Mortality and pathology of hybrid catfish, Clarias macrocephalus (Günther) × Clarias gariepinus (Burchell), associated with Edwardsiella ictaluri infection in southern Thailand

Abstract

Enteric septicaemia of catfish (ESC) caused by Edwardsiella ictaluri is becoming an increasing problem in aquaculture and has been reported worldwide in a variety of fish species. This study reports ESC in hybrid catfish, Clarias macrocephalus (Günther) × Clarias gariepinus (Burchell), cultured in southern Thailand. The bacteria were identified as E. ictaluri by conventional and rapid identification systems, as well as by genetic and phylogenetic characterization. Analysis of 16S rRNA indicated 100% homology to the 16S rRNA sequence of several E. ictaluri strains in GenBank. Plasmid profiles demonstrated 4.0- and 5.6-kb plasmids, compared with the 4.8- and 5.6-kb plasmids in the US isolates, and representative genes of three of the four known pathogenicity islands of US isolates were present. Serologically, lipopolysaccharide (LPS) purified from the Thai isolates was not recognized by a monoclonal antibody against the LPS of US isolates. Fish experimentally infected with E. ictaluri showed 23-100% mortality within 14 days with a 168-h LD50 of 6.92 × 10(7) CFU mL(-1) by immersion and a 96-h LD50 of 1.58 × 10(6) CFU fish(-1) by intraperitoneal injection. Examination of tissue sections obtained from both naturally and experimentally infected fish indicated that infection of hybrid catfish with E. ictaluri produced lesions in several organs including liver, kidney, spleen, heart and brain. Histopathology findings included cellular necrosis, focal haemorrhage, infiltration of lymphocytes and multifocal granulomatous inflammation in the infected organs.

Identification and characterization of Edwardsiella ictaluri from diseased Pangasius pangasius, cultured in Cirata Lake, Indonesia

“…In 1976 there were observed natural outbreaks of E. ictaluri in Georgia, Alabama, USA, Japan, South Africa and also in Asia. E. ictaluri is primarily recognized as a disease of catfish species and is known to cause an economically important bacterial disease of farmed catfish in some countries (Hawke and Khoo 2004;Suanyuk et al 2014). Species E. ictaluri is the most widespread family member of the genus Edwardsiella, which had been detected in over 20 species of freshwater and marine fish from 25 countries in the America, Europe, Asia, Australia, Africa and the Middle East (Hawke and Khoo 2004).…”

Concurrent infections of Flavobacterium columnare and Edwardsiella ictaluri in striped catfish, Pangasianodon hypophthalmus in Thailand

“…Among bacterial pathogens, E. ictaluri and F. columnare are recognized as the most highly pathogenic bacteria that cause enteric septicemia of catfish (ESC) and columnaris disease in freshwater fish respectively (Declercq et al, 2013;Hawke et al, 1981). E. ictaluri was reported in channel catfish (Ictalurus punctatus) in the United States (Hawke et al 1981), walking catfish (Clarias batrachus) and hybrid catfish (Clarias macrocephalus × Clarias gariepinus) in Thailand (Boonyaratpalin and Kasornchan, 1986;Kasornchandra et al, 1987;Suanyuk et al, 2014), striped catfish in Vietnam and Indonesia (Crumlish et al, 2002;Ferguson et al, 2001;Yuasa et al, 2003), wild ayu (Plecoglossus altivelis) in Japan (Nagai et al, 2008), yellow catfish (Pelteobagrus fulvidraco) in China (Ye et al, 2009), as well as cultured Nile tilapia (Oreochromis niloticus) (Soto et al, 2012). F. columnare is one of the oldest known bacterial pathogens, having affected the global population of aquaculture freshwater fish species since the beginning of the last century (Bernardet, 1989;Bernardet and Bowman, 2006;Declercq et al, 2013).…”

Development of a Monoclonal Antibody Specific to the IgM Heavy Chain of Bighead Catfish (Clarias macrocephalus): A Biomolecular Tool for the Detection and Quantification of IgM Molecules and IgM+ Cells in Clarias Catfish

“…Bighead catfish are slow growing, defective in fry production, susceptible to infectious disease, and sensitive to various environmental conditions [4]. These constraints strongly affect catfish production in Thailand [5][6][7]. As an alternative, the production of hybrid catfish (female bighead catfish, C. macrocephalus x male African catfish, C. gariepinus) has attracted attention in the catfish industry in Thailand and Southeast Asia.…”

“…As an alternative, the production of hybrid catfish (female bighead catfish, C. macrocephalus x male African catfish, C. gariepinus) has attracted attention in the catfish industry in Thailand and Southeast Asia. Hybrid catfish are known as "big-aui" in Thai [7]. More specifically, hybrid catfish acquire major commercially-desirable characteristics from their parents, such as good meat quality, rapid growth, improved feed conversion, increased survival, resistance to many diseases, and tolerance to many environmental conditions.…”

“…More specifically, hybrid catfish acquire major commercially-desirable characteristics from their parents, such as good meat quality, rapid growth, improved feed conversion, increased survival, resistance to many diseases, and tolerance to many environmental conditions. Therefore, bighead catfish are increasingly being used for hybrid catfish production in Thailand [2][3][4][5][6][7].…”