Parasitology



Transmission of Orientia tsutsugamushi, the aetiological agent for scrub typhus, to co-feeding mites


S. P. FRANCES a1a2c1, P. WATCHARAPICHAT a3, D. PHULSUKSOMBATI a3 and P. TANSKUL a1
a1 Department of Medical Entomology, US Component, Armed Forces Research Institute for Medical Sciences, 315/6 Rajvithi Road, Bangkok, Thailand
a2 Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, Queensland 4052, Australia
a3 Department of Veterinary Medicine, Royal Thai Component, Armed Forces Research Institute for Medical Sciences, 315/6 Rajvithi Road, Bangkok, Thailand

Abstract

Experiments were conducted to investigate the potential for transmission of Orientia tsutsugamushi, the aetiological agent for scrub typhus, when naturally infected mite larvae were co-feeding with uninfected larvae. Larvae from colonies of Leptotrombidium deliense and L. imphalum infected with O. tsutsugamushi were used. Transmission of O. tsutsugamushi to previously uninfected L. deliense and Blankaartia acuscutellaris co-fed with infected L. deliense was shown to occur. The overall minimum rate of acquisition was 1·6% (4/258) for L. deliense and 2·5% (3/119) for B. acuscutellaris. When individual infected L. deliense were co-fed with B. acuscutellaris acquisition of O. tsutsugamushi was not detected. However, when 4 and 8 infected larvae were co-fed with B. acuscutellaris acquisition of O. tsutsugamushi was detected. Transmission of O. tsutsugamushi was not observed when uninfected L. deliense were co-fed with infected L. imphalum. This novel transmission route may explain the occurrence of rickettsiae in genera other than Leptotrombidium spp, which are considered to be the main vectors of O. tsutsugamushi.

(Received August 23 1999)
(Revised October 29 1999)
(Revised December 11 1999)
(Accepted December 11 1999)


Key Words: scrub typhus; Orientia tsutsugamushi; Rattus rattus; trombiculid mites; co-feeding transmission.

Correspondence:
c1 Corresponding author: Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, Queensland 4052, Australia. Tel: +61 7 33324807. Fax: +61 7 33324800. E-mail: Steve.Frances.233022@army.defence.gov.au


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