Clinical response of silvered leaf monkeys (Presbytis cristatus) to infection with strains of Rickettsia tsutsugamushi virulent and avirulent for mice.

Silvered leaf monkeys (Presbytis cristatus) inoculated with avirulent strains of Rickettsia tsutsugamushi showed little or no signs of disease, whereas those inoculated with moderately or fully virulent strains developed severe disease. Infection with the virulent strains produced early leukocytosis followed by leukopenia and significant decreases in packed-cell volumes. In animals infected with avirulent strains, these parameters were normal throughout the experimental period.