Comparison of C. immitis infection between resistant DBA/2 and sensitive C57BL/6 mice. Mice were infected (i.n.) and then sacrificed at the indicated intervals. The right lung and spleen of each mouse was homogenized and cultured quantitatively. Each symbol represents an individual mouse and the horizontal lines are the geometric mean ± standard error of the mean. The infection proceeded more rapidly in the lungs of the C57BL/6 mice and dissemination to the spleen occurred only in this strain, another indication of their increased susceptibility to infection. P-values comparing lung CFU were calculated with an unpaired Student’s t-test using GraphPad Prism (San Diego, CA). There was no significant difference between CFU in the lungs of the two strains on day 10 after infection.