Control Methods for Ichthyophthirius multifiliis Disease in Farmed Yellow Catfish

(1) Pathogen: Ichthyophthirius multifiliis.

(2) Symptoms: On the skin, fins and gills of diseased fish, small white cyst-like spots can be seen with the naked eye; in severe cases, the body surface appears to be covered with a white film. Diseased fish respond sluggishly or float at the water surface. Due to bacterial infection at the affected sites, the fish body surface becomes inflamed, or locally necrotic, scales fall off, fins split diagonally, gill epithelium proliferates, and death occurs due to impaired movement and difficulty breathing in the gill area.

(3) Prevalence and harm: Ichthyophthirius multifiliis parasitizes the gills and body surface of yellow catfish. The suitable water temperature for reproduction of Ichthyophthirius multifiliis in yellow catfish is 15-25°C, pH 6.5-8; outbreaks are rare in summer. When stocking density is excessive and feed is insufficient, and when fish are thin and weak, they are particularly susceptible to infection by Ichthyophthirius multifiliis.

(4) Control methods

① Production measures such as clearing ponds with quicklime, disinfecting fingerlings, and rational stocking can prevent the spread of Ichthyophthirius multifiliis disease.

② Soak diseased fish in formaldehyde at 60-80 mg/L for 10-18 minutes (adjust flexibly according to water temperature), soak again the next day, and transfer to another pond for rearing. Thoroughly disinfect the original pond with formaldehyde. This method is only effective in the early stages of the disease; if detection is late and the diseased fish are covered with small white spots, even with continuous medication, the loss of fry and fingerlings will still be very large.