JP2014133720A - Ameba extermination method for fish, bath medicine for ameba extermination for fish, ameba extermination agent for fish, and feeding stuff - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ameba extermination method for fish having a high extermination effect to ameba at a low concentration and inexpensively and safely utilizable, a bath medicine for ameba extermination for fish, an ameba extermination agent for fish, and a feeding stuff.SOLUTION: Provided is a bath medicine obtained by dissolving or dispersing active ingredients into water and used for exterminating protist of ameba parasitic to fish. The active ingredients being one or more kinds of compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and their isomers and derivatives, and the concentration thereof is 0.3 to 20 ppm, and also provided are an ameba extermination method for fish where fish is immersed into the bath medicine, an ameba extermination agent for fish including the active ingredients, and a feeding stuff for fish including the same.

Description

  TECHNICAL FIELD The present invention relates to a fish amoeba extermination method, a fish amoeba extermination bath, a fish amoeba extermination agent, and a feed useful for extermination of amoeba parasitic on fish.

  Amoeba causes serious economic damage to farmed fish such as cultured salmon in Europe and America and Australia. This amoeba is a protist consisting of single cells that can only be seen with a microscope. Most of the amoeba parasitizing the fish parasitize the host gills and inhibits gas exchange, thereby causing developmental disorders. Unless treated as such, a large number of cultured fish are drowned. According to one estimate, amoeba causes more than $ 1 billion annually in the global aquaculture industry.

  Currently, a freshwater bath for 2 hours is being implemented as a measure for cultured fish amoebae. However, if it is not repeated regularly, it will not be effective, and the economic and physical burden will be very high. There is also a risk of applying a great deal of stress. Furthermore, it has been reported that 6% to 10% or more of amoebae survive even after a fresh water bath (see Non-Patent Document 1), which is suggested to cause reinfection. One reason why all amoeba cannot be killed is that in the freshwater bath, water does not penetrate into the gill tissue, so only the amoeba on the surface of the gill is killed. It may be ineffective. In addition, since amoeba forms a biofilm (biofilm), it has been suggested that the effect of a fresh water bath on the amoeba in the biofilm cannot be expected so much. This biofilm is known to be the most difficult to counter.

  As a parasite parasitism reducing agent for cultured fish that can reduce parasites infested fish without excessive labor, time, and cost, and without giving stress to the cultured fish, for example, in Patent Document 1 , Caffeine, eugenol, carvacrol, thymol, paracresol, citronellal, anisaldehyde, cinhydraldehyde, and coixenolide are used as active ingredients.

  Evaluation of the killing effect on amoeba in vitro has been carried out by many research institutions. Among these, when using bithionol, which is considered to be the most effective, it has been reported that the number of survivors decreased but could not be killed at a final concentration of 5 ppm for 24 hours (see Non-Patent Document 1). ).

  Experiments using garlic extract also reported that amoeba was not completely killed at 25 ppm for 24 hours.

JP 2006-306777 A

VL Findlay, BL Munday, Furtherstudies on acquired resistance to amoebic gill disease (AGD) in Atlanticsalmon, Salmo salar L. Journal of Fish Diseases, Volume 21, Issue 2, March 1998, 121-125, DOI: 10.1046 / j .1365-2761.1998.00086.x RL Florent, J. Becker, MD Powell, Further development of bithionol therapy as a treatment for amoebic gilldisease in Atlantic salmon, Salmo salar L., Journal of Fish Diseases, Volume32, Issue 5, May 2009, 391-400, DOI: 10.1111 / j.1365-2761.2008.01001.x

  However, the parasitic infestation agent for cultured fish described in Patent Literature 1 is intended for body surface parasites such as Benedenia, and therefore the effect on amoeba that is parasitic on the outside of the gills and in the tissue is not always clear. . Moreover, the parasite-reducing agent for cultured fish described in the same document is used by mixing with feed, and its applicability to use as an external preparation such as a medicinal bath solution is not necessarily clear. Furthermore, Benedenia is a protozoan parasite and is considered to be a completely different organism from protozoa such as amoeba, and its mitigation effect on protozoa has not been clarified.

  In addition, regarding the control of amoeba parasitic on fish, there are currently no effective treatment methods other than fresh water baths and the above methods, and treatment / preventive drugs having a high control effect have not been established.

  The present invention has been made in view of such circumstances, and has a high concentration-controlling effect on amoeba in a low concentration and in a short time, a fish amoeba-controlling method that can be used safely and inexpensively, a medicinal bath solution for fish amoeba-controlling, An object is to provide an amoeba control agent and feed for fish.

  The present invention provides a fish amoeba extermination method according to the following [1] to [7], a fish amoeba extermination chemical bath solution according to the following [8] to [9], and the following [10] to [10] The above-mentioned problems are solved by providing the amoeba-controlling agent for fish described in [11] and the feed for fish described in [12] to [14] below.

[1] A method for controlling protists of the genus Amoeba parasitic on fish, wherein the active ingredient is one or more selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof A fish amoeba extermination method for immersing fish in a chemical bath solution in which a seed compound is dissolved or dispersed in water at a concentration of 0.3 to 20 ppm.
[2] The fish amoeba extermination method according to the above [1], wherein the water is fresh water or seawater.
[3] The fish amoeba extermination method according to the above [2], wherein the water is fresh water.
[4] A method for controlling protists of the genus Amoeba parasitic on fish, wherein the active ingredient is one or more selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof. A method for controlling fish amoebae, wherein a composition containing a seed compound is orally administered or fed to fish.
[5] The fish amoeba extermination method according to the above [4], wherein the content of the compound contained in the composition is 50 to 4000 ppm.
[6] The method of controlling amoebic fish according to any one of [1] to [5] above, wherein the fish belongs to the Salmoniformes salmonidae.
[7] The fish amoeba extermination method according to any one of [1] to [6], wherein the protist is Neoparamoeba spp.

[8] A medicinal bath solution in which an active ingredient is dissolved or dispersed in water, which is used to combat amoebial protists that parasitize fish, wherein the active ingredient comprises thymol, cinnamaldehyde, perylaldehyde, A medicinal bath solution for controlling amoeba for fish, which is one or more compounds selected from the group consisting of geraniol and isomers and derivatives thereof, and the concentration of the active ingredient is 0.3 to 20 ppm.
[9] The medicinal bath solution for controlling amoebic fish according to the above [8], wherein the water is fresh water.

[10] An amoeba controlling agent for fish comprising as an active ingredient one or more compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof.
[11] The amoeba controlling agent for fish according to the above [10], wherein the content of the active ingredient is 50 to 4000 ppm.

[12] A fish feed comprising one or more compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof.
[13] The feed for fish according to the above [12], wherein the content of the compound is 50 to 4000 ppm.
[14] The fish feed according to the above [12] or [13], which is a feed for fish belonging to the Salmoniformes Salmonidae.

  In the present invention, “1 ppm” means that 1 part by weight of the active ingredient or compound is contained with respect to 1,000,000 parts by weight of the medicinal bath solution, amoeba controlling agent or feed.

  According to the amoeba control method of the present invention using a drug bath solution containing thymol, cinnamaldehyde, perillaldehyde, geraniol, isomers and derivatives thereof as active ingredients, the concentration is as low as 0.5 to 100 ppm and within a short time. In addition, the amoeba parasitizing the fish gills can be almost completely killed. In addition, even when added to feed, it exerts a high control effect against amoeba and the like by short-term administration. These active ingredients are obtained from natural herbs and essential oils, and they exhibit excellent effects in very small amounts and short-term use. It has an excellent effect that the risk of side effects is low, and it can be used cheaply and safely. Thus, according to the present invention, a fish amoeba extermination method, a fish ameba extermination chemical bath solution, and a fish amoeba extermination agent which has a high extinction effect on amoeba in a low concentration and in a short time and can be used safely and inexpensively And feed is provided.

  The fish amoeba extermination method according to the first embodiment of the present invention (hereinafter may be abbreviated as “amoeba extermination method” or “the present method”) includes thymol, cinnamaldehyde, perylaldehyde as active ingredients. By immersing fish in a chemical bath solution in which one or more compounds selected from the group consisting of geraniol and isomers and derivatives thereof are dissolved or dispersed in water at a concentration of 0.3 to 20 ppm This is a method for extermination of amoebia protists (hereinafter sometimes abbreviated as “amoeba etc.”) parasitic on fish.

  The chemical bath used in the present method comprises one or more compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof at a concentration of 0.3 to 20 ppm. Dissolved or dispersed in water.

  The active ingredients thymol, cinnamaldehyde, perillaldehyde, and geraniol are compounds having molecular structures represented by the following structural formulas 1 to 4, respectively, and are known as components of essential oils obtained mainly from plants. It has been. These compounds are plant or essential oils of those plants (eg, thyme (thyme) for thymol, cinnamon oil for cinnamaldehyde, perilla or perilla oil for perilaldehyde, geranium for geraniol ) May be isolated using any known method, or may be chemically synthesized using any method.

In addition to the above compounds, these isomers or derivatives may be used as the active ingredient of the medicinal bath solution as long as it has the activity of controlling protozoa belonging to the genus Amoeba parasitic on fish. Examples of the isomers of the above compounds include structural isomers (for example, carvacrol and 3-methyl-4-isopropylphenol, which are structural isomers of thymol), and geometric isomers (for example, (Z) -cinnamaldehyde. ), Optical isomers (for example, 4 (R) -perylaldehyde) and the like. Examples of the derivatives of the above compounds include those having a substituent in the aromatic ring, such as oxime, imide (Schiff base), hydrazide, semicarbazide, etc. produced by the reaction of an aldehyde group with a nitrogen compound.
In addition, you may use what mixed arbitrary 2 or more types of said compounds and those isomers and derivatives in arbitrary ratios as an active ingredient of a chemical bath liquid.

  Among these compounds, cinnamaldehyde is particularly preferable, and amoeba parasitized inside the gill by being immersed in a chemical bath solution at a low concentration of about several ppm for a short time (several minutes to several tens of minutes). Can be removed almost completely.

  The concentration of the active ingredient contained in the chemical bath solution is 0.3 to 20 ppm, preferably 0.5 to 10 ppm, more preferably 3 to 10 ppm. If the concentration of the effective concentration is less than 0.3 ppm, the amoeba and the like cannot be sufficiently controlled. If the concentration exceeds 20 ppm, adverse effects on fish such as an increase in the risk of drowning due to anesthetic action are remarkable. May develop.

The water used for the production of the chemical bath may be seawater, but may be artificial seawater, fresh water, and a mixture thereof in any ratio. The water used for the production of the chemical bath may be subjected to a treatment for removing harmful components such as suspended matters, bacteria, and heavy metals, if necessary. About a process, it can carry out using ultrafiltration and arbitrary well-known methods.
As water, it is preferable to use fresh water having a certain amount of amoeba activity alone.

  In order to improve the solubility or dispersibility of the compound used as the active ingredient in water, the chemical bath solution may contain fats and oils such as fish oil, alcohols, emulsifiers, nonionic surfactants and the like. Moreover, you may contain the arbitrary additives generally used for the medicine bath liquid for fish. Examples of such additives include other drugs such as antibiotics, preservatives, antioxidants and the like.

  The method for producing the chemical bath liquid is not particularly limited, and can be carried out using any known method for mixing the above-described components and dissolving or dispersing the active ingredient in water. In advance, the concentration range described above is applied to an appropriate solvent such as a water-soluble organic solvent such as water or alcohol, an oil or fat, or a mixed solvent obtained by mixing any two or more of these at an arbitrary ratio. Alternatively, a stock solution dissolved at a higher concentration may be prepared, added at a predetermined ratio in water, and finally diluted so as to be in the above concentration range.

  The fish species to which this method is applied include any fish that develops an amoeba infection, but in particular, the turbot (shrimp) and salmonids, where parasitism such as amoeba to Ella is a major problem (Salmoniformes) Fish belonging to the order Salmonidae, specific examples include chum salmon, atlantic salmon, sockeye salmon, coho salmon, king salmon, calaf trout, salmon trout, cherry salmon, trout salmon, steelhead and the like.

  Protozoa belonging to the genus Amoeba that are subject to extermination by this method include those that parasitize fish and cause disease, causing a decline in the yield of cultured fish due to drowning and a reduction in commercial value. However, Neoparamoeba pemaquidensis etc. which are causative parasites of amoeba mania (AGD) are mentioned especially.

  In the case of a medicinal bath solution containing several ppm of active ingredients, parasitic amoeba and the like can be almost completely killed by immersing fish in the medicinal bath solution for several tens of minutes to several hours. Depending on the type of the active ingredient, the fish may be in an anesthetized state, but it recovers quickly by returning to water that does not contain the active ingredient after the medicine bath.

  The fish amoeba extermination method according to the second embodiment of the present invention is a method of exterminating amoebia protists that are parasitic on fish, and as active ingredients, thymol, cinnamaldehyde, perilaldehyde, geraniol and these A method of controlling amoebial protists parasitic on fish by orally administering or feeding a fish with a composition comprising one or more compounds selected from the group consisting of isomers and derivatives of is there.

  The type of compound contained in the composition, the fish species to be controlled, the amoeba to be controlled, and the like are the same as in the case of the chemical bath solution according to the first embodiment, and thus detailed description thereof is omitted. The content of the above compound in the composition for oral administration or feeding is not particularly limited, but is, for example, 50 to 4000 ppm, and is appropriately adjusted according to the fish species, body weight, culture conditions, type of compound, etc. The

  The composition may be orally administered by being contained in feed and fed at the time of feeding. The form of the feed is not particularly limited, and may be blended so as to have a predetermined content in the feed used during normal cultivation.

  Next, examples carried out for confirming the effects of the present invention will be described.

Example 1: Evaluation of amoebicidal activity in vitro The evaluation of amoebicidal activity is described in Florent et al.
in vitro toxicity of bithionol and bithionol sulphoxide to Neoparamoeba spp., the
causative agent of amoebic gill disease (AGD) '' Dis
Aquat Organ. 2010 Sep 17; 91 (3): 257-62. The outline of the method is shown below.
(1) A petri dish having an amoeba uniformly attached to the bottom of a round petri dish was prepared.
(2) Washed once with sterile seawater before use.
(3) Sterile seawater adjusted so that the final concentration of the additive becomes an arbitrary concentration (5 ppm, 1 ppm, 0.3 ppm) was added. (4) Ten minutes after adding the seawater adjusted with the additive, Petri dishes were observed under a microscope after 1 hour, 2 hours, and 24 hours, and the survival state of amoeba was observed.
(5) Amoebae adhered to the bottom of the petri dish and no abnormalities were observed in its morphology, and those that were separated from the bottom were collected using a centrifuge.
(6) The recovered amoeba was confirmed to be alive or dead using neutral red staining.

  The experimental results for cinnamaldehyde, perillaldehyde, and geraniol are shown in Table 1 below, along with similar experimental results performed on bithionol as a control (blank) and comparative example.

  From the results of Table 1, it was confirmed that cinnamaldehyde exhibited an anti-amoeba effect within 10 minutes at a final concentration of 1 ppm or more. In addition, an anti-amoeba effect was observed when perillaldehyde was 5 ppm or more and within 1 hour, and geraniol was observed within 5 ppm or more and 10 minutes. On the other hand, in the control group where nothing was added, almost all amoeba survived even after 24 hours. On the other hand, in the case of adding bithionol, although the decrease in the number of survival was observed at 5 ppm for 1 hour, the amoeba survived.

  In the case of bithionol, the survival of amoeba was observed despite contact for 24 hours at a final concentration of 5 ppm, whereas all the amoeba died within 1 hour of 5 pppm for these three test substances. From these results, it was confirmed that these compounds showed high anti-amoeba activity in a short time by administration at a low concentration.

  Especially for cinnamaldehyde, an anti-amoeba effect was observed within 10 minutes at a low concentration of 1 ppm or more. Moreover, even when the final concentration was 0.3 ppm and within 10 minutes, the effect of reducing amoeba was observed, suggesting that it was the substance having the most excellent anti-amoeba activity among these test substances.

Example 2: Examination of safety Based on the results of Example 1, the above three types of test substances were examined for conditions when actually used outdoors. The most important thing to consider in use is that amoeba parasitizes the surface or tissue of the gills, and further sensitizes them to gera for a certain concentration and time by generating biofilms. I must.

  According to the results of Example 1, theoretically, cinnamaldehyde has a concentration of 1 ppm for 10 minutes, perylaldehyde has a concentration of 5 ppm for 1 hour, and geraniol has a concentration of 5 ppm for 10 minutes. Can be expected. A fish bath is used as a method to sensitize these easily and continuously to gills. When performing a medicinal bath, analogs of these substances have been reported to be efficiently absorbed from the skin and penetrate tissue. For example, eugenol and carvacrol, which are the same monoterpenes, are excellent in absorption from the skin and gills, and are widely used as general anesthetics for fish. For this reason, using it by mixing with a fresh water bath or seawater is expected to be effective against an amoeba that has entered the tissue. Furthermore, cinnamaldehyde, perillaldehyde, geraniol, etc. have been reported as substances having high permeability to biofilms.

  Therefore, if the minimum effective concentration of these substances is maintained in fresh water or seawater, it can be expected that not only the surface of the gills but also the amoeba in the tissue is effectively reduced. Treatment can also be expected for amoeba in biofilm, which is considered to be the most difficult to remove. This method requires a concentration greater than the minimum effective concentration in seawater or fresh water. In order to do this, the safety to the fish when mixed with seawater or fresh water must be ensured. In view of the above, the following experiments were conducted to ensure the safety of these test substances.

  30 salmons of about 100 g were prepared in a tank of 350 L seawater or fresh water. The final concentration of each substance was adjusted to 20 ppm, 10 ppm, 5 ppm, and 1 ppm for seawater and fresh water in these tanks. However, the test of 1 ppm was only cinnamaldehyde because of the minimum effective concentration. After the start of the test, the state of each fish was confirmed and the time during which all fish were safe was measured. The test time was a maximum of 2 hours (120 minutes). Table 2 below shows the results of studies on the chemical bath prepared using seawater.

  Safety at a final concentration of 10 ppm in a medicinal bath prepared with seawater (maximum immersion time for all fish to survive) was 60 minutes for cinnamaldehyde, 45 minutes for perilaldehyde, and 75 minutes for geraniol. It was. After completion of the test, all fish were anesthetized, but were resuscitated when returned to normal tanks. At a final concentration of 5 ppm, all fish survived without any problems when immersed in a 2-hour bath.

  It has been reported that amoeba decreases when anesthesia is performed in seawater using eugenol and carvacrol, which are the same monoterpene friends. However, in the in vitro experiment of Experiment 1, the final concentration of anti-amoeba activity of eugenol or carvacrol was 20 ppm (data not shown). From this, it can be expected that the above-mentioned three kinds of substances having higher anti-amoeba activity than eugenol and carvacrol and having similar tissue permeability are the most excellent substances for a chemical bath. In the case of carrying out a chemical bath in seawater, it was confirmed that it is desirable to carry out each substance within 30 minutes if the final concentration is 10 ppm. Moreover, when examining by changing a density | concentration, it is desirable to carry out by suppressing within 60 minutes by 5 ppm of final density | concentration. In the unlikely event that a fish falls into an anesthesia state, safety is ensured by immediately stopping the medicine bath and returning it to seawater. The safety of the method seems very high.

  Table 3 below shows the results of studies on the chemical bath solution prepared using fresh water.

  Regarding safety in fresh water, safety at a final concentration of 10 ppm was cinnamaldehyde 60 minutes, perilaldehyde 50 minutes, and geraniol 65 minutes. As in the case of the drug bath solution prepared using seawater, after all fish were anesthetized, they were returned to normal tanks and immediately revived. At a final concentration of 5 ppm, all fish survived after 2 hours of bathing.

  The safety in fresh water was almost the same as seawater. For this reason, about a chemical bath, it is possible to implement on the same conditions as seawater. By administering these substances, there is a high possibility of killing amoeba in tissues that could not be killed by a fresh water bath alone. In addition, it is highly possible to handle biofilms that are difficult to handle. For this reason, a higher therapeutic effect can be expected when implemented in combination with a fresh water bath.

Example 3: Examination of killing effect of gill parasite amoeba by addition to feed In addition to carrying out amoeba countermeasures in the medicinal bath of Example 2, by adding these substances to the diet and orally administering them, There is a possibility of preventing infection. This method can be carried out with less labor compared to medicinal baths, and the burden on fish seems to be small. However, there are no reports on the absorption, pharmacokinetics, metabolism, and excretion of these substances in fish, and there is no method other than actual evaluation using fish. In order to prove the therapeutic effect on fishes infected with amoeba by orally administering these substances, these diets are administered to salmon infected with amoeba, and the number of amoeba compared to the control group If it decreases, the effect is recognized.

Prepare end-stage infected fish infected with amoeba. These should be used after evaluating the amoeba infection macroscopically before the start of the test and selecting similar ones. In these evaluations, the degree of inflammation caused by Ella amoeba was classified into five levels, and the one with the most intense inflammation was used. The feed adjusted to a final concentration of 2000 ppm was forcibly administered to the salmon for 3 days at a rate of 2.5% / Kg · BW. Can be judged reliably.) Three days later, it was taken up and the number of gills of amoeba was evaluated. The number of evaluations was 3 each.
Evaluation was performed by the method of Philip et al. (Int J Parasitol. 2005
Nov; 35 (13): 1417-23. Epub 2005 Jul 18). Specifically, it is as follows.
(1) All the gills were extracted.
(2) Sterile seawater was placed in a test tube for 5 minutes and stirred slowly to release the amoeba from the gills.
(3) 2 hours after seeding the petri dish, the amoeba adhering to the petri dish is measured.
(4) The measuring method confirmed the visual field of 10-30, and took the average.
(5) The effect was verified in comparison with the control group.

  Table 4 below shows the average number of amoeba fields after oral administration of each test substance for 3 days.

In the control group to which nothing was administered, a large number of parasites were isolated from the gills of fish used in all experiments, adhered to the bottom of the petri dish, and more than 50 amoeba could be confirmed in all fields of view. Almost no amoeba was observed in each field of view in the 3 mice treated with cinnamaldehyde, or 2 to 5. The number of amoeba was almost not recognized in each visual field in the 3 tails of the group to which perylaldehyde was administered. The number of amoeba was almost not recognized in each visual field in the 3 fishes in the geraniol-administered group.
By administering these three test substances, the number of gills of amoeba in Ella was reduced.

  From the above results, it was suggested that these three kinds of compounds are orally administered to control amoeba infection. This suggests that by oral administration of these three test substances, they were reliably absorbed from the intestinal tract, distributed in gills, excreted and killed parasites. Therefore, it seems possible to suppress amoebiasis by oral administration.

  The fish amoeba extermination method, the fish amoeba extermination chemical bath solution, the fish amoeba extermination agent and the feed provided by the present invention can be used for exterminating amoeba parasitizing the salmon and other cultured fish.

Claims (14)

A method of combating amoebial protists that parasitize fish,
As an active ingredient, one or more compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof were dissolved or dispersed in water at a concentration of 0.3 to 20 ppm. A method for combating fish amoeba, comprising immersing fish in a chemical bath.   The fish amoeba extermination method according to claim 1, wherein the water is fresh water or seawater.   The fish amoeba extermination method according to claim 2, wherein the water is fresh water. A method of combating amoebial protists that parasitize fish,
A composition comprising one or more compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof as an active ingredient is orally administered or fed to fish. Characteristic amoeba extermination method for fish.   The fish amoeba extermination method according to claim 4, wherein the content of the compound contained in the composition is 50 to 4000 ppm.   6. The fish amoeba extermination method according to any one of claims 1 to 5, wherein the fish belongs to the family Salmoniformes (Salmonidae).   7. The fish amoeba extermination method according to any one of claims 1 to 6, wherein the protist is Neoparamoeba spp. A medicinal bath solution in which an active ingredient is dissolved or dispersed in water, used to control amoebial protists that parasitize fish.
The active ingredient is one or more compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof,
A medicinal bath solution for controlling amoebic fish, wherein the concentration of the active ingredient is 0.3 to 20 ppm.   9. The fish bath solution for controlling amoeba of fish according to claim 8, wherein the water is fresh water.   An amoebic control agent for fish, comprising as an active ingredient one or more compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof.   The amoeba control agent for fish according to claim 10, wherein the content of the active ingredient is 50 to 4000 ppm.   A fish feed comprising one or more compounds selected from the group consisting of thymol, cinnamaldehyde, perillaldehyde, geraniol and isomers and derivatives thereof.   The feed for fish according to claim 12, wherein the content of the compound is 50 to 4000 ppm.   14. The fish feed according to claim 12 or 13, which is a fish feed belonging to the Salmoniformes salmonidae (Salmonidae).