Gastrointestinal Pathogenesis in Aquatic Animals - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 59

A B

C D

Fig. 3.4 Scanning electron microscopy images of ex vivo European sea bass intestinal Vibrio challenge.
Posterior intestinal sacs exposed to (A) PBS (as a control), (B) V. anguillarum ,(C) V. harveyi and (D) V.
alginolyticus. Bacteria were inoculated at log 7CFUml -1 for 1 h and incubated at 20 ∘ C. From a qualitative
perspective it is evident that V. anguillarum and V. harveyi caused more brush border damage,
characterized by necrotic enterocytes and disorganized microvilli, than V. alginolyticus , which seemed to
have a negligible effect. Scale bars = 10 μ m. (Source: Peggs et al ., unpublished.)

3.2.2 Vibrio salmonicida
Cold water vibriosis is a bacterial infection caused by Vibriosalmonicida (Egidius etal. 1986),
which has been reclassified as Aliivibrio salmonicida (Urbanczyk et al. 2007). The most sus-
ceptible species is Atlantic salmon in Norway, Scotland and the Shetland Islands, but the
disease has also been recorded in rainbow trout and Atlantic cod (Bruno et al. 1986; Press
and Lillehaug 1995). Pathological changes in experimentally infected Atlantic salmon include
pale liver, haemorrhagic swim bladder and intestine, and bloody fluid in the peritoneal cavity.
The bacterium is spread through the vascular system. In the early stages of the disease the
bacteria were noticed exclusively inside the vascular system. The most severe damage was
revealed in the heart, red muscle fibres and the lamina propria of the intestine (Totland et al.
1988). However, the intestinal epithelium showed no structural changes, suggesting that the
digestive tract is not the main infection route.

3.2.3 Vibrio vulnificus
Vibrio vulnificus is a bacterial pathogen virulent with respect to humans, eels, tilapia and
shrimp. The strains virulent for European eel are classified as biotype 2 (Fouz and Amaro
2003). The disease caused by these bacteria affects eels cultured in brackish (serovar E)
and fresh water (serovar A) (Fouz et al. 2006; 2010). Results obtained by Fouz et al.