56
By use of the Rapid ID32 Strep system, the isolates were equated with Gemella
haemolysin (good identifi cation – 96 % confi dence).
Pathogenicity
Str. ictaluri infected juvenile channel catfi sh by immersion (≥10
7 CFU/fi sh) and
injection (≥10
7 CFU/fi sh) methods causing low level mortalities within 21 days, but
only at high doses (Pasnik et al. 2009 ).
Disease Control
Passive immunisation of channel catfi sh with fi sh antiserum followed by challenge
led to some protection and an indication of the involvement of antibodies in the
process (Pasnik et al 2011 ).
Streptococcus iniae
Characteristics of the Disease
Str. iniae was initially recovered from an Amazon freshwater dolphin, Inia geoffrensis (Pier and Madin 1976 ). The association with fi sh diseases came when it was
described as a cause of mortality in tilapia hybrids (Tilapia nilotica x T. aurea)
(Perera et al. 1994 ) and later in dusky spinefoot (Siganus fuscenscens) (Sugita 1996 )
and hybrid striped bass (Stoffregen et al. 1996 ). Str. shiloi was named as a result of
an outbreak of disease in St. Peter’s fi sh and rainbow trout within Israel during 1986
when the disease spread rapidly, and caused severe economic losses in farmed fi sh
(Eldar et al. 1994 ). Diseased tilapia were lethargic, swam erratically, and showed
signs of dorsal rigidity. In rainbow trout, the disease signs were consistent with a
septicaemia, with brain damage including meningitis (Eldar et al. 1994 ; Eldar and
Ghittino 1999 ). Str. iniae, was diagnosed as causing disease in two tanks of hybrid
striped bass in a commercial farm, using recirculating freshwater, in the USA
(Stoffregen et al. 1996 ), in white spotted rabbitfi sh (Siganus canaliculatus) in
Bahrain (Yuasa et al. 2003 ), in barramundi (Lates calcarifer) in Australia (Bromage
et al. 1999 ) and in caged and wild fi sh from the Red Sea (Colorni et al. 2002 ). The
pathogen appears to be spreading, and has now been recognized in red porgy ( Pagrus
pagrus ) and gilthead sea bream ( Sparus aurata ) in Spain (El Aamri et al. 2010 ). In
the case of Nile tilapia, there is evidence that enhanced mortalities may well ensue
where co-infection, namely with ichthyophthiriasis, occurs (Xu et al. 2009 ). Channel
catfi sh, which were farmed in China, have been found with acute septicaemia, and
linked to infection with Str. iniae. Here, bacterial cells were observed in the macrophages (Chen et al. 2011 ). Str. iniae serotype II infection led to rainbow trout displaying lethargy, discoloration, loss of orientation, bilateral exophthalmia, corneal
2 Gram-Positive Bacteria (Anaerobes and ‘Lactic Acid’ Bacteria)
By use of the Rapid ID32 Strep system, the isolates were equated with Gemella
haemolysin (good identifi cation – 96 % confi dence).
Pathogenicity
Str. ictaluri infected juvenile channel catfi sh by immersion (≥10
7 CFU/fi sh) and
injection (≥10
7 CFU/fi sh) methods causing low level mortalities within 21 days, but
only at high doses (Pasnik et al. 2009 ).
Disease Control
Passive immunisation of channel catfi sh with fi sh antiserum followed by challenge
led to some protection and an indication of the involvement of antibodies in the
process (Pasnik et al 2011 ).
Streptococcus iniae
Characteristics of the Disease
Str. iniae was initially recovered from an Amazon freshwater dolphin, Inia geoffrensis (Pier and Madin 1976 ). The association with fi sh diseases came when it was
described as a cause of mortality in tilapia hybrids (Tilapia nilotica x T. aurea)
(Perera et al. 1994 ) and later in dusky spinefoot (Siganus fuscenscens) (Sugita 1996 )
and hybrid striped bass (Stoffregen et al. 1996 ). Str. shiloi was named as a result of
an outbreak of disease in St. Peter’s fi sh and rainbow trout within Israel during 1986
when the disease spread rapidly, and caused severe economic losses in farmed fi sh
(Eldar et al. 1994 ). Diseased tilapia were lethargic, swam erratically, and showed
signs of dorsal rigidity. In rainbow trout, the disease signs were consistent with a
septicaemia, with brain damage including meningitis (Eldar et al. 1994 ; Eldar and
Ghittino 1999 ). Str. iniae, was diagnosed as causing disease in two tanks of hybrid
striped bass in a commercial farm, using recirculating freshwater, in the USA
(Stoffregen et al. 1996 ), in white spotted rabbitfi sh (Siganus canaliculatus) in
Bahrain (Yuasa et al. 2003 ), in barramundi (Lates calcarifer) in Australia (Bromage
et al. 1999 ) and in caged and wild fi sh from the Red Sea (Colorni et al. 2002 ). The
pathogen appears to be spreading, and has now been recognized in red porgy ( Pagrus
pagrus ) and gilthead sea bream ( Sparus aurata ) in Spain (El Aamri et al. 2010 ). In
the case of Nile tilapia, there is evidence that enhanced mortalities may well ensue
where co-infection, namely with ichthyophthiriasis, occurs (Xu et al. 2009 ). Channel
catfi sh, which were farmed in China, have been found with acute septicaemia, and
linked to infection with Str. iniae. Here, bacterial cells were observed in the macrophages (Chen et al. 2011 ). Str. iniae serotype II infection led to rainbow trout displaying lethargy, discoloration, loss of orientation, bilateral exophthalmia, corneal
2 Gram-Positive Bacteria (Anaerobes and ‘Lactic Acid’ Bacteria)