DIE-OFF, CARP - USA (04): (MICHIGAN)
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Date: Thu 21 Jul 2011
Source: Hometown Life.com, Gannett News Service [edited] <http://www.hometownlife.com/article/20110721/NEWS11/107210364>
Local carp die-off turns out to be short-lived
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According to Kensington Metropark officials, an estimated 700 carp died last month [June 2011] at Kent Lake and portions of the Huron River.
However, the die-off -- likely due to a virus called spring viremia of carp, according to the Michigan Department of Natural Resources [DNR] -- was thankfully short-lived, said Huron-Clinton Metroparks Chief of Communications Denise Semion.
Semion said the die-off continued for only a few days after dead carp were first reported by boaters at Kent Lake and a segment of the Huron River just east of the lake.
"We have had no incidents since, and we're estimating between 600 and 700 fish died," said Semion. She noted that the lake is about 800 acres [324 ha] in size, equating to approximately one dead fish per acre.
"We did receive reports then of things being unsightly, and we did hear complaints of odors," she said.
Semion said cleanup crews worked diligently to remove dead fish to reduce any risk posed by dead or decomposing fish, like _E. coli_ bacteria.
The disease that likely caused the die-off affects only species of carp and posed no human health risk.
Jim Francis, a fisheries biologist for the DNR, said last month [June 2011] that evidence pointed to spring viremia of carp, primarily because no other fish were otherwise affected.
Francis said spring viremia of carp -- which causes infected fish to become extremely lethargic -- has been confirmed in portions of southeastern Michigan before, including Woodland Lake in Brighton Township.
"Based on the reports we've gotten and the evidence, what we're seeing is consistent with what spring viremia of carp does," Francis said. "Typically, when we get calls for fish die-offs, people assume (it's caused by) water contamination, but if there were poison in the water, it would kill indiscriminately."
Semion said cleanup crews sent samples of the dead carp to the DNR, which forwarded them to labs at Michigan State University. Results, she said, are expected within a few weeks.
[Byline: Frank Konkel]
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Communicated by:
HealthMap Alerts via ProMED-mail
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[While it may be spring viremia of carp, it may well be Koi herpes virus as well. Neither disease can be diagnosed by visual signs alone.
Both affect only carp, so to claim one over the other may be premature.
Spring viremia of carp (SVC) is a contagious viral disease of carp and related species. Outbreaks can cause substantial economic losses.
SVC can be highly fatal in young fish, with mortality rates up to 90 percent. In Europe, where this disease has been endemic for at least 50 years, 10-15 percent of 1-year-old farmed carp are lost to SVC each year. The causative virus can be spread by fomites and parasitic invertebrates, and is difficult to eradicate; once it is established in a pond, elimination of the virus may require the destruction of all aquatic life. Since 2002, several SVC outbreaks have been reported in the US, with both cultivated and wild species affected.
The clinical signs of SVC can include darkening of the skin, swollen eyes, abdominal swelling, pale gills, trailing fecal casts, and protrusion of the anus. Infected fish may be lethargic and show areas of bleeding in the gills and skin. Diseased fish tend to gather at the water inlet or sides of the pond, swim and breathe more slowly than normal, and react sluggishly to stimuli. Loss of equilibrium, with resting and leaning, are seen in the late stages. Concurrent bacterial infections (carp-dropsy complex) or parasitic infections influence the symptoms and mortality rate.
It could be koi herpesvirus, since only carp are affected, and carp are a type of koi. When results from the diagnostic laboratory are returned, then the exact cause of death of these fish may more likely be found.
Koi herpesvirus (KHV), also known as cyprinid herpesvirus-3 or CyHV-3, is a highly contagious viral disease capable of causing significant morbidity and mortality in common carp (_Cyprinus carpio_). In many countries, the common carp is a foodfish and also has been selectively bred for the ornamental fish industry, where it is known as koi. Almost all countries have reported KHV, which was first recognized in 1996 in England. However, publications (Pokorova et al) in 2005 report that Australia does not have the disease.
The most significant sign of KHV is the sudden appearance of mass mortality within 1-2 days of initial infection. Aside from mass mortality, the other common signs are white patches or necrosis of the gills. Other clinical signs are sunken eyes, bleeding gills, and secondary bacterial infection or parasite infestation.
There is no treatment for KHV. Prevention is the key. For cultured fish, inquiring about any mortalities may give a buyer a clue that some fish may be carriers.
Photo of carp:
<http://pond.dnr.cornell.edu/nyfish/Cyprinidae/common_carp.jpg>.
For further information, subscribers are referred to Chapter 2.3.6.
"Koi Herpesvirus Disease" in OIE's manual of Diagnostic Tests for Aquatic Animals -- 2010, available online at <http://www.oie.int/fileadmin/Home/eng/Health_standards/aahm/2010/2.3.06_KHVD.pdf>.
Portions of this comment were extracted from <http://www.cfsph.iastate.edu/Factsheets/pdfs/spring_viremia_of_carp.pdf>.
- Mod.TG]
[The state of Michigan can be located on the HealthMap/ProMED-mail interactive map at <http://healthmap.org/r/0_ua>. - Sr.Tech.Ed.MJ]
[see also:
Die-off, carp - USA (03): (MI) 20110629.1976 Die-off, carp - USA (02): (MI) 20110625.1948 Die-off, carp - USA: (MI) 20110622.1907] .................................................sb/tg/mj/lm/ll
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