Scrub typhus infection in rats in four habitats in Peninsular Malaysia.

Rickettsia tsutsugamushi isolations were attempted from blood samples obtained from rats captured in four adjacent habitats near Kuala Lumpur, Malaysia. Antibody surveys were also made. Rickettsial infections were most frequent in rats captured in the forest and in lalang grass (Imperata cylindrica) and least frequent in the most extensively disturbed habitat, an Orang Asli (aborigine) village. Forest rats such as Rattus sabanus (31%), as well as rats in the subgenus R. (Rattus), i.e. R. tiomanicus (26%) and R. argentiventer (35%) had frequent active infections. The house rat R. exulans had less frequent infections (15%). Frequency of antibody occurrence followed a similar pattern. No marked seasonal differences in the frequency of infections could be detected during the 18-month study.