Plaut, S. M., Ader, R., Friedman, S. B. et al. 1969. Social factors and resistance to malaria in the mouse: Effects of group vs. individual housing on resistance to Plasmodium berghei infection. Psychosomatic Medicine 31, 536-552.

Mortality rate of malaria-infected mice was related to number of animals per cage, population sizes ranging from 1 to 20. This was independent of age, sex, and number of animals per cage infected. Individually housed mice died as fast as grouped mice with room temperature at 82[degrees]F rather than 70[degrees]F. If housing conditions were reversed after infection, mortality was dependent primarily on postreversal conditions. This, combined with failure to discriminate between differentially housed animals by weight, parasitemia, reticulocytosis or hematocrit on the sixth day after infection suggested that differences in mortality rate arise from responses to situations occurring after that day. Since cage size did not affect mortality rate, it was concluded that the housing effect is dependent upon population size, rather than density. Finally, grouped mice separated by screening died as slowly as individuals, suggesting a role of physical contact in the high mortality rate of grouped mice.