Trichodina spp.

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Trichodina species are ciliated protozoan parasites of marine and freshwater species of fish. In large numbers they can cause skin and gill disease and can ultimately lead to the death of the fish.

The organisms are saucer-shaped and have a prominent denticular (tooth-like) internal cytoskeleton ring.

Life Cycle

Certain species of Trichodina live in salt, brackish or freshwater areas. Some have a preference for the gill, some for the skin, and some parasitise both.

Trichodina species reproduce by simple binary fission. Most species are host specific and presumably spread from fish to fish by incidental contact between susceptible host fish, as well as through contact with the organism in the water column.

Clinical Signs

Infected fish may 'flash' in an attempt to scratch off the organisms. Superficial white lesions may appear on the body and the fins may become frayed.

Scales may loosen and opportunistic bacteria may lead to secondary infections causing ulcerations and erosions.

Fish may show respiratory compromise from damage to the gills.


Water quality parameters should be obtained for a base-line examination.

Skin scrapes of mucus from the skin surface may reveal rapidly spinning ciliated organisms.

Gill, fin and skin biopsies can also be examined and will reveal the organism.


As the life cycle is direct, a single treatment is usually adequate.

Chemical treatment is most commonly used: a formalin bath or a salt bath, copper sulphate or potassium permanganate.

Flushing the system may help reduce infestation levels.

Trichodina spp. Learning Resources
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Test your knowledge using flashcard type questions
Ornamental Fish Q&A 19


Lim, C. (2001) Nutrition and Fish Health Routledge

Rosenthal, K. (2008) Rapid review of exotic animal medicine and husbandry: pet mammals, birds, reptiles, amphibians, and fish Manson Publishing

Leitritz, E. (1980 Trout and Salmon Culture ANR Publications

Tucker, C. (1990) Channel Catfish Farming Handbook Springer

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