Effect of essential oils of local medicinal plants on Saprolegnia parasitica

Objective: One of the most destructive oomycete pathogens on fish is Saprolegnia parasitica. It is endemic to all fresh water habitats around the world and is partly responsible for the decline of natural populations of fresh water fish. Saprolegnia parasitica Coker is the main agent of saprolegniosis, one of the most important causes of economic losses in the rainbow trout farming, affecting all developmental stages. Method & Materials: Essential oils from the aerial parts of seven medicinal plants (Zagross Mountains), used for the treatment of rainbow trout diseases in Iran, were screened for anti-Saprolgnia parasitica activity. The essential oils were obtained by water-distillation using a Clevenger-type system. The antimicrobial activity was carried out by using the serial dilution method. These plants included Thymus danensis (Lamiaceae), Thymus spp. (Ilam) (Lamiaceae), Tanacetum parthenium (Asteraceae), Mentah longifloia (Lamiaceae), Satureja bachteriacum (Lamiaceae), Hyssopus officinalis (Lamiaceae) and Myrtus communis (Myrtaceae). Results & Conclusion: The results showed that essential oils from 2 medicinal plants showed anti-Saprolegnia parasitica activity, including Thymus danensis and Thymus spp. (Ilam). In general, our study suggests that natural products derived from some of the medicinal plants have the potential to be used as health rainbow trout. The most active constituents (essential oils) of many spices having wide spectra of antimicrobial activity are aromatic phenolic compounds, such as thymol and carvacrol in oregano and thyme.