Cestoda, Tapeworms, Cestodes.
Caryophyllidea, Caryophyllids. Worms several centimeters long, living in the intestines of fish. Livebearing toothcarps, barbs, and goldfish are susceptible. It is introduced with tubifex worms, daphnia, cyclops, and wild fish, though this happens rarely. Since the adult worm dies without an intermediate host, light infestations do not even require treatment.
Caryophylliasis.
A parasitic disease caused by tapeworms such as Caryophyllaeus fimbriceps, laticeps, and Khawia sinensis of the class Cestoidea. Fish become infected with these worms by eating tubifex. Mature worms parasitize the fish intestines, where they lay fertilized eggs. The eggs are released into the water with fish excrement, settle to the bottom, and develop embryos within 30-40 days. There, at the bottom, they are eaten by tubifex worms. Inside the tubifex, the larva sheds its protective shell and penetrates the body cavity of its new intermediate host.
Fish become infected by eating tubifex worms that harbor young parasites in their body cavities. In the fish intestine, the parasites grow intensively and in a month and a half to two months, reaching adult size, become sexually mature. Then the parasite’s development cycle repeats. It cannot spread further without an intermediate host. Many species of aquarium fish of all ages suffer from caryophylliasis, but livebearers (guppies, swordtails, platys, mollies), barbs, and varieties of goldfish are most susceptible. Worms rarely become a serious problem.
Symptoms: •— One of the clinical signs of the disease is fish emaciation. The parasitism of several caryophyllaeids in the intestine causes inflammation characterized by swelling of the mucous membrane. Sometimes intestinal blockage is observed. The second, less typical sign of caryophylliasis is an enlargement of the front part of the fish’s abdomen due to a large number of worms parasitizing the intestine, where they can live for up to a year, depending on the size and species of the fish. Scale protrusion is not observed. This sign is especially characteristic of males and juvenile fish, as abdominal enlargement in females is due to the presence of eggs.
Cases of perforation not only of the intestine but also of the abdominal wall of the fish have been repeatedly observed. In this case, some of the worms emerged through the rupture site of the abdominal wall with their posterior ends, while their anterior ends remained in the intestine, making it look like a bundle of white ribbons fluttering behind the fish. Fish become lethargic, swim near the surface, and lose their appetite. Movement coordination is impaired.
Treatment: Infected fish are destroyed. For treatment, one of the medications is added to concentrated foods: kamala (0.01 grams per fish, twice, every other 
day); phenasal or divermin (1% of food weight). A special granulated medicinal food containing 1% phenasal (cyprinocystin) can also be used (twice, with an 8-day interval). The medications are added to dry food.
Parasites can be removed using niclosamide (Niclosamid). The drug is best given to fish with agar-based food. The drug excreted with feces is toxic to fish at concentrations starting from 0.2 mg/l. Therefore, treatment should be carried out in a quarantine aquarium. Enough niclosamide should be added to the food so that its concentration in the excreta does not exceed 0.1 mg/l, i.e., no more than 10 mg of niclosamide can be given with food for a 100-liter aquarium. After treatment, the water must be changed and the substrate cleaned to remove fish excrement.
Prevention: It should be borne in mind that the disease can only occur in fish that have been fed tubifex worms. Feeding fish tubifex should be avoided whenever possible. Disinfection of tubifex with weak solutions of trypaflavine and table salt partially rids them of protozoa—the pathogens of ichthyophthiriasis, chilodonelliasis, costiosis, etc. These solutions do not kill caryophyllid larvae.
