Viral Hemorrhagic Septicemia
VHS is a serious rhabdovirus (rod-shaped) viral pathogen of fresh and saltwater fish that is infecting fish in the Great Lakes region of the US and Canada. It was first discovered in the mid-20th Century in Europe where it infected rainbow trout. From there it spread and developed into 4 different viral strands expanding it host range to a wide variety of fish, such as but not limited to common carp, white bass, and walleye. Although the pathway for the introduction of VHS into the Great Lakes is uncertain, it is believed that contamination occurred via ballast water discharge.
VHS causes hemorrhaging of fish tissue, including internal organs, and can lead to mortality in infected fish. Symptoms of infected fish may include hemorrhaging that is especially apparent on fin margins, eyes, and in the body cavity; VHS causes darkened colorations and bloats the abdomen of infected fish. Infected fish display physiological effects, as VHS causes lethargy or abnormal swimming and unusual darting behavior. It is not harmful to humans, and not all infected fish develop the disease, but infected fish can easily spread the disease to other fish. VHS is contracted through urine, feces and sexual fluids that often enter through the gills or wounds on fish.
VHS is responsible for killing fish in all 5 Great Lakes, as well as: the St. Lawrence River, Skaneateles Lake, Seneca-Cayuga Canal, Conesus Lake, and a private pond in Ronsomville, and several inland lakes in Wisconsin and Michigan. VHS has been named by the World Organization of Animal Health as a transmissible disease with the potential to negatively impact the environment and economy. Below is a photo of a VHS induced fish-kill and impact on native fish.
Habitat: VHS was historically a cool-water disease caused by several distinct strains of VHS, each strain occupies a different region of the globe and infects slightly different groups of host fish species. However, the Great Lakes strain is designated Type IV-b and has been shown to infect some warm-water species, causing kills in warmer waters up to 70°F. It is inactive at temperatures above 70°F and therefore cannot infect humans.
Signs of Infection: confirming VHS infection requires sophisticated laboratory testing and cannot be based solely on observation as VHS shares similar signs/symptoms with many other fish diseases. Furthermore, at low VHS infection levels, symptoms may not be apparent in fish at all. However, as VHS infection spreads, fish will display widespread hemorrhages (bleeding) throughout the body surface (eye, skin, and fins), and within internal organs (bladder, intestine, kidney, etc.)
There is no known cure for VHS but there are preventive measures that can be taken. Do not move live fish between water bodies. DISPOSE of unwanted baitfish and fish parts in the trash.
Do not move any water between water bodies. DRAIN water from boat, motor, bilge, live wells and bait containers before leaving the water access.
Clean, Drain, and Dry boat, trailer, and recreational equipment, especially after leaving known VHS infected waters.
If you catch a suspected diseased fish that is alive or dead place the fish in a clean plastic bag and it cool but not frozen. Be sure to note the date, location fish species and total amount of dead fish seen. Then call the local Department of Natural Resources fisheries office or the DNR pathology lab in your area. The State Duty Office can be reached at 1-800-422-0798.
Title Photos: Dr. Mohamed faisal, (dnr.state.mn.us). VHS induced fishkill photo: (New York Invasive Species Information). Clean, drain, dry logo: (yankeelake.mylaketown.com).
“NYIS.” NYSIS.info. New York Invasive Species Information, n.d. Web. 30 July 2015. <http://www.nyis.info/index.php?action=invasive_detail&id=28>.
“Viral Hemorrhagic Septicemia Novirhabdovirus VHS.” Invasives.org. Center for Invasive Species and Ecosystem Health, n.d. Web. 30 July 2015. <http://www.invasive.org/browse/subinfo.cfm?sub=62031>.
“Viral Hemorrhagic Septicemia (VHS) in New York.” DEC.NY.GOV. Department of Environmental Conservation, 2015. Web. 30 July 2015. <http://www.dec.ny.gov/animals/25328.html>.