Tapeworms (Cestodes): causes, symptoms and treatment

Tapeworms (Cestodes) (Bothriocephalus acheilognathi and other Cestoda) — etiology, symptoms, diagnosis, active-substance medication, recovery and prevention; mortality without treatment: moderate.

Overview

Segmented intestinal tapeworms acquired via copepod or other intermediate host. Common in wild-caught fish; cause emaciation despite normal appetite. Causative agent: Bothriocephalus acheilognathi and other Cestoda. Transmission: nutritional. Incubation: 30-90 days. Reported mortality without treatment: moderate.

Symptoms

emaciation despite eating
swollen abdomen
white segments in feces
loss of appetite over time
anemia
stunted growth

Causes

Outbreaks are typically triggered by chronic stress, poor water quality, temperature swings, overcrowding, or the introduction of unquarantined fish. The pathogen spreads via ingestion of infected intermediate hosts (copepods, tubifex, snails) or contaminated feed. The agent is not directly contagious between cohabitants, but it shares risk factors with the rest of the stock.

Diagnosis

Diagnosis is based on clinical signs (visible worms, white stringy feces, weight loss despite eating) and microscopic examination of fresh faeces for eggs or fragments of Bothriocephalus acheilognathi and other Cestoda.

Treatment

Effective treatment requires isolating affected fish in a quarantine tank, identifying the pathogen, administering the appropriate active substance at the correct dose and duration, and supporting recovery with stable water parameters and nutrition.

Step 1: Quarantine

Set up a bare-bottom quarantine tank with a mature sponge filter, heater, and aeration. Match temperature and pH to the display tank, and acclimate fish slowly. A bare bottom simplifies daily siphoning and prevents medication from being absorbed by substrate.

Step 2: Medication

Praziquantel in food. Praziquantel-soaked food at 400 mg/kg fish daily for 3-5 days; in-water 2.5 mg/L for non-feeding fish. (duration: 3-5 days)

Step 3: Recovery

After medication, perform a 30-50% water change and run fresh activated carbon for 24-48 hours to remove residues. Continue feeding a high-quality, varied diet with vitamins and immunostimulants. Reintroduce fish to the display tank only after at least one week without recurrence of symptoms.

Prevention

quarantine wild-caught fish with prazi
freeze live foods 7 days before feeding
avoid feeding wild copepods
general cure prophylaxis