Progress Report
Ceratomyxa impacts on upper Klamath River salmon
Project Dates: October 10, 2008 - June 30, 2009
Submitted to:
Oregon Department of Fish and Wildlife
Submitted by:
Jerri Bartholomew and Charlene Hurst
Department of Microbiology
Oregon State University
Corvallis, Oregon 97331-3804
Project Summary
Severe infections by Ceratomyxa shasta have caused high mortality in migrating juvenile
salmon in the lower Klamath River during the past decade. These effects are most evident in
the river below Iron Gate Dam, and current research suggests strategies for reducing disease
effects. However, levels of C. shasta detected in the Williamson River, upper Klamath basin, are
even higher. Defining the parasite’s distribution, the fish that support it’s lifecycle and the
conditions that result in this highly infectious area are critical to making decisions that will
reduce disease effects basin-wide and allow successful reintroduction of salmon into the upper
basin.
Project Objectives
Objective 1. Ceratomyxa shasta distribution and abundance.
WMR sampling: Water sampling and processing
was conducted as described by Hallett and
Bartholomew (2006). Briefly, at 22 sites, 4 x 1 L
samples of water were collected, filtered and the
filter was processed for testing using a molecular
assay that provides a measure of parasite
density for each sample. Sample sites were
selected based on accessibility and GPS
coordinates, and site descriptions were recorded.
Data from water samples collected in September
2008 show that areas with the highest C. shasta
densities are between the mouth of the
Williamson River and Rkm 11.4, and above the
confluence of Spring Creek at Rkm 33. Use of a
standard curve in the assay allows for estimation
of parasite concentration. Values from these sites
indicate approximately 10-100 parasite spores/L
(figure 4a and b). Slightly lower parasite densities
(1-10 spores/L) were detected from samples
collected from Rkm 15 to 20, just below the
Figure 1: WMR with sampling sites
confluence of the Sprague River. The parasite is absent from both the Spring Creek and
Sprague River tributaries (<1 spore/L).
Parasite distribution in September suggests that polychaete populations exist above Rkm 33,
where the second peak in parasite concentration occurred, allowing for the completion of the
parasite’s life cycle. The data also suggests that the Sprague River and Spring Creek may not
contribute to parasite levels in the WMR as less than 1 spore/L was detected at these sampling
locations. A decrease in parasite concentrations occurred below Spring Creek confluence,
possibly as a result of a dilution effect from the mixing of Spring Creek with the WMR. Where
the Sprague joins with the WMR at Rkm 20, no decline was observed, and in fact, parasite
concentration increases after this point.
2a
2b
Figures 2a and b: (2a) Cycle
threshold values (Ct) for qPCR
analysis
of
water
samples
collected from the WMR. The
values from three liters of river
water from each site were
averaged together to obtain the
value displayed on the graph.
The lower Ct values indicate
higher concentrations of parasite
DNA. (2b) A summary figure of
the distribution and abundance of
C. shasta along the WMR from
data collected September 2008.
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Interpretation of results: Data collected during September 2008 provides baseline data for this
system. To determine if the high levels above the Sprague River are a result of myxospore input
from spawning fish, or actinospore release from polychaetes, we need to repeat sampling at
these sites during early summer when actinospore release should predominate. Further
research should help pinpoint the source(s) of parasites into the system.
Objective 2. Parasite effects on Chinook salmon
To establish polychaete populations for parasite challenge studies, worms were collected from
the mouth of Klamath Lake in September 2008. Polychaetes were divided between six tanks
and densities were estimated in an effort to monitor worm survival through the course of the
experiment
In each of 2 replicate tanks, polychaetes were dosed
with myxospores isolated from either Chinook salmon
infected in the lower basin (genotype I) or susceptible
rainbow trout infected in the upper basin (genotype II).
The targeted dose was approximately 1,000
spores/worm. Another pair of tanks was not seeded and
designated as controls
Actinospore release was monitored by collecting and
filtering water from each tank on a biweekly basis
starting October 9, 2008. Susceptible strain rainbow trout
and Klamath River Chinook salmon were added to
tanks on the outflow of the paired polychaete tanks Figure 3: Tank set-up for laboratory
(Fig 3) as soon as a distinct peak indicated the experiments. Polychaete tanks on
release of actinospores from the water sample data. the top rack and fish tanks on the
bottom.
Fish are fed daily and monitored for signs of disease.
Preliminary Results and Interpretation: Rainbow trout have succumbed to infection in tanks
receiving effluent from polychaetes seeded with genotype II. Rainbow trout also appear to have
become infected in tanks receiving effluent from the unseeded control polychaetes. This is not
completely unexpected, as some polychaetes collected from the wild would be naturally infected
(presumably with either genotype 0 or II, which have been detected in the Williamson).
However, rainbow trout have also become infected in the tanks seeded with genotype I. This
could either be a result of the background level of infection, or they may also be susceptible to
this genotype. This study is continuing and genetic analysis of the samples should resolve these
questions.
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