University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln US Fish & Wildlife Publications US Fish & Wildlife Service 1985 EDWARDSIELLA INFECTIONS OF FISHES G. L. Bullock U.S. Fish and Wildlife Service Roger L. Herman U.S. Fish and Wildlife Service Follow this and additional works at: https://digitalcommons.unl.edu/usfwspubs Part of the Aquaculture and Fisheries Commons Bullock, G. L. and Herman, Roger L., "EDWARDSIELLA INFECTIONS OF FISHES" (1985). US Fish & Wildlife Publications. 132. https://digitalcommons.unl.edu/usfwspubs/132 This Article is brought to you for free and open access by the US Fish & Wildlife Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in US Fish & Wildlife Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. EDWARDS/ELLA INFECTIONS OF FISHES G. L. Bullock and Roger L. Herman u.s. Fish and Wildlife Service National Fisheries Center-Leetown National Fish Health Research Laboratory Box 700, Kearneysville, West Virginia 25430 FISH DISEASE LEAFLET 71 UNITED STATES DEPARTMENT OF THE INTERIOR Fish and Wildlife Service Division of Fishery Research Washington, D.C. 20240 1985 Introduction ing or erratic pattern. Gross external lesions vary with species. Channel catfish often develop small, cutane­ The genus Edwardsiella was suggested by Ewing et ous ulcerations; in advanced cases, however, larger al. (1965) to encompass a group of enteric bacteria depigmented areas mark the sites of deep muscle generally described under vernacular names such as abscesses (Meyer and Bullock 1973). The flounder paracolon. The type species is E. tarda, which is an Para/iehthys olivaeeus and the cichlid Ti/apia nUotiea opportunistic pathogen of many animals. Meyer and develop swollen abdomens due to ascites (Nakat­ Bullock (1973) reported E. tarda as a pathogen of sugawa 1983; Kubota et al. 1981), and the bream Evyn­ channel catfish (Ieta/urus punetatus) and named the nis japonicus develops ulcers on the head (Kusuda et disease emphysematous putrefactive disease of catfish. al. 1977). Diseased common carp (Cyprinus carpio), However, the organism described by Hoshina (1962) Japanese eel, and striped bass (Morone saxatilis) show as the fish pathogen Parae%baetrum anguillimor­ hemorrhages on the body and fins (Miyazaki and tiferum is now recognized as beingE. tarda (Wakabay­ Egusa 1976b; Sae-Oui et al. 1984). In eels, lesions on ashi and Egusa 1973). internal organs may perforate the body wall, and in Hawke (1979) isolated several strains of a bacterium striped bass, epithelial hyperplasia sometimes gives the closely resembling E. tarda from diseased cultured fish a tattered appearance. channel catfish, but later research showed it to be a Internally, the most common gross lesion consists distinct new species named E. ieta/uri (Hawke et al. of light-colored nodules on the kidneys, spleen, or 1981). Accordingly, the name applied to E. ieta/urus liver. Histologically such lesions are focal necrotic infections in catfish is enteric septicemia. areas, often with abundant bacteria, both free and within macrophages. These lesions may be walled off by fibrocytes and epitheloid cells, or be invasive and spread into adjacent skeletal muscle. Two forms of the Etiology and Diagnosis disease have been described from Japanese eels (Miyazaki and Egusa 1976a, b): in the more common Edwardsiella tarda and E. icta/uri are both gram­ form the initial lesions occur in the kidneys (sup­ negative motile rods that are cytochrome oxidase purative interstitial nephritis) and in the second form negative and ferment glucose with production of acid the liver is the primary organ affected (suppurative and gas. The two species can be differentiated hepatitis). Histopathology of internal organs is gen­ biochemically in that E. tarda produces both indol and erally similar in Japanese eels, tilapia, and striped bass. hydrogen sulfide whereas E. ieta/uri produces neither. Tilapia sometimes also shows intestinal abscesses and Additionally, the two species do not cross-react gill inflammation. Striped bass have epidermal hyper­ serologically. plasia and necroses (particularly in the cephalic canals Presumptive diagnosis of E. tarda or E. ieta/uri is of the lateral line system) in which masses of E. tarda based on clincal signs and on isolation and serological may occur. identification of the causative agents. A positive slide Large abscesses that develop in muscles of channel agglutination test with antiserum specific for E. tarda catfish and striped mullet (MugU eepha/us), and in in­ or E. ieta/uri provides a confirmatory diagnosis. ternal organs of Japanese eels emit a malodorous gas Rogers (1981) developed a fluorescent antibody test when punctured. and enzyme immunoassay that identify E. tarda and E. ieta/uri, both in culture and in infected tissues. Horiuchi et al. (1980) also demonstrated that an indi­ rect fluorescent antibody test in which tissue impres­ Edwardsiella ictaluri sions are used was effective in detecting and diagnos­ ing E. tarda in Japanese eels (Anguilla japoniea). Channel catfish infected with E. ieta/uri refuse feed, tend to hang at the surface, and swim with a spiral movement that includes erratic bursts. Gross external Pathology lesions include hemorrhages around the mouth, on the lateral and ventral portions of the body, and on the Edwardsiella tarda fins. Other signs include pale gills, exophthalmia, and small ulcerations on the body. Ulceration in the fon­ Fish infected with E. tarda sometimes become tanelle of the frontal bones gives the disease one of lethargic, "hang" at the surface, and swim in a spiral- its common names, "hole-in-the-head disease." Inter- 2 nally, petechiae occur or develop throughout the Table 1. Fish hosts of Edwardsiella tarda and Edwardsiella visceral mass and in the peritoneum and body ictal uri. musculature. Some fish develop ascites, and the liver, kidneys, and spleen are commonly enlarged (Plumb Edwardsiella tarda and Schwedler 1982; Rogers 1983). Danios (Dania devaria) infected with E. ieta/uri Atlantic salmon Sa/mo sa/ar swim erratically in a spinning pattern, but gross lesions Black skirted tetra Gymnocorymbus sp. have not been observed in this species. Brown bullhead lcta/urus nebu/osis Channel catfish leta/urus punctatus Histopathology has been described for both natural Chinook salmon Oncorhynchus tshawytscha and experimental infections of channel catfish ] apanese eel Anguilla japonica (Areechon and Plumb 1983; Jarboe et al. 1984; Blazer Emerald shiner Notropis atherinoides et al. 1985). Chronic natural infections are character­ Hirame flounder Paralichthys o/ivaceus ized by infiltrates of mononuclear cells that include Goldfish Carassius auratus Grass carp Ctenopharyngodon idella bacteria-laden macrophages, and diffuse necrosis and Largemouth bass Micropterus sa/moides inflammation occur in visceral organs. Inflammation Striped mullet Mugil cepha/us of the intestinal submucosa and mucosa is common. Striped bass Morone saxatilis Blazer et al. (1985) reported diffuse inflammation of Nile tilapia Tilapia nilotica the olfactory bulb and telencephalon, and considered Yellowtail Serio/a /a/andei the nares a possible route of infection. Jarboe et al. Edwardsiella icta/uri (1984) detected no lesions in the brain but did not ex­ amine the olfactory tract. Areechon and Plumb (1983) Brown bullhead leta/urus nebu/osis found necrotic lesions in the liver, spleen, kidneys, and Channel catfish lcta/urus punctatus pancreas of channel catfish that had been injected with Dania Danio devario Green knifefish Eigenmannia virescens E. ieta/uri; due to the acute course of the experimen­ Blue tilapia Tilapia aurea tal infection, the intestine did not become involved. White catfish leta/urus catus Host and Geographic Range Edwardsiella tarda has been isolated from many 1983). Fish that survive epizootics serve as carriers and, warm water fishes and some coldwater fishes, whereas because E. tarda is prevalent in the intestines of turkey E. ieta/uri has been isolated only from a few species vultures (Cathartes aura), birds may also be an impor­ of warm water fishes (Table I). Additionally, E. tarda tant reservoir of infection (Winsor et al. 1981). causes disease in such other animals as marine mam­ Catfish that survive epizootics of E. ieta/uri prob­ mals, pigs, turtles, alligators, ostriches, skunks, and ably serve as reservoirs of infection, since fish are the snakes. It has also occasionally infected humans (Clar­ only known host and the bacterium survives less than ridge et al. 1980; Nagel et al. 1982). In contrast, E. 8 days in pond water (Rogers 1983). ieta/uri is limited to fish, and survivors of epizootics probably become carriers. The geographic range of E. tarda is worldwide, Incubation Period whereas that of E. ieta/uri is still confined to the cat­ fish growing areas of the United States (Rogers 1983). Incubation time is temperature related; channel cat­ fish that were infected with E. tarda and held at 27 DC died within 10 days (Meyer and Bullock 1973). In Source and Reservoir of Infection studies at the National Fish Health Research Laboratory, striped bass held at 22 DC began dying Because E. tarda is ubiquitous, many animals can within 72 h after a 90-s bath exposure. serve as reservoirs of infection. Furthermore, the en­ Hawke (1979) reported that channel catfish injected vironment can be a source of infectivity because this with E. ieta/uri died within 96 h, and that fish exposed bacterium survives as long as 76 days in pond water to this bacterium in aquarium water died within 2 and mud (Ishihara and Kusuda 1982; Minagawa et al. weeks. 3 Control Blazer, V. S., E. B. Schotts, Jr., and W. D. Waltman. 1985. Pathology associated with Edwardsiella ictaluri in catfish Prevention (Ietalurus punctatus) and danio (Danio devario). J. Fish BioI. In press. Because both E. tarda and E. ieta/uri are principal­ First report of Edwardsiella ictaluri in a species other than ly pathogens of warmwater fishes held in ponds, it is channel catfish. difficult to prevent disease outbreaks by following specific management procedures.