CERATONOVA SHASTA MONITORING STUDIES IN THE DESCHUTES RIVER BASIN

Ceratonova shasta is a freshwater, myxozoan parasite that is native to the Pacific North West of North America. It causes enteronecrosis in salmonids which, in the Deschutes River Basin, has resulted in high mortality in cultured juvenile salmon at the Pelton Facility and in adult salmon returning to both the Round Butte and Warm Springs hatcheries. Transmission occurs through waterborne stages: actinospores released from polychaete worms infect salmonid fishes and develop into myxospores which then infect polychaetes (see life cycle on left). The parasite proliferates in each host (not in water). 

“By understanding the relationships between the parasite, its hosts, and the natural habitats and conditions that are favorable or unfavorable for infection, strategies can be developed to limit the exposure of fish to areas where the risk of infection of C. shasta may be higher, or develop management strategies based upon predicted water and climate conditions to improve the survival and viability of wild and hatchery salmonids.” Cyndi Baker, PhD, CTWSRO.

Through collaboration with the Confederated Tribes of the Warm Springs Reservation of Oregon (CTWSRO), USFWS, and ODFW we have developed a parasite monitoring program which contributes to our understanding of the role of pathogens (such as Ceratonova shasta) in juvenile and pre-spawn mortalities of adult Spring Chinook salmon of the Deschutes River Basin. Monitoring is primarily through quantification of waterborne stages of the parasite.

 

Map of the Deschutes River, Oregon All water sampling sites along the Deschutes River Map of the Warm Springs River, Oregon
Deschutes River, a tributary of the Columbia River, in central Oregon. Study sites are shown as yellow diamonds. Red circles represent sites at which ISCO water sampling and sentinel fish exposures were conducted. Map of the Deschutes River basin including major tributaries as well as spatial (green and red) and temporal (red) water sampling sites. Temporal water sample collection sites on the Warm Springs River and at the mouth of the Warm Springs River on the Deschutes River (DRV). Sites are represented by open circles (2017), dark grey circles (2018), and black circles filled with dark grey (2017 & 2018). The black bar represents the Warm Springs National Fish Hatchery, a migration barrier to salmonids. The Pelton Trap located below the Pelton Dam is included for reference. *Note the DRV site is on the Deschutes mainstem.    

 

Water Samples

We conduct two types of water sampling to provide high resolution data on the spatial and temporal abundance of Ceratonova shasta – regular monitoring as well as spatially intensive sporadic longitudinal sampling. Collection of river water samples for regular monitoring occurs at two index sites established in 2015; once a week all year round at Oak Springs and every other week from April through October at Pelton Dam (sites marked in red on map above). Beginning in 2017, monitoring will occur at a further 8 sites that span from the town of Bend to Heritage Landing at the mouth of the Deschutes River (see map above). Longitudinal sampling occurs approximately twice a year (in spring and summer) at 16-24 sites.

At the established index sites, solar-powered automatic samplers (ISCOs) collect 1L of water every 2 hours for 24 hours, from which 4 1L samples are manually taken, whereas samples are collected manually at the remaining index and longitudinal sites. Regardless of collection method, each 1L sample is filtered through a 5-micron nitrocellulose membrane using a vacuum pump, and any captured DNA in 3 of the replicate samples is extracted using a kit. A quantitative PCR (qPCR) specific for C. shasta is used to detect and quantify any parasite DNA present (Hallett & Bartholomew 2006). Cq values generated by the qPCR are converted to numbers of parasite spores per liter of water using reference samples with known quantities of spores. The Warm Springs tribal biologists and members of ODFW are integral to the collection and filtration of the ISCO water samples.

 

Collecting water samples
on the Deschutes River
Filtering a water sample
using a vacuum pump
Folding the filter paper
with captured material

 

Temporal Water Sample Monitoring at Oak Springs (left) and Pelton Trap (right)

Density of Ceratonova shasta in water samples collected at Oak Springs Density of Ceratonova shasta in water samples collected at Pelton Trap
Mean Ceratonova shasta density (y-axis) in the Deschutes River at the Oak Springs Hatchery (gray triangles). Overlays are discharge m3/s (blue, second y-axis) and river water temperature (red, third y-axis) over time (x-axis). Mishandled samples are represented by X's. Each point is the mean C. shasta density from triplicate water samples collected using an automatic sampler (ISCO). Data from 2015 and 2016 were collected and processed by Vojnovich et al., 2016.

Mean Ceratonova shasta density (y-axis) in the Deschutes River at the Pelton Trap (black circles). Overlays are discharge m3/s (blue, second y-axis) and river water temperature (red, third y-axis) over time (x-axis). Each point is the mean C. shasta abundance from triplicate water samples collected using an automatic sampler (ISCO). Data from 2015 and 2016 were collected and processed by Vojnovich et al., 2016.

 

 Water Sample Monitoring on the Warm Springs River

 

Density of Ceratonova shasta in Warm Springs River 2017 Density of Ceratonova shasta in Warm Springs River 2018

2017 Warm Springs River temporal water sample monitoring sites. Each data point is the mean Ceratonova shasta spores/L from 3 1L replicate samples. *Note that DRV is located on the Deschutes River at the mouth of the Warm Springs River. ** 2017 sites WBA, WBE, WMC, and WUP were combined as WCF in 2018. ***2017 site WLO was moved further downstream and renamed WLW in 2018.

2018 Warm Springs River temporal water sample monitoring sites. Each data point is the mean Ceratonova shasta spores/L from 3 1L replicate samples. *Note that DRV is at the confluence of the Warm Springs River and the Deschutes River mainstem.

Longitudinal Water Sampling Schedule

2015:  August 17th

2016:  June 7th, and August 30th

2017:  June 6th, and August 30th

2018:  May 2nd, June 5th, July 10th, and August 29th.
 

Density of Ceratonova shasta in spatial water samples Density of Ceratonova shasta in water samples in August 2016
2016: June August

 

Density of Ceratonova shasta in spatial water samples Density of Ceratonova shasta in water samples collected during longitudinal sampling August 2017
2017: June August
 Density of Ceratonova shasta in water samples Density of Ceratonova shasta in water samples in June 2018 Density of Ceratonova shasta in water samples in July 2018 Density of Ceratonova shasta in water samples in August 2018
 2018: May  June  July  August

 

Genotyping

There are multiple genetic types of C. shasta simultaneously present in the Deschutes River Basin (Stinson & Bartholomew 2012). While genotype I infects our target species (Chinook salmon) most commonly, we will be analyzing samples for all genotypes of C. shasta. We do this by amplifying the variable ITS1 region using a PCR assay and then we sequence that amplicon (Atkinson & Bartholomew 2010). From the sequencing chromatogram, we can determine the proportion of each genotype present in a sample. We use the total spore density to then determine the number of spores of each genotype in a sample.  

Thus, in addition to determining the abundance of total C. shasta in the river, we will also determine the relative proportions of the various genotypes and their spatial and temporal distributions.  These data will be aligned with salmonid migration (juveniles and adults) to investigate whether parasite genotype abundance corresponds with the life history of its salmonid host.

Predicted genotypes

Our hypotheses were that C. shasta genotype abundance and corresponding salmonid host abundance would be correlated. We also explored the hypotheses from Stinson and Bartholomew (2012) that there would be a correlation between the spatiotemporal distribution of genotypes and salmonid hosts with type I in the upper basin (between the Round Butte Dam and DBF) with the reintroduction of Chinook salmon. Using fish passage data provided by PGE in combination with genotyped fish tissue data from Stinson and Bartholomew (2012), the expected results of these hypotheses are displayed graphically below. This figure does not account for resident trout populations (which carry type O and II) as they have not been quantified in the Deschutes River.

Expected distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin if all proposed hypotheses are supported.

Expected distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin if all proposed hypotheses are supported. The black bar represents the Round Butte Dam complex, a migration barrier for anadromous fish. The relative area of each pie graph indicates the density of Ceratonova shasta in 1L water samples whereas the color in each graph represents the genotype proportions at each site.    

Observed genotypes

Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin.  Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin.
2016: June August

 

Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin. Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin.
2017: June August

 

Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin. Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin. Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin. Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin. Distribution and density of the salmonid parasite Ceratonova shasta in the upper and lower Deschutes River Basin.
2018: May June July August

 
 References

Atkinson and Bartholomew (2010) Disparate infection patterns of Ceratomyxa shasta (Myxozoa) in rainbow trout Oncorhynchus mykiss and Chinook salmon Oncorhynchus tshawytscha correlate with ITS­1 sequence variation in the parasite. International Journal for Parasitology 40:599­604

Hallett SL, Bartholomew JL (2006) Application of a real-time PCR assay to detect and quantify the myxozoan parasite Ceratomyxa shasta in river water samples. Diseases of Aquatic Organisms 71:109-118.

Hallett SL, Ray RA, Hurst CN, et al. (2012) Density of the waterborne parasite Ceratomyxa shasta and its biological effects on salmon. Applied and Environmental Microbiology 78:3724–3731.

Stinson MET and Bartholomew JL (2012) Predicted Redistribution of Ceratomyxa shasta Genotypes with Salmonid Passage in the Deschutes River, Oregon. Journal of Aquatic Animal Health 24:274-280.

 

These research efforts are possible through contribution (funding and efforts) provided by: CTWSRO, CRITFC-PCSRF (research and graduate support 2017-2018), ODFW (Graduate Fellowship 2015-2016 & 2017-2018), LCRFHC-USFWS

For an overview of Deschutes River studies (sentinel fish exposures and water sampling) conducted in 2015 and 2016, please click on the following link:   “ODFW Fellowship Report 2015-2016”

For further details about the research conducted in 2017 and 2018, please refer to Kalyn Hubbard's MS thesis: Spatiotemporal Distribution of Ceratonova shasta and its Genotypes in the Deschutes River Basin

Data shared here are preliminary and subject to modification.

Image credits: Kalyn Hubbard, Stephen Atkinson.