Effects of Para-aminobenzoic Acid in Experimental Tsutsugamushi Disease (Scrub Typhus)

Abstract

The therapeutic effect of p-aminobenzoic acid (PABA) against exptl. tsutsugamushi disease was tested in 4 expts. The animals employed in these tests were Gerbillus gerbillus and G. pyramidum. In expts. I and II, the animals were infected with a strain of Rickettsia orientalis from the Imphal Valley, India. Powdered PABA was mixed with dried bread and this diet was fed to the gerbilles from the day of inoculation. In expt. II, one group of infected animals received 10 mg. of PABA subcut. twice daily, beginning on the 7th post-inoculation day. There were no survivors in either expt., but the survival time of the treated animals was slightly greater than in the untreated controls. In expts. III and IV a strain of R. orientalis from Ceylon was used, and the highly soluble Na salt of PABA was used instead of the relatively insoluble acid. This drug was administered in the diet of the gerbilles from the time of inoculation and supplemented by subcut. injns. beginning on the 6th or 7th days of disease. In these 2 expts. there were 21 survivors of 31 treated animals, while only 2 of 32 control animals survived. These results indicate that the Na salt of PABA has a beneficial therapeutic action in the treatment of exptl. tsutsugamushi infection, but tests using larger numbers of animals and other strains of R. orientalis are necessary before final conclusions can be made.