Wahli T, Matthews R A
Centre for Fish and Wildlife Health, University of Berne, Switzerland.
Dis Aquat Organ. 1999 May 31;36(3):201-7. doi: 10.3354/dao036201.
Ichthyophthirius multifiliis exposed to naturally immunised carp established short-term infections, the majority of parasites actively emerging within 2 h of entering the epidermis. A small, but significant, number of these expelled parasites were shown to retain theront-like properties with the capacity to directly re-invade a further fish host. Infectivity fell rapidly with time in the host and was comparable to that of trophonts of a similar age artificially induced to emerge from non-immune hosts with the aid of MEM (minimal essential medium). Trophonts recovered with MEM from immune carp 2 to 8 h post infection rarely established infections upon exposure to susceptible new hosts and no infections resulted from older trophonts recovered after 8 to 24 h exposure; older trophonts, however, represented only a small percentage of the original parasite population. A low level of infectivity was recorded in trophonts collected with the aid of MEM from non-immune carp after up to 24 h of infection. The results are discussed in relation to theront transformation and evasion of the host immune response.
多子小瓜虫感染自然免疫的鲤鱼后会建立短期感染，大多数寄生虫在进入表皮后2小时内就会活跃地钻出。这些排出的寄生虫中有一小部分但数量可观的被证明保留了速殖子样特性，具备直接再次侵入另一条鱼宿主的能力。在宿主体内，感染力会随着时间迅速下降，这与借助MEM（最低限度基本培养基）从非免疫宿主中人工诱导出的同龄滋养体的感染力相当。感染后2至8小时用MEM从免疫鲤鱼中回收的滋养体在接触易感新宿主时很少能建立感染，而在感染8至24小时后回收的较老滋养体则不会导致感染；不过，较老的滋养体仅占原始寄生虫种群的一小部分。在感染长达24小时后借助MEM从非免疫鲤鱼中收集的滋养体中记录到了低水平的感染力。本文结合速殖子转化和宿主免疫反应的逃避对结果进行了讨论。
