Ray R Adam, Rossignol Philippe A, Bartholomew Jerri L
Department of Fisheries and Wildlife, Nash Hall, Oregon State University, Corvallis, Oregon 97331, USA.
Dis Aquat Organ. 2010 Dec 7;93(1):63-70. doi: 10.3354/dao02281.
The myxozoan parasite Ceratomyxa shasta is a significant pathogen of juvenile Chinook salmon Oncorhynchus tshawytscha in the Klamath River, California, USA. This parasite requires 2 hosts to complete its life cycle: a freshwater polychaete (Manayunkia speciosa) and a salmonid. The complex life cycle and large geographic area where infection occurs make it difficult to monitor and manage ceratomyxosis. We present a model for ceratomyxosis-induced mortality in O. tshawytscha, from which parameters important to the persistence of C. shasta are identified. We also experimentally quantify specific parameters from the model and identify a mortality threshold (a critical parameter), by naturally exposing native O. tshawytscha to C. shasta in the Klamath River. The average percent mortality that resulted from these experimental challenges ranged from 2.5 to 98.5% over an exposure dose of 4.4 to 612 x 10(6) parasites. This experiment identified a non-linear mortality threshold of 7.7 +/- 2.1 x 10(4) actinospores fish(-1) for Chinook salmon from the Iron Gate Hatchery on the Klamath River. Below this threshold no mortality occurred and above it mortality increased dramatically, thus providing a target by which to reduce parasitism in emigrating juvenile O. tshawytscha.
粘孢子虫寄生虫夏斯塔角孢子虫（Ceratomyxa shasta）是美国加利福尼亚州克拉马斯河中小奇努克鲑（Oncorhynchus tshawytscha）幼鱼的一种重要病原体。这种寄生虫需要两个宿主来完成其生命周期：一种淡水多毛类动物（马尼恩基亚虫，Manayunkia speciosa）和一种鲑科鱼类。其复杂的生命周期以及感染发生的广阔地理区域使得监测和管理角孢子虫病变得困难。我们提出了一个关于夏斯塔角孢子虫感染导致奇努克鲑死亡的模型，从中确定了对夏斯塔角孢子虫持续存在至关重要的参数。我们还通过在克拉马斯河将本地奇努克鲑自然暴露于夏斯塔角孢子虫下，对模型中的特定参数进行了实验量化，并确定了一个死亡阈值（一个关键参数）。在4.4至612×10⁶个寄生虫的暴露剂量范围内，这些实验性挑战导致的平均死亡率在2.5%至98.5%之间。该实验确定了克拉马斯河铁门孵化场的奇努克鲑的非线性死亡阈值为7.7±2.1×10⁴个放射孢子/鱼。低于此阈值无死亡发生，高于此阈值死亡率急剧增加，从而为降低洄游奇努克鲑幼鱼的寄生虫感染提供了一个目标。
