Rediscovering Remedies: New Methods For Treating Velvet Disease

As EU countries consider banning many chemical therapeutants\r\nused in fish farming, researchers suggest using humic substances and hydrogen\r\nperoxide as sustainable and environmentally friendly treatments for parasitic\r\ndiseases.

In a recent article in Reviews in\r\nAquaculture, researchers have compared multiple treatments for\r\nvelvet disease, a parasitic infection that impacts both freshwater and marine\r\nfinfish. The review lays out the risks and benefits of existing treatments for\r\nvelvet disease and explores the new treatment options that could replace\r\nchemical-based therapies. Though they overwhelmingly concluded that additional\r\nresearch was needed to determine the best treatment for parasitic diseases, the\r\nresearchers suggested that hydrogen peroxide and peracetic could be used as\r\ntherapeutants that will not leave environmental residues. They also proposed\r\nutilising feed supplements (like pre- and probiotics) to reduce biological\r\nstress in fish. The review also highlighted the utility of humic substances\r\n(major components of natural organic matter) as natural immunostimulants.

Background

Velvet disease, also known as rust or gold rust disease, is\r\na parasitic infection that impacts warm-water fish. The parasite weakens the\r\nimmune system and causes skin damage. It also leaves the fish susceptible to\r\nsecondary infections. Since the EU’s regulatory frameworks governing disease\r\ntreatments in aquaculture are expected to change, there is an urgent need for\r\nalternative therapeutants. Currently, treatments for velvet disease and other\r\nparasitic infections contain copper, malachite green or methylene blue – all of\r\nwhich can be toxic to other organisms in the surrounding environment. These\r\ntreatments also leave residues in the water after they are used. An additional\r\nconcern regarding the use of chemical treatments is that over time, the target\r\nparasites become resistant to them.

Acknowledging the\r\ntrade-offs

The researchers found that hydrogen peroxide and peracetic\r\nacid degrade into harmless residues and could be classed as environmentally\r\nfriendly. Current literature has demonstrated that the substances can treat\r\nvarious pathogens, including parasites. However, since they have a high\r\noxidative capacity, their use could add to the stress levels of infected fish –\r\nmaking it less effective as a treatment.

Dietary supplementation with vitamins and biotics can reduce\r\nstress levels and make fish less susceptible to infections. However, there is a\r\nrisk of over-supplementation. The researchers concluded that more studies\r\nneeded to be conducted. Additional research would indicate the best method and\r\ndosage needed for dietary supplements to be effective in preventing and treating\r\nvelvet disease. The researchers found humic substances promising. Current\r\nstudies into the compounds have demonstrated that they improve growth,\r\nvitality, lifespan and food conversion rates in farmed fish. Research has also\r\nindicated that they increase overall immune health and could therefore make\r\nfish less susceptible to velvet disease. However, studies are still in their\r\npreliminary and pilot stages, so humic supplementation should not be viewed as\r\na magic bullet in disease treatment.

Recommendations

In general, the researchers recommended concentrating on two aspects of\r\ndisease prevention : Treat the invading parasite with a naturally-occurring substance, or\r\none that doesn’t leave a residue in the environment. Make the fish less susceptible to parasites through dietary and\r\nenvironmental fortification

Source : The Fish Site