Staff from the Oregon Department of Fish and Wildlife (ODFW) uncovered the parasite after observing elevated mortality rates among rainbow trout at three hatcheries.
Oregon authorities have culled approximately 160,000 rainbow trout to contain the spread of a newly identified pathogen.
Staff from the Oregon Department of Fish and Wildlife (ODFW) uncovered the parasite after observing elevated mortality rates among rainbow trout at three hatcheries. Despite attempts with antibiotics and other treatments, the health of the fish did not improve.
Collaborating with Oregon State University’s College of Veterinary Medicine and the OSU Department of Microbiology, genetic testing confirmed the presence of parasites belonging to the class Myxozoa.
Diseases caused by myxosporeas in farmed fish with the most significant economic impact worldwide are proliferative kidney disease (PKD) caused by the malacosporean T. bryosalmonae, and whirling disease, caused by a myxosporean M. cerebralis; both diseases affect salmon.
These are the top five infectious diseases in Norwegian farmed salmon
Researchers determined that the pathogen can spread through water and adversely affect fish kidney and urinary systems.
The infected rainbow trout, measuring 8 to 10 inches in length, were discovered at hatcheries located in the Elk River, Rock Creek, and Klamath Falls.
According to Aimee Reed, ODFW’s senior fish pathologist, rising temperatures and decreased water flow, possibly exacerbated by climate change, create favorable conditions for myxozoan parasites.
The Oregon Department of Fish and Wildlife has implemented “biosecurity measures” to prevent the parasite from spreading further. Measures include disinfecting ponds and raceways and euthanizing the majority of infected fish.
Approximately 500 of the infected trout were sent to a laboratory for further analysis by ODFW and OSU researchers.
ODFW hatcheries typically rear and release nearly 4 million rainbow trout annually.
Reed emphasized the importance of stringent biosecurity measures in safeguarding fish populations. She described the incident as a disappointing loss but stressed the necessity of preventing the parasite’s proliferation to mitigate risks to other fish species.
