The nutritional background of the host alters the disease course in a fish–myxosporean system

Abstract

The aim of the present work was to determine if a practical plant protein-based diet containing vegetable oils (VO) as the major lipid source could alter the disease course when challenged with the myxosporean Enteromyxum leei, a wide-spread parasite in the Mediterranean basin causing heavy economic losses. Gilthead sea bream (Sparus aurata) fed for 9 months either a fish oil (FO) diet or a blend of VOs at 66% of replacement (66VO diet) were challenged by exposure to parasite-contaminated water effluent. All fish were periodically and non-lethally sampled to obtain biometrical data and to know their infection status. After 102 days of exposure, fish were euthanized and haematological, biometrical, histological, immunological, glutathione and anti-oxidant data were obtained from tissue, blood and serum samples. Anorexia appeared in both exposed groups, but feed intake reduction was higher in 66VO fish. The signs of disease (lower growth, condition factor, specific growth rate, haematocrit) as well as the disease course were worse in fish from 66VO group, with a higher prevalence and intensity of infection, a higher percentage of fish harbouring the parasite in the entire intestinal tract, and a faster establishment of the parasite. Parasite intensity of infection was negatively correlated with growth parameters and haematocrit in both groups, and with complement, lysozyme and hepatic total glutathione in 66VO fish.

Novel horizontal transmission route for Enteromyxum leei (Myxozoa) by anal intubation of gilthead sea bream Sparus aurata

“…The posterior intestine seems to be the first target site for Enteromyxum leei in gilthead sea bream, followed by the anterior portion. These differential preferences have also been observed in other infection routes, such as effluent (Estensoro et al 2010), cohabitation and even oral routes (Cuadrado 2009). Similarly, in natural infections, a higher prevalence of infection was found in the rectum than in the proximal intestine in asymptomatic fish (Fleurance et al 2008).…”

Molecular profiling of the gilthead sea bream (Sparus aurata L.) response to chronic exposure to the myxosporean parasite Enteromyxum leei

“…(Cuesta et al, 2006b;Sitjà-Bobadilla et al, 15 2006; Álvarez-Pellitero et al, 2008). In a subsequent study investigating the effects of gilthead sea bream nutritional status on E. leei disease progression, total serum peroxidases, lysozyme and nitric oxide were also significantly reduced in exposed fish fed either fish oil or a vegetable oil-based diet (Estensoro et al, 2011). Other immune parameters such as the phagocytic activity of macrophages and/or respiratory burst of leukocytes were also decreased in different hosts infected with other parasites (Mustafa et al, 2000;Fast et al, 2002;Scharsack et al, 2004;Karagouni et al, 2005).…”

A histology-based fish health assessment of farmed seabass (Dicentrarchus labrax L.)

“…It is known that the intestinal epithelium is an important site for the absorption of nutrients, immunity, osmotic balance, recycling of enzymes and macronutrients (Alvarez-Pellitero, 2011;Urán et al, 2008) and the distal intestine is the principal site for the endocytosis of proteins (Rombout et al, 1985). On the other hand the increased use of plant feedstuffs in farmed fish diets can affect the gut integrity and increase the deleterious effect of gut pathogens (Couto et al, 2014;Estensoro et al, 2011;Mourente et al, 2007;Oliva-Teles, 2012;Urán et al, 2008). Integrity of intestine is assumed to be a key factor for the growth and welfare of farmed fish.…”