Infections by atypical strains of the bacterium Aeromonas salmonicida

Abstract

SUMMARY Infections due to atypical strains of the Gram-negative bacterium Aeromonas salmonicida cause atypical furunculosis and related diseases of both feral and cultivated fish stocks in freshwater and marine environment. More than 20 farmed and 30 wild fish species have been reported to harbor atypical A. salmonicida. The isolated strains are found to be a heterogeneous group as regards many phenotypic and genotypic characteristics. The clinical and pathological features of infection are different as many factors are involved, e.g. various hosts, strains and environment. Infections of fish in the temperate regions of the Northern hemisphere are most frequently reported, although disease problems have also occurred in other parts of the world as Australia, the Mediterranean and Chile. In Iceland atypical furunculosis has been the main bacterial disease in the salmonid farming industry. As diseases caused by atypical strains are of emerging importance worldwide, the prospects of their control by vaccination need to be considered. Currently all commercially available A. salmonicida vaccines are produced from typical A. salmonicida strains for prevention of classical furunculosis in salmonids. There is, however, evidence of cross protection against atypical furunculosis in Atlantic salmon vaccinated with commercial oil based furunculosis vaccine. Icelandic fish farmers have since 1992 vaccinated salmonids by injection with an autogenous bacterin produced by a commercial vaccine producer against atypical A. salmonicida and recently halibut farmers in Norway have started to use an autogenous injection vaccine against atypical furunculosis. YFIRLIT Sýkingar atýpiskra stofna bakteriunnar Aeromonas salmonicida Sýkingar atýpiskra stofna Gram-neikvaeðu bakteriunnar Aeromonas salmonicida valda kýlaveikibroður og hliðstaeðum sjukdomum i villtum og raektuðum fiski, baeði i fersku vatni og sjo. Bakterian hefur verið einangruð ur yfir 20 tegundum eldisfisks og meira en 30 tegundum af villtum fiski. Rannsoknir a stofnasofnum hafa leitt i ljos toluverðan breytileika a svipfari og erfðaeiginlei kum atýpiskra A. salmonicida stofna. Sjukdomseinkenni eru breytileg og hafa ýmsir þaettir þar ahrif, s.s. mismunandi hýslar, stofnar og umhverfi. Sjukdomsvandamal eru algengust a norðlaegum sloðum, en þo hafa komið upp vandamal i oðrum heimshlutum eins og i Astraliu, Miðjarðarhafslondum og Chile. Kýlaveikibroðir er sa bakteriusjukdomur sem mestum skaða hefur valdið i islensku fiskeldi. Þar sem vandamal vegna sýkinga af voldum atýpiskra A. salmonicida stofna hafa aukist a veraldarvisu er nauðsynlegt að ihuga moguleika a notkun boluefna sem sjukdomsvarnar. Rannsoknir hafa leitt i ljos toluverðan mun a sýkiþattum mismunandi A. salmonicida stofna. Týpiskir stofnar eru einsleitur hopur hvað varðar framleiðslu ensima sem eru virk i sýkingu bakteriunnar, en meðal atýpiskra stofna er mikill breytileiki. Sem stendur eru oll markaðsett A. salmonicida boluefni framleidd til varnar klassiskri kýlaveiki i laxfiskum. Til eru niðurstoður sem sýna krossvorn gegn kýlaveikibroður i laxi sem var bolusettur gegn klassiskri kýlaveiki. Islenskir fiskeldis