Development and preliminary evaluation of an IgM dot-immunobinding assay (IgM-DIA) for rapid serodiagnosis of scrub typhus infection

An IgM dot-immunobinding assay (IgM-DIA) was developed for the diagnosis of scrub typhus infection. The whole cell antigens of Karp, Kato and Gilliam strains of Rickettsia tsutsugamushi were immobilized onto nitrocellulose paper and reacted with patients sera. The presence of IgM R. tsutsugamushi specific antibody in the patient sera could be detected by the observation of a visible brown dot on the nitrocellulose paper. The IgM-DIA has a sensitivity of 90.4% and specificity of 81.4% as compared to the indirect immunoperoxidase test. The IgM-DIA is rapid, simple, cost-effective, does not require microscope or incubator. It is recommended as a rapid screening test for the diagnosis of scrub typhus infection in the field or rural area within the hyperendemic region.