570
Pathogenicity
The source of infection would seem to be water, with gills as a principle portal of
entry into the eel (Marco-Noales et al. 2001 ). In other work, intramuscular injection
of eels with large numbers of bacterial cells, i.e. 4.85 × 10
8 , resulted in 80 % mortality in the population within 7 days, at a water temperature of 25 °C. This confi rms
the pathogenicity, albeit weak, of V. vulnifi cus . The pathogenicity mechanisms, contained in ECP, that are lethal to fi sh (Lee et al. 1997 ) included haemolysins, lipases,
phospholipases and proteases (Amaro et al. 1992 ). Evidence has been presented
which attributed virulence to the LPS O side chain (Amaro et al. 1997 ). Interestingly,
cultures from diseased European eel produced opaque, translucent colonies, and the
cells possessed a capsule, which was not essential for the development of disease
(Biosca et al. 1993 ). Virulence is related to the presence of plasmids (Lee et al.
2013 ). In particular, the plasmid in biotype 2 contains a rtxA gene that encodes a
multifunctional, autoprocessing repeats-in-toxin (MARTX), which is involved in
the lysis of eukaryotic cells, including epithelial cells and phagocytes, and may act
in fi sh during the onset of septic shock (Lee et al. 2013 ).
To date, 28 plasmid profi les have been identifi ed among 112 strains with biotype
I lacking high molecular weight plasmids with the exception of a 48 kb putative
conjugative plasmids that was present in just under half of isolates. Biotype 2 possessed the 68–70 kb virulence plasmid, with the majority also possessing a 52–56 kb
putative conjugative plasmid. Biotype 3 strains possessed a 48 kb putative
conjugative plasmid. Gene vep07 is regarded as essential for virulence (Roig and
Amaro 2009 ).
Disease Control
Vaccine Development A vaccine, coined Vulnivaccine which contains capsular
antigens and toxoids (being the best of several alternatives; Collado et al. 2000 ) of
serovar E that was administered by immersion for 1 h in three doses at 12 day intervals, has been evaluated in eels with a results that protection (RPS = 60–90 %) was
correlated with serum and local (mucus) antibody levels (Esteve-Gassent et al.
2003 ) with the eels responding to 70–80 kDa OMP, protease and LPS (EsteveGassent and Amaro 2004 ). During fi eld trials by prolonged immersion and boostering after 14 and 24–28 days of 9.5 million glass eels in Spain and parallel experiments
in Denmark, Vulnivaccine achieved RPS of 62–86 % (Fouz et al. 2001 ). With the
appearance of a second serotype, i.e. A, a bivalent vaccine was constructed, and
verifi ed to be effective in terms of protection and humoral and local immunity following application orally, by anal and oral intubation and by i.p. injection
(RPS = 80–100 %) (Esteve-Gassent et al. 2004 ). A combination vaccine with inacti10 Vibrios
Pathogenicity
The source of infection would seem to be water, with gills as a principle portal of
entry into the eel (Marco-Noales et al. 2001 ). In other work, intramuscular injection
of eels with large numbers of bacterial cells, i.e. 4.85 × 10
8 , resulted in 80 % mortality in the population within 7 days, at a water temperature of 25 °C. This confi rms
the pathogenicity, albeit weak, of V. vulnifi cus . The pathogenicity mechanisms, contained in ECP, that are lethal to fi sh (Lee et al. 1997 ) included haemolysins, lipases,
phospholipases and proteases (Amaro et al. 1992 ). Evidence has been presented
which attributed virulence to the LPS O side chain (Amaro et al. 1997 ). Interestingly,
cultures from diseased European eel produced opaque, translucent colonies, and the
cells possessed a capsule, which was not essential for the development of disease
(Biosca et al. 1993 ). Virulence is related to the presence of plasmids (Lee et al.
2013 ). In particular, the plasmid in biotype 2 contains a rtxA gene that encodes a
multifunctional, autoprocessing repeats-in-toxin (MARTX), which is involved in
the lysis of eukaryotic cells, including epithelial cells and phagocytes, and may act
in fi sh during the onset of septic shock (Lee et al. 2013 ).
To date, 28 plasmid profi les have been identifi ed among 112 strains with biotype
I lacking high molecular weight plasmids with the exception of a 48 kb putative
conjugative plasmids that was present in just under half of isolates. Biotype 2 possessed the 68–70 kb virulence plasmid, with the majority also possessing a 52–56 kb
putative conjugative plasmid. Biotype 3 strains possessed a 48 kb putative
conjugative plasmid. Gene vep07 is regarded as essential for virulence (Roig and
Amaro 2009 ).
Disease Control
Vaccine Development A vaccine, coined Vulnivaccine which contains capsular
antigens and toxoids (being the best of several alternatives; Collado et al. 2000 ) of
serovar E that was administered by immersion for 1 h in three doses at 12 day intervals, has been evaluated in eels with a results that protection (RPS = 60–90 %) was
correlated with serum and local (mucus) antibody levels (Esteve-Gassent et al.
2003 ) with the eels responding to 70–80 kDa OMP, protease and LPS (EsteveGassent and Amaro 2004 ). During fi eld trials by prolonged immersion and boostering after 14 and 24–28 days of 9.5 million glass eels in Spain and parallel experiments
in Denmark, Vulnivaccine achieved RPS of 62–86 % (Fouz et al. 2001 ). With the
appearance of a second serotype, i.e. A, a bivalent vaccine was constructed, and
verifi ed to be effective in terms of protection and humoral and local immunity following application orally, by anal and oral intubation and by i.p. injection
(RPS = 80–100 %) (Esteve-Gassent et al. 2004 ). A combination vaccine with inacti10 Vibrios