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Characterization of the 56-kDa type-specific antigen (TSA) genes of Orientia tsutsugamushi (OT) from three naturally infected, laboratory-reared mite colonies comprising three species (Leptotrombidium deliense [Ld], Leptotrombidium imphalum [Li], and Leptotrombidium chiangraiensis [Lc]) has revealed the presence of single and coexisting OT genotypes found in individual chiggers. The Karp genotype was found in all of the chiggers examined, whereas Gilliam and UT302 genotypes were only observed in combination with the Karp genotype. From analysis of these OT genotypes after transmission from chiggers to mice it was determined that with the Lc and Li mites, the OT genotype composition in the rodent spleens post-infection had not changed and therefore resembled that observed in the feeding chiggers. However, only the Karp genotype was found in rodents after feeding by Ld chiggers carrying Karp and Gilliam genotypes. The current findings reveal a complex association among the host, pathogen, and vector.
Financial support: This work was supported by the Military Infectious Disease Research Program and the United States Army Medical Research and Materiel Command, Fort Detrick, MD.
Authors' addresses: Ratree Takhampunya, Bousaraporn Tippayachai, Sommai Promsathaporn, Surachai Leepitakrat, Taweesak Monkanna, and Anthony L. Schuster, Department of Entomology, AFRIMS, Bangkok, Thailand, E-mails: RatreeT@afrims.org, BousarapornT@afrims.org, SommaiP@afrims.org, SurachaiL@afrims.org, TaweesakM@afrims.org, and Schuster.Anthony@afrims.org. Melanie C. Melendrez, Viral Diseases Branch, Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, E-mail: email@example.com. Daniel H. Paris, Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand, E-mail: firstname.lastname@example.org. Allen L. Richards, Rickettsial Diseases Research Program, Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, MD, E-mail: email@example.com. Jason H. Richardson, Entomology Branch, Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, E-mail: Jason.H.Richardson@us.army.mil.