Protozoan disease

White spot or Icthyophthiriasis

• Causative agent is Icthyophthirius multifiliis
• Most dangerous fish parasite.
• Burrows beneath the fish skin and often kills them.

Symptoms:

• Small whitish nodules/cysts of 1 mm diameter appear on the skin, gills, and fins.
• In advanced stages, the entire body surface may become covered with nodules/cysts.
• Diseased fish swim and respond to stimuli slowly.
• Fish rub themselves against other objects or jump out of the water in the early stages.
• The parasite may invade the cornea causing inflammation and blindness.

Control:

• Disinfect the pond with quicklime ( 500 kg/ha), rear fry at a reasonable density, and quarantine and disinfect fingerlings before stockings.
• Immerse fingerlings in 6 ppm malachite green for half an hour.
• Formalin 1:5000 dip treatment hourly for one week.
• Pond treatment with CuSO₄ @ 0.5 ppm weekly.
• Dip the diseased fish in 2-3% common salt solution for about 2-3 min for one week.