What are protozoan diseases in pufferfish?

Pathogen: Cryptocaryon irritans, with a spherical or oval body similar to Ichthyophthirius multifiliis, measuring 0.066-0.45×0.034-0.36mm, covered entirely with cilia and generally having four bead-like macronuclei.

Epidemiology: Cryptocaryon irritans mainly parasitizes the gills, skin, fins and other parts of marine fish. It is prevalent in coastal sea areas from mid-May to August each year. The suitable breeding temperature for Cryptocaryon irritans is 20-25°C, and it is transmitted by *cysts and their larvae.

Symptoms: First, a large number of small white spots appear on the body surface. In severe cases, the fish body is covered with a layer of white film. Due to the destruction caused by the parasites, secondary bacterial infections can occur, resulting in inflammation and necrosis of the fish epidermis, scales that easily fall off, and fin rays that rot and split. When parasitizing the gills, it destroys the gill filaments, and after bacterial infection, it causes gill rot. When the parasites invade the cornea of the fish, it causes inflammation and blindness. Sick fish have reduced appetite, become thin, and swim erratically. The parasites can be identified by observation under a microscope.

Prevention and control methods: 1. Density should not be too high; 2. Soak sick fish in 0.4-1ppm malachite green for 5-10 minutes, then bathe again the next day; 3. Bathe in 60ppm formalin for 15-20 minutes, or for a planted tank, splash 20-30ppm over the entire tank; 4. Prepare insecticide powder with freshwater at 50ppm and soak for 5 minutes.