Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


nocardiosis of fish



nocardiosis of fish


  • Last modified
  • 03 January 2018
  • Datasheet Type(s)
  • Animal Disease
  • Preferred Scientific Name
  • nocardiosis of fish
  • Overview
  • Nocardiosis is a disease of both saltwater and freshwater fish caused by actinomycetes of the genus Nocardia. Cases of piscine Nocardia are not as widely reported as mycobacteriosis in fish. Some nocardial...

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Preferred Scientific Name

  • nocardiosis of fish

International Common Names

  • English: granulomatous disease; nocardiosis
  • French: nocardiose


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Nocardiosis is a disease of both saltwater and freshwater fish caused by actinomycetes of the genus Nocardia. Cases of piscine Nocardia are not as widely reported as mycobacteriosis in fish. Some nocardial infections in fish may be misinterpreted as mycobacterial disease, as they both result in similar clinical signs and gross pathology. Nocardia asteroides, described by Eppinger in 1891, is considered the type species of the genus (Gordon and Mihm, 1962). Nocardia farcinica had been formerly regarded as the type species, but this was changed due to the absence of an authentic strain in any culture collection and the paucity of references to N. farcinica in the literature. The first case of fish nocardiosis caused by N. asteroides was reported in neon tetra, Hyphessobrycon innesi (Valdez and Conroy, 1963).

The taxonomy of bacteria in the genus Nocardia is not as well organized as in other groups (Austin and Austin, 1987), so there is a need for bacteriological taxonomists to modify the classification of nocardioform bacteria and help to eliminate any confusion.

[Based upon material originally published in Woo PTK, Bruno DW, eds., 1999. Fish diseases and disorders, Vol. 3 Viral, bacterial and fungal infections. Wallingford, UK: CABI Publishing.]

Hosts/Species Affected

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Information on fish nocardiosis is very limited in comparison with mycobacteriosis in fish. However, this does not mean that nocardial infection is less of a problem in fish than mycobacteriosis. Nocardia asteroides has been reported to be the cause of granulomatous disease in neon tetras kept in aquaria in Argentina (Conroy, 1964). Snieszko et al. (1964) reported nocardial infection in hatcheryreared fingerling rainbow trout, Oncorhynchus mykiss, in Lee Town, West Virginia, USA, and subsequently Campbell and MacKelvie (1968) isolated Nocardia in brook trout, Salvelinus fontinalis, from Canada. Nocardiosis was also observed in cultured yellowtails, Seriola quinqueradiata and Seriola purpurascens, in Japan (Kubota et al., 1968). An outbreak of nocardiosis was recorded in Formosa snakehead fish (Channidae) from Taiwan (Hsu et al., 1987). Nocardia seriolae was later isolated from cultured yellowtail (S. quinqueradiata) and Japanese flounder (Paralichthys olivaceus) (Kudo et al., 1988).

Nocardioform actinomycetic organisms were isolated from many species of freshwater fish affected with epizootic ulcerative syndrome (EUS) in India (Chakrabarty and Dastidar, 1991). Crayfish (Austropotamobius pallipes) have been reported with nocardial infection showing melanized nodules throughout the tail muscle (Fisheries and Oceans Canada, 2004a). Pacific oyster (Crassostrea gigas) are also susceptible to Nocardia sp., causing mortality during the hot season in several embayments in British Columbia, Canada and Washington state, USA (Friedman and Hedrick, 1991; Friedman et al., 1991).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Sea Areas

Atlantic, SouthwestPresentConroy, 1964b
Pacific, NorthwestPresentKubota et al., 1968; Hsu et al., 1987


IndiaPresentChakrabarty and Dastidar, 1991
JapanPresentKubota et al., 1968
-HonshuPresentFisheries and Oceans Canada, 2004b
-KyushuPresent Not invasive Kitao et al., 1989
-ShikokuPresentItano and Kawakami, 2002
TaiwanPresentHsu et al., 1987; Chen et al., 1989; Chen and Tung, 1991; Chen et al., 2000


NigeriaPresentOgbulie and Cobiajuru, 2003

North America

CanadaPresentCampbell and MacKelvie, 1968
-British ColumbiaPresent Invasive Friedman and Hedrick, 1991; Friedman et al., 1991
USAPresentPresent based on regional distribution.
-CaliforniaPresentFisheries and Oceans Canada, 2004b
-VirginiaPresent Not invasive Valdez and Conroy, 1962
-WashingtonPresent Invasive Friedman and Hedrick, 1991; Friedman et al., 1991
-West VirginiaPresentSnieszko et al., 1964
-WyomingPresent Not invasive Money et al., 2004

South America

ArgentinaPresent Not invasive Conroy, 1964b


UKPresentFisheries and Oceans Canada, 2004a; Alderman et al., 1986


AustraliaPresentPresent based on regional distribution.
-New South WalesPresentWhittington et al., 1999
-TasmaniaPresentBransden et al., 2000


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Histopathological examinations of infected organs have revealed characteristic granulomas, each with a centre of necrotic material, a peripheral cellular zone of numerous histiocytes, lymphocytes and a few multinucleated giant cells, all of which are partially circumscribed by a fibrous capsule. Engelhardt (1987) noted that colonies of weakly acid-fast bacteria were present within and at the periphery of several granulomas. Hsu et al. (1987) observed numerous disseminated abscesses, encapsulated by granulation tissue, in the pleura and viscera of infected Formosa snakehead fish.


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Nocardiosis is a systemic chronic granulomatous disease of fish caused by several species of the bacterium Nocardia. Severe emaciation, inactivity and skin discoloration are the clinical signs of this disease. In advanced stages, cachexia, ascites, dermal ulceration, focal necrotic areas within skeletal muscle and pale areas in the swollen kidney, spleen, heart and liver may be observed (Kubota et al., 1968). The appearance of small nodules on the gills of infected yellowtails has been reported (Kusuda et al., 1974).

As already mentioned, nocardiosis may be misdiagnosed as mycobacteriosis, because of the similarity between the clinical signs and gross pathology associated with the two diseases. Positive differentiation can only be made by isolation and identification of the causative agent. In addition, histological sections of the infected organs should be examined. Nocardioform bacteria can grow on similar kinds of media to mycobacteria. After 24 h of growth on nutrient agar, typical colonies of Nocardia are seen. These are raised, folded, granular or powdery, 1-4 mm in diameter, yellow or tan, and with aerial mycelium around the edges (Engelhardt, 1987). Nocardial granulomas without the epithelioid cells in the earliest stages of development are easily confused with piscine mycobacteriosis. Furthermore, while acid-fast organisms are present in the Nocardia lesion, they only show a positive reaction for Nocardia with Fite-Faraco acid-fast stain. Morphologically, Nocardia appear filamentous, branched and beaded and are 5-50 mm long, while mycobacteria are usually 1-3 mm in length (Wolke and Stroud, 1978).

More specific and sensitive methods have been applied for diagnosis including antibody-based and DNA based methods. Chen et al. (2000) described immunohistochemistry using polyclonal antibodies to detect Nocardia seriolae in sea bass. However, more specific probes such as monoclonal antibodies have not been employed yet.

Polymerase chain reaction (PCR), employing primers to the 16S-23S rRNA internal transcribed spacer, has also been used to detect Nocardia seriolae in yellowtail fish (Kono et al., 2002). As a sensitive and specific method, PCR could be useful for detection of the pathogen in both diseased fish and carriers.

List of standard diagnostic tests with range of results.

Clinical signs++-
Antibodies-based methods-+++++
DNA probes- in situ hybridisation-++++

- the method is presently unavailable or unsuitable; + the method has application in some situation but cost, accuracy or other factors severely limits; ++ the method is a standard method with good diagnostic sensitivity and specificity; +++ the method is the recommended method for reasons of availability, specificity and sensitivity.

List of Symptoms/Signs

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SignLife StagesType
Finfish / Abscess - Skin and fins Aquatic:Adult Diagnosis
Finfish / Cessation of feeding - Behavioural Signs Aquatic:Adult Sign
Finfish / Change in cloudiness - Eyes Aquatic:Adult Diagnosis
Finfish / Creamy white nodules / granulomas - Organs Aquatic:Adult Diagnosis
Finfish / Cysts - Gills Aquatic:Adult Diagnosis
Finfish / Discoloration - Skin and fins Aquatic:Adult Diagnosis
Finfish / 'Dropsy' - distended abdomen, 'pot belly' appearance - Body Aquatic:Adult Sign
Finfish / Fish rubbing body on hard surfaces - Behavioural signs Aquatic:Adult Sign
Finfish / Generalised lethargy - Behavioural Signs Aquatic:Adult Sign
Finfish / Haemorrhaging - Body Cavity and Muscle Aquatic:Adult Sign
Finfish / Mortalities -Miscellaneous Aquatic:Adult Diagnosis
Finfish / Necrotic musculature - Body cavity and muscle Aquatic:Adult Sign
Finfish / Nodules - Gills Aquatic:Adult Diagnosis
Finfish / Pop-eye - Eyes Aquatic:Adult Diagnosis
Finfish / Scale loss - Skin and Fins Aquatic:Adult Diagnosis
Finfish / Ulceration - Skin and fins Aquatic:Adult Diagnosis

Disease Course

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No studies have yet been undertaken on the pathogenicity of nocardioform bacteria. Kusuda et al. (1989) demonstrated that yellowtails immunized with attenuated live N. kampachi showed an increase in the number of active lymphocytes and granulocytes within 72 h.


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The routes by which infection takes place are not known. Most cases of piscine nocardiosis involve the oral cavity, but, experimentally, oral exposure has not been established as a primary route of infection. Sindermann (1990) suggested that farmed fish may be infected via contaminated feed. In Atlantic salmon farms, Bransden et al. (2000) suggested that phylloplane flora containing a high proportion of Gram-positive bacteria may introduce the pathogen into fish tanks via falling leaf litter from the overhanging trees.

Impact Summary

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Fisheries / aquaculture Negative
Human health Negative
Trade/international relations Negative

Zoonoses and Food Safety

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Several species of Nocardia are known to be human pathogens. For example, Nocardia asteroides frequently occur in immunocompromised patients. Nocardiosis is a suppurative disease of the lung and may spread to the brain and meninges. N. asteroids can also lead to cutaneous nocardiosis (Rapini and Shook, 2001). Although there is no report of disease transmission from fish to man via consumption, fish should be totally cooked. Infected fish should be also handled with great precaution.


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Austin B; Austin DA, 1987. Bacterial fish pathogens: disease in farmed and wild fish. Bacterial fish pathogens: disease in farmed and wild fish., 364pp.; [Ellis Horwood Series in Aquaculture and Fisheries Support]; many ref.

Beaman BL; Moring SE; Ioneda T, 1988. Effect of growth stage on mycolic acid structure in cell walls of Nocardia asteroides GUH-2. Journal of Bacteriology, 170:1137-1142.

Bransden MP; Carson J; Munday BL; Handlinger JH; Carter CG; Nowak BF, 2000. Nocardiosis in tank-reared Atlantic salmon, Salmo salar L. Journal of Fish Diseases, 23(1):83-85.

Campbell G; MacKelvie RM, 1968. Infection of brook trout (Salvelinus fontinalis) by nocardiae. Journal of the Fisheries Research Board of Canada, 25:423-425.

Chakrabarty AN; Dastidar SG, 1991. Repeated isolation of chemoautotrophic nocardioform bacteria from fish epizootic ulcerative syndrome. Indian Journal of Experimental Biology, 29(7):623-627.

Chen SC; Lee JL; Lai CC; Gu YW; Wang CT; Chang HY; Tsai KH, 2000. Nocardiosis in sea bass, Lateolabrax japonicus, in Taiwan. Journal of Fish Diseases, 23(5):299-307.

Chen SC; Tung MC, 1991. An epizootic in large mouth bass (Micropterus salmoides Lacepode) caused by Nocardia asteroides in fresh water pond in southern Taiwan. Journal of the Chinese Society of Veterinary Science, 17(1):15-22.

Chen SC; Tung MC; Tsai WC, 1989. An epizootic in Formosa snake-head fish, Channa maculata Lacepede, caused by Nocardia asteroides in fresh water pond in southern Taiwan. COA Fisheries Series no. 15. Report on Fish Diseases Research (IX) Republic of China, 95-105.

Chinabut S, 1999. Mycobacteriosis and nocardiosis. Fish diseases and disorders. Volume 3: viral, bacterial and fungal infections., 319-340.

Conroy DA, 1964. Nocardiosis as a disease of tropical fish. Veterinary Record, 76:676.

Duijn Cvan Jr, 1981. Tuberculosis in fishes. Journal of Small Animal Practice, 22(6):391-411.

Engelhardt JA, 1987. Abdominal swelling in a gourami. Laboratory Animals, 13-14.

Eppinger H, 1891. Uber eine neue pathogene Cladothrix und eine durch sie hervorgerufene pseudotuberculosis. Beitrage zur Pathologischen Anatomie und Allgemeinon Pathologie, 9:287-328.

Fisheries and Oceans Canada, 2004. Nocardia sp. (Bacterial disease) of crayfish. Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish. Online. Accessed on 3 March 2005.

Fisheries and Oceans Canada, 2004. Nocardiosis of oysters. Synopsis of infectious diseases and parasites of commercially exploited shellfish. Online. Access on 16 March 2005.

Frerichs GN; Roberts RJ, 1989. The bacteriology of teleosts. In: Roberts RJ, ed. Fish Pathology. London: Baillière Tindall, 289-319.

Friedman CS; Beaman BL; Chun JongSik; Goodfellow M; Gee A; Hedrick RP, 1998. Nocardia crassostreae sp. nov., the causal agent of nocardiosis in Pacific oysters. International Journal of Systematic Bacteriology, 48(1):237-246.

Friedman CS; Beattie JH; Elston RA; Hedrick RP, 1991. Investigation of the relationship between the presence of a Gram-positive bacterial infection and summer mortality of the Pacific oyster, Crassostrea gigas Thunberg. Aquaculture, 94(1):1-15.

Friedman CS; Hedrick RP, 1991. Pacific oyster nocardiosis: isolation of the bacterium and induction of laboratory infections. Journal of Invertebrate Pathology, 57(1):109-120.

Ghittino P, 1972. The principal aspects of bacterial fish diseases in Italy. Diseases of fish, 25-38; [Symposia of The Zoological Society of London No.30].

Goodfellow M; Orchard VA, 1974. Antibiotic sensitivity of some nocardioform bacteria and its values as a criterion for taxonomy. Journal of General Microbiology, 83:375-387.

Gordon RE, 1966. Some strains in search of a genus, Corynebacterium, Mycobacterium, Nocardia or what? Journal of General Microbiology, 40:329-343.

Gordon RE; Mihm JM, 1962. The type species of the genus Nocardia. Journal of General Microbiology, 27:1-10.

Hsu FS; Chu HM; Weng CN, 1987. An enzootic of nocardiosis in fish. The Memoirs of Parasitology in Fish Disease, 2:16-21.

Isik K; Chun JongSik; Hah YungChil; Goodfellow M, 1999. Nocardia salmonicida nom. rev., a fish pathogen. International Journal of Systematic Bacteriology, 49(2):833-837.

Itano T; Kawakami H, 2002. Drug susceptibility of recent isolates of Nocardia seriolae from cultured fish. Gyobyo Kenkyu = Fish Pathology, 37(3):152-153.

Kageyama A; Poonwan N; Yazawa K; Mikami Y; Nishimura K, 2004. Nocardia asiatica sp. nov., isolated from patients with nocardiosis in Japan and clinical specimens from Thailand. International Journal of Systematic and Evolutionary Microbiology, 54:125-130.

Kariya T; Kubota S; Nakamura Y; Kira K, 1968. Nocardia infection in cultured yellotail (Seriola quinqueradiata and S. Purpurascens). 1. Bacteriological study. Fish Pathology, 3:16-23.

Kitao T; Ruangpan L; Fukudome M, 1989. Isolation and classification of a Nocardia species from diseased giant gourami Osphronemus goramy.. Journal of Aquatic Animal Health, 1(2):154-162.

Koch R, 1882. Die Aetiologie der Tuberculose. Berliner Klinische Wochenschrift, 19:221-230.

Kono T; Ooyama T; Chen ShihChu; Sakai M, 2002. Sequencing of 16S-23S rRNA internal transcribed spacer and its application in the identification of Nocardia seriolae by polymerase chain reaction. Aquaculture Research, 33(14):1195-1197.

Kubota S; Kariya T; Nakamura Y; Kira K, 1968. Nocardial infection in cultured yellowtails (Seriola quinqueradiata and S. purpurascens). II. Histological study. Fish Pathology, 3:24-33.

Kudo T; Hatai K; Seino A, 1988. Nocardia seriolae sp. nov. causing nocardiosis of cultured fish. International Journal of Systematic Bacteriology, 38(2):173-178.

Kusuda R, 1975. Nocardial infection in cultured yellowtails. In: Proceedings of the Third US-Japan Meeting on Aquaculture. Special Publication of Fishery Agency, Japanese Government and Japan Sea Regional Fisheries Research Laboratory, Nijata, Japan, 63-66.

Kusuda R; Kawahara E, 1987. Direct and indirect fluorescent antibody identification of yellowtail pathogens. Nippon Suisan Gakkaishi (Bulletin of the Japanese Society of Scientific Fisheries), 53:389-394.

Kusuda R; Kimura Y; Hamaguchi M, 1989. Changes in peripheral and peritoneal leucocytes in yellowtail, Seriola quinqueradiata immunized with Nocardia kampachi. Bulletin of the Japanese Society of Scientific Fisheries, 55:1183-1188.

Kusuda R; Nakagawa A, 1978. Nocardial infection of cultured yellowtail. Fish Pathology, 13(1):25-31; [13 fig.].

Kusuda R; Taki H, 1973. Studies on a nocardial infection of cultured yellowtail - I. Morphological and biochemical characteristics of Nocardia insolated from diseased fishes. Bulletin of the Japanese Society of Scientific Fisheries, 39(9):937-943; [2 fig., 5 tab.].

Kusuda R; Taki H; Takeuchi T, 1974. Studies on a Nocardia infection of cultured yellowtail. II. Characteristics of Nocardia kampachi isolated from a gill-tuberculosis of yellowtail. Bulletin of the Japanese Society of Scientific Fisheries, 40(4):369-373; [1 fig., 3 tab. See RMVM 11, 1836].

Lechevalier MP; Horan AC; Lechevalier H, 1971. Lipid composition in the classification of nocardiae and mycobacteria. Journal of Bacteriology, 105:313-318.

Money DJ; Hotchkiss PM; Smith CE, 2004. Nocardia-like filamentous bacteria causes mortality in juvenile Snake River cutthroat trout. American Fisheries Society/Fish Health Section, Fish Health Newsletter, 32(3):10-13.

Ogbulie JN; Cobiajuru IO, 2003. Bacteriological water quality changes and substrate specificity of isolates associated with Clarias lazera culture system. Journal of Aquatic Sciences, 18(2):105-112.

Rapini RP; Shook B, 2001. Nocardiosis. Emedicine. Online. Accessed on 16 March 2005.

Ridell M, 1981. Immunodiffusion studies of some Nocardia strains. Journal of General Microbiology, 123:69-74.

Snieszko SF; Bullock GL; Dunbar CE; Pettijohn LL, 1964. Nocardial infection in hatchery-reared fingerling rainbow trout (Salmo gairdneri). Journal of Bacteriology, 88:1809-1810.

Tsukamura M; Mizrino S; Tsukumura S, 1981. Numerical analysis of rapidly growing scotochromogenic mycobacteria, including Mycobacterium obuense sp. nov., nom. rev., Mycobacterium rhodesiae sp. nov., Mycobacterium aichierse sp. nov., nom. rev., and Mycobacterium tokaiense sp. nov., nom. rev. International Journal of Systematic Bacteriology, 31:263-275.

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