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All of this was culled from the scientific literature. It seemed worthwhile to look for actual peer reviewed, scientific facts about ich rather than just rely on the anecdotal knowledge that gets passed around through various aquarium sites. This is just a fraction of the stuff I came up with:
(1) What we call "ich" or "ick" is not actually ich - which refers to the freshwater parasite. What we are actually referring to is Cryptocaryon irritans ("ich') or Oodinium ("Marine Velvet"). The freshwater parasite is actually only distantly related.
(2) There are at least four different genetically distinct strains of Cryptocaryon irritans and they are prone to something called "founder effect" where they can become distinct from earlier populations if cut off from them.
(3) Some of the aquarist literature claims that Cryptocaryon and Oodinium are rare in the wild and while they do occur, fish almost never die due to these diseases. This is because the fish are spaced so far apart and the currents are strong enough that it is hard for the parasite to find another host before it dies in the free-floating stage. However, there has been some more recent articles that state that it is possibly more frequent in the wild than previously thought - but the infections are not as severe and it is rarely a cause of death.
(4) There have been studies on single species of fish that have used some interesting treatments. A group in Florida treated red snapper at fisheries for Cryptocaryon using a combination of hypERsalinity and quinine based drugs (what humans take for malaria) with a 100% success rate. A Japan group used cow lactoferrin (the hormone that produces milk in cows) and caprylic acid (in separate studies) given orally to a group of sea bream to treat Cryptocaryon infection and also had 100% success rate.
(5) While Cryptocaryon is non-specific (meaning it will pretty much infect any fish), the progression of the disease at different temperatures varies depending on what species is infected. In one study that I read, temperature had no effect at all in the progression of the disease in one fish, higher temperatures were more beneficial to another fish and lower temperatures were more beneficial to the third species.
(6) Hyposalinity absolutely does work as it messes up the balance between the protozoan and its environment. If you drop the salinity enough, the parasite will actually explode in its free floating state. In order to have this happen to 100%, you have to drop the salinity to the equivalent of 50% natural sea water and 50% fresh water. Unless of course you have a strain of Cryptocaryon that is adapted to estuarine conditions (of which there is at least one strain). In the case, you would need to drop the salinity further. You can kill Cryptocaryon with higher salinities but it will take long. At anything less OR more than normal salinities, the Cryptocaryon parasite did not grow and develop normally.
(7) Fish CAN become immune to Cryptocaryon infections and that immunity seems to last about 6 months, unless there is repeated exposure. This was tested experimentally separately in the thick-lipped mullet and mummichogs, but I think would could extrapolate those results to other fish in our reef tanks.
There have been a lot fewer controlled studies done on Marine Velvet - I'll have to see what else I can dig up earlier. I just thought that some of this might be of interest to people, considering the prevalance of threads on "ich" here.
(1) What we call "ich" or "ick" is not actually ich - which refers to the freshwater parasite. What we are actually referring to is Cryptocaryon irritans ("ich') or Oodinium ("Marine Velvet"). The freshwater parasite is actually only distantly related.
(2) There are at least four different genetically distinct strains of Cryptocaryon irritans and they are prone to something called "founder effect" where they can become distinct from earlier populations if cut off from them.
(3) Some of the aquarist literature claims that Cryptocaryon and Oodinium are rare in the wild and while they do occur, fish almost never die due to these diseases. This is because the fish are spaced so far apart and the currents are strong enough that it is hard for the parasite to find another host before it dies in the free-floating stage. However, there has been some more recent articles that state that it is possibly more frequent in the wild than previously thought - but the infections are not as severe and it is rarely a cause of death.
(4) There have been studies on single species of fish that have used some interesting treatments. A group in Florida treated red snapper at fisheries for Cryptocaryon using a combination of hypERsalinity and quinine based drugs (what humans take for malaria) with a 100% success rate. A Japan group used cow lactoferrin (the hormone that produces milk in cows) and caprylic acid (in separate studies) given orally to a group of sea bream to treat Cryptocaryon infection and also had 100% success rate.
(5) While Cryptocaryon is non-specific (meaning it will pretty much infect any fish), the progression of the disease at different temperatures varies depending on what species is infected. In one study that I read, temperature had no effect at all in the progression of the disease in one fish, higher temperatures were more beneficial to another fish and lower temperatures were more beneficial to the third species.
(6) Hyposalinity absolutely does work as it messes up the balance between the protozoan and its environment. If you drop the salinity enough, the parasite will actually explode in its free floating state. In order to have this happen to 100%, you have to drop the salinity to the equivalent of 50% natural sea water and 50% fresh water. Unless of course you have a strain of Cryptocaryon that is adapted to estuarine conditions (of which there is at least one strain). In the case, you would need to drop the salinity further. You can kill Cryptocaryon with higher salinities but it will take long. At anything less OR more than normal salinities, the Cryptocaryon parasite did not grow and develop normally.
(7) Fish CAN become immune to Cryptocaryon infections and that immunity seems to last about 6 months, unless there is repeated exposure. This was tested experimentally separately in the thick-lipped mullet and mummichogs, but I think would could extrapolate those results to other fish in our reef tanks.
There have been a lot fewer controlled studies done on Marine Velvet - I'll have to see what else I can dig up earlier. I just thought that some of this might be of interest to people, considering the prevalance of threads on "ich" here.
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