Isen Subich Maria Mercè


Business Development Manager Aquaculture Health at Nutriad International


Utilizzo di un integratore funzionale nell’alimentazione dell’orata come strategia per la prevenzione delle malattie da parassiti e la promozione della crescita

The impact of parasitic disease outbreaks, and the subclinical effects of its infections in aquaculture, are increasing recent years. Estimates of the world annual losses in finfish farming due to parasites range from one to 10 percent of harvest size, with an annual cost that can reach up to US$9.58 billion (Shinn et al., 2015). In Mediterranean fish farming, one of the major parasitic diseases is enteromyxosis, caused by Enteromyxum leei. This microscopic, internal parasite infects the intestinal tract of fish. Wide host range and geographical distribution makes this parasite a highlighted genus in terms of economic impact in aquaculture species, not only in the Mediterranean basin but also worldwide. Severity of enteromyxosis will vary depending on the host, production system, environmental conditions, etc. but the typical affection is reduced growth and emaciation. In gilthead sea bream (Sparus aurata), enteromyxosis has a chronic course leading to a cachectic syndrome with anorexia, anaemia, weight loss, severe epaxial muscle atrophy and, eventually, death. Direct mortality is most often moderate, being the reduction of growth (decreased SGR) and loss of the feed performance (increased FCR) the main drivers of the losses. There are no effective prescription medicines, nor vaccine available, so the application of good farm management practices is a must to avoid the disease economic impact.

Health management, aimed at disease prevention and avoiding the costs of disease and corrective measures, is becoming a must for the aquaculture industry to maintain its sustainable and profitable growth. As part of the health management strategy, health promoting feed additives such as herbal extracts, organic acids, etc. can make an important role not only improving fish resistance, also reducing pathogenicity of the parasite.

The effect a commercially available health-promoting feed additive (SANACORE ® GM) was tested during a laboratory controlled challenge with E. leei. Group performance and biometrical values were monitored, and an in-depth parasitological examination and quantification of parasite loads was carried out at the end of the trial. The results showed that the feed additive mitigated the anorexia and growth arrestment observed in fish with a basal diet. This effect was maximum in the higher dose feed, whose growth performance was not different to the unchallenged controls. Treated groups also presented lower prevalence of infection and a lower parasite load, although the differences in the mean intensity of infection were no statistically significant. Although the reduction of parasite levels was similar with both doses of additive tested, the pathogeny of the infection was mostly suppressed with the higher dose, while only mitigated in the lower dose. Lab results will be discussed in view of the results obtained in the field for this functional feed additive against Enteromyxum leei in Mediterranean seabream (Sparus aurata).



Effetti sul branzino di un integratore funzionale durante la stagione fredda

Health promoting feed additives have already become a standard ingredient in premium feeds for salmon and many other fish species. These functional feeds are designed to reduce the impact of fish diseases and parasites on productivity. A wide range of additives with different modes of action are currently offered to fish including yeast extracts, phytobiotics, probiotics, prebiotics, organic acids and their derivates. Functional feeds containing gut health promotors deliver with every meal an adequate concentration of natural compounds which can work through multiple mechanisms to reduce the success of the parasitic infestation or bacterial infection. Natural compounds with anti-parasitic activity can work directly on gut parasites or reach the blood and/or mucus to affect ecto-parasites, whereas immune modulators can change the composition and thickness of the mucus.

In this study, a tank trial was carried out in the Atlantic area of South Spain, at the fish farm Finca Veta La Palma, located at the centre of the Guadalquivir River’s estuary marshes. The farm produces European seabass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) in earthen ponds. The objective of the study was to determine the effect of a functional, phytobiotic feed additive on the performance and health of seabream and seabass throughout the changing culture conditions during winter and spring. The use of unfiltered, untreated brackish water originating from the pond farm resulted in a natural disease challenge throughout the trial and imitated the fluctuating environmental conditions encountered in the pond farm.

An unexpected gill fluke infection occurred during the month of February affecting only the seabass tanks. The diagnosis confirmed an ectoparasite infestation by Diplectanum sps as predominant species. A treatment with 100 ppm formaline bath was applied twice during the episode. Average mortality in this period was 11,15±6,74% for control groups (CF) and 4,05±4,66% for the treatment (S). No mortality was recorded in the seabream tanks and the evaluation of the gill wet mounts did not show the presence of any parasite. The histopathological analyses of European seabass gill samples indicate that the degree of gill injury between the CF and S groups were similar, however the impact of Trichodina infection was higher in the CF group. Similarly, impact of Epitheliocystis intracellular colonies was slightly higher in CF group. Prevalence of monogenean parasites (Diplectanum sps.) was low but monogenean related pathology was significant in this species. The gill damage score provides information on tissue response to insult (e.g. inflammation, lamellar hyperplasia, lamellar fusion and edema). Gill damage score was slightly higher in group CF (8,92) than in group S (7,75). With regard to liver injury, the score was markedly higher in group CF fish (4,57) in comparison to group S fish (2,40). Higher score was a consequence of a higher impact of lipidosis signs at moderate levels and focal degenerative/inflammatory lesions on group CF fish.

Concerning the microbial analyses, Richness (R) and diversity (H’) indexes showed an increased diversity of the microbial population present in the S group, for both European seabass and Gilthead

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