Sarah Bjork

My graduate studies focus on Ceratomyxa shasta and the factors that influence infection in the fish and polychaete host. I have examined the effects of temperature and desiccation on polychaete survival, as well as obtained preliminary data on the effects of temperature on the survival, maturation and release of C. shasta actinospores from Manayunkia speciosa.  I investigated the effects of velocity on survival and infection of M. speciosa as well as the effect of water velocity on fish infection. After establishing an infected M. speciosa colony at the SDL, my studies focused on the infective dose for susceptible rainbow trout and the effects of parasite concentration and fish size on infective dose. The route of C. shasta infection in the fish host was also identified.

I am also investigating the defense mechanisms used by Klamath River Chinook salmon to survive C. shasta infection. It is hypothesized that these fish resist parasites at the site of entry, prevent parasite proliferation, or are capable of mounting an effective immune response against the parasite. QPCR and histology data indicate no evidence for resistance of parasite penetration in the gills. At sub-lethal doses, parasites are isolated in the intestine, or are found in the lumen of the intestine prior to parasite maturation. I am also comparing the expression of cytokines in the intestine of a susceptible and resistant strain of Chinook salmon in response to C. shasta infection.

	Ceratomyxa shasta actinospores being released from a live polychaete host, Manayunkia speciosa, into the surrounding freshwater. Spores are about 5-8µm in size.
	The effect of parasite concentration on prevalence of infection and mortality of a susceptible strain of rainbow trout
	Ceratomyxa shasta actinospores labeled with CFSE attached to a rainbow trout gill filament
	In situ hybridization of Ceratomyxa shasta in the gills
	The progression of Ceratomyxa shasta development from replication in the gills to release into the blood of its salmonid host