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Charlene Hurst, Bartholomew Lab, PhD Candidate
|Office||514 Nash Hall|
My research interest is aquatic animal health, which I was first introduced to during my final years as an undergraduate at California State University, Long Beach. During this time, I also interned for the National Oceanic and Atmospheric Administration (NOAA) and became more interested specifically in salmonids and natural resource management. I have combined both of these interests in my PhD in microbiology curriculum by working with a disease of salmonids caused by the parasite, Ceratomyxa shasta, as well as pursuing a Certificate in Fisheries Management.
I recently graduated with a Master’s degree in Microbiology from Oregon State University in Dr. Jerri Bartholomew’s Laboratory. My Master’s thesis was divided into two main components (see below). The first involved assessing Ceratomyxa shasta density and distribution in the Williamson River tributary of the upper Klamath basin and how our findings could impact anadromous salmonid reintroductions. The second assessed the differential mortality of parasite genotypes I and II in coho and Chinook salmon as well as rainbow trout in a series of cross-infection studies.
I decided to continue my PhD in microbiology under Dr. Jerri Bartholomew’s mentorship because many unanswered questions arose during my master’s research. Preliminary data have shown that although mortality occurs with only one genotype, many genotypes are able to gain entry into the host. This finding has led to the focus of my PhD on the outcomes of mixed genotype infections and how these outcomes could change depending on the timing and order of infection. I am currently conducting combined field and lab studies with resistant and susceptible fish stocks to address questions concerning mixed infections.
NOAA Office of Education Graduate Sciences Program
NSF/NIH (PI Oriol Sunyer)
Flyfisher's Club of Oregon
Hatfield Marine Science Center Bill Wick Marine Fisheries Award
Hurst, C. N., R. A. Holt and J. L. Bartholomew. 2012. Dam removal and implications for fish health: Ceratomyxa shasta in the Williamson River, Oregon, USA. North American Journal of Fisheries Management 32: 14-23.
Hallett, S.L., Ray, R.A., Hurst, C.N., Holt, R.A., Buckles, G.R., Atkinson, S.D. & Bartholomew, J.L. (2012) Density of the Waterborne Parasite, Ceratomyxa shasta, and Its Biological Effects on Salmon. Applied and Environmental Microbiology 78: 3724-3731.
Hurst, C. 2011. Ceratomyxa shasta-related concerns for reintroduced anadromous salmonids into the Upper Klamath Basin, CA-OR, USA. Master’s thesis. Oregon State University, Corvallis, OR.
Hurst, C. N. and J. L. Bartholomew. 2012. Ceratomyxa shasta genotypes cause differential mortality in their salmonid hosts. Journal of Fish Diseases.
Distribution and Density of Ceratomyxa shasta in the Williamson River, Oregon: The Williamson River (WMR) is in the upper portion of the Klamath basin and drains into Klamath Lake. Our monitoring studies over several years have indicated densities of C. shasta near the mouth of the WMR similar to the high densities found in the lower basin. The presence of high densities of the parasite in the WMR is unexpected, as there is no anadromous fish passage into this portion of the river due to a series of dams. The goal for this part of the project was to determine the distribution and density of C. shasta and identify the factors responsible. This was conducted by selecting 22 representative sites along the river and in the major tributaries, Spring Creek and Sprague River, and collecting water samples. These samples were then processed using qPCR to quantify the number of parasites present at each location. From these results we have identified two areas of high density consistent over three years of sample collection. The stocking of a susceptible strain of rainbow trout has likely contributed to the high densities found in the Williamson River.
Ceratomyxa shasta Strain Host Specificity: Recently, a fellow graduate student in our lab identified four strains of Ceratomyxa shasta in a variety of fish from the Klamath basin. The hypothesis was that each of the strains had different host specificities based upon field data from naturally infected wild and hatchery fish and also our sentinel studies. To test this hypothesis we set up polychaete populations in a controlled laboratory setting and exposed them each to a different strain of the parasite. We then exposed Iron Gate Chinook and coho salmon and rainbow trout to each of the different parasite strains. We found that certain strains were responsible for mortality in certain host species. In addition we were further able to divide strain II into two biotypes each found in different host species; IIR in rainbow trout and IIC in coho salmon. Parasite host specificity is an important trait to consider, especially when planning for the reintroduction of anadromous salmonids into the upper basin. Parasite strains specific for salmon present in the lower basin may be carried into the upper basin. Additionally, strains already present could become amplified due to the increased number of hosts to the area.
Funding for Master's Research