Research

Fish Diseases
Microbiology and Parasitology
Molecular & Non-lethal Diagnostics
Myxozoan Parasites
Molecular Systematics
Taxonomy & Nomenclature

Prospective Projects at ESF

Ongoing and Recent Projects

Ichthyophonus hoferi in Alaskan fishes
The choanoflagellate parasite Ichthyophonus hoferi has been implicated in pre-spawning mortalities in returning Yukon River Chinook salmon in Alaska. Sufficient numbers of fish must be allowed to migrate upriver for productive spawning and subsistence fisheries. Thus, a potential loss due to disease must be accounted for when setting escapement goals in the lower river. However, the number of infected individuals that enter the river is difficult to evaluate as signs of disease may not be apparent at this early stage. I developed a molecular based detection method for I. hoferi and this method is ideal for rapid screening of large populations of fish to assess the distribution of I. hoferi.

Myxozoan parasites
Myxozoans are primarily parasites of fishes, but also infect amphibians, reptiles, birds, and rarely mammals. Many myxozoan infections are relatively benign suggesting a long history of coevolution with their host. However, those associated with disease and tissue damage in economically important fish species are most well known. A frequently cited example of myxozoan parasitism is whirling disease, caused by Myxobolus cerebralis in salmonid fishes. Identification of myxozoan species is primarily by spore morphology. However, classification schemes using this limited character set is inconsistent with phylogenetic relationships. My goal is to use molecular systematics to develop classification schemes that reflect shared evolutionary history as opposed to arbitrary groupings. I have collaborators in Australia, Europe, China, and India on these ongoing studies.

Mycobacteriosis
Mycobacteriosis is one of the most common diseases of zebrafish (Danio rerio) used in laboratory research. The use of zebrafish in research is expanding greatly, yet little is known about the diseases that occur in these fish. This is particularly important in longterm experiments or where zebrafish are used as disease models, becausebackground infections in experimental populations can seriously compromise the validity of the research findings. I have identified several Mycobacterium species of importance in fish which I am investigating at research facilities throughout the US.

Other pathogens - Fish and Beyond
In a recent collaboration with researchers at the Oregon State University College of Veterinary Medicine, we used DNA sequence analysis to determine the identity of a morphological variant of Fascioloides magna, the giant liver fluke, in elk.

Blastocystis hominis is the most common intestinal protozoan infecting humans in the United States, but it is probably the least understood. The parasite is also the most frequently diagnosed intestinal protozoan in Oregon, identified four times more often than Giardia. It is only recently that Blastocystis is seriously being considered as a cause of gastrointestinal disease. Studies suggest that there are multiple genetically diverse sub-types of Blastocystis, and that certain ones are more responsible for the disease in human. My goal is to determine which sub-types are present in Oregon, matching these types to their clinical presentation.