Hershberger P K, Hart L M, MacKenzie A H, Yanney M L, Conway C M, Elliott D G
a U.S. Geological Survey, Western Fisheries Research Center, Marrowstone Marine Field Station, 616 Marrowstone Point Road , Nordland , Washington 98358 , USA.
b U.S. Geological Survey, Western Fisheries Research Center, 6505 Northeast 65th Street , Seattle , Washington 98115 , USA.
J Aquat Anim Health. 2015 Dec;27(4):217-21. doi: 10.1080/08997659.2015.1095809.
The protistan parasite Ichthyophonus sp. occurs in coastal populations of Pacific Herring Clupea pallasii throughout the northeast Pacific region, but the route(s) by which these planktivorous fish become infected is unknown. Several methods for establishing Ichthyophonus infections in laboratory challenges were examined. Infections were most effectively established after intraperitoneal (IP) injections with suspended parasite isolates from culture or after repeated feedings with infected fish tissues. Among groups that were offered the infected tissues, infection prevalence was greater after multiple feedings (65%) than after a single feeding (5%). Additionally, among groups that were exposed to parasite suspensions prepared from culture isolates, infection prevalence was greater after exposure by IP injection (74%) than after exposure via gastric intubation (12%); the flushing of parasite suspensions over the gills did not lead to infections in any of the experimental fish. Although the consumption of infected fish tissues is unlikely to be the primary route of Ichthyophonus sp. transmission in wild populations of Pacific Herring, this route may contribute to abnormally high infection prevalence in areas where juveniles have access to infected offal.
原生动物寄生虫Ichthyophonus sp.存在于整个东北太平洋地区太平洋鲱（Clupea pallasii）的沿海种群中，但这些食浮游生物的鱼类被感染的途径尚不清楚。研究了在实验室挑战中建立Ichthyophonus感染的几种方法。在腹腔内（IP）注射来自培养物的悬浮寄生虫分离物后，或在反复投喂感染鱼组织后，感染最有效地建立起来。在投喂感染组织的组中，多次投喂后的感染率（65%）高于单次投喂后的感染率（5%）。此外，在暴露于由培养分离物制备的寄生虫悬浮液的组中，腹腔注射暴露后的感染率（74%）高于通过胃插管暴露后的感染率（12%）；将寄生虫悬浮液冲洗过鳃并没有导致任何实验鱼感染。虽然食用感染鱼组织不太可能是Ichthyophonus sp.在太平洋鲱野生种群中传播的主要途径，但在幼鱼能够接触到感染内脏的地区，这条途径可能导致异常高的感染率。
