Agriculture Reference
In-Depth Information
3.2.1 Vibrio anguillarum
Vibrioanguillarum
, often named
Listonellaanguillarum
(MacDonnell and Colwell 1985), and
Vibrio ordalii
are important pathogens of salmonids, eels and marine fish (e.g. European sea
bass,
Dicentrarchus labrax
L.; sea bream; and turbot,
Scophthalmus maximus
), and are the
major causative agents of vibriosis (Pedersen
et al.
1999). The mode of transmission of the
bacterium has been studied in several species indicating that
V. anguillarum
can invade fish
epithelia at more than one site including the skin and the intestinal tract (Birkbeck and Ringø
2005; Toranzo
et al.
2005).
Grisez
et al.
(1996) investigated the infection route of
V. anguillarum
after oral challenge,
with live feed, to juvenile turbot. The technique was established by Chair
et al
. (1994) by
bioencapsulation of
V. anguillarum
in
Artemia
nauplii. High concentrations of bacteria could
be incorporated in this way (5 × 10
8
V. anguillarum
cells per 6000
Artemia
), and after feeding
turbot for 12 days a mortality rate of 61% was recorded. The bacteria were released from the
Artemia
mainly in the anterior part of the intestine (the section from the end of the pyloric
portion of the stomach to the beginning of the posterior intestine). Thereafter, the bacteria
were transported through the intestinal epithelium by endocytosis and released to the lam-
ina propria (Grisez
et al.
1996). From the lamina propria the bacteria were transported via
the blood to the liver. In another study spotted wolffish (
Anarhichas minor
Olafsen) fry were
bath challenged with
V. anguillarum
(Ringø
et al.
2006). As a result of infection, detach-
ment and loss of enterocytes were observed in both the foregut and the hindgut (Figure 3.1).
Loss of epithelial integrity allowed translocation of bacteria to the vasculature of the lamina
propria. Several studies have induced experimental infection of rainbow trout. Baudin
et al.
(1987) challenged rainbow trout by dipping in a suspension of
V. anguillarum
(10
5
bacterial
ml
-1
) and reported that the anterior and posterior intestines were both infected a few hours
after exposure, demonstrating contamination by both oral and anal routes. The adherence of
V. anguillarum
to the gut of rainbow trout has also been studied (Horne and Baxendale 1983).
Three distinct regions of gut - the anterior region with pyloric caeca, the posterior intestine
and the intervening section - were cut longitudinally and incubated with bacteria. Bacteria
adhered to the immersed gut sections. Bacteria consistently adhered in greater numbers to the
anterior and midgut regions followed by the oesophagus, stomach and lower gut. Interestingly
these differences were not found
in vivo
(Horne and Baxendale 1983) which may be related
to the different physicochemical environment
in vivo
. In a study by Sandlund
et al.
(2010) the
comparative susceptibility of turbot, halibut (
Hippoglossus hippoglossus
L.) and Atlantic cod
yolk-sac larvae to challenges with
Vibrio
spp. was investigated. The larvae were bath chal-
lenged with
V. anguillarum
serotypes O1, O2a and O2b. The O2a serotype was pathogenic to
all three fish species, while the O1 serotype was only pathogenic to halibut and cod. The O1
serotype produced more severe infections and necrosis and bacteria were present in a series of
tissues including the dermis, GI tract, brain and eye, while larvae exposed to the O2a serotype
had bacteria solely in the GI tract. In Japan, vibriosis was a huge problem for ayu (
Plecoglossus
altivelis
Temminck and Schlegel) aquaculture in the 1980s (Muroga and De La Cruz 1987).
Experimental infection of ayu by immersion in
V. anguillarum
resulted in bacterial popula-
tions present in skin, thereafter in muscle, spleen and liver and then in the gills and intestine.
Ransom
et al.
(1984) performed a comparative study regarding localization and histopathol-
ogy on waterborne infection of three species of Pacific salmon, the chum (
Oncorhynchus keta
Walbaum), coho (
Oncorhynchus kisutch
Walbaum) and Chinook (
Oncorhynchus tshawytscha
Walbaum) salmon, with
V. anguillarum
and
V. ordalii
. This study also presented data from
Search WWH ::
Custom Search