628
whole cell vaccine/fi sh/day [containing 1 × 10
10 cells/g of feed] incorporated in a
polysaccharide matrix, termed MicroMatrix
TM
, has been described and demonstrated promise (Tobar et al. 2011 ). Research has highlighted a relationship between
antibody titre and protection. Consequently, there was a need for several rounds of
oral vaccination to maintain high antibody tire, and thus protection (Tobar et al.
2015 ).
Antimicrobial Compounds Sensitivity was recorded to clarithromycin, chloramphenicol, erythromycin, gentamicin, oxytetracycline, sarofl oxacin, streptomycin
and tetracycline, but not to penicillin or spectinomycin (Cvitanich et al. 1991 ).
Rickettsia-Like Organisms
Characteristics of the Disease
An increasing number of publications have described rickettsia-like organisms
(RLO) as causal agents of disease (e.g. Rodger and Drinan 1993 ; Chen et al. 1994 ;
Khoo et al. 1995 ; Palmer et al. 1997 ; Jones et al. 1998 ; Corbeil et al. 2005 ; Timur
et al. 2013 ). Whether or not these organisms correspond with Piscirickettsia salmonis has not been always established. For example, Chern and Chao ( 1994 ) reported
that the RLO caused mass mortalities in tilapia from Taiwan during October 1992
to February 1993, with disease signs including the presence of white nodules and
microscopic granulomas on all the organs, and an enlarged spleen. Subsequently,
Comps et al . 1996 ) described a small coccoid organism from the brain of juvenile
sea bass obtained from the South of France. These were derived from a population
which suffered 20 % mortalities. Also, an RLO has been identifi ed among grouper
in Taiwan (Chen et al. 2000b ), tilapia (Mauel et al. 2003 ) and white sea bass in the
USA (Chen et al. 2000a ) and farmed Atlantic salmon in Tasmania and Canada
(Cusack et al. 2002 ). Moribund grouper displayed dark lesions, splenomegaly (with
white nodules), necrosis in the liver, kidney and spleen, and the blood was thin
(Chen et al. 2000b ). However, it is diffi cult from the literature to determine the signifi cance of the Tasmanian RLO to fi sh (Corbeil et al. 2005 ). RLOs were associated
with systemic granulomas in sea bass, with infected fi sh displaying anorexia and
lethargy leading to high mortalities (Timur et al. 2013 ).
An intracellular RLO has been linked with red-mark syndrome (Fig. 11.1 ) in the
UK and strawberry disease [an infl ammatory skin condition] in the USA as result of
immunohistochemistry using polyclonal antibodies to Piscirickettsia salmonis, a
quantitative PCR and 16S rRNA sequencing (Lloyd et al. 2008 , 2011 ; Metselaar
et al. 2010 ). However, intact cells of the pathogen have not been observed nor has
culturing been achieved, to date. Therefore, a question surrounds the interpretation
of the serological data. However, the disease appears to be spreading, and has now
bee reported to occur in farmed rainbow trout in Turkey (Kubilay et al. 2014 ).
11 Miscellaneous Pathogens
whole cell vaccine/fi sh/day [containing 1 × 10
10 cells/g of feed] incorporated in a
polysaccharide matrix, termed MicroMatrix
TM
, has been described and demonstrated promise (Tobar et al. 2011 ). Research has highlighted a relationship between
antibody titre and protection. Consequently, there was a need for several rounds of
oral vaccination to maintain high antibody tire, and thus protection (Tobar et al.
2015 ).
Antimicrobial Compounds Sensitivity was recorded to clarithromycin, chloramphenicol, erythromycin, gentamicin, oxytetracycline, sarofl oxacin, streptomycin
and tetracycline, but not to penicillin or spectinomycin (Cvitanich et al. 1991 ).
Rickettsia-Like Organisms
Characteristics of the Disease
An increasing number of publications have described rickettsia-like organisms
(RLO) as causal agents of disease (e.g. Rodger and Drinan 1993 ; Chen et al. 1994 ;
Khoo et al. 1995 ; Palmer et al. 1997 ; Jones et al. 1998 ; Corbeil et al. 2005 ; Timur
et al. 2013 ). Whether or not these organisms correspond with Piscirickettsia salmonis has not been always established. For example, Chern and Chao ( 1994 ) reported
that the RLO caused mass mortalities in tilapia from Taiwan during October 1992
to February 1993, with disease signs including the presence of white nodules and
microscopic granulomas on all the organs, and an enlarged spleen. Subsequently,
Comps et al . 1996 ) described a small coccoid organism from the brain of juvenile
sea bass obtained from the South of France. These were derived from a population
which suffered 20 % mortalities. Also, an RLO has been identifi ed among grouper
in Taiwan (Chen et al. 2000b ), tilapia (Mauel et al. 2003 ) and white sea bass in the
USA (Chen et al. 2000a ) and farmed Atlantic salmon in Tasmania and Canada
(Cusack et al. 2002 ). Moribund grouper displayed dark lesions, splenomegaly (with
white nodules), necrosis in the liver, kidney and spleen, and the blood was thin
(Chen et al. 2000b ). However, it is diffi cult from the literature to determine the signifi cance of the Tasmanian RLO to fi sh (Corbeil et al. 2005 ). RLOs were associated
with systemic granulomas in sea bass, with infected fi sh displaying anorexia and
lethargy leading to high mortalities (Timur et al. 2013 ).
An intracellular RLO has been linked with red-mark syndrome (Fig. 11.1 ) in the
UK and strawberry disease [an infl ammatory skin condition] in the USA as result of
immunohistochemistry using polyclonal antibodies to Piscirickettsia salmonis, a
quantitative PCR and 16S rRNA sequencing (Lloyd et al. 2008 , 2011 ; Metselaar
et al. 2010 ). However, intact cells of the pathogen have not been observed nor has
culturing been achieved, to date. Therefore, a question surrounds the interpretation
of the serological data. However, the disease appears to be spreading, and has now
bee reported to occur in farmed rainbow trout in Turkey (Kubilay et al. 2014 ).
11 Miscellaneous Pathogens