EFFECT OF DIETARY SUPPLEMENTATION WITH OREGANO (ORIGANUM VULGARE HIRTUM) AND ROSEMARY (ROSMARINUS OFFICINALIS) ESSENTIAL OILS ON FISH PARASITES IN GILHEAD SEA BREAM(SPARUS AURATA L.) AND EUROPEAN SEA BASS (DICENTRARCHUS LABRAX L.).
Introduction
Outbreaks of parasitic diseases act as major limiting factor for fish farming, meaning that producers have to make use of massive amounts of disinfectants in order to avoid economic losses. Fish culture is under pressure to decrease the use of chemotherapeutics because of the risk caused to humans by chemical residues in food. Use of herbal medicines within animal production has shown promise. Herbal medicines are natural, biodegradable and have antimicrobial activity against various pathogens, including fish pathogens. The essential oil of oregano has shown varying degrees of protection from infestations from myxosporean parasites in sea bream (Sparus aurata L.1758) and sharpsnout sea bream (Puntazzo puntazzo, Cetti 1977), (Athanassopoulou et al., 2004 a, b). Finally, in sea bass (Dicentrarchus labrax, L. 1758), the oregano essential oil , as dietary supplement, increased the protection against mixed infections of parasites (lice, copepods) and bacteria of the genus Vibrio spp. (Yiagnisis et al., 2009).
Materials and methods
Gilthead sea bream and European sea bass, 1-3g weight, reared in cages 7x7x8m with 10000 fish/cage for two months and three months respectively (summer time) with dietary supplementation of 0, 0.5%, 1% oregano essential oil and 0.5% and 1% rosemary essential oil. Before starting of the rearing, an examination of 50 fish from each cage, for parasite count, was held and all fish were free of parasites. The essential oils were diluted in fish oil and added to feeds. At the end of each experiment, 20 fish per cage were examined for parasites. Fresh smears from gills, bile and kidneys were examined under the microscope.
Results
At the end of experiment all concentrations of essential oils were effective in reducing parasites Furnestinia echeneis from the gills, compared to control. Better results gave the essential oil of 1% rosemary, decreasing by 60 times the average number of parasites / fish compared to the control, then the essential oil of 1% oregano reducing 8.5 times the average number of parasites / fish compared to control. The essential oil of rosemary gave excellent results in reducing myxosporean parasite Polysporoplasma sparis from the kidney of the sea bream. Specifically, the 1% concentration of the essential oil of rosemary eliminated the parasite, while the concentration of 0.5% of the oil reduced 10 times the parasite compared to control (Figure 1). The essential oil of oregano was not as effective as the essential oil of rosemary against Polysporoplasma sparis. Both essential oils induced small reduction in Sparicotyle chrysophrii parasites. For sea bass, both essential oils were effective against Diplectanum aequans and Lernarthropus kroyeri (Table I). The essential oil of oregano (both concentrations) gave the best results.
Discussion and conclusion
Both essential oils showed antiparasitic activity against different fish parasites. Although there are some studies about the antiparasitic action of essential oil of oregano, there is no report about the use of rosemary essential oil against fish parasites. This is the first report about the use of rosemary essential oil as antiparasitic for fish. Essential oils of oregano and rosemary are promising treatments for some parasitic infections in intensively cultured fish.
References
Athanassopoulou, F., E. Karagouni, E. Dotsika , V. Ragias, J. Tavla, P. ,Christofilloyanis,I. Vatsos,I., 2004a. Efficacy and toxicity of orally administrated anti-coccidial drugs for innovative treatments of Myxobolus sp. infection in sharpsnout sea bream Puntazzo puntazzo. Diseases of Aquatic Organisms, 62 (3), 217-226.
Athanassopoulou, F, E. Karagouni, E. Dotsika , V. Ragias, J. Tavla, P. Christofilloyanis,I.,
2004 b. Efficacy and toxicity of orally administrated anti-coccidial drugs for innovative
treatments of Polysporoplasma sparis Sitja-Bobadilla & Alvarez-Pellitero1885 infection in Sparus aurata L. Journal of Applied Ichthyology, 20 (5), 345-354.
M.Yiagnisis, M.N. Alexis, K. Bitchava, A. Govaris and F. Athanassopoulou. Effect of dietary oregano essential oil supplementation on combined infections by pathogenic bacteria-parasites (Sea lice and Copepods) in European sea bass Dicentrarchus labrax L., 2009. The 14th EAFP International Conference "Diseases of Fish and Shellfish", Sep 14- Sep 19, 2009, Prague, Czech Republic. Book of Abstracts, O-123 p.139.
