In vitro antifungal activity of plant extracts on Saprolegnia parasitica from cutaneous lesions of rainbow trout (Oncorhynchus mykiss) eggs

Saprolegnia parasitica Coker is the main agent of saprolegniosis, one of the most important causes of economic losses in the rainbow trout farming industry in Iran. In this work, seven essential oils (2 species) and ethanol extracts (5 species) were tested against a strain of S. parasitica from cutaneous lesions of Oncorhynchus mykiss eggs, using a continuously agitated broth technique that allows both the minimum inhibitory concentration (MIC > 50 % ) and the minimum lethal concentration (MLC > 99.9 % ) to be evaluated. The essential oils of Thymus daenensis and Thymus khuzestanicum (MIC > 50 % = 0.63 µl ml -1 and MLC > 99.9 % = 22 µl ml -1 ) and ethanol extracts of Tanacetum parthenium and Mentha longifolia (MIC > 50 % = 31.25 and 62.5 µg ml-1 and MLC > 99.9 % = 600 and 550 µg ml-1, respectively) showed higher inhibition against S. parasitica than the other extracts. In general, our study suggests that natural products derived from some medicinal plants have the potential to be used as health rainbow trout eggs.