Molecular Prevalence of Ceratonova shasta in Aquatic Sediment Samples Obtained from Post-Fire Areas in Las Plumas National Forest
IAAAM 2016
Christine A. Richey1*; Kirsten V. Kenelty1; Kristina Van Stone Hopkins2; Melanie Reed1; Brittany N. Stevens1; Esteban Soto1
1Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, USA; 2United States Forest Service, Quincy, CA, USA


Ceratonova (formerly Ceratomyxa) shasta, a myxozoan parasite, is the causative agent of the serious intestinal disease ceratomyxosis in salmonids. The parasite lifecycle requires both a salmonid host and an intermediate host, the benthic freshwater polychaete Manayunkia speciosa.1 Traditionally, C. shasta detection methods have included sentinel fish exposures and subsequent histological examination or PCR, parasite spore detection in environmental water samples via filtration and PCR, and intermediate host sampling. Environmental DNA (eDNA), defined by Thomsen and Willersley (2015) as "genetic material obtained directly from environmental samples (soil, sediment, water, etc.) without any obvious signs of biological source material," has the potential to be a powerful tool for evaluating the presence of microorganisms, of which direct observation is impossible, and for assessing biodiversity in aquatic environments.2 Furthermore, it has been shown that eDNA shed from fish is more highly concentrated in aquatic sediment than in water samples.3 In this study, we investigated the presence of eDNA in river sediment samples collected from areas affected by recent fire activity in Las Plumas National Forest, California, USA. Wildfires have been implicated as promoting environmental conditions suitable for the survival and success of myxozoan intermediate hosts by causing erosion of fine sediments into stream channels.4,5 Sediment samples were collected from 23 different watersheds during the fall of 2015. Extracted DNA from sediment samples (~ 10 g) was used as a template in a previously described TaqMan probe real-time PCR (qPCR) assay, specific for the detection of C. shasta.6 Four of the analyzed sediment samples were found to be positive for C. shasta. Future research will investigate the correlation of parasite eDNA with ceratomyxosis incidence in sentinel triploid rainbow trout (Oncorhynchus mykiss), intermediate host (Manayunkia speciosa) abundance estimated with qPCR, and C. shasta spores in the water column at a given location quantified using qPCR. With this information, we hope to validate the use of eDNA as a non-invasive, rapid, sensitive, and specific method for establishing risk of infection.

* Presenting author

Literature Cited

1.  Hallett SL, Bartholomew JL. Myxobolus cerebralis and Ceratomyxa shasta. In: Buchmann K, Woo PTK, eds. Fish Parasites: Pathobiology and Protection. Cambridge, MA: CABI; 2012:131–162.

2.  Thomsen PF, Willerslev E. Environmental DNA - an emerging tool in conservation for monitoring past and present biodiversity. Biological Conservation. 2015;183:4–18.

3.  Turner CR, Uy KL, Everhart RC. Fish environmental DNA is more concentrated in aquatic sediments than surface water. Biological Conservation. 2015;183:93–102.

4.  Granath WO Jr. Effects of habitat alteration on the epizootiology of Myxobolus cerebralis, the causative agent of salmonid whirling disease. The Journal of Parasitology. 2014;100(2):157–165.

5.  Helvey JD, Tiedemann AR, Anderson TD. Plant nutrient losses by soil erosion and mass movement after wildfire. Journal of Soil and Water Conservation. 1985;40(1):168–173.

6.  Hallett SL, Bartholomew JL. Application of a real-time PCR assay to detect and quantify the myxozoan parasite Ceratomyxa shasta in river water samples. Diseases of Aquatic Organisms. 2006;71(2):109–118.


Speaker Information
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Christine A. Richey, DVM
Department of Medicine and Epidemiology
School of Veterinary Medicine
University of California
Davis, CA, USA

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