Virulence of Aeromonas hydrophita and some other bacteria isolated from European eels Anguilla anguilla reared in fresh water

Abstract

ABSTRACT. Studies were conducted to determine the pathogenicity for European eels Anguilla anguffla and rainbow trout Oncorhynchus mykiss of several stra~ns of the species Aeromonas hydrophila, A. jandaei, A. sobria, A. caviae. Plesiomonas shigelloides. Vibrio anguillarum, Pseudomonas fluorescens and Shewanella putrefaciens isolated from an eel farm. Virulence of 20 isolates obtained during epizootics from diseased eels, asymptomatic carriers and tank water and of 20 isolates obtained during the absence of disease from healthy eels and water was evaluated by 2 challenge methods: intraperitoneal injection (IP) and bath exposure. Of the isolates tested by IP, all strains of A. hydrophila. and those of A. jandaei mainly from epizootics, were pathogenic for eels (LD,, dose 105.4 to 107.5 cfu fish-'). Strains of these species caused an ulcerous disease by bath exposure to 10' to 10' cfu ml-'. In contrast, rainbow trout were less susceptible to infection caused by A. hydrophila and A. jandaei isolates, perhaps because of the lower water temperatures at which they were held during challenge. The epizootics in the eel populations occurred in spring and summer when water temperatures were 17 to 22 "C. The data indicate that A. hydrophila and A. jandaei are European eel pathogens and that infections may occur by waterborne transmission. Therefore, the presence of these bacteria in the farm environment probably constitutes a health hazard for eels.

Occurrence of Edwardsiella tarda in wild European eels Anguilla anguilla from Mediterranean Spain

“…Until now, E. tarda has never been associated with epizootics affecting wild or farmed eels in Europe (Biosca et al 1991, Esteve et al 1993, Høi et al 1998). The infectivity experiments reported here clearly demonstrated that E. tarda was responsible for the disease signs occurring in some wild European eels from Albufera Lake (Valencia, Spain).…”

“…In Europe, E. tarda has not been associated with bacterial infections affecting the European eel Anguilla anguilla (Biosca et al 1991, Esteve et al 1993, Høi et al 1998, even though intensive eel farming is widely practised to satisfy market demands and supplement declining wild eel stocks. The occurrence of edwardsiellosis in eel has so far been limited to the Japanese and Taiwanese aquaculture industry (Wakabayashi & Egusa 1973, Chang & Liu 2002.…”

“…All plates were incubated at 28°C for 24 to 48 h. Colonies of each morphological type were picked and transferred to TSA-1 plates for purification. Bacterial isolates were routinely subjected to conventional tests as previously described (Esteve et al 1993). API 20E strips (BioMérieux) were used to identify oxidative and fermentative bacteria (Edwardsiella spp.…”

Bacterial and parasitic factors diagnosed in eel farmed in Poland in the years 2010-2014

“…Rzadziej notowane są: Aeromonas jandanei, Pseudomonas fluorescens, Shewanella putrefaciens, Aeromonas sobria, Aeromonas caviae, Aeromonas salmonicida i Flavobacterium spp. Gatunki i szczepy tych bakterii różnią się patogennością, co ma wpływ na przebieg kliniczny zakażeń oraz zmiany patologiczne i śmiertelność (7,8,13,14,17). Drobnoustroje te występują w środowisku naturalnym, jak również w obiektach hodowlanych.…”

Pathogenic Aeromonas hydrophila Serogroup O:14 and O:81 Strains with an S Layer

“…Aeromonas hydrophila, a gram-negative motile rod, is considered one of the most important bacterial pathogens of aquatic animals in temperate areas, as it has been isolated from diseased fish, eels, frogs, and turtles (10,25,38,47). A. hydrophila has been increasingly reported as one of the most common Aeromonas species associated with human intestinal disease (1,24,36) and systemic illnesses in immunocompromised patients (14,15,45).…”