Performing a basic examination in fish - Veterinary Medicine
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Performing a basic examination in fish
You have the skills to care for fish, so take the opportunity to accept these aquatic creatures as patients. Be sure to explore husbandry issues, since inappropriate care is often the underlying cause of many disorders in fish.


Copepods are another group of parasitic crustaceans with a diversity of body forms with variable appendages. An example is Lernaea species (anchor worm), which is an elongated copepod that embeds its head into the skin of fish, leaving its Y-shaped egg sacs to hang from the fish. These sacs can easily be seen grossly. The anchor worm has a direct life cycle and lives in fresh water.

Figure13: Argulus species infestation on the caudal fins of a goldfish. The parasite has a flattened, saucer-shaped appearance.
Organophosphates are the typical treatment for parasitic crustacean infestations. Dichlorvos and trichlorfon are the most commonly used organophosphates for treating fish with parasitic crustacean, monogenean, or leech infestation. Trichlorfon (0.5 to 1 mg/L) as a prolonged immersion or dichlorvos (0.5 to 2 mg/L) as a 30-to 60-minute bath is effective.1,2 Diflubenzuron (Dimilin—PondCare) is a chitin synthesis inhibitor that when used at a dose of 0.01 mg/L as a prolonged immersion treatment can also rid fish of crustacean copepod infestation.

Terry W. Campbell, MS, DVM, PhD
Department of Clinical Sciences
College of Veterinary Medicine and Biomedical Sciences
Colorado State University
Fort Collins, CO 80523


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8. McAllister PE. Goldfish, koi, and carp viruses. In: Stoskopf MK, ed. Fish medicine. Philadelphia, Pa: WB Saunders Co, 1993;478-486.

9. Hedrick RP, Gilad O, Yun S, et al. A herpesvirus associated with mass mortality of juvenile and adult koi, a strain of common carp. J Aquatic Anim Health 2000;12:44-57.

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