14.03.2007

Ichthyophthiriosis - the White Spot Disease ICH

Temperature and salt treatment of the parasite Ichthyophthirius multifiliis

While for a long time no disease have occurred in my tanks, I have been a little bit too careless and mostly failed to consider a quarantine at the onset of new fish. Approximatly one week after a new acquisition of some fish I recognized scattered 1mm large white dots at the Kuhli Loaches. A short time later, the dots have also occurred in one of my breeding tanks at the Cape Lopez Killifish (Aphyosemion australe) and also in my large living room tank at various fish. Within a very short time the disease has also spread across three tanks, even before an outbreak of the disease were noticed.

The White Spot Disease (Ichthyophthirius multifiliis) is probably the most common disease in aquarium fish and is often compared with the commmon cold in humans. If left untreated, the disease causes in most cases the loss of the affected fish.

The Ichthyo often occurs shortly after new fish are placed into the aquarium. Then, the fish dealer is often accused of selling diseased fish. However, this is often not true, because in most aquariums there is a host-parasite equilibrium, that can not been seen and is not disturbing the fish. At the arrival of new fish, whose immune systems does not knwo the existing Ichthyo strain, that can multiply quickly and also affects the old stock. Conversely, the long-established fish are even not immune for unknown Ichthyo strains. Due to the fact that they are already settled, they are less susceptible to disease than the newly added fish. A quarantine of newly acquired fish would help therefore not necessarily.

Malachite green oxalate

After this happend, I was looking around for alternative treatment options. Since I have all my tanks equipped with biofilters and I don't want to poison my catfish and my shrimp, I did not use drugs. Commercially available drugs usually contain Malachite green oxalate. Malachite green oxalate is very toxic and a suspected carcinogen, therefore you should handle it very carefully. In addition, the drug damages the filter bacteria and is very sensitive to light. It is recommended to bypass the biofilter during treatment to prevent the death of the bacteria. In addition, both freshwater shrimp and catfish are responding sensitive to several drugs. Especially shrimp are affected by heavy metals (especially copper) in the water.

Life cycle of Ichthyophthirius multifiliis

To perform a successful treatment without commercial medicaments, one should the life cycle of the Ichtyo should be considered shortly:

Ichthyophthirius multifiliis is a ciliate like the familiar paramecium. The ectoparasite reaches in its vegetative form a size of up to 1 mm, which means that this disease can be diagnosed by observation. The parasite lives in the epidermis, which he only breaks for reproduction. Thereby the host can suffer from serious skin injuries. The parasite sinks to the ground beginning with the formation of cysts. By repeated cell divisions, up to 1000 so-called theronts ( also called swarmers) of 50 - 70 microns are created, which can again infect fish. After no more than 70 hours the swarmers must have found a host again. The duration of the reproduction process is temperature dependent. At 4 ° C, it takes about 6 days at 25 to 28°C only 10 to 12 hours. During the growth in the skin the pathogens can not been treated. The treatment must be directed directly against the free-swimming swarmers. Fish that have survived a White Spot Disease often develop a strong immunity against the pathogen strain.

Salt treatment plus temperature increase

For the above reasons, I did not perform a treatment with Malachite green oxalate, and have decided instead to pursue a salt treatment with temperature increase

The advantages of salt as a medicament are:

On the search for a possible pure salt without impurities that cause turbidity of the water, I found dishwasher salt. This salt must be very pure, to protect the sensitive ion exchanger in the dishwasher. During the solution of this salt the water keeps crystal clear, as with the use of sea salt.

The effect of salt addition is a shift of the ion spectrum and the osmotic conditions in the water. Protozoa can much worse adapt to that than fish, so salt is slightly disinfectant. The mucus production of the fish skin is stimulated so that it is more difficult for the swarms to infect the fish.

The increase in temperature acts directly on the temperature sensitive swarms. The higher the temperature, the faster the swarms are dying. This has already been well demonstrated at an aquarium strain of the parasite at a temperature of 28°C. An increase to 30°C should be in any case sufficient if the fish tolerate that.

Therapy

In the literature, a concentration of 3 g salt per 10 liters of water is given as a therapeutical effective dose. I have put this dosage in two stages to preserve the filter bacteria. Therefore I have used a level teaspoon that is equivalent to about 3g salt. Because my fish have tolerated this salt concentration without problems, I have carefully add more salt in several stages up to about 6 g/10 l.

The temperature was raised within 24 hours at 30°C. Ventilation appeared to be not necessary, because the fish have not been in respiratory distress. The plants have provided the water in the treated tanks with sufficient oxygen and in the breeding tank an air-driven mat filter was installed.

It is often reported that certain fish species do not tolerate such a temperature and / or salinity increase. The following species have easily overcome at me an increase in temperature to 30 °C and a salinity of 6 g salt per 10 l water.

Especially the neon and the armored catfish are often rumored that they tolerate salinization poorly. The killifish and the cardinal fish should be sensitive to high temperatures, but I can not confirm this assumptions.

After two weeks no more dots could be seen. The plants have suffered no harm from the treatment. As we see, Lyretail Killifish males were again soon in the mood for a brawl.

Through several small water changes the salt can be removed from the water. However, desalting should not be too fast, because some fish respond more sensitive to the desalting than on salinization. At several small water changes of about 20 to 30% with a few days distance, there are certainly no problems.

© Andreas Jäger