Occurrence of Orientia tsutsugamushi in chiggers (Acari: Trombiculidae) and small animals in an orchard near Bangkok, Thailand

• Published in: Journal of medical entomology Vol. 36; no. 4; pp. 449 - 453
• Main Authors: Frances, S.P, Watcharapichat, P, Phulsuksombati, D, Tanskul, P
• Format: Journal Article
• Language: English
• Published: Lanham, MD Entomological Society of America 01-07-1999; Oxford University Press
• Subjects: Animals; antibodies; Antibodies, Bacterial - analysis; aschoshoengastia (laurentella); aschoshoengastia indica; Biological and medical sciences; disease vectors; ecology; ectoparasites; Female; Fundamental and applied biological sciences. Psychology; Immunoglobulin G; infection; infection rate; leptotrombidium deliense; Liver; Male; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; Muridae; Orientia tsutsugamushi; Orientia tsutsugamushi - immunology; Orientia tsutsugamushi - isolation & purification; Rats; Rattus rattus; scrub typhus; Scrub Typhus - microbiology; Scrub Typhus - veterinary; small mammals; Thailand; Trombiculiasis - microbiology; Trombiculidae; Trombiculidae - classification; Trombiculidae - microbiology; Tupaia; Tupaia glis; Vectors. Intermediate hosts; Thailand; Asia; Tupaia glis; Scrub typhus; Reservoir; Scandentia; Orchard; Acari; Rickettsial infection; Pathogenic; Bacteria; Rattus rattus; Vector; Rickettsialosis; Fauna; Rodentia; Host; Infection; Rickettsiales; Acariformes; Arachnida; Vertebrata; Mammalia; Actinedida; Arthropoda; Bacteriosis; Ectoparasite; Invertebrata; Trombiculidae
• ISSN: 0022-2585; 1938-2928
• DOI: 10.1093/jmedent/36.4.449

The ecology of Orientia tsutsugamushi (Hayashi) was studied in chiggers and small animals in an orchard near Bangkok, Thailand. Small animals were trapped monthly between July and November 1992 and examined for the presence of O. tsutsugamushi and ectoparasitic chiggers. A total of 40 Rattus rattus (L.) and 16 Tupaia glis (Diard) was trapped. O. tsutsugamushi was isolated from liver and spleen samples of 30.8% of R. rattus and 18.6% of T. glis. Antibodies to O. tsutsugamushi were detected in 95% of R. rattus, and IgG antibodies persisted for up to 10 mo after removing rats from potential reinfection in the field. A total of 1,133 chiggers was identified and examined for the presence of O. tsutsugamushi using a direct fluorescent antibody test, and 2.6% Leptotrombidium deliense Walch, 5.1% Aschoshoengastia indica Hirst, 2.6% A. (Laurentella) sp. #2 and 0.9% A. (Laurentella) sp. #4 were infected. Forty-four pools of chiggers from these animals were triturated and injected into mice. Seven pools were obtained from T. glis and 1 was positive for O. tsutsugamushi, and 3 of 37 pools from R. rattus were positive. A proportion of the engorged chiggers collected was reared to the adult stage, and the progeny of these adults tested for the presence of O. tsutsugamushi. The progeny of 186 females was tested, and the progeny of 2 L. deliense was found to be naturally infected with O. tsutsugamushi.