Foott J S, Stone R, Fogerty R, True K, Bolick A, Bartholomew J L, Hallett S L, Buckles G R, Alexander J D
a U.S. Fish and Wildlife Service , California-Nevada Fish Health Center , 24411 Coleman Fish Hatchery Road, Anderson , California 96007 , USA.
b Department of Microbiology , Oregon State University , 226 Nash Hall, Corvallis , Oregon 97331 , USA.
J Aquat Anim Health. 2016 Jun;28(2):75-84. doi: 10.1080/08997659.2015.1103803.
Severe infection by the endemic myxozoan parasite, Ceratonova (synonym, Ceratomyxa) shasta, has been associated with declines in and impaired recovery efforts of populations of fall-run Chinook Salmon Oncorhynchus tshawytscha in the Klamath River, California. The parasite has a complex life cycle involving a polychaete worm host as well as a salmon host. Myxospore transmission of this parasite, from salmon to polychaete, is a life cycle step during which there is a potential for applied disease management. A 3-year data set on prevalence, intensity, and spore characteristics of C. shasta myxospores was obtained from adult Chinook Salmon carcasses surveyed in the main stem of the Klamath River and three of its tributaries, Bogus Creek and the Shasta and Trinity rivers. Annual prevalence of myxospore detection in salmon intestines ranged from 22% to 52%, and spore concentration values per intestinal scraping ranged from 3.94 × 10(2) to 1.47 × 10(7) spores. A prevalence of 7.3% of all carcasses examined produced >5.0 × 10(5) spores, and these carcasses with "high" spore counts accounted for 76-95% of the total spores in a given spawning season. Molecular analysis of visually negative carcasses showed that 45-87% of these samples had parasite DNA, indicating they contained either low spore numbers or presporogonic stages of the parasite. Myxospores were rarely found in carcasses of freshly spawned adults but were common in decomposed carcasses of both sexes. The date of collection or age (based indirectly on FL) did not influence detection. The longer prespawn residence time for spring-run Chinook Salmon compared with that for fall-run Chinook Salmon in the Trinity River was associated with higher spore loads. The dye exclusion method for assessing spore viability in fresh smears indicated an inverse relationship in spore integrity and initial spore concentration. A carcass-removal pilot project in Bogus Creek for 6 weeks in the fall of 2008 (907 carcasses removed) and 2009 (1,799 carcasses removed) failed to measurably influence the DNA quantity of C. shasta in targeted waters. Combined with the high numbers of carcasses that contributed myxospores, we therefore deemed that this labor-intensive approach is not a viable management option to reduce the infectivity of C. shasta in Chinook Salmon in the Klamath River. Received January 23, 2015; accepted September 28, 2015.
地方性粘孢子虫寄生虫——夏斯塔角孢子虫（Ceratonova，同义词为Ceratomyxa shasta）的严重感染，与加利福尼亚州克拉马斯河秋季洄游的奇努克鲑（Oncorhynchus tshawytscha）种群数量下降及恢复努力受损有关。该寄生虫具有复杂的生命周期，涉及多毛类蠕虫宿主和鲑鱼宿主。这种寄生虫从鲑鱼到多毛类蠕虫的粘孢子传播，是其生命周期中的一个阶段，在此阶段有可能进行疾病管理应用。从克拉马斯河干流及其三条支流——博格斯溪、沙斯塔河和特里尼蒂河调查的成年奇努克鲑鱼尸体中，获得了一份为期3年的关于夏斯塔角孢子虫粘孢子的患病率、感染强度和孢子特征的数据集。鲑鱼肠道中粘孢子检测的年患病率在22%至52%之间，每次肠道刮片的孢子浓度值在3.94×10²至1.47×10⁷个孢子之间。在所有检查的尸体中，7.3%的尸体产生的孢子数>5.0×10⁵个，这些孢子数“高”的尸体在给定的产卵季节中占总孢子数的76 - 95%。对外观呈阴性的尸体进行分子分析表明，这些样本中有45 - 87%含有寄生虫DNA，这表明它们要么含有低数量的孢子，要么含有寄生虫的孢子形成前期阶段。在刚产卵的成年鱼尸体中很少发现粘孢子，但在两性的腐烂尸体中很常见。采集日期或年龄（间接基于叉长）不影响检测结果。与特里尼蒂河秋季洄游的奇努克鲑鱼相比，春季洄游的奇努克鲑鱼产卵前停留时间更长，其孢子负荷更高。在新鲜涂片上评估孢子活力的染料排除法表明，孢子完整性与初始孢子浓度呈反比关系。2008年秋季（清除907具尸体）和2009年秋季（清除1799具尸体）在博格斯溪进行的为期6周的尸体清除试点项目，未能显著影响目标水域中夏斯塔角孢子虫的DNA数量。再加上贡献粘孢子的大量尸体，因此我们认为这种劳动密集型方法不是降低克拉马斯河奇努克鲑鱼中夏斯塔角孢子虫感染性的可行管理选择。2015年1月23日收到；2015年9月28日接受。
