Ichthyophthirius multifiliis, often described in the literature simply as Ich or Ichthy, is a well-known parasitic ciliate within aquaristics.
It can be described as an obligate parasite, as it is almost always present, but is not a problem for normal healthy fish, as their immune defense suppresses the parasite.
Now you can ask yourself why your own fish fall prey to an ichthyo infection? In general, fish that have recently survived an ichthyo infection are immune to a new infestation for about six to seven months due to increased mucus production. This mucus formation prevents new pathogens (trophonts) from settling in the skin. This immunity is presumably triggered by an antibody directed against proteins within the membrane of the hawkmoths, thus preventing them from docking on the fish. However, this process does not kill the parasite. Thus, our fish do not have generalized immunity to a new infestation, as the increased mucus production subsides again. The pathogen gains access via new fish in the aquarium as well as via plants.
Ichthyo can only survive with fish! A permanent stage without fish does not exist.
Within the literature, as well as the relevant Internet, numerous different data about protracted courses of the disease can be found, partly with more or less strong, lethal consequences. One reason could be, as can be read with other ciliates, that the hawkmoths exchange genetic material among each other and this is a reason for different severe courses of the disease. There are probably different Ichthyo strains, because otherwise the completely different courses can hardly be explained.
The reproduction rate of Ichthyo is strongly temperature dependent and ranges from several days at low temperatures, to hours at high to very high (28° degrees and more) temperatures. During its parasitic phase, the parasite secretes a substance that triggers an immune reaction in the fish, resulting in increased skin cell thickening and mucous membrane formation at that particular site. This is also the main reason why drugs do not reach it. Within this protective shell, the parasite now grows up to 50 times its size and we take note of this growth as white dots on the skin.
If we now notice white spots on the fish, the infection is already in full swing! Once the parasite has completed its development cycle on the fish, it migrates into the outer mucous layer of the mucosa, pierces it and then leaves the fish as a free swarm. During this tomonth phase, which can last up to six hours maximum, the parasite is quite sensitive to drugs. After the tomonth phase, Ichthyo attaches itself to parts of plants or mulm at the bottom and forms cysts there, in which it divides into approx. 1000 to 4000 cells. These so-called tomites develop further and form cilia, with which they can move around quite well, swimming. After their complete development, they then start the active search for a new host as so-called theronte, free swarmers. Only within this phase, they can be controlled with drugs. If the parasite does not find a new host within a maximum of 70 hours, it dies. In the case of common ichthyo infections, only Protazol from Sera is currently able to combat the parasite already on the fish. Other medications only affect the swarming phase. The fish must therefore cope with the infection alone!
Temperature increases to over 28° C to shorten the development cycle of the parasite should be done with great caution. Ichthyo can also affect the gills and the warmer the water, the lower the oxygen content in the water. In addition, medications deplete oxygen. It is therefore extremely important to introduce additional oxygen sources or, if the fish show problems with breathing, to lower the temperature again!
Recent evidence points to a close relative of Ichthyophthirius multifiliis, which shows itself to be extremely persistent and resistant to various drug treatments, but nevertheless exhibits the same symptoms of common Ichthyophthiosis. Presumably it is also this, more or less, multi-resistant representative, with which all medications, which one gets in the trade, fail.
According to Dr. Lechleiter this parasite is called Neoichthyophthirius schlotfeldii. A close relative of Ichthyophthirius multifiliis. It is a very difficult to remove ciliate that can reproduce directly in the fish skin, and without entering a swarming phase! The main distinguishing feature mentioned by Lechleiter is a difference in the nucleus which is not horseshoe-shaped as usual, but ring-shaped.
The outstanding feature of this parasite is that it does not parasitize externally on skin and gills, but encapsulates itself in the gill epithelium and skin. This makes it even more difficult to catch it with medication.
It is well known that all parasites that spread externally on fish are considered isoosmotic. They have different solutions, but the same number of dissolved particles. That is, their content of salt is equal to the content of salt, of the medium water surrounding them.
Freshwater fish live in water with a very low salt content. Consequently, the salt content in their bodies is higher than that of the water around them. This causes them to constantly absorb water through their body surface, in addition to their gills, and thus constantly excrete water containing urea. In seawater fish, the process is different.
If we now increase the salt concentration in the water to about 1%, this will not kill our fish, but it is enough to kill the parasites. Usually, the salt content in fresh water is 0.1%. In comparison, seawater would be at about 3.5% salinity.
If you now use brilliant green in combination with formalin, the usual Ichthyo ciliate is history quite quickly. However, we are then again talking about triphenylmethane dye, as contained in malachite green oxalate. This brings us back to the toxicity of malachite green oxalate and the retention time in the fat of the fish of up to 30 days (Untergasser). Malachite green oxalate is toxic. By the way, this is the main reason why it is forbidden to use it in commercial fish in Germany!
Possibly, however, Neoichthyophthirius schlotfeldii should show a much better effect in combination with formalin than with methylene blue. Preparations containing copper show no effect on Neoichthyophthirius schlotfeldii! Against this background, use would be pointless if previously water conditioners are used regularly and neutralize the copper in the drug immediately.
The use of peracetic acid can also be used against Ichthyo in the swarming phase as a safe remedy. The advantage here is the oxidizing effect, even at low temperatures, and no expected adaptation of the microorganisms due to the non-specific effect.
It can be described as an obligate parasite, as it is almost always present, but is not a problem for normal healthy fish, as their immune defense suppresses the parasite.
Now you can ask yourself why your own fish fall prey to an ichthyo infection? In general, fish that have recently survived an ichthyo infection are immune to a new infestation for about six to seven months due to increased mucus production. This mucus formation prevents new pathogens (trophonts) from settling in the skin. This immunity is presumably triggered by an antibody directed against proteins within the membrane of the hawkmoths, thus preventing them from docking on the fish. However, this process does not kill the parasite. Thus, our fish do not have generalized immunity to a new infestation, as the increased mucus production subsides again. The pathogen gains access via new fish in the aquarium as well as via plants.
Ichthyo can only survive with fish! A permanent stage without fish does not exist.
Within the literature, as well as the relevant Internet, numerous different data about protracted courses of the disease can be found, partly with more or less strong, lethal consequences. One reason could be, as can be read with other ciliates, that the hawkmoths exchange genetic material among each other and this is a reason for different severe courses of the disease. There are probably different Ichthyo strains, because otherwise the completely different courses can hardly be explained.
The reproduction rate of Ichthyo is strongly temperature dependent and ranges from several days at low temperatures, to hours at high to very high (28° degrees and more) temperatures. During its parasitic phase, the parasite secretes a substance that triggers an immune reaction in the fish, resulting in increased skin cell thickening and mucous membrane formation at that particular site. This is also the main reason why drugs do not reach it. Within this protective shell, the parasite now grows up to 50 times its size and we take note of this growth as white dots on the skin.
If we now notice white spots on the fish, the infection is already in full swing! Once the parasite has completed its development cycle on the fish, it migrates into the outer mucous layer of the mucosa, pierces it and then leaves the fish as a free swarm. During this tomonth phase, which can last up to six hours maximum, the parasite is quite sensitive to drugs. After the tomonth phase, Ichthyo attaches itself to parts of plants or mulm at the bottom and forms cysts there, in which it divides into approx. 1000 to 4000 cells. These so-called tomites develop further and form cilia, with which they can move around quite well, swimming. After their complete development, they then start the active search for a new host as so-called theronte, free swarmers. Only within this phase, they can be controlled with drugs. If the parasite does not find a new host within a maximum of 70 hours, it dies. In the case of common ichthyo infections, only Protazol from Sera is currently able to combat the parasite already on the fish. Other medications only affect the swarming phase. The fish must therefore cope with the infection alone!
Temperature increases to over 28° C to shorten the development cycle of the parasite should be done with great caution. Ichthyo can also affect the gills and the warmer the water, the lower the oxygen content in the water. In addition, medications deplete oxygen. It is therefore extremely important to introduce additional oxygen sources or, if the fish show problems with breathing, to lower the temperature again!
Recent evidence points to a close relative of Ichthyophthirius multifiliis, which shows itself to be extremely persistent and resistant to various drug treatments, but nevertheless exhibits the same symptoms of common Ichthyophthiosis. Presumably it is also this, more or less, multi-resistant representative, with which all medications, which one gets in the trade, fail.
According to Dr. Lechleiter this parasite is called Neoichthyophthirius schlotfeldii. A close relative of Ichthyophthirius multifiliis. It is a very difficult to remove ciliate that can reproduce directly in the fish skin, and without entering a swarming phase! The main distinguishing feature mentioned by Lechleiter is a difference in the nucleus which is not horseshoe-shaped as usual, but ring-shaped.
The outstanding feature of this parasite is that it does not parasitize externally on skin and gills, but encapsulates itself in the gill epithelium and skin. This makes it even more difficult to catch it with medication.
It is well known that all parasites that spread externally on fish are considered isoosmotic. They have different solutions, but the same number of dissolved particles. That is, their content of salt is equal to the content of salt, of the medium water surrounding them.
Freshwater fish live in water with a very low salt content. Consequently, the salt content in their bodies is higher than that of the water around them. This causes them to constantly absorb water through their body surface, in addition to their gills, and thus constantly excrete water containing urea. In seawater fish, the process is different.
If we now increase the salt concentration in the water to about 1%, this will not kill our fish, but it is enough to kill the parasites. Usually, the salt content in fresh water is 0.1%. In comparison, seawater would be at about 3.5% salinity.
If you now use brilliant green in combination with formalin, the usual Ichthyo ciliate is history quite quickly. However, we are then again talking about triphenylmethane dye, as contained in malachite green oxalate. This brings us back to the toxicity of malachite green oxalate and the retention time in the fat of the fish of up to 30 days (Untergasser). Malachite green oxalate is toxic. By the way, this is the main reason why it is forbidden to use it in commercial fish in Germany!
Possibly, however, Neoichthyophthirius schlotfeldii should show a much better effect in combination with formalin than with methylene blue. Preparations containing copper show no effect on Neoichthyophthirius schlotfeldii! Against this background, use would be pointless if previously water conditioners are used regularly and neutralize the copper in the drug immediately.
The use of peracetic acid can also be used against Ichthyo in the swarming phase as a safe remedy. The advantage here is the oxidizing effect, even at low temperatures, and no expected adaptation of the microorganisms due to the non-specific effect.
