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1-1-1985

EDWARDSIELLA INFECTIONS OF FISHESG. L. BullockU.S. Fish and Wildlife Service

Roger L. HermanU.S. Fish and Wildlife Service

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EDWARDS/ELLA INFECTIONS OF FISHESG. L. Bullock and Roger L. Herman

u.s. Fish and Wildlife ServiceNational Fisheries Center-LeetownNational Fish Health Research LaboratoryBox 700, Kearneysville, West Virginia 25430

FISH DISEASE LEAFLET 71

UNITED STATES DEPARTMENT OF THE INTERIORFish and Wildlife ServiceDivision of Fishery ResearchWashington, D.C. 20240

1985


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IntroductionThe genus Edwardsiella was suggested by Ewing et(1965) to encompass a group of enteric bacteria

is E. tarda, which is anistic pathogen of many animals. Meyer andE. tarda as a pathogen of(Ieta/urus punetatus) and named theemphysematous putrefactive disease of catfish.the fish pathogen Parae%baetrum anguillimor-

is now recognized as beingE. tarda (WakabayHawke (1979) isolated several strains of a bacteriumE. tarda from diseased cultured

to be aE. ieta/uri (Hawke et al.Accordingly, the name applied to E. ieta/urusis enteric septicemia.

Etiology and DiagnosisEdwardsiella tarda and E. icta/uri are both gramnegative motile rods that are cytochrome oxidasenegative and ferment glucose with production of acidand gas. The two species can be differentiatedbiochemically in that E. tarda produces both indol andhydrogen sulfide whereas E. ieta/uri produces neither.Additionally, the two species do not cross-reactserologically.Presumptive diagnosis of E. tarda or E. ieta/uri isbased on clincal signs and on isolation and serologicalidentification of the causative agents. A positive slideagglutination test with antiserum specific for E. tardaor E. ieta/uri provides a confirmatory diagnosis.Rogers (1981) developed a fluorescent antibody test

and enzyme immunoassay that identify E. tarda and. ieta/uri, both in culture and in infected tissues.Horiuchi et al. (1980) also demonstrated that an indirect fluorescent antibody test in which tissue impresions are used was effective in detecting and diagnosE. tarda in Japanese eels (Anguilla japoniea).

PathologyEdwardsiella tarda

Fish infected with E. tarda sometimes become"hang" at the surface, and swim in a spiral-

ing or erratic pattern. Gross external lesions vary withspecies. Channel catfish often develop small, cutaneous ulcerations; in advanced cases, however, largerdepigmented areas mark the sites of deep muscleabscesses (Meyer and Bullock 1973). The flounderPara/iehthys olivaeeus and the cichlid Ti/apia nUotieadevelop swollen abdomens due to ascites (Nakatsugawa 1983; Kubota et al. 1981), and the bream Evyn-nis japonicus develops ulcers on the head (Kusuda etal. 1977). Diseased common carp (Cyprinus carpio),Japanese eel, and striped bass (Morone saxatilis) showhemorrhages on the body and fins (Miyazaki andEgusa 1976b; Sae-Oui et al. 1984). In eels, lesions oninternal organs may perforate the body wall, and instriped bass, epithelial hyperplasia sometimes gives thefish a tattered appearance.Internally, the most common gross lesion consistsof light-colored nodules on the kidneys, spleen, orliver. Histologically such lesions are focal necroticareas, often with abundant bacteria, both free andwithin macrophages. These lesions may be walled offby fibrocytes and epitheloid cells, or be invasive andspread into adjacent skeletal muscle. Two forms of thedisease have been described from Japanese eels(Miyazaki and Egusa 1976a, b): in the more commonform the initial lesions occur in the kidneys (suppurative interstitial nephritis) and in the second formthe liver is the primary organ affected (suppurativehepatitis). Histopathology of internal organs is generally similar in Japanese eels, tilapia, and striped bass.Tilapia sometimes also shows intestinal abscesses andgill inflammation. Striped bass have epidermal hyperplasia and necroses (particularly in the cephalic canalsof the lateral line system) in which masses of E. tardamay occur.Large abscesses that develop in muscles of channelcatfish and striped mullet (MugU eepha/us), and in internal organs of Japanese eels emit a malodorous gaswhen punctured.

Edwardsiella ictaluriChannel catfish infected with E. ieta/uri refuse feed,tend to hang at the surface, and swim with a spiralmovement that includes erratic bursts. Gross externallesions include hemorrhages around the mouth, on thelateral and ventral portions of the body, and on thefins. Other signs include pale gills, exophthalmia, and

small ulcerations on the body. Ulceration in the fontanelle of the frontal bones gives the disease one ofits common names, "hole-in-the-head disease." Inter-


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nally, petechiae occur or develop throughout thevisceral mass and in the peritoneum and bodymusculature. Some fish develop ascites, and the liver,kidneys, and spleen are commonly enlarged (Plumband Schwedler 1982; Rogers 1983).Danios (Dania devaria) infected with E. ieta/uriswim erratically in a spinning pattern, but gross lesionshave not been observed in this species.Histopathology has been described for both naturaland experimental infections of channel catfish(Areechon and Plumb 1983; Jarboe et al. 1984; Blazeret al. 1985). Chronic natural infections are characterized by infiltrates of mononuclear cells that includebacteria-laden macrophages, and diffuse necrosis andinflammation occur in visceral organs. Inflammationof the intestinal submucosa and mucosa is common.Blazer et al. (1985) reported diffuse inflammation ofthe olfactory bulb and telencephalon, and consideredthe nares a possible route of infection. Jarboe et al.(1984) detected no lesions in the brain but did not examine the olfactory tract. Areechon and Plumb (1983)found necrotic lesions in the liver, spleen, kidneys, andpancreas of channel catfish that had been injected withE. ieta/uri; due to the acute course of the experimental infection, the intestine did not become involved.

Host and Geographic RangeEdwardsiella tarda has been isolated from manywarm water fishes and some coldwater fishes, whereas

E. ieta/uri has been isolated only from a few speciesof warm water fishes (Table I). Additionally, E. tardacauses disease in such other animals as marine mammals, pigs, turtles, alligators, ostriches, skunks, andsnakes. It has also occasionally infected humans (Clarridge et al. 1980; Nagel et al. 1982). In contrast, E.ieta/uri is limited to fish, and survivors of epizooticsprobably become carriers.The geographic range of E. tarda is worldwide,whereas that of E. ieta/uri is still confined to the catfish growing areas of the United States (Rogers 1983).

Source and Reservoir of InfectionBecause E. tarda is ubiquitous, many animals canserve as reservoirs of infection. Furthermore, the environment can be a source of infectivity because this

bacterium survives as long as 76 days in pond waterand mud (Ishihara and Kusuda 1982; Minagawa et al.

Table 1. Fish hosts ofEdwardsiella tarda and Edwardsiellaictal uri.

Atlantic salmonBlack skirted tetraBrown bullheadChannel catfishChinook salmon] apanese eelEmerald shinerHirame flounderGoldfishGrass carpLargemouth bassStriped mulletStriped bassNile tilapiaYellowtail

Brown bullheadChannel catfishDaniaGreen knifefishBlue tilapiaWhite catfish

Edwardsiella tardaSa/mo sa/arGymnocorymbus sp.lcta/urus nebu/osisleta/urus punctatusOncorhynchus tshawytschaAnguilla japonicaNotropis atherinoidesParalichthys o/ivaceusCarassius auratusCtenopharyngodon idellaMicropterus sa/moidesMugil cepha/usMorone saxatilisTilapia niloticaSerio/a /a/andei

Edwardsiella icta/urileta/urus nebu/osislcta/urus punctatusDanio devarioEigenmannia virescensTilapia aurealeta/urus catus

1983). Fish that survive epizootics serve as carriers and,because E. tarda is prevalent in the intestines of turkeyvultures (Cathartes aura), birds may also be an important reservoir of infection (Winsor et al. 1981).Catfish that survive epizootics of E. ieta/uri probably serve as reservoirs of infection, since fish are theonly known host and the bacterium survives less than8 days in pond water (Rogers 1983).

Incubation PeriodIncubation time is temperature related; channel catfish that were infected with E. tarda and held at 27 DCdied within 10 days (Meyer and Bullock 1973). Instudies at the National Fish Health ResearchLaboratory, striped bass held at 22 DC began dyingwithin 72 h after a 90-s bath exposure.Hawke (1979) reported that channel catfish injectedwith E. ieta/uri died within 96 h, and that fish exposed

to this bacterium in aquarium water died within 2weeks.


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ControlPrevention

Because both E. tarda and E. ieta/uri are principally pathogens of warmwater fishes held in ponds, it isdifficult to prevent disease outbreaks by followingspecific management procedures. At present, E. ie-ta/uri is more damaging than E. tarda as a cause ofmortality of cultured catfishes (J . A. Plumb, personalcommunication). Outbreaks of E. ieta/uri infectionsoccur at water temperatures of 24-28 C, and are thusrestricted essentially to May-June and SeptemberOctober. Management procedures that reduce stressduring these months may lessen the severity ofoutbreaks.

An experimental E. ieta/uri vaccine produced hightiters in channel catfish (Rogers 1983). Commercialproduction of vaccines for both Edwardsiellapathogens is feasible.Treatment

Outbreaks of E. tarda or E. ieta/uri can be controlled by feeding Terramycin at the rate of 2.5-3.0 g/lOO lb of fish per day for 10 days. However, astrain of Terramycin-resistant E. tarda from channelcatfish was reported by Hilton and Wilson (1980). Additionally, the potentiated sulfonamide Romet hasproved effective in controlling E. ieta/uri outbreaks,and the drug is in the process of registration with theU.S. Food and Drug Administration for use on E. ic-ta/uri infections in catfishes.

Annotated BibliographyAmandi, A., S. F. Hiu, J. S. Rohovec, and J. L. Fryer. 1982.

Isolation and characterization of Edwardsiella tarda fromfall chinook salmon (Oncorhynchus tshawytscha). Appl.Environ. Microbiol. 43(6): 1380-1384.First description of Edwardsiella tarda infection in salmon.The E. tarda isolate was also pathogenic for steelhead andrainbow trout.

Areechon, N., and J. A. Plumb. 1983. Pathogenesis of Ed-wardsiella ictaluri in channel catfish, Ietalurus punctatus.J. World Maricult. Soc. 14:249-260.A description of hematological and histopathologicalchanges after intraperitoneal injection of Edwardsiellaictaluri.

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Blazer, V. S., E. B. Schotts, Jr., and W. D. Waltman. 1985.Pathology associated with Edwardsiella ictaluri in catfish(Ietalurus punctatus) and danio (Danio devario). J. FishBioI. In press.First report of Edwardsiella ictaluri in a species other thanchannel catfish.

Clarridge, J. E. , D. M. Musher, V. Fanstein, and R. J.Wallace, Jr. 1980. Extraintestinal human infection causedby Edwardsiella tarda. J. Clin. Microbiol. 11(5):511-514.Edwardsiella tarda is an uncommon enteric bacterium thathas been found generally in animal hosts and occasionally in human feces. Three cases of extraintestinal infectionin man that were caused by E. tarda included a typhoidlike illness, peritonitis with sepsis, and cellulitis from awound received by an angler while fishing. The microbiology of E. tarda and the previous reports of infectionscaused by this organism are reviewed.

Coles, B. M., R. K. Stroud, and S. Sheggeby. 1978. Isolation of Edwardsiella tarda from three Oregon sea mammals. J. Wildl. Dis. 14(3):339-341.Edwardsiella tarda was isolated from the peritoneal exudate of a northern (Steller) sea lion (Eumetopias jubata)with peritonitis, and from the liver of a harbor porpoise(Phocena phocena) , and a California sea lion (Zalophuscalifornianus). These findings indicate that E. tarda is anopportunistic invader of sick or injured marine mammals.

Ewing, W. H. , A. C. McWhorter, M. R. Escobar, andA. H.Lubin. 1965. Edwardsiella, a new genus of Enterobac-teriaceae based on a new species, E. tarda. Int. Bull.Bacteriol. Nomencl. Taxon. 15(1):33-38.A full description of a new species and genus to be included in the family Enterobacteriaceae. The generic nameEdwardsiella and the species name Edwardsiella tarda aresuggested.

Hawke, J. P. 1979. A bacter ium associated with disease ofpond cultured channel catfish, Ietalurns punctatus. J. Fish.Res. Board Can. 36(12):1508-1512.Original description of Edwardsiella ictaluri. Thecharacteristics of this bacterium were compared with thoseof E. tarda; although the organism was described as aspecies of Edwardsiella, the species name was not officiallyassigned until 1981.

Hawke, J. P., A. C. McWhorter, A. G. Steigerwalt, andD. J. Brenner. 1981. Edwardsiella ietaluri sp. nov., thecausative agent of enteric septicemia of catfish. Int. J. Syst.Bacteriol. 31(4):396-400.On the basis of biochemical and serological tests, theauthors described a new species of Edwardsiella and proposed ictaluri as the specific epithet.


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Herman, R. L., and G. L. Bullock. 1985. Pathology causedby Edwardsiella tarda in striped bass. Trans. Am. Fish.Soc. In press.This is the first report of Edwardsiella tarda from stripedbass. Pathogenicity was proved by contact infection.Characteristic histopathology consisted of epithelialhyperplasia and necrosis associated with the lateral linecanals, and abscess formation in the anterior kidney andother internal organs.

Hilton, L. R., and J. L. Wilson. 1980. Terramycin-resistantEdwardsiella tarda in channel catfish. Prog. Fish-Cult.42(3):159.Description of a Terramycin- resistant Edwardsiella tardaisolated from an epizootic among channel catfish.

Horiuchi, M., T. Sato, H. Takagi, and K. Tozuka. 1980.Studies on rapid diagnosis system of main bacterialdiseases of pond-cultured eels in Japan-II. Applicationresults of direct immunofluorescence for diagnosis of Edwardsiellosis in field cases. Fish Pathol. 15(2):63-67.The direct fluorescent antibody test was found to be reliable in diagnosing Edwardsiella tarda infection fromkidney or liver smears.

Hoshina, T. 1962. On a new bacterium, Paracolobactrumanguillimortiferum n. sp. Bull. Jpn. Soc. Sci. Fish.28(1):162-164.The original description of Edwardsiella tarda in Japan.

Ishihara, S., and R. Kusuda. 1981. Experimental infectionof elvers and anguillettes with Edwardsiella tarda bacteria.Bull. Jpn. Soc. Sci. Fish. 47(8):999-1002.Elvers and anguillettes (larger eels) were challenged withEdwardsiella tarda by 1- or 3-h bath exposures, or by addition of bacteria to feed. Both routes of infection produced mortality in elvers but not in larger eels.

Ishihara, S., R. Kusuda. 1982. Growth and survival ofEdwardsiella tarda bacteria in environmental water. Bull.Jpn. Soc. Sci. Fish. 48(4):483-488.Edwardsiella tarda survived for up to 76 days in pondwater. This long survival time may aid in transmission ofE. tarda.

Jarboe, H. H., P. R. Bowser, and H. R. Robinette. 1984.Pathology associated with a natural Edwardsiella ictaluriinfection in channel catfish (letalurus punctatus Rafinesque). J. Wildl. Dis. 20(4):352-354.A clinical description that includes behavior, gross signs,histopathology, and hematocrit values. Lesions differedfrom those described in other reports, and it is suggestedthat the route of infection may alter clinical signs.

Kubota, S. S., N. Kaige, T. Miyazaki, and T. Miyashita.1981. Histopathological studies on Edwardsiellosis oftilapia-1. Natural infection. Bull. Fac. Fish. Mie Univ.9:155-165.Nile tilapia with gross signs including pale body colorascites, prolapsed anus, and cloudy eyes were found tohave abscesses primarily in the liver, spleen, and kidney.These lesions progressed to granuloma formations.

Kusuda, R., T. Itami, M. Munekiyo, and H. Nakajima.1977. Characteristics of a Edwardsiella sp. from arepizootic of cultured crimson sea breams. Bull. Jpn. Soc.Sci. Fish. 43(2):129-134.A disease outbreak among cultured sea bream was causedby a variant of Edwardsiella tarda. The bacterium differedfrom typical E. tarda strains in being nonmotile and afermenter of arabinose and sorbitol.

Kusuda, R., T. Toyoshima, Y. Iwamura, and H. Sako. 1976.Edwardsiella tarda from an epizootic of mullets (MugUcephalus) in Okitsu Bay. Bull. Jpn. Soc. Sci. Fish.42(3):271-275.An epizootic among striped mullet was found to be causedby Edwardsiella tarda. Affected fish swam erratically ina whirling pattern, and bore large malodorous bodyabscesses.

Meyer, F. P. , and G. L. Bullock. 1973. Edwardsiella tardoa new pathogen of channel catfish (letalurus punctatus)Appl. Microbiol. 25(1):155-156.First description of Edwardsiella tarda in catfish.

Minagawa, T., T. Nakai, and K. Muroga. 1983. Edwardsiellatarda in eel culture environment. Fish Pathol.17(4):243-250.Field surveys on the presence and abundance of Edward-siella tarda in water and mud of eel culture ponds weremade during each of the four seasons of the year in1981-1982. The incidences of E. tarda in water and mudsamples from 30 ponds were 900/0 and 91 % in summer,97% and 100% in autumn, 48% and 25% in winter, and73% and 75% in spring. The density of organisms wasalso highest during the two warmer seasons.

Miyashita, T. 1984. Pseudomonas f/uorescens and Edward-siella tarda isolated from diseased tilapia. Fish Pathol.19(1):45-50.Cultured tilapia suffered chronic mortality from Psuedo-monas f/uorescens and Edwardsiella tarda. Infectionscaused by P. f/uorescens were characterized by hemorrhage, particularly in the ovary, and those caused by theE. tarda showed discrete colonies in the spleen.

Miyazaki, T., and S. Egusa. 19760. Histopathological studies of Edwardsiellosis of the Japanese eel (Anguilla


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japonica)-1. Suppurative interstitial nephritis form. Fishpathol. 11(1):33-44.The nephritic infection is characterized by abscesses in thekidney. Advanced lesions may penetrate the musculatureand perforate the skin.

Miyazaki, T., and S. Egusa. 1976b. Histopathological studies of Edwardsiellosis of the Japanese eel (Anguillajaponica)-II. Suppurative hepatitis form. Fish Pathol.11(2):67-76.Description of hepatic abscesses that predominate in thisform of Edwardsiella infection.

Mushiake, K., K. Muroga, and T. Nakai. 1984. Increasedsusceptibility of Japanese eel Anguillajaponica to Edwardsiella tarda and Pseudomonas anguilliseptica following exposure to copper. Bull. Jpn. Soc. Sci. Fish.50(11): 1797-1801.Exposure of eels for 24 to 48 h to 100-340 ppm copperincreased susceptibility to Edwardsiella tarda. The authorsspeculated that susceptibility was a result of a stressresponse.

Nagel, P. , A. Serritella, and T. J. Layden. 1982. Edwardsiella tarda gastroenteritis associated with a pet turtle.Gastroenterol. Annu. 82:1436-1437.Describes a patient who developed gastroenteritis that wasinduced by Edwardsiella tarda, seemingly from exposureto a diseased turtle.

Nakatsugawa, T. 1983. Edwardsiella tarda isolated fromcultured young flounder. Fish Pathol. 18(2):99-101.First isolation of Edwardsiella tarda from a Hirameflounder. Diseased fish showed accumulations of asciticfluid. The isolate killed yellowtails into which it wasinjected.

Owens, D. R., S. L. Nelson, and J. B. Addison. 1974. Isolation of Edwardsiella tarda from swine. Appl. Microbiol.27(4):703-706.Edwardsiella tarda was isolated from the intestinal tractof a 2- month-old pig. This is the first reported isolationof E. tarda from swine in the United States. Swine havebeen reported as potential carriers of E. tarda, but pathogenicity of the organism for swine has not beendetermined.

Plumb, J. A., and D. J. Sanchez. 1983. Susceptibility of fivespecies of fish to Edwardsiella ictaluri. J. Fish Dis.6(3):261-266.Injection of 1.5 X 103 to 1.5 X 108 Edwardsiella ictaluricells killed all channel catfish within 10 days; however,among tilapia, golden shiner (Notemigonus crysoleucus),bighead carp (Aristichthys nobilis), and largemouth bass(Micropterus salmoides) 70070 were refractive.

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Plumb, J . A., and T. E. Schwedler. 1982. Enteric septicemiaof catfish (ESC): a new bacterial problem surfaces.Aquaculture 18(4):26-27.Description of Edwardsiella ictaluri infection of channelcatfish, including clinical signs, pathology, severity, andchemotherapy.

Rogers, W. A. 1981. Serological detection of two species ofEdwardsiella infecting catfish. Pages 169-172 in D. P.Anderson and W. Hennessen, eds. Proceedings of the International Symposium on Fish Biologics: Serodiagnosticsand Vaccines, Kearneysville, West Virginia, 26-30 April1981.An enzyme immunoassay test for identification of Edwardsiella tarda and E. ictaluri compared favorably withthe fluorescent antibody procedure. When clinical specimens were used, both procedures provided identificationof either pathogen within 20 min.

Rogers, W. A. 1983. Edwardsiellosis in fishes. Pages 153-159in D. P. Anderson, M. Dorson, and Ph. Dubourget, eds.Antigens of fish pathogens. Les Antigenes des microorganismes pathogenes des poissons. Fondation MarcelMerieux, Lyon, France.A general review of Edwardsiella tarda and E. ictaluri.

Sae-Oui, D., K. Muroga, and T. Nakai. 1984. A case ofEdwardsiella tarda infection in cultured colored carpCyprinus carpio. Fish Pathol. 19(3):197-199.Description of the first recorded Edwardsiella tarda infection in carp. The epizootic killed 60 colored (koi) carp.Affected fish showed hemorrhage and erythema on thebody.

Ullah, Md. A., and T. Arai. 1983. Pathological activitiesof the naturally occurring strains of Edwardsiella tarda.Fish Pathol. 18(2):65-70.Authors demonstrated that Edwardsiella tarda strains produced hemolysins and dermotoxins, and suggested thatthese toxins may be virulence factors.

Wakabayashi, H., and S. Egusa. 1973. Edwardsiella tarda(Paracolobactrum anguillimortijerum) associated withpond-cultured eel disease. Bull. Jpn. Soc. Sci. Fish.39(9):931-936.Description of morphological and biochemicalcharacteristics of 22 strains of Edwardsiella tarda isolatedfrom diseased eels.

Winsor, D. K., A. P. Bloebaum, and J. J. Mathewson. 1981.Gram-negative, aerobic, enteric pathogens among intestinal micro flora of wild turkey vultures (Cathartes aura)in west central Texas. Appl. Environ. Microbiol.42(6): 1123-1124.


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The prevalence of Edwardsiella tarda and other entericbacteria in the intestines of turkey vultures suggested thatthey may be reservoirs of the pathogens.Wyatt, L. E. , R. Nickelson II, and C. Vanderzant. 1979.

Edwardsiella tarda in freshwater catfish and their environment. Appl. Environ. Microbiol. 38(4):710-714.Edwardsiella tarda was isolated from 47, 88, and 791170 of

skin, visceral, and dressed-fish samples, respectively. Itwas also isolated from 30% of imported dressed fish, from75% of the water samples and 64% of the mud samplesfrom catfish ponds and from 100% of the frogs, turtlesand crayfish from catfish ponds. The incidence of d w a r d ~siella increased during summer, as water temperatures increased. The significance of the incidence of Edwardsiel/ain catfish, catfish disease, and public health could not besubstantiated.

Note: Use of trade names does not imply U.S. Government endorsement of commercial products.

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