Trichodina or Trich sturgeon parasite

Trichodina or commonly called Trich by koi keepers is another parasites that you can't see without a microscope. If infected your fish's immunity system will be run down and other complications such as ulcers, fin rot and other bacterial infections will take hold.  It is similar in habit to Costia and Chilodonella.  All three are microscopic and are basically treated with the same medications that kills (ichIchthyophthirius or white spot).  Trichodina is not as common as the others and is not quite as dangerous though it still sets the koi or goldfish up for other problems.Trichodina is a microscopic protozoan parasite measuring 50 - 100µm in diameter. As trichodina moves it spins in circles, from the side it looks like a spinning flying saucer. Trichodina continually spins and can quickly change from place to place on the fish.

On the underside of Trichodina there is a complicated attachment organ known as the adhesive or sucking disk. It can be easily seen at 100x magnification. When seen from above three concentric rings are apparent. The inner ring is composed of hook-like structures called denticles, called the denticular ring or corona. The middle ring or striated band overlaps these hooks. The outer ring is composed of a flexible, thin membrane bordered with hairlike organs (cilia). The parasite moves about it’s host by means of the ciliary girdle, which also serves to propel it through the water.

Life Cycle

 Trichodina reproduce by both binary fission (dividing in two) and conjugation, it appears that reproduction is not a simple procedure for these protozoa. Fish have a resistance to the propagation of parasites, but bad conditions in the pond is an ideal environment for Trichodina. As the fish makes more mucous to protect itself, so the bacteria will increase and in so doing will provide ideal conditions for the propagation of Trichodina. Presence of large numbers of this parasite is indicative of poor water quality and/or overstocking and often occur with other ectoparasites.

Symptoms

fish take on a milky appearance due to an increase in mucus secretion
flashing and rubbing
lethargy in those fish who are seriously affected
ceasing feeding
sitting on the bottom with their fins clamped

As fish react to Trichodina in the same way as they do to other parasites by flashing and rubbing the only way to make a definite diagnosis is to examine a skin scrape under the microscope.

Although Trichodina does not feed on the fish and is quite harmless at low levels, in large numbers they can be very irritating to the fish and the sucking discs used by Trichodina to attach itself can cause tissue damage leading to secondary infections. Severe infestation of the gills can lead to suffocation.

Treatment

Before using any treatment please take into account the fish being treated. Not all treatments are safe with all fish.
Chemical treatments for Trichodina include Formalin, Malachite Green, Chloramine-T and Potassium Permanganate.
 Do not use Formalin, Potassium Permanganate or any treatments that state not to be used with Golden Orfe (Leciscus sp.) or Rudd (Scardinius reythrophathalmus) if you have sturgeon in your pond!

Chloramine-T or Malachite Green can be used in a pond containing sturgeon but do not use a Malachite and Formalin mixture.

Proprietary treatments available for the treatment of Trichodina, most of which are based on the chemicals mentioned above. Always check the labels to make sure the treatment is suitable for your fish. If in doubt consult a vet. Do not overdose. Chemical treatments are toxic not only to the parasite but also to the fish, especially those already weakened by disease. It is recommended that extra aeration is used when treating fish and reduce feed levels.

What to Expect Next

Once Trichodina is eradicated from your pond you should not have any residual affect from either the parasite or the treatment except maybe that the fish have been stressed so that they are susceptible to anything that may come along.  Just be "gentle" with the fish for a while and keep an eye out for ulcers or other problems that arise when fish are stressed. Remember secondary infection from bacteria is a possibility.