Recombinant chimeric antigens comprising unmodified and modified reactive polypeptide fragments of expressed product of the recombinant 56 kDa proteins of multiple strain of scrub typhus, such as Karp, Kato (Ktr56), Gilliam (Gmr56), and TA763 (TAr56). The invention is useful for detecting prior exposure to a number of strains of scrub typhus, based on the strength of reaction toward the chimeric protein and as a component in vaccine formulations and production of immune globulins for passive prophylaxis and immunity in subjects against heterologous infections.