Development of antibody to Rickettsia tsutsugamushi in soldiers in Malaysia.

Abstract Malaysian, British and New Zealand soldiers were tested for evidence of infection with Rickettsia tsutsugamushi after several weeks' exposure to the infection during field exercises in Malaysia. 39 (5·0%) of 787 British and New Zealand soldiers developed immunofluorescent antibody (IFA) to R. tsutsugamushi to a titre of 1:50 and two (0·3%) to a titre of 1:100. 11 (1·5%) of 751 Malaysian soldiers also developed low titres ≤1:100. These low antibody levels were not correlated with clinical disease, and their significance is unknown. Seven (0·9%) of the Malaysians showed an IFA rise to ≥1:200, and three of these experienced febrile illnesses, one lasting two weeks. An additional eight Malaysian soldiers had an IFA titre of ≥1:400 when first tested and six of these also had a Proteus OXK agglutinin titre of ≤1:160, indicating infection shortly before the study.