468
There were white nodules in the heart, kidney, liver (swollen) and spleen (swollen).
The intestinal mucosa was thickened. Some fi sh had bloody ascites (Olsen et al.
2006 ). Francisellosis has become associated with a chronic infl ammatory granulomatous disease (= visceral granulomatosis) in which the affected fi sh contain large
numbers of intracellular Gram-negative cocco-bacilli (Mikalsen et al. 2007 ; Zerihun
et al. 2011 ; Gjessing et al. 2011 ). Since the 1980s wild caught cod have been fi shed
sporadically from the southern North Sea, and thought at the time to be infected
with mycobacteria. Farmed cod with similar disease signs have been subsequently
recovered. Therefore, it is concluded that the disease in wild fi sh pre- dates that in
farmed animals (Zerihun et al. 2011 ).
In Japan, the marine fi sh species, three-line grunt (Parapristipoma trilineatum)
was observed with white granulomas. Intracellular bacteria were found in the kidney and spleen from which DNA was extracted and small subunit rRNA amplifi ed
by PCR, and sequenced. The outcome was 97.3–98.5 % homology to Francisella,
with Francisella philomiragia as the closest neighbour (Kamaishi et al. 2005 ).
In a third study, Francisella -like bacteria were associated with mortalities in
freshwater-reared (water temperature = 20–29 °C) hybrid striped bass. Here, the fi sh
became lethargic, darker pigmented and demonstrated skin haemorrhages over the
abdomen, mild to moderate bilateral exophthalmia, swollen kidney and spleen, and
interstitial granulomas (Ostland et al. 2006 ).
550–60 % mortalities have been attributed to farmed tilapia in Costa Rica when
infected fi sh displayed a range of non-specifi c signs including anaemia, anorexia,
erratic swimming and exophthalmia (Soto et al. 2009 ).
Characteristics of the Pathogen
A Gram-negative intracellular cocco-bacillary organism was recovered from farmed
Atlantic cod in Norway during 2005, and equated with Francisella (Olsen et al.
2006 ). Seven cultures were examined by phenotypic and molecular methods resulting in a proposal for a new subspecies, i.e., Francisella philomiragia subsp. noatunensis to accommodate them (Mikalsen et al. 2007 ). This became re-classifi ed as Fr.
noatunensis (Ottem et al. 2009 ; Mikalsen and Colquhoun 2010 ).
Box 8.1: Francisella noatunensis
Cultures develop initially small convex, opaque colonies on cysteine heart
agar at 22 °C but not at 37 °C. These colonies comprise non-motile, small
(variable sizes), weakly Gram-negative strictly aerobic, weakly catalase positive, oxidase negative, non-haemolytic, H 2 S producing, facultatively intracellular cocco-bacilli, which grow at 10–30 °C optimally at 22 °C, and only
slightly at 30 °C. Acid and alkaline phosphatase, esterase C4, esterase lipase
C8, ß-lactamase and naphthol-AS-BI-phosphohydrolase are produced. Acid
is not produced from a variety of carbohydrates, namely arabinose, glucose,
maltose, mannitol, ribose, sorbitol, sucrose or trehalose.
8 Francisellaceae Representatives
There were white nodules in the heart, kidney, liver (swollen) and spleen (swollen).
The intestinal mucosa was thickened. Some fi sh had bloody ascites (Olsen et al.
2006 ). Francisellosis has become associated with a chronic infl ammatory granulomatous disease (= visceral granulomatosis) in which the affected fi sh contain large
numbers of intracellular Gram-negative cocco-bacilli (Mikalsen et al. 2007 ; Zerihun
et al. 2011 ; Gjessing et al. 2011 ). Since the 1980s wild caught cod have been fi shed
sporadically from the southern North Sea, and thought at the time to be infected
with mycobacteria. Farmed cod with similar disease signs have been subsequently
recovered. Therefore, it is concluded that the disease in wild fi sh pre- dates that in
farmed animals (Zerihun et al. 2011 ).
In Japan, the marine fi sh species, three-line grunt (Parapristipoma trilineatum)
was observed with white granulomas. Intracellular bacteria were found in the kidney and spleen from which DNA was extracted and small subunit rRNA amplifi ed
by PCR, and sequenced. The outcome was 97.3–98.5 % homology to Francisella,
with Francisella philomiragia as the closest neighbour (Kamaishi et al. 2005 ).
In a third study, Francisella -like bacteria were associated with mortalities in
freshwater-reared (water temperature = 20–29 °C) hybrid striped bass. Here, the fi sh
became lethargic, darker pigmented and demonstrated skin haemorrhages over the
abdomen, mild to moderate bilateral exophthalmia, swollen kidney and spleen, and
interstitial granulomas (Ostland et al. 2006 ).
550–60 % mortalities have been attributed to farmed tilapia in Costa Rica when
infected fi sh displayed a range of non-specifi c signs including anaemia, anorexia,
erratic swimming and exophthalmia (Soto et al. 2009 ).
Characteristics of the Pathogen
A Gram-negative intracellular cocco-bacillary organism was recovered from farmed
Atlantic cod in Norway during 2005, and equated with Francisella (Olsen et al.
2006 ). Seven cultures were examined by phenotypic and molecular methods resulting in a proposal for a new subspecies, i.e., Francisella philomiragia subsp. noatunensis to accommodate them (Mikalsen et al. 2007 ). This became re-classifi ed as Fr.
noatunensis (Ottem et al. 2009 ; Mikalsen and Colquhoun 2010 ).
Box 8.1: Francisella noatunensis
Cultures develop initially small convex, opaque colonies on cysteine heart
agar at 22 °C but not at 37 °C. These colonies comprise non-motile, small
(variable sizes), weakly Gram-negative strictly aerobic, weakly catalase positive, oxidase negative, non-haemolytic, H 2 S producing, facultatively intracellular cocco-bacilli, which grow at 10–30 °C optimally at 22 °C, and only
slightly at 30 °C. Acid and alkaline phosphatase, esterase C4, esterase lipase
C8, ß-lactamase and naphthol-AS-BI-phosphohydrolase are produced. Acid
is not produced from a variety of carbohydrates, namely arabinose, glucose,
maltose, mannitol, ribose, sorbitol, sucrose or trehalose.
8 Francisellaceae Representatives