626
Diagnosis
Serology Isolation in cell culture or detection in acridine orange stained smears or
by iFAT has been advocated (Lannan and Fryer 1991 ; Lannan et al. 1991 ). A monoclonal based ELISA was successful and specifi c in detecting Piscirickettsia in
infected fi sh tissues (Aguayo et al. 2002 ).
Molecular Methods PCR technology offers promise for the detection of
Piscirickettsia salmonis (e.g. Heath et al. 2000 ; Mauel and Fryer 2001 ; Venegas
et al. 2004 ), and systems has already been designed which is capable of detecting 1
tissue culture infectious dose (Mauel et al. 1996 ) and 1–10 genome equivalents
(competitive PCR; Heath et al. 2000 ). Subsequently, a PCR was described that was
effective with a few millilitres of serum (Marshall et al. 1998 ). The benefi t of this
system is that the test could be carried on live fi sh, such as valuable broodstock. A
Taq Man PCR was specifi c and sensitive (0.5 TCID 50 /ml) (Corbeil et al. 2003 ). Realtime PCR has been successful at specifi cally detecting the pathogen in paraffi n sections of fi sh tissue (Karatas et al. 2008 ). A multiplex PCR was developed for the
simultaneous detection Aer. salmonicida, Pis. salmonis, Str. phocae and V. anguillarum . The detection limit using purifi ed total bacterial DNA was 500 fg/μl for Pis.
salmonis . The limits of detection using spiked tissues, i.e. kidney, liver, muscle or
spleen, were 100 cells (Tapia-Cammas et al. 2011 ).
Use of Microwave Radiation The use of microwave radiation [700 w energy from
a domestic microwave] has been suggested for Pis. salmonis (Larenas et al. 1996 ).
Epizootiology
It is presumed that the pathogen is passed directly between fi sh, or via invertebrate
vectors. Data have shown that physical contact may be necessary for horizontal
transmission between salmonids (Almendras et al. 1997 ). Certainly, the pathogen
appears to survive extracellularly (Lannan and Fryer 1994 ), and 16S rDNA product
has been recovered from bacterioplankton DNA obtained from the coastal environment in the USA (Mauel and Fryer 2001 ). Using competitive PCR, Heath et al .
( 2000 ) reported 3–4 × 10
3 cells or their DNA in surface seawater in a net pen in
southern Chile.
Pathogenicity
Coho salmon, Atlantic salmon and white sea bass were infected and clinical disease
with mortalities resulted after i.p. injection with cell lines of the rickettsia (Garcés
et al. 1991 ; Arkush et al. 2005 ). Some differences have been detected in the comparative virulence of isolates to coho salmon from British Columbia, Chile and
Norway (House et al. 1999 ). For example, the LD 50 dose for a Scottish isolate was
11 Miscellaneous Pathogens
Diagnosis
Serology Isolation in cell culture or detection in acridine orange stained smears or
by iFAT has been advocated (Lannan and Fryer 1991 ; Lannan et al. 1991 ). A monoclonal based ELISA was successful and specifi c in detecting Piscirickettsia in
infected fi sh tissues (Aguayo et al. 2002 ).
Molecular Methods PCR technology offers promise for the detection of
Piscirickettsia salmonis (e.g. Heath et al. 2000 ; Mauel and Fryer 2001 ; Venegas
et al. 2004 ), and systems has already been designed which is capable of detecting 1
tissue culture infectious dose (Mauel et al. 1996 ) and 1–10 genome equivalents
(competitive PCR; Heath et al. 2000 ). Subsequently, a PCR was described that was
effective with a few millilitres of serum (Marshall et al. 1998 ). The benefi t of this
system is that the test could be carried on live fi sh, such as valuable broodstock. A
Taq Man PCR was specifi c and sensitive (0.5 TCID 50 /ml) (Corbeil et al. 2003 ). Realtime PCR has been successful at specifi cally detecting the pathogen in paraffi n sections of fi sh tissue (Karatas et al. 2008 ). A multiplex PCR was developed for the
simultaneous detection Aer. salmonicida, Pis. salmonis, Str. phocae and V. anguillarum . The detection limit using purifi ed total bacterial DNA was 500 fg/μl for Pis.
salmonis . The limits of detection using spiked tissues, i.e. kidney, liver, muscle or
spleen, were 100 cells (Tapia-Cammas et al. 2011 ).
Use of Microwave Radiation The use of microwave radiation [700 w energy from
a domestic microwave] has been suggested for Pis. salmonis (Larenas et al. 1996 ).
Epizootiology
It is presumed that the pathogen is passed directly between fi sh, or via invertebrate
vectors. Data have shown that physical contact may be necessary for horizontal
transmission between salmonids (Almendras et al. 1997 ). Certainly, the pathogen
appears to survive extracellularly (Lannan and Fryer 1994 ), and 16S rDNA product
has been recovered from bacterioplankton DNA obtained from the coastal environment in the USA (Mauel and Fryer 2001 ). Using competitive PCR, Heath et al .
( 2000 ) reported 3–4 × 10
3 cells or their DNA in surface seawater in a net pen in
southern Chile.
Pathogenicity
Coho salmon, Atlantic salmon and white sea bass were infected and clinical disease
with mortalities resulted after i.p. injection with cell lines of the rickettsia (Garcés
et al. 1991 ; Arkush et al. 2005 ). Some differences have been detected in the comparative virulence of isolates to coho salmon from British Columbia, Chile and
Norway (House et al. 1999 ). For example, the LD 50 dose for a Scottish isolate was
11 Miscellaneous Pathogens