Chilodonella fish parasite

Chilodonella is a ciliated ( having small hairlike organs) protozoan that causes infected fish to secrete excessive mucus. Infected fish may flash and show similar signs of irritation. Many fish die when infestations become moderate (five to nine organisms per low power field on the microscope) to heavy (greater than ten organisms per low power field).
Chilodonella is easily identified using a light microscope to examine scrapings of skin mucus or gill filaments.

Life Cycle

Chilodonella is capable of surviving over a wide temperature range but prefers a range of 5-10 degrees C, this gives it an advantage in early spring over the fishes immune system. As is true of many parasites, it can reman dormant for long periods, waiting for favourable conditions.

Reproduction is asexual, usually by binary fission (cell division) but they can also reproduce by conjunction.

Symptoms

These are not exclusive to Chilodonella and may also be caused by other parasites and/or environmental conditions. Chilodonella may also be found on fish that have already been weakened by other parasites.

Chilodonella will mainly affect the gills and the area between the head and the dorsal fin. Fish that are infected will present as lethargic, gasping at the surface of the water. They will show increased gill movements, rigid fins and will flash and rub themselves. Due to an increase in the production of mucus the skin will have an almost milky appearance. In particularly severe infestations the skin may be swollen and flake off.

The examination of skin and gill scrapes under a microscope is needed to make a positive diagnosis. Chilodonella will leave the host immediately after death so it is unlikely that you will find it in scrapes taken from dead a fish.

Treatment

Please note
Before using any treatment please take into account the fish being treated. Not all treatments are safe with all fish.

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!

Acriflavine can be used with sturgeon.

Also be aware that fish weakened by extreme infestation may not survive the treatment, coupled with this is the fact that Chilodonella can be resistant to treatment, so mortality rates may be high.

Chemical treatments to use include Malachite & Formalin, salt baths or Acriflavine with salt. However, salt should not be used with zeolite filters as it will cause the release ammonia, nitrite etc back into the water. It will also kill any plants.

If in doubt about wether or not a treatment is suitable, consult a vet. Do not overdose. These are chemical treatments, and as such, are toxic not only to the parasite but also to the fish. It is sensible practise to add extra aeration and reduce feed levels when treating with chemicals.

Be cautious before using any chemical treatments. Symptoms, such as flashing, may be caused by high nitrite levels. Adding chemicals in these circumstances will do more harm than good. It is advisable to test the water quality before using any treatment.

Prevention

Prevention is better than cure as with all parasites and disease. Healthy fish will be able to fight off most diseases and parasites. Poor water quality, overcrowding and poor nutrition will cause stress and weaken the immune system.