Diagnosis
The diagnosis of "Ich" can easily be confirmed by microscopic examination of skin and gills. Remove several "white spots" from an infected fish, then mount them on a microscope slide with a few drops of water and cover with glass. The mature parasite is large, dark in color (due to the thick cilia covering the entire cell), and has a horseshoe-shaped nucleus which is sometimes visible under 100x magnification. The adult parasite moves slowly in a tumbling manner and is easily recognized. The immature forms are smaller, translucent, and move quickly.
Typical behaviours of clinically infected fish include:
- Anorexia (loss of appetite, refusing all food, with consequential wasting)
- Rapid breathing
- Hiding abnormally/ not schooling
- Resting on the bottom
- Flashing
- Rubbing and scratching against objects
A subclinically infected fish will not show any of these signs. For example, a healthy fish with a newly attached trophozoite will not yet have clinical disease. The trophozoite will not become visible to the naked eye until it has fed on the fish and grown to one or two millimetres. A trophozoite attached to the gills usually is not readily seen. A subclinically infected fish may initially only have a single trophozoite.
Read more about this topic: Ichthyophthirius Multifiliis