Disease data

Enteric Septicaemia of Catfish (Edwardsiellosis)

Previously listed diseases
Fish
Bacterial disease; Gram negative bacteria; Edwardsiella ictaluri

Summary from the online OIE Diagnostic Manual

Enteric septicaemia of catfish ( ESC ) is caused by the bacterium Edwardsiella ictaluri , which belongs to the Enterobacteriaceae family ( 11 ) . ESC is one of the most important infectious disease problems in the commercial catfish industry in the United States of America ( USA ) . Most reported cases of disease caused by E. ictaluri are in channel catfish (Ictalurus punctatus) , but the bacterium has been isolated from related North American catfish including blue catfish (I. furcatus), white catfish (Ameiurus catus), and brown bullhead (A. nebulosus)( 11 ) . ESC has also been reported from Clarias batrachus in Thailand ( 12 ) and from several ornamental species ( 13, 37 ) . The susceptibility of other species including salmonids has been shown experimentally ( 4 ) . Edwardsiella ictaluri should not be confused with E. tarda , another member of the same genus that is frequently found in aquatic animals and is responsible for opportunistic infections in fish and mammals, including humans.

Several studies have shown that E. ictaluri is a very biochemically and antigenically homogeneous species ( 5, 21, 33, 38 ) .

Acute outbreaks of ESC occur within a limited temperature range, from 18 to 28°C. This critical temperature window makes spring and autumn the most common periods for outbreaks in regions where channel catfish are normally cultured. However, low-level mortality due to ESC can occur in carrier populations outside of this temperature range. Other environmental factors ( poor water quality, high stocking density and other stressors ) predispose the host to ESC. Edwardsiella ictaluri is considered to be a true obligate pathogen.

Two clinical forms of ESC occur in channel catfish, a chronic encephalitis and an acute septicaemia ( 20, 22, 30 ) . In the chronic form the bacterium infects the olfactory sacs, and migrates along the olfactory nerves to the brain, generating granulomatous inflammation. This meningo-encephalitis causes abnormal behaviour, with alternating listlessness and chaotic swimming. In late stages of this disease, swelling develops on the dorsum of the head as the inflammatory process erodes the connective tissue in this region. This swelling ulcerates exposing the brain. This has lead to the term 'hole in the head disease', used in the industry. In the acute form of ESC the bacterium is thought to infect through the intestinal mucosa ( 3 ) , and then to establish a bacteraemia. The affected fish display petechial haemorrhages around the mouth, on the throat, the abdomen and at the base of the fins. Multifocal distinct 2 mm diameter raised haemorrhagic cutaneous lesions that progress to depigmented ulcers also occur. Anaemia, moderate gill inflammation and exophthalmia are common signs. Internally, haemorrhages and necrotic foci are scattered in the liver and other internal organs. Haemorrhagic enteritis, systemic oedema, accumulation of ascitic fluid in the body cavity and enlargement of the spleen are nonspecific signs. Histological examination reveals a systemic infection of all organs and skeletal muscles, with the most severe changes being diffuse interstitial necrosis of the anterior and posterior kidney. Focal necrosis in the liver and spleen are also generally seen.

Fish from a population that has recovered from the disease are considered to be carriers. These fish will have protective immunity and may have high levels of E.-ictaluri- specific antibodies. Occasional losses due to recurrent ESC will occur in these populations, especially after a stress is induced. Edwardsiella ictaluri has been detected in the kidney of such fish well over 4 months after exposure ( 2, 14 ) , suggesting that carrier fish act as the natural reservoir for the organism. It is believed that shedding with faeces is the main means of dissemination into the environment. The pathogen persistence and the common practice of continual partial harvest and stocking within a production pond have contributed to the success of this pathogen and the prevalence of ESC in the industry. Moreover, the agent can survive in pond sediments for an extended period of time ( 27 ) , and this may be another important factor in disease recurrence in given areas. Researchers have found the bacterium in the gut of fish-eating birds by performing fluorescent antibody tests on ingesta, but generally no E. Ictaluri could be cultured indicating that the bacteria were not viable ( 34, 40 ) . This suggests that birds are not an important means of disseminating this pathogen.

ESC may be controlled through chemotherapy and/or prophylactic measures. The most common antimicrobial treatments are oral application of potentiated sulfonamide sulfadimethoxine ormethoprim or oxytetracycline, but plasmid-mediated resistance to these antibiotics does occur ( 6 ) . Many producers are now focusing on alternative methods to reduce losses. This relies on management to reduce stress in fish, the cessation of feeding when ESC-induced losses are detected ( 41 ) and on vaccination.

Countries affected

Country Year Status View Records
Australia 2011 Reported present or known to be present View Records
Cuba 2006 Year of last reported occurrence View Records
Japan 2010 Reported present or known to be present View Records
Thailand 2006 Reported present or known to be present View Records
United States of America 2006 Reported present or known to be present View Records
Vietnam 2012 Occurrence limited to certain zones View Records

Species affected

Species Disease occurence Abstract
Brachydanio rerio Unknown World Animal Health in 2001. Part 1. Reports on the animal health status and disease control methods.
Clarias batrachus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Clarias batrachus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Clarias batrachus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Ictalurus catus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus catus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ictalurus catus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Ictalurus furcatus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ictalurus furcatus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Ictalurus melas Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus natalis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus nebulosus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus nebulosus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ictalurus nebulosus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Ictalurus punctatus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus punctatus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ictalurus punctatus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).

Countries affected

Country Year Status View Records
China (Peoples Rep. of) 2009 Reported in country for the first time View Records
Indonesia 2003 Reported in country for the first time View Records
Japan 20018 Reported present or known to be present View Records
United States of America 2003 Reported present or known to be present View Records
Vietnam 2002 Pathogen detected for the first time View Records

Species affected

Species Disease occurence Abstract
Clarias batrachus Natural occurrence Edwardsiella ictaluri from walking catfish, Clarias batrachus L., in Thailand.
Danio devario Natural occurrence Recovery of Edwardsiella ictaluri from danio (Danio devario).
Eigenmannia virescens Natural occurrence Edwardsiella ictaluri in the green knife fish, Eigenmannia virescens.
Ictalurus catus Natural occurrence Susceptibility of five species of fish to Edwardsiella ictaluri.
Ictalurus nebulosus Natural occurrence Susceptibility of five species of fish to Edwardsiella ictaluri.
Ictalurus punctatus Natural occurrence A bacterium associated with disease of pond cultured Channel catfish.
Noturus gyrinus Natural occurrence Isolation of Edwardsiella ictaluri from tadpole madtom in a southwestern New Jersey river.
Oncorhynchus mykiss Experimental demonstration Susceptibility of non-ictalurid fishes to experimental infection with Edwardsiella ictaluri.
Oncorhynchus tshawytscha Experimental demonstration Susceptibility of non-ictalurid fishes to experimental infection with Edwardsiella ictaluri.
Pangasius hypophthalmus Natural occurrence First isolation of Edwardsiella ictaluri from cultured striped catfish Pangasius hypophthalmus in Indonesia.
Pangasius hypophthalmus Natural occurrence Identification of Edwardsiella ictaluri from diseased freshwater catfish, Pangasius hypophthalmus (Sauvage), cultured in the Mekong Delta, Vietnam.
Pelteobagrus fulvidraco Natural occurrence First case of Edwardsiella ictaluri infection in China farmed yellow catfish Pelteobagrus fulvidraco.
Plecoglossus altivelis Natural occurrence Outbreaks of Edwardsiella ictaluri infection in ayu Plecoglossus altivelis in Japanese rivers.
Puntius conchonus Natural occurrence Exotic bacterial pathogens Edwardsiella tarda and Edwardsiella ictaluri from imported ornamental fish Betta spendens and Puntius conchonius, respectively: isolation and quarantine significance.

Countries affected

Country Year Status View Records
Australia 2011 Reported present or known to be present View Records
China (Peoples Rep. of) 2009 Reported in country for the first time View Records
Cuba 2006 Year of last reported occurrence View Records
Indonesia 2003 Reported in country for the first time View Records
Japan 20018 Reported present or known to be present View Records
Thailand 2006 Reported present or known to be present View Records
United States of America 2006 Reported present or known to be present View Records
Vietnam 2012 Occurrence limited to certain zones View Records

Species affected

Species Disease occurence Abstract
Brachydanio rerio Unknown World Animal Health in 2001. Part 1. Reports on the animal health status and disease control methods.
Clarias batrachus Natural occurrence Edwardsiella ictaluri from walking catfish, Clarias batrachus L., in Thailand.
Clarias batrachus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Clarias batrachus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Clarias batrachus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Danio devario Natural occurrence Recovery of Edwardsiella ictaluri from danio (Danio devario).
Eigenmannia virescens Natural occurrence Edwardsiella ictaluri in the green knife fish, Eigenmannia virescens.
Ictalurus catus Natural occurrence Susceptibility of five species of fish to Edwardsiella ictaluri.
Ictalurus catus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus catus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ictalurus catus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Ictalurus furcatus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ictalurus furcatus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Ictalurus melas Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus natalis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus nebulosus Natural occurrence Susceptibility of five species of fish to Edwardsiella ictaluri.
Ictalurus nebulosus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus nebulosus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ictalurus nebulosus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Ictalurus punctatus Natural occurrence A bacterium associated with disease of pond cultured Channel catfish.
Ictalurus punctatus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ictalurus punctatus Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ictalurus punctatus Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Noturus gyrinus Natural occurrence Isolation of Edwardsiella ictaluri from tadpole madtom in a southwestern New Jersey river.
Oncorhynchus mykiss Experimental demonstration Susceptibility of non-ictalurid fishes to experimental infection with Edwardsiella ictaluri.
Oncorhynchus tshawytscha Experimental demonstration Susceptibility of non-ictalurid fishes to experimental infection with Edwardsiella ictaluri.
Pangasius hypophthalmus Natural occurrence First isolation of Edwardsiella ictaluri from cultured striped catfish Pangasius hypophthalmus in Indonesia.
Pangasius hypophthalmus Natural occurrence Identification of Edwardsiella ictaluri from diseased freshwater catfish, Pangasius hypophthalmus (Sauvage), cultured in the Mekong Delta, Vietnam.
Pelteobagrus fulvidraco Natural occurrence First case of Edwardsiella ictaluri infection in China farmed yellow catfish Pelteobagrus fulvidraco.
Plecoglossus altivelis Natural occurrence Outbreaks of Edwardsiella ictaluri infection in ayu Plecoglossus altivelis in Japanese rivers.
Puntius conchonus Natural occurrence Exotic bacterial pathogens Edwardsiella tarda and Edwardsiella ictaluri from imported ornamental fish Betta spendens and Puntius conchonius, respectively: isolation and quarantine significance.