Graduate Thesis Or Dissertation
 

Distribution and epizootiology of infectious pancreatic necrosis and infectious hematopoietic necrosis of salmonid fishes in Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/4j03d282m

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  • The distribution in Oregon of two viruses affecting salmonid fishes was determined by examination of hatchery and feral fish. Infectious pancreatic necrosis virus (IPNV) was isolated from fish at the Oregon Department of Fish and Wildlife Research Laboratory, Corvallis, Roaring River, Fort Klamath, and Wizard Falls Hatcheries. Fish collected at Elk, Cache, and Sparks Lakes were also found to be infected with IPNV. An epizootic caused by IPNV occurred at Wizard Falls Hatchery in 1974. Infectious hematopoietic necrosis virus (IHNV) was isolated from fish at Round Butte, Wizard Falls, and Elk River Hatcheries, and the Upper Metolius River. Epizootics due to IHNV occurred at Round Butte and Wizard Falls Hatcheries in 1975. The fish dying from IHNV at Wizard Falls Hatchery were also infected with IPNV, the first reported case of double virus infection in fish. The isolation of IHNV at Elk River Hatchery extended the range of the fish viruses into the Oregon coastal waterways for the first time. The occurrence of IPNV at hatcheries was controlled by destruction of infected stocks, sanitation of facilities and identification of a source of virus-free eggs. After sanitation the hatcheries were restocked with virus-free eggs and fish. The infection of hatchery fish by IHNV was not controlled due to its presence in trout and salmon brood stocks and in feral fish in waters above the hatcheries. Isolates of IPNV from sites in Oregon were compared serologically. Determination of 100% endpoint titers were found to be too variable for accurate comparisons; 50% endpoint titers were less variable and were used in this study. Only one serotype of IPNV was found in Oregon, but considerable antigenic variation was seen. There were two antigenic subtypes among the IPNV isolates examined: a Willamette Valley subtype and a Deschutes River subtype. The viruses isolated from the 1974 and 1975 Wizard Falls Hatchery IPNV epizootics were found to be antigenically dissimilar, indicating a separate source of infection for each epizootic. The 1975 epizootic had as its source eggs from Roaring River Hatchery broodstock. The origin of the virus in the 1974 epizootic was not determined. The source of infection of the 1973 Fall River Hatchery epizootic was shown to be eggs taken from virus-infected Eastern brook trout in Elk Lake.
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file details MulcahyDanielM1977.pdf 2017-08-17 Öffentlich Herunterladen