Transstadial and Transovarial Transmission ofOrientia tsutsugamushiinLeptotrombidium imphalumandLeptotrombidium chiangraiensis(Acari: Trombiculidae)

Abstract

Transovarial transmission of Orientia tsutsugamushi (Hayashi) in laboratory colonies of Leptotrombidium chiangraiensis Tanskul & Linthicum and Leptotrombidium imphalum (Vercammen-Grandjean & Langston) (Acari: Trombiculidae) was studied for two generations. In L. chiangraiensis, the transovarial and filial infection rate was 100% in each generation. Only infected females were produced. In L. imphalum, the transovarial infection rate of the parental generation was 100% but declined to 93.3% in the F1 generation. The overall filial infection rate was 100% in the F1 but was only 62.3% in the F2 generation. In infected lines, only infected females were produced in the F1 generation, but 1.5% of the F2 progeny were infected males. Lower rates of transovarial transmission in L. imphalum may be the cause of the lower natural infection rates found in nature.

Variable clinical responses of a scrub typhus outbred mouse model to feeding by Orientia tsutsugamushi infected mites

“…Owing to lack of CD-1 mice in our laboratory, we studied responses by ICR mice. The scrub typhus-mouse model developed helped better understand scrub typhus (Frances et al 2000a(Frances et al , 2001Frances and Linthicum 2002;Lerdthusnee et al 2002;Phasomkusolsil et al 2009) but a complete description of our mouse model and its clinical response following feeding by infected vector mites has not been described previously. Mouse clinical outcomes and virulence of each chigger line are critical for vaccine experimental design which is the ultimate goal for scrub typhus prevention and eradication.…”

“…Each mouse used was permanently identified, by ear notching method (Otis and Foster 1938). Generally, chiggers become fully engorged within 2-3 days and drop from the mouse's inner ear (Phasomkusolsil et al 2009). After 3 days, we checked the mites' feeding status by gently poking them with a small paint brush and considered any moving chigger as fully fed.…”

“…Several species of laboratory animals have been utilized in the development of a vaccine for scrub typhus, with mice being used most extensively (Ridgway et al 1986). Laboratory mice have been used to characterize the role of chiggers in their transmission of O. tsutsugamushi to vertebrate hosts (Frances 2005;Frances et al 2000aFrances et al , 2001Frances et al , 2002Lerdthusnee et al 2002;Phasomkusolsil et al 2009). But the study of mice clinical presentation of scrub typhus disease following a natural feeding procedure has never been described fully or published elsewhere.…”

Characterization Based on the 56-Kda Type-Specific Antigen Gene of Orientia tsutsugamushi Genotypes Isolated from Leptotrombidium Mites and the Rodent Host Post-Infection

“…Twelve O. tsutsugamushi-infected mite colonies (four lines of L. chiangraiensis, seven lines of L. imphalum, and one line of L. deliense) are maintained in an animal biosafety level-3 (ABSL-3) facility at AFRIMS (Table 1). 19 Larval mites were fed the ears of Institute of Cancer Research (ICR) mice from a Charles River Technology (BioLASCO, Taiwan) colony maintained by the Department of Veterinary Medicine, AFRIMS, whereas nymphs and adults were fed a diet of springtail eggs (protocol #09-11, Maintenance of the Leptotrombidium larval mite colonies: chigger feeding on ICR mice [Mus musculus]).…”

Transovarial Transmission of Orientia tsutsugamushi in Leptotrombidium palpale (Acari: Trombiculidae)

“…Previous studies on transovarial transmission occurred in L. pallidum [16] and L. scutellare [1] in Japan. Additionally, it was proven that O. tsutsugamushi was transmitted transovarially through eggs in the infected colonies of L. fletcheri , L. arenicola , L. deliense , L. imphalum , and L. chiangraiensis [3], [8], [11], [15].…”