Table: Protistan Parasites of Fishes - Merck Veterinary Manual

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Protistan Parasites of Fishes

Protistan Parasites of Fishes

	Parasites	Tissue	Susceptible Species	Signs	Diagnosis	Treatment
External ciliates (motile)	Ichthyophthirius (FW), Cryptocaryon (SW)	Gills, skin, fins	All	White spot disease; no spots visible if on gills only	Wet mount	FW—formalin, CuSO₄; SW—formalin, Cu²⁺, decreased salinity, chloroquine (efficacy not completely demonstrated)
	Trichodina (FW, SW), Chilodonella (FW), Brooklynella (SW)	Gills, skin, fins	All	High respiration rate, piping, excess mucus, flashing, loss of condition	Wet mount	FW—formalin, CuSO₄; SW—formalin, Cu²⁺
	Tetrahymena (FW), Uronema (SW)	Skin, eye, muscle	All (“guppy killer”)	Mucus, flashing, intra-ocular lesions, exophthalmos	Wet mount	External as above; improve sanitation Internal: no treatment
External (sessile)	Ambiphyra, Apiosoma, Epistylus	Gills, skin, fins	Primarily pond fish	Excess mucus, flashing, piping, loss of condition	Wet mount	Formalin, KMnO₄, CuSO₄ Management—decrease crowding, correct sanitation
External flagellates	Ichthyobodo, Cryptobia (see also Internal flagellates)	Gills, skin, fins	All	Blue slime, flashing, piping, excess mucus, loss of condition	Wet mount	Formalin, CuSO₄, KMnO₄, salt
External dinoflagellates	Piscinoodinium (FW), Amyloodinium (SW)	Gills, skin	Tiger barbs, many marine fishes, including clownfish and red drum	Mortality, lethargy, piping; “velvet” (if on skin)	Wet mount	Copper sulfate, chloroquine (nonfood fish only); freshwater dips for marine food fish
Internal flagellates	Spironucleus	Intestine	All cichlids, bettas, gouramis, other aquarium fishes	Weight loss (anorexia), mortality of fry and juveniles	Wet mount	Metronidazole (nonfood fish only)
	Cryptobia iubilans	Stomach	African cichlids	Extreme weight loss, anorexia	Wet mount, histology	None; management—correct sanitation, feeding, stocking density, cull affected fish
	Trypanosoma	Blood	Wild-caught Ioricariids	Anemia, mortality	Wet mount	None
Coccidia	Various genera	Intestine	Multiple	Weight loss, mortality	Histology	Sulfamethazine (efficacy questionable)
Note: FW = freshwater; SW = saltwater