Its that time of year again -- flu season, but for the sturgeon at the U.S. Fish and Wildlife Services Bozeman Fish Technology Center (Center), it is worse than weathering a bad cold. A group of yearling shovelnose sturgeon, a species native to the Missouri River, was diagnosed with a potentially lethal virus recently that has killed approximately 2,000 three-inch fish. Preliminary results indicate the stations young of the year pallid sturgeon may also be harboring the virus. The Center raises and studies shovelnose sturgeon and its endangered cousin, pallid sturgeon, to help recover wild populations. Research focuses on captive rearing and propagation and on the sturgeon reproductive and immune system. The recent virus outbreak, although disheartening for its terminal effect on this rare prehistoric fish, provides an opportunity for researchers at the Center to study how the virus is transmitted and the sturgeon's immune response -- valuable information for sturgeon recovery efforts.
Worldwide, sturgeon species have been found to be susceptible, when under stress, to a strain of virus known as iridovirus. Outbreaks of the iridovirus in captivity can result in massive die-offs of young sturgeon. The virus has been identified among pallid, shovelnose, white, Atlantic, and Russian sturgeon species. Experts hypothesize each sturgeon species may have its own viral strain not transmittable to other sturgeon or fish. Little is known about how the virus affects wild sturgeon populations or the long-term effects to sturgeon that survive outbreaks, but its impact on captive rearing programs can be devastating. The virus has no known effect on humans.
Until recently, the virus has only been detectable through analysis of virus-infected cells in tissue samples from fins or body parts of sick sturgeon. With results of new research, tools are being developed that allow detection of the virus in asymptomatic sturgeon through non-lethal sampling which could lead to prophylactic treatments that prevent infection and die-offs. Dr. Ron Hedrick at University of California in Davis is developing a technique whereby the virus can be detected through polymerase chain reaction, a process of extrapolating and amplifying the virus DNA. With the recent outbreak of iridovirus in shovelnose sturgeon at the Bozeman Fish Technology Center, Dr. Molly Webb and Linda Beck, researchers at the Center, are evaluating blood parameters such as cortisol levels and are measuring the physiological response through activation of specialized cells in the immune system of sturgeon infected with the virus.
"Its heart wrenching to see our sturgeon dying," commented Dr. Molly Webb, Reproductive Physiologist at the Center, ?but if there's a silver lining, its a hope that our studies will help us raise healthier sturgeon for recovery and better understand how iridovirus affects wild sturgeon populations."
About 700 of the 4,000 infected 3-inch yearling shovelnose sturgeon will be used in research projects. However, the Center must euthanize the remaining shovelnose, because sick fish cannot be stocked into the wild and the threat of spreading the virus to water sources and the endangered pallid sturgeon at the Center is too great. The Center is working with the State of Montana Fish Health Coordinator, Jim Peterson, to minimize loss of fish during the quarantine period. Meanwhile, scientists will move ahead on important research to improve virus detection and prevent future iridoviral outbreaks affecting sturgeon conservation efforts worldwide.
- FWS -
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