10.11. Tapeworms

There is a close relative of flukes known as tapeworms. Tapeworms live in the digestive tract of a fish as adults. The larval stage of some species of tapeworms live inside the body cavity of the fish. In other fish tapeworms, snails and even birds can harbor the larvae stages. Per Norbury 2022;

“Cestodes, known as tapeworms, are endoparasites. Due to their complex life cycle, cestodes are not common parasites in most aquaculture systems. The adult parasite typically resides in the digestive tract, and adult cestode infections in fish are usually asymptomatic.”

Signs of tapeworms include many of the symptoms of many other diseases of fish, like hollow belly, dropsy, bloat and swim bladder problems. But tapeworms are found in fish which just don’t “thrive” and are smaller and thinner than their tankmates.

The only way to diagnose tapeworms is by examining the feces of the fish under a microscope. Even then the segments shed by a tapeworm are rarely seen. As a result, this is a disease a home fish keeper will rarely know they have.

Many breeders just automatically “deworm” all the fish they get in their quarantine tanks. They give three treatments two weeks apart. Praziquantel in the food is the drug of choice. They normally mix the praziquantel with levamisole or fenbendazole to pick up nematode worms. This is an excellent idea if one can get the medications.

It is easy to make medicated food. Heat 1/4 cup water (two ounces or 58 milliliters, not a lot) in the microwave. Then blend seven grams of plain animal derived gelatin (Knox gelatin, one packet) into the hot solution with vigorous stirring. Take two tablespoons of dry commercial fish food (pellets or flake) and mix it with just a little of the hot water/ gelatin mixture. Add hot water/gelatin until you get a paste like consistency. If it gets too watery just add more food. To get gel food to float simply mix in a little whipped cream at this point.

Then add roughly 1/16 teaspoon (a 1% to 2% addition) of the medication to the mud. Mix and mash the whole mass thoroughly.  Spread it out into a pancake about 1/8th inch (3 mm) thick on a plastic film or a plate. Then put in the refrigerator. If you plan on keeping it for more than two weeks put it in a small plastic bag and freeze.

Feed it to your fish once every two weeks for at least one month (I do three months).

Studies other than Medication in the Food

There are some studies of Praziquantel (Norbury 2022) which show PZQ to be effective against cestodes when used as a bath treatment. Most of the fish involved were known mulm eaters, like the grass carp. The mechanism is that PZQ is insoluble in water. When added to water as a powder or as a solution in alcohol it precipitates into the mulm where it is ingested.

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