480
Molecular Methods A PCR has been developed for the detection of Ps. anguilliseptica , with a detection limit of 170–200 cells/PCR tube within 8 h (Blanco et al.
2002 ). A TaqMan probe RT-PCR targeted the 16S rRNA gene, and was specifi c and
sensitive, detecting 300 pg of Ps. anguilliseptica genomic DNA (Kang et al. 2015 ).
Epizootiology
Red spot disease, also known as ‘Sekiten-byo’, was fi rst recognised in pond- cultured
eels ( Anguilla japonica ) in Japan (Wakabayashi and Egusa 1972 ). Since then, it has
developed into one of the most destructive diseases of eels in Japan (Nakai and
Muroga 1979 ). During 1981, the disease was recognised in European eels ( A.
anguilla ) within Scotland (Nakai and Muroga 1982 ; Ellis et al. 1983 ; Stewart et al.
1983 ). Conceivably, the disease is spreading, and this may refl ect the natural migratory patterns of wild eel populations, or the rapid increase in intensive eel cultivation during the mid 1970s. A spread to other fi sh groups has now occurred. The
pathogen was recovered from striped jack at water temperatures of 14–16 °C during
February to April, 1993 (Kusuda et al. 1995 ), diseased rainbow trout, sea trout and
whitefi sh (Coregonus sp.) in Finland during 1986–1991 (Wiklund and Lönnström
1994 ), wild Baltic herring (Clupea harengus membras) (Lönnström et al. 1994 ), sea
bass, sea bream and turbot in France (Berthe et al. 1995 ), and as a winter disease
outbreak in sea bream in Spain (Doménech et al. 1997 ). However, in Finland, there
was some evidence also for the presence of V. anguillarum and Aer. salmonicida.
Very little has been published about the epizootiology of Sekiten-byo. The disease is recognised, however, to be prevalent in brackish water, when the water temperature is between 20 and 27 °C (Muroga et al. 1977 ). Indeed, temperature is
considered to be the major factor in infl uencing epizootics. All the available information points to the seriousness of outbreaks in terms of high mortalities. Thus in
one outbreak of the condition in Scotland, 67,000 elvers (96 % of the total) plus 154
adult eels (3.9 % of the total) died (Stewart et al. 1983 ). These authors observed that
generally the large adult eels fared worse than smaller adults. Nevertheless, the
greatest losses occurred with elvers. It is interesting to note that the disease eliminated 14 % of the total weight of the farm stock. This represents a signifi cant investment; therefore, Sekiten-byo has the potential to be a severe economic problem.
Molecular typing techniques have been evaluated using 52 isolates, with three
major genomic groups recognized by repetitive extragenic palindromic PCR (REPPCR) and repetitive intergenic consensus PCR (ERIC-PCR). These groups comprised isolates from eels, turbot and blackspot sea bream, and other fi sh species
(gilthead sea bream, sea bass and salmonids) (Beaz-Hidalgo et al. 2008 ).
9 Pseudomonads
Molecular Methods A PCR has been developed for the detection of Ps. anguilliseptica , with a detection limit of 170–200 cells/PCR tube within 8 h (Blanco et al.
2002 ). A TaqMan probe RT-PCR targeted the 16S rRNA gene, and was specifi c and
sensitive, detecting 300 pg of Ps. anguilliseptica genomic DNA (Kang et al. 2015 ).
Epizootiology
Red spot disease, also known as ‘Sekiten-byo’, was fi rst recognised in pond- cultured
eels ( Anguilla japonica ) in Japan (Wakabayashi and Egusa 1972 ). Since then, it has
developed into one of the most destructive diseases of eels in Japan (Nakai and
Muroga 1979 ). During 1981, the disease was recognised in European eels ( A.
anguilla ) within Scotland (Nakai and Muroga 1982 ; Ellis et al. 1983 ; Stewart et al.
1983 ). Conceivably, the disease is spreading, and this may refl ect the natural migratory patterns of wild eel populations, or the rapid increase in intensive eel cultivation during the mid 1970s. A spread to other fi sh groups has now occurred. The
pathogen was recovered from striped jack at water temperatures of 14–16 °C during
February to April, 1993 (Kusuda et al. 1995 ), diseased rainbow trout, sea trout and
whitefi sh (Coregonus sp.) in Finland during 1986–1991 (Wiklund and Lönnström
1994 ), wild Baltic herring (Clupea harengus membras) (Lönnström et al. 1994 ), sea
bass, sea bream and turbot in France (Berthe et al. 1995 ), and as a winter disease
outbreak in sea bream in Spain (Doménech et al. 1997 ). However, in Finland, there
was some evidence also for the presence of V. anguillarum and Aer. salmonicida.
Very little has been published about the epizootiology of Sekiten-byo. The disease is recognised, however, to be prevalent in brackish water, when the water temperature is between 20 and 27 °C (Muroga et al. 1977 ). Indeed, temperature is
considered to be the major factor in infl uencing epizootics. All the available information points to the seriousness of outbreaks in terms of high mortalities. Thus in
one outbreak of the condition in Scotland, 67,000 elvers (96 % of the total) plus 154
adult eels (3.9 % of the total) died (Stewart et al. 1983 ). These authors observed that
generally the large adult eels fared worse than smaller adults. Nevertheless, the
greatest losses occurred with elvers. It is interesting to note that the disease eliminated 14 % of the total weight of the farm stock. This represents a signifi cant investment; therefore, Sekiten-byo has the potential to be a severe economic problem.
Molecular typing techniques have been evaluated using 52 isolates, with three
major genomic groups recognized by repetitive extragenic palindromic PCR (REPPCR) and repetitive intergenic consensus PCR (ERIC-PCR). These groups comprised isolates from eels, turbot and blackspot sea bream, and other fi sh species
(gilthead sea bream, sea bass and salmonids) (Beaz-Hidalgo et al. 2008 ).
9 Pseudomonads