Hello! My name is Johnny Shelley and I am a 4th year veterinary student at Louisiana State University School of Veterinary Medicine. I had the good fortune to just complete a four week clinical externship at the Idaho Fish Health Center and Dworshak National Fish Hatchery, and I wanted to share some of the experiences I had while visiting the beautiful northwest for the first time.
I am actually a veterinary student odd ball in that I went to veterinary school with the sole intention of specializing in the area of aquatic animal medicine with an emphasis in fish health. I wanted to make sure that during my clinical rotations I was exposed to a variety of different aquatic animal health settings since I don’t know where my career may take me. I initially contacted the Olympia Fish Health Center about doing an externship that specialized in the area of cold water fish diseases. Fortunately for me their availability did not fit mine, so they suggested that I should contact the Idaho Fish Health Center. After contacting the center I got a quick response from the center’s veterinarian, Dr. Marilyn “Guppy” Blair, and she was very receptive to my coming out to learn and work. It turns out that I lucked out by doing my externship at the Idaho Fish Health Center because it is not only on the grounds of the Dworshak National Fish Hatchery, but it is also works very closely with various Nez Perce Tribal hatcheries and acclimation sites.
I drove into Orofino/Ahsahka on April 22nd and I was immediately captivated by the beauty of the land and the unique location of the Idaho Fish Health Center. On my first day at the center I was immediately welcomed in and treated as a part of the team. After learning a little bit about the wild fish health survey that is annually conducted at the fish health center from fish health specialist Laura Sprague, she took me to the Nez Perce Tribal Hatchery at Cherry Lane to do monthly monitoring on their Fall Chinook Salmon. Monthly fish health check monitoring is done at all Nez Perce hatcheries and acclimation sites, in addition to being conducted at the Dworshak Hatchery, to ensure that disease does not run rampant prior to release, as well as minimizing the release of fish carrying disease in to the wild. During health checks, gill clips and skin scrapes are taken to look for possible parasites and infectious bacteria. Additionally, fish necropsies are performed to observe any potential abnormalities and samples of the spleen, kidney and gill are taken for viral and bacterial monitoring. I was able to travel to Kooskia National Fish Hatchery with Dr. Blair to perform health monitoring on the spring Chinook salmon that are held there. I also traveled with fish health specialist Rick Cordes to the North Lapwai Valley acclimation site to pick up Fall Chinook Salmon sub-yearlings to bring back to the lab for their health check.
Dr. Blair showed me how to perform enzyme-linked immunosorbent assays (ELISAs), which are screening tests for disease where specific antibodies are used to detect for the presence or absence of a specific antigen. Enzyme-linked secondary antibodies are also added to the samples along with a chemical that is converted by the enzyme into a color if the sample is positive for the antigen. The presence and quantity of the antigen can be measured by light absorbance through a spectrophotometer. ELISA is predominately used at the Idaho Fish Health Center to detect for the presence of Renibacterium salmoninarum which is the causative agent of Bacterial Kidney Disease. During my stay I also learned about the methods that are utilized to detect viruses in aquacultured fish. The center’s virologist, Corie Samson, showed me how they culture cell lines which are used to check for the presence or absence of viruses, primarily infectious pancreatic necrosis (IPN) and infectious hematopoietic necrosis (IHN) viruses. I also learned the methods for viral plating and extractions. Fish that are positive for viruses are culled from the population and the samples are sent off to another laboratory to determine the specific genetic viral strains. I also was able to expand on my knowledge of quantitative and nested polymerase chain reaction (PCR) tests through the tutelage of both Laura and Rick. The basics of PCR are that it is used to amplify a specific region of a DNA strand and in fish health can be used to detect and/or identify bacteria and viruses from tissue culture assays. I also was shown by Rick how surveillance is done for Nucleospora salmonis and Myxobolus cerebralis which is the causative agent of whirling disease. Whirling disease can cause bone destruction and it is detected by digesting the skull bones of fish and looking for M. cerebralis spores in the dissolved “skull soup” that is left over. Definitive diagnosis of whirling disease and many of the other cold water fish diseases can be done by histology. Histology is the study of microscopic anatomy of cells and tissues, and is commonly performed by sectioning and staining samples on glass slides so that they may then be observed through light microscopy. Dr. Blair took the time to show me how the process of preparing a histology slide is conducted and even let me attempt to section some tissue samples for myself. Additionally I was able to go through a histology slide set and observe various normal tissues and tissues that were infected with common bacteria and viruses.
In addition to my duties in the health lab, I was also able to take part in other activities at the Dworshak Hatchery and in the surrounding communities. On one of my Saturdays I was able to take part in some of the fish production duties that are conducted at the hatchery. I spent my morning in the hatchery with fish culturist Rick Allain where he showed me how to do hourly feedings and raceway cleanings for the steelhead fry. I spent my afternoon with the hatchery manager Mark Drobish, where he showed me how they feed and clean the raceways for the Fall and Spring Chinook Salmon fingerlings. He also took me around and showed me how the water is pumped into the hatchery facility, and how it is degassed and maintained in order to rear healthy fish. I think both Rick and Mark had confidence in me in the fact I was a veterinary student who had prior knowledge and experience with fish, which I guess is not the norm for externing students, because both of them left me to my work without really hovering over me or double checking everything I did. I also was able to be a part of a couple of outreach opportunities, which I understand can be very important in getting community support. I went with Dr. Blair and Corie to Kamiah Elementary where we talked to the 5th grade classes about what the Idaho Fish Health Center does and we went over basic fish anatomy. Afterwards the students got to split up and we helped them conduct their own fish necropsies, which they seemed to love. I also got to take part in the annual Kid’s Fishing Day, which I think is a wonderful way to give back to the community and say thank you for their support. It truly is wonderful to see a child’s face light up when they catch their very first fish.
During the health monitoring of the fall Chinook salmon, conducted at the Dworshak Hatchery, it was noticed that some of the fish were showing a sickle cell appearance of their red blood cells. Sickle cell in fish has been attributed to folic acid deficiency, anoxia, and lead toxicity. At the time the raceway of fish were not showing any other visible signs of illness either internally or externally other than some had slightly hemorrhagic and edematous intestines, and it was not believed that any of the above mentioned possibilities were the cause . The day before I was to leave we were called back to check on the same raceway because some of the fish were showing erratic swimming behavior and appeared to have external “grayish white” lesions on their heads. We collected some of the fish that were indeed swimming in a lethargic and upside down manner, as well as had the visible lesions. Upon closer examination the lesions were determined to be a fungus, which was as yet unidentified when I had to leave. Some of the fish were also still exhibiting the sickle cell shape of their red blood cells. Unfortunately for me, I had to leave before a definitive diagnosis could be made. As with all of the fish health monitoring checks we took samples for bacteriology and virology, and since I plan on keeping in touch with the staff at the Idaho Fish Health Center hopefully I will be able to find out what the definitive cause is.