What is it about?

Skin flukes (Gyrodactylus) are common primary ectoparasites of fish, particularly in the koi hobby. Gyrodactylus graze on the fish’s skin and gills causing severe damage that can lead to heavy mortalities. A variety of medicines traditionally used for treating flukes including trichlorfon, praziquantel, flubendazole, formalin, and potassium permanganate proved ineffective in this pond, indicating the population of flukes were possibly multi-drug resistant. As a last resort, a novel way of using household vinegar as prolonged immersion method was devised and proved successful. The paper demonstrates the safe use of this technique and warns about the risks.

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Why is it important?

It is a method to treat koi infected with skin fluke parasites that have developed drug-resistance to normal medications used to eradicate them from fish ponds.


This method was devised through the practical experience of a fish veterinarian who noticed during his practice the absence of parasites when water conditions became acidic, below the pH of 5. This technique can only be used in fish species tolerant of acidic conditions, and only be conducted by experienced fish veterinarians.

Richmond Loh

Read the Original

This page is a summary of: A novel approach using vinegar to eradicate recalcitrant skin flukes in koi fish: a case report, Companion Animal, September 2023, Mark Allen Group,
DOI: 10.12968/coan.2023.0026.
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