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Thread: Prazi Problem??

  1. #1
    Daihonmei MikeM's Avatar
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    Prazi Problem??

    What’s the problem with Praziquantel? I regularly see comments that Prazi does not work for someone to eliminate flukes, and they end up doing multiple PP treatments or taking risks with Supraverm. Others praise it to high heaven as completely effective. Those for whom it has not worked are often suspected of not using it properly, not allowing enough time before doing large water changes, or some other ‘consumer fault’. Prazi has worked well for me as a single dose, although for several years flukes returned each Spring. (Not an issue for several years.) I suspect some eggs survived treatment, allowing the pest to re-populate over the course of a year. I recently came across an article on the Simi Koi website that gives great emphasis to how water temperature affects the effectiveness of Prazi. I do not recall such emphasis being made by anyone else. I am thinking this could be a factor explaining some of the different results experienced by folks. ….BTW, Simi Koi was once a well-known dealer whose advertising was seen across the U.S. Some years ago the business re-focused on pond building and maintenance and no longer has a retail shop. The article is reproduced in the next post.
    Last edited by MikeM; 07-06-2017 at 09:51 AM.

  2. #2
    Daihonmei MikeM's Avatar
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    From Simi Koi website:


    “Praziquantel: Gill and Skin Flukes:
    A trematodicide. Praziquantel induces a rapid contraction of schistosomes(a worm or fluke)by a specific effect on the permeability of the cell membrane. The drug further causes vacuolization(causes more and larger spaces or cavities within each individual cell)and disintegration of the cells as well as the schistosome tegument(the fluke body covering). Bursting of the cell walls might be a much simpler way of describing it and may be equally correct.
    Praziquantel must be ingested by the fluke to work. The dosage is one gram per 100 gallons of water. Currently the directions suggest using level tablespoons to measure the product. That is a mistake. In my experience a level tablespoon may hold anywhere from 2.5 to 4.5 grams of product. Not only is this wasteful and inaccurate; it is also very expensive. Please use a gram scale. Calibrate it often.

    Since it does not mix readily with water a label dosage ProformC may be used, or it can be dosed with the ProformC as part of [a combined treatment described elsewhere]. Once it is fully dissolved it does not seem to filter out or precipitate. It simply degrades over time. When using Praziquantel, the water temperature should be in the mid-seventies(US). The first and all succeeding treatments should last seven days each whether treating for gill flukes (Dactylogyrus) or skin flukes (Gyrodactylus). 25% water changes should be made between treatments. Re-dosing will immediately bring it to the strength needed to kill flukes. I strongly recommend a second if not a third application of this product due to the life cycle of the flukes as well as the thickness of the slime coat on Koi. In colder waters (60*F to 70*F) a third and even a fourth application should be considered when treating for gill flukes. Because of the cost of Praziquantel and the reduced treatment time it is well worth the effort to bring the temperature up to optimum.

    Praziquantel as a kicker:
    At times I've had situations where the standard doses and protocol of the ProformC and Praziquantel simply doesn't seem to work. In those situations I dose with a standard dose on day one. Then I wait 48 hours and re-dose with another standard treatment and allow that to stand for ten days. At the end of ten days I scrape and scope. If the water temperature is in the mid-seventies the flukes will be gone. Lower temperatures will require a repetition of the treatments after a 50% water change. I have never seen any ill effect whether in soft or hard water with this treatment. Although I am simply using ProformC as a mixing agent I like to see it used at full dosage just in case there are other parasites not found in the scrape and scope procedure.”

  3. #3
    Honmei ricshaw's Avatar
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    I followed Russ Peters (and others) advice and used 20 grams per 1000 gallons.

  4. #4
    Daihonmei MikeM's Avatar
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    Since Prazi does no harm to the fish, a double dose is certainly going to be more effective. The issue is the double cost. For those with higher end koi, however, the cost is small compared to the value of the fish. And, the cheaper treatments commonly available (Supaverm, organo-phosphates) involve real risks for the koi.

    I came across an article by Karl Schoeler in which he gives some back ground on dosage and his practice of using 15 grams per 1,000 gallons:

    "....the success of Praziquantel is tied to one thing more than any other: It must be ingested by the fluke. Here's where koi keepers have sometimes said that flukes, especially gill flukes seem to be resistant to Praziquantel. There are two reasons for this: First, as we've become more adept at finding flukes with a microscope we can say that there still are some there. In the past people just assumed that the parasite was eradicated after the label treatments were followed. Parasites are nearly always present. Second, and this is really why flukes appear to be resistant, Koi and other bottom feeders put out a significantly heavier slime coat compared to other more predatory fish. Because they feed on the bottom, and churn up the mud in their hunt, they need more protection for their gills. Then there is one more factor: When flukes attach themselves they stimulate the slime coat that further embeds them and makes them even harder to treat. So, when gill flukes are discovered by flashing symptoms and a scrape and scope, we are dealt a difficult hand. Medicating with something which will sooner or later be ingested by the fluke, and yet using something safe even at significantly higher doses where necessary. Testing of Praziquantel was done by Victoria Burnley Vaughn and she arrived at a dosage of 1 gram per 100 gallons of water for eradicating flukes. I do not know of any other conditions which may affect this dosage except some water conditioners containing a slime coat enhancing chemical such as Novaqua or Ultimate.
    My testing was done in hard water: 20-28 grains of hardness, a Kh of 220 -275 and a Ph of 7.2 to 7.8. I used Praziquantel at a rate of 4.5 grams per 300 gallons followed in 48 hours by a duplicate treatment as a kicker. This represents a 50% over treatment if the first dosage maintained its efficacy.
    Since Praziquantel is completely dissolved and becomes liquid the efficacy of the dose should remain for several days. Although the directions for Praziquantel indicate the use of a level tablespoon treating 300 gallons I would strongly suggest the use of a gram scale. A tablespoon can hold anywhere between 2.5 to 4.5
    grams of Praziquantel. It all depends on how it is scooped up. At $150.00 for 100 grams of Praziquantel, precise measuring is important. In my testing, I found no ill effects on koi even when overdosed by 50%. That is important for the hobbyist since many people have a tendency to over estimate the number of gallons of water in their pond. Koi, whether domestic or high end Japanese, were unfazed by the treatment. Although Praziquantel is relatively expensive it does represent about the best thing we have for fluke treatments in well-filtered, closed systems. "

    I find the 'duplicate treatment' after 48 hours rather surprising since all I have read indicates that Prazi remains in the water for a very long time until removed through water changes. I have not seen any studies of how long it takes for Prazi to degrade, but it sure isn't 48 hours. So, it seems this approach results in a tripling of the standard recommended dosage... an expensive treatment indeed!

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