After poor water quality, parasites are one of the next most important causes of disease in ornamental fish. Although many species of fish can and do become infested with many different species of parasites, there are definite trends in species susceptibility. These trends are useful for formulating prophylactic quarantine protocols and at the same time pose many questions regarding parasite life history, pathogenicity, and species integumentary and immunologic susceptibility.

At our facility, we have intensive breeding programs and also import a wide variety of wild caught fish from South America, Asia and Africa. Because we wholesale hundreds of species fish, only a sampling of 36 of the more common varieties are included in this presentation. Both imported fish and several of our farm bred and raised fish are represented.

A sample of fish from each batch, usually two to four individuals, is checked for several reasons. In the case of imported fish, new suppliers and new species are checked to establish most common parasite loads as an aid in formulating quarantine protocols. Also, fish coming in from our ponds are routinely checked to determine if holding periods must be extended to treat problems. Finally, and most obviously, fish are checked if problems begin to arise in previously healthy fish.

The sample period for this presentation was approximately one year. There are several biases, in that many protocols and most common parasite loads had already been established prior to the sampling period chosen, so that prophylactic quarantine protocols were already in effect. In addition, parasites which were easily identifiable on gross visual inspection, e.g. Ichthyophthirius, were often treated without a microscopic examination. Therefore, as in the case for Ich, actual prevalences were higher in many of these species. A more in-depth discussion as to who, what, where, when, and why will be given during the actual presentation.

Table 1.

Key for Table

Some interesting (but not comprehensive) trends

Goldfish, Otocinclus, decker cory, rainbow fish, spotted and figure 8 puffers, and raphael catfish are highly susceptible to monogenetic trematodes, such as Gyrodactylus. Cardinals, female bettas, and angelfish were relatively clean of external parasite loads (translation: potential bias for "well-ness checks" or water quality, bacteria or other problems most likely). Platies, bale sharks and clown loaches are relatively susceptible to Ich. Guppies are fairly susceptible to Tetrahymena and Oodinium. Kuhli loaches weren't dying most commonly because of external parasites.