UNDIAGNOSED DIE-OFF, FISH - USA (02): (GEORGIA), COLUMNARIS
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Date: 27 May 2011
Source: Savanna Now [edited]
<http://savannahnow.com/news/2011-05-26/bacteria-blame-ogeechee?>
A bacterial disease is the direct cause of a large fish kill on the Ogeechee River, the Georgia Environmental Protection Division (EPD) announced Thursday [26 May 2011].
But the disease being fingered, columnaris, is only a threat to fish when they're under environmental stress, and EPD has still not pinpointed the cause of that stress. Humans are not known to be affected by this bacterium.
State, federal and local agencies became aware of reports of dead fish on the river late last week. A comprehensive sampling and lab analysis of water, fish tissue and sediment began Sunday. The investigation continues to try to pinpoint why the fish were stressed enough to succumb to the bacteria. In the meantime, EPD continues to advise citizens in Bryan, Bulloch, Chatham, Effingham and Screven counties not to swim in or consume fish from the Ogeechee River until further notice.
As a holiday weekend begins, the Blackwater river's legions of swimmers, fishermen and boaters are sure to be disappointed. Dead fish have been reported from Screven County, about a half mile below King America Finishing Inc., a large textile factory, to Ga. 204 at the Chatham-Bryan county border.
Ogeechee Riverkeeper Dianna Wedincamp wants more information. "It's very disappointing because we (already) know that the fish are under a lot of stress," she said. "We want to know what's causing the stress."
The Riverkeeper organization is doing its own analysis of water, tissue and sediment samples and is awaiting lab results.
"There's a ban on swimming or eating fish from Screven to Chatham, so we know there are more issues," she said. "We're planning to get to the bottom of that. We'll be on the river all day tomorrow [28 May 2011]."
[Byline: Mary Landers]
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[I am a little uncertain of the precise name of the organism. The causative agent of columnaris is a bacterial organism that has had its name changed from _Myxobacteria_ to _Flexibacter_ and may be now called _Cytophaga_. However, some of the best references still list it by older names.
A presumptive diagnosis of columnaris disease can be made by the detection of long, slender gram-negative rods in smears of gills or scrapings obtained from cutaneous lesions. Frequently, material scraped from such lesions and examined under phase contrast microscopy in a wet mount will reveal the presence of unique, characteristic "haystack" colonies that are of diagnostic significance (Isolation of the organism on cytophaga medium; Annacker and Ordal 1959).
Columnaris disease, caused by the bacterium _Flexibacter columnaris_ may result in acute or chronic infections in both coldwater and warmwater fishes. It occurs both as external or systemic infections that result in significant losses of hatchery-reared fish, particularly at warm summer temperatures (Pacha and Ordal 1970; Becker and Fujihara 1978).
Epizootics of columnaris disease frequently occur in natural populations, and high losses of fish may be observed. Wood (1974) describes strains of high and low virulence; highly virulent forms attack gill tissue, and the latter strains are primarily responsible for cutaneous infections. Some disagreements still exist concerning proper taxonomic placement of this organism (Snieszko and Bullock 1976). However, Bergey's Manual of Determinative Bacteriology (8th
ed.) classifies it as a flexibacterium.
In many species of fish, the 1st sign of the disease may be the appearance of discolored, gray, patchy areas in the area of the dorsal fin. These characteristic "saddleback" lesions may progress until skin erosion exposes underlying muscle tissue. These lesions may become yellow and cratered and are often prominent in the mouth and head regions (Wood 1979). Virulent strains of _F. columnaris_ may attack gill tissue and cause a "gill rot" condition (Wood 1974). Systemic infections due to less virulent strains may occur with no apparent external signs. However, cutaneous infections seem to be more prevalent in most species of fish.
Research has shown that _Flexibacter columnaris_ can be transmitted from fish to fish directly through the water when virulent strains are involved. Individual infected fish within a population harbor the bacteria over winter (Wood 1974) and serve as sources of infection during the following summer months when stresses occur due to overcrowding and water temperatures above 12.2 C (54 F), etc.
Microcysts formed by _F. columnaris_ have been shown experimentally to remain viable over a period of several years. Some uncertainty still exists as to the possibility that these forms are sources of infection under natural conditions (Wood 1979).
The period between exposure to _F. columnaris_ and the outbreak of clinical disease varies depending upon the virulence of the strain of bacteria and the ambient water temperature. Strains of high virulence may induce acute disease within 24 hours, whereas less virulent forms may require from 48 hours to several weeks (Warren 1981). Holt et al.
(1975) have shown experimentally that a high degree of correlation exists between clinical disease and high water temperatures. Their studies also revealed that host species differ in the time from exposure to death. Existing data reveal that the disease has a pronounced seasonal occurrence. Both natural and hatchery epizootics are concentrated during the warm summer months.
In closed water systems, such as in a farm-raised situation or in aquariums, there are several treatments. However, in an open water system such as this, the treatment may be quite different.
References:
Amend, D.E 1970. Myxobacteria linfections of salmonids: prevention and treatment. p. 258-265. In SE Snieszko (ed.) A symposium on diseases of fishes and shellfishes. Am. Fish. Sot., Spec. Publ. No. 5, Bethesda, MD. 526 p.
Anacker, R.L., and E.J. Ordal. 1959. Studies on the myxobacterium Chondrococcus columnaris. I. Serological typing. J. Bact. 78: 25-32.
Becker, C.D., and M.F. Fujihara. 1978. The bacterial pathogen Flexibacter column & and its epizootiology among Columbia River fish.
Am. Fish. Sot., Monogr. No. 2, Bethesda, MD. 92 p.
Bullock, G.L., D.A. Conroy, and SE Snieszko. 1971. Book 2A: Bacterial diseases of fishes, TEH. Publications. Inc., Neptune City, NJ. 151 p.
Holt, R. A., J.E. Sanders, J, L. Zinn, J.L. Fryer, and K.S. Pilcher.
1975. Relation of water temperature to Flexibacter column infection in steelhead trout (Salmogairdnerz), coho (Oncorhyncus kisutch) and chinook (0. tshauytscha) salmon. J. Fish. Res. Board Can. 32:
1553-1559.
Pacha, R.E. and E.J. Ordal. 1970. Myxobacterial diseases of salmonids. p. 243-257. In S.E Snieszko (ed.) A symposium on diseases of fishes and shellfishes. Am. Fish. SIX., Spec. Publ. No. 5, Bethesda, MD.
Snieszko, S.E, and G.L. Bullock. 1976. Columnaris disease of fishes.
U.S. Fish Wildl. Serv., Fish Dis. Leafl. No. 45, Washington, DC. 10 p.
Warren, J. W. 1981. Diseases of hatchery fish. A fish disease manual.
U.S. Fish Wildl. Serv., Reg. 3, Twin Cities, MN. 91 p.
Wedemeyer, G.H. 1974. Stress as a predisposing factor in fish diseases. U.S. Fish Wildl. Serv., Fish Dis. Leafl. No. 38, Washington, DC. 8 p.
Wood, J. W. 1974. Diseases of Pacific salmon: their prevention and treatment. Wash. State Dep. Fish. Olympia, WA. 82 p.
Portions of this comment were extracted from:
<http://www.glfc.org/pubs/SpecialPubs/sp83_2/pdf/chap23.pdf>. - Mod.TG]
[see also:
Undiagnosed die-off, fish - USA (GA) 20110526.1599] .................................................sb/tg/msp/lm/ll
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