Gastrointestinal Pathogenesis in Aquatic Animals - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 66

by feeding contaminated fish (Kawahara and Kusuda 1987). Sea bass exposed to P. damsela
subsp. piscicida bacteria in dialysis tubing, surgically implanted in the abdominal cavity,
revealed necrosis of intestinal cells in the lamina propria and submucosa with infiltration
of inflammatory cells (Poulos et al. 2004). Strong adhesion of the bacteria to intestines of
sea bream, European sea bass and turbot was demonstrated by Magarinos et al. (1996b).
Furthermore, infection with P. damsela induced intestinal inflammatory responses as shown
by modulated expression of TNF-α and IL-β mRNA (Montero et al. 2010).
3.9 STREPTOCOCCOSIS
Streptococcosis is a septicaemic disease that affects both farmed and wild fresh and marine
water fish. The disease has been reported in turbot, yellowtail, Japanese eel, striped bass
( Morone saxatilis Walbaum), striped mullet ( Mugil cephalus L.) and menhaden ( Brevoortia
patronus Goode) (Kusuda and Salati 1993; Romalde etal. 1996). The causative agents of strep-
tococcosis include Lactococcus garvieae , Lactococcus piscium , Streptococcus iniae , Strep-
tococcus agalactiae , Streptococcus parauberis , Enterococcus spp. and Vagococcus salmoni-
narum (Toranzo et al. 2005). Possible routes of infection have been investigated by bath
exposure and intragastric inoculations with food and faeces contaminated with an Enterococ-
cus strain isolated from diseased turbot (Romalde et al. 1996). The invasive capacity of the
bacterium was limited after bath challenge. However, intragastric inoculations with contam-
inated food or faeces established an infective state that resulted in mortalities 16 to 20 days
after inoculation (Romalde et al. 1996).
3.10 ' CANDIDATUS ARTHROMITUS '
' Candidatus arthromitus ' is the name of a Gram-positive endospore-forming segmented fila-
mentous bacterium (SFB), the causative agent of rainbow trout gastroenteritis (RTGE) occur-
ring predominantly in the summer season (Michel et al. 2002). No formal taxonomic criteria
are applicable due to the unculturability of the bacterium (Michel et al. 2002; Manzano et al.
2010). The disease was first described in France in 1992 and then in Spain, Italy, the United
Kingdom and Croatia (Del-Pozo et al. 2009; 2010a). Autopsies of RTGE infected fish reveal
acute enteritis with a haemorrhagic and oedematous intestinal mucosa. Pathological changes
also include multifocal detachment of the mucosal layer resulting in a direct exposure of the
lamina propria to the digestive lumen (Del-Pozo etal. 2010b). The whole digestive tract includ-
ing the stomach and pyloric caeca may be filled with a mucoid material (Michel et al. 2002).
Most affected fish contained segmented filamentous bacteria in the distal intestine and pyloric
caeca. These bacteria were also observed in some apparently healthy fish although in lower
numbers than in fish affected with RTGE (Del-Pozo et al. 2010b; 2010c).
3.11 MYCOBACTERIUM spp.
Mycobacteriosis is a common disease in both wild and captive fish. Over 167 species
of fish have been documented to be susceptible to mycobacteriosis (Jacobs et al. 2009).