Frances S P, Watcharapichat P, Phulsuksombati D
Department of Entomology, U.S. Army Component, Armed Forces Research Institute of Medical Sciences, 315/6 Rajvithi Road, Bangkok, 10400, Thailand.
J Med Entomol. 2001 Jan;38(1):17-21. doi: 10.1603/0022-2585-38.1.17.
Vertical transmission of Orientia tsutsugamushi (Hayashi), the etiologic agent for scrub typhus, was studied in two lines of naturally infected Leptotrombidium deliense Walch. In one line of mites originating from a single adult (V3M), the rate of filial transmission was 100% for the first two laboratory generations, but declined to 86.6% in the third laboratory generation. The vertical infection rate in this line of mites was 100% for the parental generation, but declined to 95.6% for the F1 generation and 88.6% for F2. The transmission of O. tsutsugamushi in another line of L. deliense (V3F) was less efficient than mites originating from V3M. In the initial laboratory generation of V3F a filial transmission rate of 100% was recorded. However, none of the F2 generation of this line transmitted rickettsiae to mice (Mus musculus L.), resulting in a filial transmission rate of 0%. Transmission of O. tsutsugamushi to mice by progeny from cohort larvae originally from the same adult (V3F) was also studied in the laboratory and these were found to be relatively poor transmitters of rickettsiae. The filial infection rate of F2 larvae was 60%, F3 was 88.8%, and F4 was 55.9%. The biology of infected L. deliense was studied and compared with uninfected mites reared under the same laboratory conditions. The results showed that infected female L. deliense laid approximately the same or more eggs as uninfected adults. The rate of development of the progeny of infected L. deliense was not significantly different from uninfected mites.
恙虫病东方体（林氏）是恙虫病的病原体，在两系自然感染的地里纤恙螨中研究了其垂直传播情况。在源自一只成年螨的一系螨（V3M）中，前两个实验室代的子代传播率为100%，但在第三个实验室代降至86.6%。这系螨的亲代垂直感染率为100%，但F1代降至95.6%，F2代降至88.6%。另一系地里纤恙螨（V3F）中恙虫病东方体的传播效率低于源自V3M的螨。在V3F的初始实验室代记录到子代传播率为100%。然而，这系的F2代均未将立克次氏体传播给小鼠（小家鼠），导致子代传播率为0%。还在实验室研究了源自同一成年螨（V3F）的同组幼虫后代将恙虫病东方体传播给小鼠的情况，发现它们是相对较差的立克次氏体传播者。F2幼虫的子代感染率为60%，F3为88.8%，F4为55.9%。研究了感染地里纤恙螨的生物学特性，并与在相同实验室条件下饲养的未感染螨进行了比较。结果表明，感染的雌性地里纤恙螨产的卵与未感染的成年螨大致相同或更多。感染地里纤恙螨后代的发育速度与未感染螨无显著差异。
