Life Vitamins

Ichthyopthirius multifilis (Ich) is the name of a ciliated protozoan that causes Ich disease in fish. It is an alarming disease for fish producers and aquarists alike. Ich is an important disease that affects goldfish, tropical fish, and food fish. It is highly contagious and rapidly spreads from one fish to another. It is particularly severe on dense populations of fish. It is found in the natural waters that abound in the southern US.

An important difference between the reproductive mechanism of Ich and other protozoans is that the former multiplies into hundreds of new parasites, whereas the latter reproduce by simple division. Unless immediate treatment measures are taken against an outbreak of Ich disease, 100% mortality of fish cannot be prevented.

Ich is the largest parasitic protozoan that affects fish. Adult organisms of Ich measure from 0.5 mm to 1 mm in size. They are oval to round in shape. Uniform cilia are observed all over the adult protozoon's body. A horse-shoe shaped nucleus can be found in older protozoans.

Ich needs a fish host so as to complete its life cycle. As a consequence, the parasites are passed from one fish to another. They cannot exist in a mass of water bereft of fish.

During their breeding stage, the Ich parasites form cysts between various layers of the host's skin. They appear to the naked eye as whitish to brownish spots on the fish surface. These are due to the mucus secreted at the site and the parasite itself. Due to these white spots, Ich disease is also known as the white spot disease. When the parasite matures, it comes out of the fish and reproduces into hundreds of baby parasites.

The baby parasites must find a fish host within a period of 48 hours at water temperatures in the range 75 to 79 degree Fahrenheit. Otherwise they face the prospect of death.

The identification of the Ich syndrome in fish is made through the characteristic white spots that appear on the skin or the gills of fish. They appear in the form of blisters on the fins or skin of affected fish. Even before the white spots appear, fish show signs of weakness, irritation, loss of energy, and decreased motility.

In case the parasites appear only on the gills, no white spots will be found on the skin, but large population of fish will die. The gills of such fish will appear very pale and swollen. At later stages, fish rub their bodies against rocks or gravel or scrape their skins against them.

White spots also appear in fish during some other diseases, so that cannot be used as the clinching evidence of Ich disease in fish. Skin scrapings and gill scrapings can help identify Ich disease in fish when the initial symptoms are observed in them.

The diagnosis of Ich disease in fish is confirmed by microscopic examination of skin and gill scrapings. This helps in taking immediate treatment measures.