute of the City of New York, Inc., New York

Although it is known that stressing an already infected animal reduces resistance to the infection, the effect of applying stress prior to infection has not been studied. In the present experiments, it was found that this procedure produced significant differences in resistance to infection. Eighty male and seventy-four female B albino C mice were assigned at random to four experimental groups as follows: 1) individually maintained before and after infection; 2) individually maintained before infection and housed in groups of 20 in cages allowing 3 square inches/animal after infection (‘crowded’ condition); 3) crowded before infection and individually maintained after infection; and 4) crowded before and after infection. These animals were infected with a dose of tubercle bacilli resulting in a chronic disease. It was found that males and females reacted differently to the experimental treatment. Males which were crowded before or after injection showed less resistance than the controls whereas females which were crowded before or after injection survived longer than the controls. Seventy-six male and sixty-six female B albino C mice were assigned to experimental groups as outlined above. These animals were infected with tubercle bacilli resulting in acute disease. The factors of sex differences, crowding before infection and crowding after infection all significantly affected the course of the disease. Males and females reacted to the experimental conditions in the same way. It was found that animals which were crowded before infection and maintained individually after infection resisted tuberculosis better than animals which were individually maintained before infection and crowded after infection.

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