Effects of dietary supplementation with oregano essential oil on prevention of the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae in juvenile chum salmon Oncorhynchus keta

Abstract

The present study performed three experiments to establish a practical prevention strategy for the ectoparasitic flagellate Ichthyobodo salmonis and ciliate Trichodina truttae in hatchery-reared juvenile chum salmon Oncorhynchus keta using dietary supplementation with oregano essential oil. Experiment 1 showed that a diet supplemented for 3 weeks with 0.02% oregano essential oil significantly prevented infection with I. salmonis and T. truttae in juveniles reared in small tanks. Experiment 2, in outdoor hatchery ponds, demonstrated that the oregano treatment completely prevented I. salmonis infection for 52 days and T. truttae infection for 38 days. Oregano-treated juvenile mortality attributable to infection with these protozoans also decreased to 7.6% of control juvenile mortality, confirming the utility of this treatment in cultured O. keta. Physiological analyses of the oregano-treated juveniles elucidated the treatment's safety in relation to their metabolism, osmoregulation, natural immunity and olfactory responses and also detected carvacrol (a major component of oregano essential oil which shows antimicrobial activity) on the skin. In experiment 3, exposure of the two protozoans to oregano essential oil revealed a weak antiparasitic action on the body surface of the juvenile O. keta. The overall results demonstrate that dietary oregano supplementation is a practical prevention strategy for I. salmonis and T. truttae in hatchery-reared juvenile O. keta and suggest the possibility that its anti-parasitic action is attributable to a component of the oil that emerges onto the skin of the body of the fish.

New Tricks for Old Guys: Recent Developments in the Chemistry, Biochemistry, Applications and Exploitation of Selected Species from the Lamiaceae Family

“…damselae of four EOs ( Origanum vulgare , Eucalyptus globulus , Melaleuca alternifolia and Lavandula angustifolia ) was evaluated by Gholipourkanani and coworkers All treatments showed antibacterial activity, and in almost all cases, the activity of the nano‐emulsions was superior to their essential oil counterparts. Origanum essential oil had a pronounced influence on the innate immunity and increased the Tilapia zillii resistance to Vibrio anguillarum and dietary supplementation with 0.02 % oregano essential oil is a practical prevention strategy for Ichthyobodo salmonis and Trichodina truttae infection in Oncorhynchus keta . Finally, a relevant and promising study on the efficacy of several EOs against Pseudomonas spp.…”

“…Origanum essential oil had a pronounced influence on the innate immunity and increased the Tilapia zillii resistance to Vibrio anguillarum [267] and dietary supplementation with 0.02 % oregano essential oil is a practical prevention strategy for Ichthyobodo salmonis and Trichodina truttae infection in Oncorhynchus keta. [268] Finally, a relevant and promising study on the efficacy of several EOs against Pseudomonas spp. isolated from fish was conducted by Kačániová et al, [269] suggesting that the EO may be used as natural compounds with antipseudomonal activity to improve the microbiological quality of freshly caught freshwater fish.…”

Gill amoebae from freshwater rainbow trout (Oncorhynchus mykiss): In vitro evaluation of antiparasitic compounds againstVannellasp.

“…This study confirmed the efficacy of garlic towards amoebae at a concentration of 16.9 mg/ml. As oregano essential oil has been shown to be effective in prevention of infection with Ichthyobodo and Trichodina in Oncorhynchus keta (Mizuno et al, 2018), we also tested oregano and found it to be effective in killing amoebae at a concentration of 17.9 mg/ml and partly effective at a concentration of 8.9 mg/ml. The bacterial lipopeptide surfactant H6 was previously shown effective against theronts of the ciliate Ichthyophthirius (Al‐Jubury et al, 2018), and it was lethal to Vannella sp.…”

“…Herbal constituents including crude extract of garlic ( Allium sativum ) and/or Origanum vulgare eliminated Trichodina sp. from tilapia ( Oreochromis niloticus ) (Chitmanat, Tongdonmuan, & Nunsong, 2005), from European eel ( Anguilla anguilla ) (Madsen, Buchmann, & Mellergaard, 2000), Ichthyophthirius multifiliis from rainbow trout ( O. mykiss ) (Buchmann, Jensen, & Kruse, 2003) and Ichthyobodo and Trichodina from Oncorhynchus keta (Mizuno et al, 2018). In addition, a bacterial lipopeptide, a biosurfactant isolated from Pseudomonas (strain H6), is able to kill the oomycete Saprolegnia diclina infecting fish eggs (Liu et al, 2015) as well as three life cycle stages of the pathogenic ciliate Ichthyophthirius multifiliis (Al‐Jubury et al, 2018).…”

Advances in our understanding of the parr–smolt transformation of juvenile salmon: a summary of the 10th International Workshop on Salmon Smoltification

“…Developing therapeutic programmes that are effective and do not have a deleterious influence on the aquatic environment is often difficult. Dietary supplementation with oregano essential oil reduced infection rate of two common ectoparasites of chum salmon Oncorhynchus keta (Walbaum 1792) in Japan, improved growth in freshwater and resulted in higher survival rates following transfer to seawater (Mizuno et al ., ).…”