JP2024045319A - A therapeutic agent for diseases caused by microsporidians and myxosporidians that parasitize marine fish. - Google Patents

Abstract

[Problem] The present invention provides a method for exterminating microsporidia or myxosporedia in marine fish (particularly farmed fish) by orally administering a drug. [Solution] The present invention provides an extermination agent for beko disease or myxosporediosis caused by microsporidia that parasitize marine fish, which contains any one of albendazole, febantel, flubendazole, fenbendazole, oxfendazole, and mebendazole as an active ingredient. [Selected Figure] Figure 1

Description

The present invention relates to an agent and a method for eliminating parasites in marine fish, and more particularly to an agent and a method for eliminating, by oral administration, beko disease or myxosporidiasis caused by microsporidia that parasitize marine fish.

The causative parasite of yellowtail downy mildew is Microsporidium serioles.
lae). In microsporidium, if it is clearly a new species and it is difficult to identify its taxonomic position at the genus level or higher, it can be placed in the collective genus Microsporidium, which is a parasite that causes downy mildew in yellowtails. This also applies in the case of . Parasitism of this insect on yellowtail was reported in 1982, and since then parasitism has also been observed on amberjack and amberjack. This disease is characterized by the formation of white, irregularly shaped, small cysts of parasites ranging from several mm to 1 cm in size on the lateral muscles of affected fish. When sporulation is completed within the cyst and the cyst collapses, the surrounding muscles melt, giving the appearance that the body surface in that area has caved in. For this reason, the appearance of irregularities on the body surface is why it is called downy mildew. The parasitism affects a wide area of the body, and sometimes the fish becomes extremely thin and dies. If the affected area is localized and there is no secondary bacterial infection, the wound will heal naturally after the cyst dissolves and the microsporidium escapes from the body. However, not all cysts melt and the main worm escapes from the body, and it is known that cysts remain in the trunk even after a long period of time before shipping, which is one of the causes of lower product value. ing. Currently, no therapeutic drug has been developed for this disease, and the damage continues.

Microsporidia-caused beko disease is also known to occur in fish species other than yellowtail, such as red sea bream and bluefin tuna.

The causative parasite of cerebral myxosporidiasis in yellowtail is Kudoa yasunagai. This parasite was discovered in 1980 in the brains of diseased fish with abnormal swimming behavior in farmed sea bass and farmed rock bream in Nagasaki Prefecture. Since the spores usually have seven spore coats and polar capsules, it was named as a new species, Septemcapsula yasunagai.
The species was described as agai. However, subsequent molecular phylogenetic analysis led to the deletion of the family Septemcapsulidae and the genus Septemcapsula, and the species was transferred to the genus Kudoa. Affected fish exhibit a characteristic swimming style that involves bending and circling the body. In the case of yellowtail, the body may also be curved. Small, spherical white cysts are seen around the brain. There is no effective measure to prevent this disease.

In fish species other than yellowtail, myxosporosis, also known as Kudoasia, is known to occur in tuna, flounder, etc., caused by myxosporidians of the genus Kudoa, and in pufferfish, myxosporidiasis, which is caused by myxosporidians of the genus Enteromyxum or Leptotheca, is known. Intestinal myxosporidiasis (also called pufferfish wasting disease) is known.

Benzimidazole drugs are known as antiparasitic drugs, and in Japan, mebendazole is used to treat pinworms, albendazole is used to treat hydatid diseases, and flubendazole is used for veterinary use against strongyles and roundworms. As pharmaceuticals, febantel and fenbendazole are approved as veterinary drugs against nematodes and tapeworms. For fisheries, febantel is approved for blowfish.

There is a report that tested the effect of albendazole on Loma salmonae, a microsporidia that parasitizes rainbow trout (Non-Patent Document 1). Gyrodactylus s, a monogenean parasite that parasitizes rainbow trout
Flubendazole, Mebendazole, Oxibendazole, Parbendazole, Triclabendazole against p.
There is a report that tested the effect of (Non-Patent Document 2). Flubendazole, Mebendazole, Oxibendazole, against Philasterides dicentrarchi, a ciliate that parasitizes turbot and sea bass.
There is a report that tested the effects of Parbendazole and Triclabendazole in vitro (Non-patent Document 3
). Albendazole, Mebendazole against Glugea anomala, a microsporidia that parasitizes sticklebacks
, There is a report that tested the effect of Fenbendazole (Non-Patent Document 4). There is a report that benzimidazole drugs are effective against Heterobotulium okamotoi, which is a monogenetic insect that parasitizes tiger puffer fish (Patent Document 1).

WO02/005649

D.J. Speare, et al., J.Comp. Path. 121, 241-248, 1999. “A Preliminary Investigation of Alternatives to Fumagillin for the Treatment of Loma salmonae Infection in Rainbow Trout”. J. L. Tojo, M. T. Santamarina, Disease of Aquatic Organisms, 33, 187-193, 1998. “Oral pharmacological treatments for parasitic diseases of rainbow trout Oncorhynchus mykiss. II: Gyrodactylus sp.”. R. Iglesias, et al., Disease of Aquatic Organisms, 49, 191-197, 2002. “Antiprotozoals effective in vitro against the scuticociliate fish pathogen Philasterides dicentrarchi”. Schmahl G., Benini J., Parasitol Res., 84(1), 41-49, 1998. “Treatment of fish parasites. 11. Effects of different benzimidazole derivatives (albendazole, mebendazole, fenbendazole) on Glugea anomala, Monies, 1887 (Microsporidia): ltrastructural aspects and efficacy studies.”

An object of the present invention is to provide an orally administered drug for downy mildew or myxosporidia in marine fish (particularly farmed fish), a method for exterminating the disease using the drug, and the like.

The inventors searched for an orally administered drug effective against downy mildew, which is an important problem in aquaculture, and searched for various existing antiparasitic drugs for animals and substances derived from natural products. As a result, the inventors discovered that some of the benzimidazole drugs sold as antiparasitic drugs for animals are effective, and completed the present invention.

The present invention relates to a therapeutic agent for diseases caused by microsporidia or myxosporea parasitizing fish, as described below in (1) to (24).
(1) Albendazole, Febantel, Fenbendazole, Oxfendazole,
A treatment for myxozoites or myxosporea disease in marine fish, comprising either mebendazole or flubendazole as an active ingredient.
(2) A treatment for beko disease according to (1), in which the causative parasite of beko disease is a microsporidia belonging to the genus Microsporidium or Spraguera.
(3) The causative parasites of myxosporidiasis are the genus Kudoa and the genus Enteromyxum.
(1) is a myxosporean organism belonging to either the genus Myxosporea, Myxosporea yxum, or the genus Leptotheca.
A treatment for myxosporidiasis.
(4) The therapeutic agent according to any one of (1) to (3), wherein the marine fish is a fish of the order Perciformes, Pleuronectiformes, or Tetraodontiformes.
(5) The fishes of the order Perciformes are fishes belonging to the genus Seriformes, the family Sparidae, or the genus Thunnus, the fishes of the order Pleuronectiformes are fishes belonging to the family Paralichthyidae, and the fishes of the order Tetraodontiformes are fishes belonging to the family Tetraodontiidae. (
4) Therapeutic agents.
(6) Fish that belong to the genus Seriola include yellowtail (Seriola quinqueradiata), amberjack (Seriola dumeril), and
i), Yellowtail amberjack (Seriola lalandi), Long-finned amberjack (Seriola rivoliana), Seriola carp
enteri, Seriola fasciata, Seriola hippos, Seriola peruana, and S.
eriola zonata, and the fish of the family Sparidae are Acanthopagrus eriola zonata.
us sivicolus), Taiwan sea bream (Argyrops bleekeri Oshima), Yellow sea bream (Dentex tumifro
ns), red sea bream (Evynnis tumifrons), red sea bream (Pagrus major), black porgy (Acanthopagrus
The fish species belonging to the genus Thunnus are either Pacific bluefin tuna (Thunnus orientalis), Atlantic bluefin tuna (Thunnus thynnus), southern bluefin tuna (Thunnus maccoyii), bigeye tuna (Thunnus o
besus), Albacore tuna (Thunnus alalunga), Yellowfin tuna (Thunnus albacares),
Longfin tuna (Thunnus tonggol) and Atlantic bluefin tuna (Thunnus atlanticus)
The fish species belonging to the family Paralichthys are: Japanese flounder (Paralichthys olivaceus), California halibut (Paralichthys californicus), summer flounder (Paralichthys dentata),
atus), Pseudorhombus pentophthalmus, Pseu
dorhombus cinnamoneus, Pseudorhombus dupliciocellatus, Pseudorhombus arsius, and Tarphops oligolepis, and the fish belonging to the family Tetraodontidae is either Takifugu rubripes or Takifugu po
rphyreus).
(7) Any of the therapeutic agents according to (1) to (6) for orally administering the active ingredient at 5 to 100 mg/kg of fish body weight per day.
(8) albendazole, febantel, fenbendazole, oxfendazole,
A treatment for nematode disease in marine fish, containing either mebendazole or ketoglutarate as an active ingredient.
(9) A therapeutic agent for treating myxozoites or myxosporea disease in marine fish, containing albendazole as an active ingredient.
(10) A therapeutic agent for myxosporidiasis, comprising albendazole or flubendazole as an active ingredient.
(11) A method for treating beko disease or myxosporediosis in marine fish, comprising orally administering to the marine fish an effective amount of any one of albendazole, febantel, fenbendazole, oxfendazole, mebendazole, and flubendazole.
(12) The method for treating beko disease according to (11), wherein the causative parasite of beko disease is a microsporidia belonging to the genus Microsporidium or Spraguera.
(13) The causative parasites of myxosporidiasis are the genus Kudoa and the genus Enteromyxum.
omyxum, or Leptotheca (1
1) A method for treating myxosporeanosis.
(14) The marine fish is a fish of the order Perciformes, Pleuronectiformes, or Tetraodontiformes, (11) to (1
Method 3).
(15) The method according to (14), wherein the fish of the order Perciformes are fishes belonging to the genus Seriola, the family Sparidae or the genus Thunnus, the fish of the order Pleuronectiformes are fishes belonging to the family Pleuronectidae, and the fish of the order Tetraodontiformes are fishes belonging to the family Tetraodontiidae.
(16) Fish belonging to the genus Seriola include yellowtail (Seriola quinqueradiata), amberjack (Seriola dumeriliata), and amberjack (Seriola quinqueradiata).
ili), Yellowtail amberjack (Seriola lalandi), Long-finned amberjack (Seriola rivoliana), Seriola ca
rpenteri, Seriola fasciata, Seriola hippos, Seriola peruana, and Seriola zonata, and the fish of the family Sparidae is Acanthopanax nigricans.
agrus sivicolus, Taiwan sea bream (Argyrops bleekeri Oshima), Yellow sea bream (Dentex tumi
frons), red sea bream (Evynnis tumifrons), red sea bream (Pagrus major), black porgy (Acanthopagrus
agrus schlegelii), or Rhabdosargus sarba, Sparus sarba, and the fishes belonging to the genus Thunnus are either Pacific bluefin tuna (Thunnus orientalis), Atlantic bluefin tuna (Thunnus thynnus), southern bluefin tuna (Thunnus maccoyii), bigeye tuna (Thunnus
obesus), albacore tuna (Thunnus alalunga), yellowfin tuna (Thunnus albacares)
, longfin tuna (Thunnus tonggol), and Atlantic bluefin tuna (Thunnus atlanticus
), and the fishes belonging to the family Paralichthys are Japanese flounder (Paralichthys olivaceus), California halibut (Paralichthys californicus), summer flounder (Paralichthys de
ntatus), Pseudorhombus pentophthalmus, Ps
eudorhombus cinnamoneus), Pseudorhombus dupliciocellatus, Pseudorhombus arsius, and Tarphops oligolepis, and the fish belonging to the Tetraodontiidae family is either Takifugu rubripes or Takifugu
porphyreus).
(17) 5 to 100 mg/kg of any one of albendazole, febantel, fenbendazole, oxfendazole, mebendazole, and flubendazole per day.
Any of the methods (11) to (16), comprising orally administering the compound to fish.
(18) Use of any of albendazole, febantel, fenbendazole, oxfendazole, mebendazole, and flubendazole in the manufacture of a medicine for the treatment of beko disease or myxosporediosis in marine fish.
(19) The use of (18), wherein the causative parasite of beko disease is a microsporidia belonging to the genus Microsporidium or Spraguera.
(20) The causative parasites of myxosporidiasis are the genus Kudoa and the genus Enteromyxum.
omyxum, or Leptotheca (1
8) Use.
(21) The marine fish is a fish of the order Perciformes, Pleuronectiformes, or Tetraodontiformes, (18) to (2)
Use of 0).
(22) Use of (21), in which the fishes of the order Perciformes are fishes belonging to the genus Seriola, the family Sparidae, or the genus Thunnus, the fishes of the order Pleuronectiformes are fishes belonging to the family Paralichthyidae, and the fishes of the order Tetraodontiformes are fishes belonging to the family Tetraodontiidae.
(23) Fish belonging to the genus Seriola include yellowtail (Seriola quinqueradiata), amberjack (Seriola dumeriliata), and amberjack (Seriola quinqueradiata).
ili), Yellowtail amberjack (Seriola lalandi), Long-finned amberjack (Seriola rivoliana), Seriola ca
rpenteri, Seriola fasciata, Seriola hippos, Seriola peruana, and Seriola zonata, and the fish of the family Sparidae is Acanthopanax nigricans.
agrus sivicolus, Taiwan sea bream (Argyrops bleekeri Oshima), Yellow sea bream (Dentex tumi
frons), red sea bream (Evynnis tumifrons), red sea bream (Pagrus major), black porgy (Acanthopagrus
agrus schlegelii), or Rhabdosargus sarba, Sparus sarba, and the fishes belonging to the genus Thunnus are either Pacific bluefin tuna (Thunnus orientalis), Atlantic bluefin tuna (Thunnus thynnus), southern bluefin tuna (Thunnus maccoyii), bigeye tuna (Thunnus
obesus), albacore tuna (Thunnus alalunga), yellowfin tuna (Thunnus albacares)
, longfin tuna (Thunnus tonggol), and Atlantic bluefin tuna (Thunnus atlanticus
), and the fishes belonging to the family Paralichthys are Japanese flounder (Paralichthys olivaceus), California halibut (Paralichthys californicus), summer flounder (Paralichthys de
ntatus), Pseudorhombus pentophthalmus, Ps
eudorhombus cinnamoneus), Pseudorhombus dupliciocellatus, Pseudorhombus arsius, and Tarphops oligolepis, and the fish belonging to the Tetraodontiidae family is either Takifugu rubripes or Takifugu
porphyreus), (22).
(24) The medicine is any one of albendazole, febantel, fenbendazole, oxfendazole, mebendazole, and flubendazole administered 5 to 100 mg per day.
Use of any of (18) to (23) for oral administration to a fish of mg/kg body weight.

The gist of the present invention is also the following (A1) to (A5), which are agents for killing microsporidians or myxosporidians parasitic on fish of the genus Seriola.
(A1) A repellent for microsporidians or myxosporidians that parasitize fish of the genus Seriola, which contains a benzimidazole drug as an active ingredient.
(A2) Microsporidium or myxosporidium is Microsporidium seriole.
olae), microsporidians belonging to the genus Spraguera, Kudoa yas
unagai), Myxobolus acanthogobii, Kudoa shiomitsui, Kudoa pericardialis, and Kudoa amamiensis (A1).
(A3) The insecticide of (A1) or (A2), wherein the benzimidazole drug is any one of albendazole, febantel, flubendazole, triclabendazole, fenbendazole, oxfendazole, and thiabendazole.
(A4) Fish belonging to the genus Yellowtail include yellowtail (Seriola quinqueradiata), amberjack (Seriola dumerili),
Kingfish (Seriola lalandi), Amberjack (Seriola rivoliana), Seriola carpente
ri, Seriola fasciata, southern amberjack (Seriola hippos), Seriola peruana, Seriola z
onata (A1) to (A3).
(A5) Any one of (A1) to (A4) for orally administering a benzimidazole drug at 0.5 to 500 mg/kg of fish weight per day.

Furthermore, the gist of the present invention is the parasite extermination methods (A6) to (A10).
(A6) A method for exterminating microsporidia or myxosporidia parasitic on fish of the genus Seriola, which comprises administering a benzimidazole drug.
(A7) Microsporidium or myxosporidium is Microsporidium seriole.
olae), Spraguera microsporidians, Kudoa yasunagai
, Myxobolus acanthogobii, Kudoa shiomitsui (Ku
doa shiomitsui), Kudoa pericardialis, or Kudoa amamiensis (A6).
(A8) The method of (A6) or (A7), wherein the benzimidazole drug is any one of albendazole, febantel, flubendazole, triclabendazole, fenbendazole, oxfendazole, and thiabendazole.
(A9) Fish belonging to the genus Yellowtail include yellowtail (Seriola quinqueradiata), amberjack (Seriola dumerili),
Kingfish (Seriola lalandi), Amberjack (Seriola rivoliana), Seriola carpente
ri, Seriola fasciata, southern amberjack (Seriola hippos), Seriola peruana, Seriola z
onata (A6) to (A8).
(A10) The method according to any one of (A6) to (A9), characterized in that the benzimidazole drug is orally administered at 0.5 to 500 mg/kg of fish body weight per day.

According to the present invention, it is possible to effectively treat, by oral administration, beko disease or myxosporea infection, which are parasitic diseases that are causing serious problems in widely cultivated marine fish, particularly fish belonging to the genus Seriola, family Sparidae, genus Thunnus, family Pleurotus, or family Tetraodontiidae.

FIG. 1 shows the test schedule in Example 7, in which the test feed was administered in two cycles during the rearing period.

The active ingredient of the therapeutic agent or antiparasitic agent of the present invention is one that is effective against downy mildew or myxosporidia among drugs classified as benzimidazole drugs. A benzimidazole drug is a drug having benzimidazole as a basic skeleton, and is a drug known as a parasitic agent and a fungicide. As a benzimidazole drug effective for downy mildew, albendazole (methyl N-(5-propylsulfanyl-1H-benzimidazol-2-yl)car
bamate), Febantel; methyl (NE)-N-[[2-[(2-methoxyacetyl)amino]-4-p
Fenbendazole; methyl N-(5-phenylsulfanyl-1H-benzimidazol-2-yl)carbamate
e) Oxfendazole; methyl N-[5-(benzenesulfinyl)-1H-benzimi
dazol-2-yl]carbamate), Mebendazole; methyl [5-(Benzoyl)benzimid
azol-2-yl]carbamate). Febantel is known to be a prodrug, the active ingredients of which are fenbendazole and oxfendazole. Benzimidazole drugs effective against myxosporosis include albendazole and flubendazole; methyl N-[5-(4-fluorobenzoyl)-1H-benzimidazol-2-yl]car
bamate), etc.

In one embodiment, the therapeutic agent or parasiticide of the present invention contains any one of albendazole, febantel, fenbendazole, oxfendazole, and mebendazole as an active ingredient and is intended to treat bekko disease in marine fish. In a preferred embodiment, the therapeutic agent or parasiticide of the present invention contains albendazole as an active ingredient and is intended to treat bekko disease in marine fish.

In yet another aspect, the therapeutic agent or antiparasitic agent of the present invention contains albendazole or flubendazole as an active ingredient and is intended to treat myxosporediosis.

Benzimidazole drugs that are effective against beko disease, especially albendazole, not only eliminate the parasites that cause beko disease before cysts form and inhibit cyst formation, but also have a therapeutic effect on infected fish that have already developed cysts.

The parasites for which the therapeutic agent or parasiticide of the present invention has an antiparasitic effect are microsporidia that cause beko disease and that parasitize marine fish, or myxosporidia that cause myxosporidiasis.
Examples of myxosporidian disease include Microsporidium seriolae, which is parasitic on yellowtail, and microsporidian cerebrospinal inflammation caused by microsporidium. Examples of myxosporidian disease include Kudoa sp., which causes Kudoa disease.
Myxosporean parasites belonging to the genus Enteromixum, which cause intestinal myxosporediosis, and Entero
Examples of myxosporean parasites include Kudoa yasunagai, which causes cerebral myxosporediosis, Myxobolus buri, which causes myxosporediosis, Kudoa shiomitsui, which causes cardiac myxosporediosis, and Kudoa pericarlis, which causes cardiac myxosporediosis.
rdialis), Kudoa amamiensis, which causes Amami Kudoa disease,
Kudoa hexapunctata, known to parasitize tuna
), Kudoa septempunctata, known to parasitize flounder
punctata, and Enteromyxum lei, known to parasitize pufferfish.
m leei, Enteromyxum fugu, Leptotheca fugu
ca fugu) are examples.

Marine fishes that are the subject of the present invention are fishes that are parasitized by the above-mentioned parasites. Examples of such marine fishes include fishes belonging to the order Perciformes, such as fishes belonging to the genus Seriola, the family Carangidae, the family Sparidae, or the family Scombridae, the genus Thunnus.

Fish species belonging to the genus Yellowtail include yellowtail (Seriola quinqueradiata) and amberjack (Seriola dum).
erili), amberjack (Seriola lalandi), amberjack (Seriola rivoliana), Seriola
carpenteri, Seriola fasciata, southern amberjack (Seriola hippos), Seriola peruana, S
An example is eriola zonata. In a preferred embodiment, the therapeutic agent or antiparasitic agent of the present invention is used for farmed fish such as yellowtail, amberjack, amberjack, amberjack, and amberjack, which are particularly commonly farmed.

The species of fish belonging to the Sparidae family are the southern black porgy (Acanthopagrus sivicolus), the Taiwan sea bream (Argyrops bleekeri Oshima), the yellow porgy (Dentex tumifrons), and the crimson sea bream (Evynnis
tumifrons), red sea bream (Pagrus major), black porgy (Acanthopagrus schlegelii), and sea bream (Rhabdosargus sarba, Sparus sarba).

Fish species belonging to the genus Tuna include bluefin tuna (Thunnus orientalis), Atlantic bluefin tuna (Thunnus thynnus), southern bluefin tuna (Thunnus maccoyii), and bigeye tuna (Thu
nnus obesus), albacore tuna (Thunnus alalunga), yellowfin tuna (Thunnus albacar)
es), Thunnus tonggol, and Atlantic bluefin tuna (Thunnus atlanti).
cus) is exemplified.

Fish that belong to the family Paralichthys include olive flounder (Paralichthys olivaceus), California halibut (Paralichthys californicus), summer flounder (Paralichthys dentatus), Pacific sole (Pseudorhombus pentophthalmus), and Pacific flounder (Pseudorhombus
cinnamoneus, Megaray (Pseudorhombus dupliciocellatus), Cardinal flounder (Pseud
orhombus arsius, and Tarphops oligolepis.

Fish that belong to the Tetraodontidae family include the Tiger Pufferfish (Takifugu rubripes), the Red Pufferfish (Takifugu po
Examples include rphyreus.

The therapeutic or antiparasitic agent of the present invention can be effective when administered orally. It can also be administered by immersing fish in a solution containing the drug in a medicinal bath or by injection.

The dosage of the therapeutic agent or parasiticide of the present invention is, for example, 5 mg to 100 mg, preferably 10 to 50 mg, per 1 kg of fish body weight per day for any fish.
Administer orally in the range of 40 mg. The administration period is 1 to 20 days, preferably 3 to 10 days.

The therapeutic agent or antiparasitic agent of the present invention uses not only the above-mentioned compound as an active ingredient alone, but also other substances such as carriers, stabilizers, solvents, excipients, diluents, etc., as necessary. Can be used in combination with ingredients. Moreover, the form may be any form commonly used for these compounds, such as powder, granules, tablets, and capsules. For fish that are sensitive to the taste and smell of compounds, methods such as coating can prevent a decrease in feed palatability and make it difficult for the compounds to leak out.

In the case of fish, drugs for oral administration are usually added to feed. When the therapeutic agent or parasiticide of the present invention is added to feed, it is preferable to use feed in which the nutritional components and physical properties required for each fish species are taken into consideration. Usually, a pellet-shaped mixture of fish meal, bran, starch, minerals, vitamins, fish oil, etc., or a pellet-shaped mixture of frozen fish such as sardines and powdered feed (mash) in which vitamins and the like have been added to fish meal, etc., is used. Since the daily feed intake is almost determined depending on the type and size of the fish, the therapeutic agent or parasiticide of the present invention is added to the feed in an amount converted to the above-mentioned dosage and administration method. The therapeutic agent or parasiticide of the present invention may be administered in a single dose or in several divided doses. Since the therapeutic agent of the present invention is used by adding it to fish feed, it is preferable to prepare a formulation suitable for adding an appropriate concentration to the feed that the fish takes in per day. Specifically, the active ingredient in the formulation is 1 to 50% by weight, preferably 5 to 30% by weight, more preferably 10 to 20% by weight.
It is preferable to prepare a formulation containing 0 to 20% by weight.

Examples of the present invention will be described below, but the present invention is not limited thereto.

<Anthelmintic effect of albendazole against beko disease>
In a land-based rearing facility, yellowtail fry were produced from fertilized eggs using seawater sterilized by sand filtration and ultraviolet light. The fry were released into a marine fish cage, reared for several days, and then transported back to the land-based facility. Rearing in the marine fish cage allowed the yellowtail fry to become naturally infected with the parasite that causes beko disease. The yellowtail fry were then transported back to the land-based facility and divided into two groups, a control group and an albendazole oral administration group, and each group was housed in a 200-liter tank. Seawater sterilized by sand filtration and ultraviolet light was poured into each group at 2.4 liters per minute. The fish were weighed on the final day of acclimation. After acclimation, the fish were fed the test feed for 10 consecutive days. Albendazole was administered at 40 mg/kg fish body weight/day, once a day. The albendazole-added feed was prepared by placing a specified amount of commercial feed and albendazole in a polyethylene bag, adding 2-fold diluted spreader SE-30 (low-sugar reduced starch syrup, Bussan Food Science Co., Ltd.) at 4% of the feed weight, and stirring. The control feed was prepared by adding only diluted SE-30 at 4% of the feed weight and stirring. After 10 days of test feed administration, the commercial feed was fed at 2% of the fish body weight. The test was conducted four times, and the number of days reared in the sea surface net cage, the water temperature during rearing in the net cage, the acclimation period after delivery to the facility, the test fish body weight at the start of the test, the feeding rate when the drug was orally administered, the period of the rearing test, the water temperature during the test, and the number of test fish are shown in Table 1.
In the fourth control group only, the fish were kept in a 500-liter tank and were reared with sand-filtered and UV-sterilized seawater poured in at 4.8 liters per minute.

At the end of the rearing experiment, all fish from both groups were removed and examined for the presence or absence of cysts in the lateral muscles by necropsy. Fish with cysts were designated as diseased fish. Evaluation was performed by comparing the incidence rate (number of diseased fish/number of test fish x 100) between the control group and the group orally administered albendazole.

Results and Discussion In the control plot, infected fish were observed in all four tests. On the other hand, in the albendazole oral administration group, no cyst-forming fish were observed in any of the tests, and the incidence of downy mildew was 0% (Table 2). Therefore, oral administration of albendazole deworms the main worms that have invaded the fish body.
It was confirmed that it inhibits cyst formation in this insect.

<Anthelmintic effect of benzimidazole drugs against downy mildew -1>
In Example 1, it was found that albendazole was effective in deworming the insects that cause downy mildew. Therefore,
We investigated the anthelmintic effects of benzimidazole drugs against downy mildew-causing insects. The fry produced in the same manner as in Example 1 were taken out to sea into a sea cage, reared for 10 days, and then transported to the land facility again. Through this marine cage rearing, young yellowtail fish were naturally infected with the parasite that causes downy mildew. The yellowtail fry brought back to the land facility were divided into 10 groups of 40 fish each (2 control groups, 2 groups treated with albendazole, 2 groups treated with febantel, 2 groups treated with triclabendazole, and 2 groups treated with flubendazole). Each was housed in a 200 liter aquarium. Water was poured into the water tank under the same conditions as in Example 1. The fish weight was measured on the final day of acclimatization, and the weight of the test fish was approximately 10 g. After acclimatization, test feed was fed for 10 consecutive days. The benzimidazole drug was administered at a dose of 40 mg/kg fish body weight/day, and was administered once a day. The benzimidazole-based drug-added feed and the control group feed were prepared in the same manner as in Example 1. After administering the test feed for 10 days, commercially available feed was fed, and the feeding amount was 2% of the fish body weight. The test was conducted twice. The breeding period was 37 days for the first test and 40 days for the second test. The water temperature during the rearing period was approximately 20.5°C.

At the end of the rearing test, all the fish were taken from all the plots, and the presence or absence of cysts in the body muscles was observed through necropsy, and the fish in which cysts were observed were designated as diseased fish. Evaluation was performed by comparing the incidence rate (number of affected fish/number of tested fish × 100), number of cysts, and cyst length in affected fish between the control group and the benzimidazole drug administration group.

Results and Discussion In both the albendazole administration area and the febantel administration area, no fish that formed cysts were observed, and the incidence of downy mildew was 0% (Tables 3 and 4). Therefore, it was reproduced that albendazole deworms the main worm and inhibits the cyst formation of the main worm, and furthermore, it was revealed that febantel also has an anthelmintic effect on the main worm. On the other hand, infected fish were observed in both the triclabendazole-treated and flubendazole-treated groups, and the incidence rate tended to be slightly higher than in the control group. Furthermore, the number and length of cysts in the affected fish were similar to those in the control group. Based on these results, it was considered that these two drugs were not deworming the main worms, but were instead promoting the onset of the disease. It has been found that not all benzimidazole drugs are effective against this parasite.

<Anthelmintic effect of benzimidazole drugs against downy mildew -2>
Continuing from Example 2, the anthelmintic effect of mebendazole, a benzimidazole drug, on the downy mildew-causing insect was investigated. The fry produced in the same manner as in Example 1 were taken offshore to a marine cage, reared for 11 days, and then transported to the land facility again. Through this marine cage rearing, young yellowtail fish were naturally infected with the parasite that causes downy mildew. The yellowtail fry brought back to the land facility were divided into 6 groups of 40 fish each (2 control groups, 2 groups treated with albendazole, and 2 groups treated with mebendazole), and each group was housed in a 200-liter aquarium. Water was poured into the water tank under the same conditions as in Example 1. The fish weight was measured on the final day of acclimatization, and the weight of the test fish was approximately 10 g. After acclimatization, test feed was fed for 10 consecutive days. The benzimidazole drug was administered at a dose of 40 mg/kg fish body weight/day, and was administered once a day. The benzimidazole-based drug-added feed and the control group feed were prepared in the same manner as in Example 1. Ten
After administering the test feed for 1 day, commercially available feed was fed, and the feeding amount was 2% of the fish body weight. The breeding period was 40 days. The water temperature during the rearing period was approximately 20.1°C.

At the end of the rearing test, all the fish were taken from all the plots, and the presence or absence of cysts in the body muscles was observed through necropsy, and the fish in which cysts were observed were designated as diseased fish. The evaluation was performed in the same manner as in Example 2.

Results and Discussion In the albendazole treatment area, no cyst-forming fish were observed, and the incidence of downy mildew was 0% (Table 5). Therefore, it was reproduced that albendazole deworms the main worm and inhibits cyst formation of the main worm. The incidence rate, number of developed fish cysts, and cyst length in the mebendazole treatment area were all lower than in the control area, demonstrating an anthelmintic effect against this parasite. However, its efficacy was considered to be lower compared to albendazole.

It was found that the anthelmintic effects of different benzimidazole drugs vary.

<Effects of albendazole and febantel on feeding in yellowtail>
From the results of Examples 1 to 4, it was revealed that the benzimidazole drugs albendazole and febantel have a high anthelmintic effect against Microsporidium seriolae, which causes beko disease in yellowtail. In order to use these drugs in yellowtail aquaculture, it is desirable that the administration of these drugs has no or low side effects that adversely affect feeding. In previous tests, water temperatures of 20°C or higher were used, and no adverse effects on feeding were observed. Therefore, we investigated whether the administration of albendazole and febantel has an adverse effect on feeding at a water temperature of approximately 18°C. Yellowtail fry were divided into six groups of 10 fish each (two control groups, two albendazole-treated groups, and two febantel-treated groups), and each group was housed in a 200-liter tank. Water was poured into the tank under the same conditions as in Example 1. The fish weight was measured on the final day of acclimation, and the test fish weighed approximately 73 g. After acclimation, the fish were fed with drug-added feed for 10 consecutive days, and then continued to be raised on commercially available feed for 20 days, and then
The fish were fed the drug-added feed for 10 consecutive days, and then reared again on the commercial feed for 29 days. The administration conditions of albendazole and febantel were 40 mg/kg fish body weight/day, and administration was once a day. The drug-added feed and the control feed were prepared according to Example 1. The amount of feed given was 1.5% of the fish body weight. The water temperature during the rearing period was approximately 18.3°C.

At the end of the rearing test, all fish were taken from all plots and their weight and body length were measured.

Results and Discussion In the albendazole-treated group, feeding activity was slightly decreased at the first administration of the drug, and it took longer for the fish to feed than in the control group. However, no decrease in feeding activity was observed during subsequent feeding or drug administration, and the fish weight and body length at the end of the experiment were comparable to those in the control group (Table 6). On the other hand, in the febantel-treated group, the fish did not eat the entire amount of drug-added feed at the first administration of the drug, leaving about 20% of the feed remaining. Even after switching to commercial feed after drug administration, about 20% of the feed remained for 10 days. No decrease in feeding activity was observed at the second administration of drug-added feed, but a decrease in feeding activity was observed for 10 days after switching to commercial feed after drug administration, and the feed was divided into two portions per day to ensure that the fish consumed the entire amount of feed. The fish weight and body length at the end of the experiment in this group were clearly lower than those in the control group and the albendazole-treated group. Therefore, it was revealed that febantel reduces the feeding activity of yellowtail at low water temperatures. These results suggest that Febantel has a higher risk of side effects on fish than albendazole.

<Study on the dosage of albendazole for deworming>
The yellowtail fry produced in the same manner as in Example 1 were released into a marine cage, raised for 11 days, and then transported back to the onshore facility. This marine cage rearing allowed the yellowtail fry to become naturally infected with the parasite that causes beko disease. The yellowtail fry were then transported back to the onshore facility and divided into 12 groups of 40 fish each (two control groups with 0 mg/kg fish weight, two groups with 5 mg/kg fish weight, and one group with 5 mg/kg fish weight).
The fish were placed in a 200-liter tank (two groups administered 10 mg/kg fish weight, two groups administered 10 mg/kg fish weight, two groups administered 20 mg/kg fish weight, two groups administered 30 mg/kg fish weight, and two groups administered 40 mg/kg fish weight). Water was poured into the tank under the same conditions as in Example 1. The fish weight was measured on the last day of acclimation, and the test fish weighed about 10 g. After acclimation, the test feed was fed for 10 consecutive days. The feed was administered once a day. The albendazole-added feed and the control feed were prepared in the same manner as in Example 1. After the 10-day administration of the test feed, the fish were fed a commercially available feed at a feed amount of 2% of the fish weight. The rearing period was 40 days. The water temperature during the rearing period was about 20.1°C.

At the end of the rearing test, all fish were taken from all groups and examined by necropsy to see whether or not there were cysts in the lateral muscles of the body. Fish in which cysts were observed were determined to be affected. Evaluation was performed in the same manner as in Example 2.

Results and Discussion In the fish treated with albendazole 5 mg/kg fish body weight, cysts of downy mildew were observed, although fewer than in the control group (Table 7). On the other hand, no fish that formed downy mildew cysts were observed in the groups where 10 mg/kg of fish body weight or more was administered. Therefore, the minimum effective dose for deworming downy mildew is 10
It was thought that the amount was about mg/kg fish weight.

<Consideration of the number of days to administer albendazole to ward off beko disease>
Wild-caught juveniles were introduced into a fish pen at a fishing ground and reared for 21 days. Rearing in the marine fish pen allowed the juvenile yellowtail to become naturally infected with the parasite that causes beko disease. The juvenile yellowtail brought to the land facility were divided into four groups (control group: 90 fish for 10 days at 0 mg/kg fish weight, 70 fish for 3 days at 40 mg/kg fish weight, 70 fish for 6 days at 40 mg/kg fish weight, 70 fish for 10 days at 40 mg/kg fish weight). Each group was housed in a 200-liter tank. Water was poured into the tank under the same conditions as in Example 1. After 2 days of acclimation, the test feed was fed. The feed was administered once a day. The weight of the test fish at the start of the experiment was approximately 8 g. The albendazole-added feed and the control feed were prepared in the same manner as in Example 1. After administration of the test feed, the fish were fed with commercially available feed, with the amount of feed being 3% of the fish's body weight. The rearing period was 22 days. The water temperature during the rearing period was 20°C for the first 10 days and then 22°C until the end of rearing.

At the end of the rearing test, all the fish were taken from all the plots, and the presence or absence of cysts in the body muscles was observed through necropsy, and the fish in which cysts were observed were designated as diseased fish. The evaluation was performed in the same manner as in Example 2.

Results and Discussion No infected fish were observed in the group treated with albendazole at 40 mg/kg for 10 days. Although a small number of infected fish were observed in the 3-day and 6-day treatment groups, the incidence rate, number of cysts, and cyst length in the affected fish were clearly lower than in the control group, and the treatment period was 3 or 6 days. However, it showed an anthelmintic effect against the main worm. In addition, one fish in each group treated with albendazole for 3 days and 10 days became thin and died due to withdrawal from food. These fish did not eat food from the time of grouping. It was surmised that transportation and environmental changes had an effect.

<Therapeutic effect of albendazole on fish with downy mildew>
Naturally caught fry were introduced into a fish tank at a fishing ground and reared for 50 days. Through this marine cage rearing, young yellowtail fish were naturally infected with the parasite that causes downy mildew. The yellowtail fry brought to the land facility were divided into 10 groups with 28 fish each (control group: 0 mg/kg fish body weight, 2 groups for 10 days, 10 mg/kg fish body weight, 3 days treatment group: 2 groups, 10 mg/kg fish body weight, 3 days treatment group).
kg fish body weight/2 groups for 10 days, 2 groups for 40 mg/kg fish body weight/3 days administration, 2 groups for 40 mg/kg fish body weight/10 days administration). Each group was housed in a 200 liter aquarium. Water was poured into the water tank under the same conditions as in Example 1. In addition, in order to understand the development status of downy mildew at the beginning of the test, 29 fish were necropsied and the number and length of cysts in the body muscles were examined. Test feed was fed after 3 days of acclimatization. Administration was once a day. The weight of the test fish at the start of the test was approximately 21 g. Albendazole-added feed and control group feed were prepared in the same manner as in Example 1. After administering the test feed, commercially available feed was fed, and the feeding amount was 2% of the fish body weight. In this test, the test feed was administered for two cycles during the rearing period, and the test schedule is shown in Figure 1. The water temperature during the rearing period was 22°C.

At the end of the rearing test, all the fish were taken from all the plots, and the presence or absence of cysts in the body muscles was observed through necropsy, and the fish in which cysts were observed were designated as diseased fish. The evaluation was performed in the same manner as in Example 2.

Results and Discussion In all albendazole-treated areas, the incidence rate, number of cysts in infected fish, and cyst length were reduced compared to the start of the test, demonstrating that albendazole has an anthelmintic effect even in infected fish where cysts were already observed. The increase in the number of infected fish in the control area at the end of the test is thought to be due to the formation of cysts by the worms at a stage that had not yet reached cyst formation, and albendazole's cyst formation inhibitory effect was confirmed once again. It was also found that albendazole administered at 10 mg/kg fish body weight for 3 days had a therapeutic effect and an inhibitory effect on cyst formation. Several dead fish were observed in each test area. The dead fish were thin, and it was presumed that they died due to anorexia, as in Example 6.

<Anthelmintic effect of benzimidazole drugs against the myxosporean Kudoa yasunagai>
The anthelmintic effect of benzimidazole drugs against Kudoa yasunagai was investigated.
The young fish produced in the same manner were released into ocean fish pens, raised for 10 days, and then transported back to the onshore facility.
The yellowtail fry were naturally infected with K. yasunagai by rearing in the marine cage. The yellowtail fry were then brought back to the onshore facility and divided into 10 groups of 40 fish each (2 control groups, 2 albendazole-treated groups, 2 febantel-treated groups, 2 triclabendazole-treated groups, and 2 flubendazole-treated groups), and were housed in 200-liter tanks. Water was poured into the tanks under the same conditions as in Example 1. The fish weight was measured on the final day of acclimation, and the test fish weighed approximately 10 g. After acclimation, the test feed was fed for 10 consecutive days. The benzimidazole drug was administered at 40 mg/kg fish weight/day, once a day. The benzimidazole drug-added feed and the control feed were prepared as described in Example 1.
The experiment was carried out in the same manner as in Example 1. After the 10-day test feed administration, the fish were fed commercial feed at a feed rate of 2% of the fish's body weight. The rearing period was 40 days. The water temperature during the rearing period was approximately 20.5°C.

At the end of the rearing test, all fish were taken from all plots, and brain smears were prepared and stained with DiffQuick. 40 fields of view were observed under a 400x optical microscope to determine the presence or absence of spores and the number of spores. The evaluation was performed by comparing the detection rate (number of detected fish/number of test fish × 100) and the number of spores of detected fish between the control area and the benzimidazole drug administration area.

Results and Discussion In the albendazole-administered area and flubendazole-administered area, the detection rate and the number of spores were
The value was clearly lower than that in the control area. On the other hand, the number of spores was higher in the febantel treated area than in the control area. Therefore, it was found that albendazole and flubendazole exert an anthelmintic effect on the main worm, and that febantel promotes the proliferation of the main worm.

Not all benzimidazole drugs are effective against this worm.
It was found that even if a product has an anthelmintic effect against beko disease, it is not necessarily effective against Kudoa yasunagai and other insects.

In addition, 7 dead fish were observed in the control plot and 1 dead fish in the albendazole plot. The dead fish were thin, and it was presumed that they died from the same cause as in Example 6.

INDUSTRIAL APPLICABILITY The present invention provides an antiparasitic drug that can be orally administered to eradicate beko disease or myxosporidiasis caused by microsporidia that parasitize marine fish.

Claims (16)

A treatment for diseases caused by microsporidia that parasitize fish of the genus Seriola, characterized by orally administering 10 to 40 mg of the active ingredient albendazole per day per kg of fish body weight. The therapeutic agent according to claim 1, wherein the microsporidium belongs to the genus Microsporidium or the genus Spraguera. The therapeutic agent according to claim 1 or 2, characterized in that the active ingredient is orally administered at 10 to 30 mg/kg of fish body weight per day. Fish of the genus Yellowtail include Seriola quinqueradiata, Seriola dumerili, Seriola lalandi, Seriola rivoliana, Seriola carpenteri, Seriola fasciata, Seriola hippos, Seriola peruana, and Seriola zonata. The therapeutic agent according to any one of claims 1 to 3, which is any of the above. The therapeutic agent according to any one of claims 1 to 4, wherein the administration period of the active ingredient is 1 to 20 days. A therapeutic agent according to any one of claims 1 to 5, wherein the administration period of the active ingredient is 3 to 10 days. The therapeutic agent according to any one of claims 1 to 6, wherein a period of 10 to 17 days during which the active ingredient is not administered is provided after administration. 8. The therapeutic agent according to any one of claims 1 to 7, wherein administration is started 9 to 23 days after introducing the young fish into the cage. A method for treating diseases caused by microsporidia that parasitize fish of the genus Seriola, comprising orally administering the active ingredient albendazole at a dose of 10 to 40 mg/kg of fish body weight per day to the fish, the method comprising treating the fish with microsporidia. The method of claim 9, wherein the microsporidian is a microsporidian belonging to the genus Microsporidium or Spraguera. The method of claim 9 or 10, wherein the daily oral dose of the active ingredient is 10 to 30 mg/kg of fish body weight. Yellowtail fish include yellowtail (Seriola quinqueradiata) and amberjack (Seriola dumerili).
, amberjack (Seriola lalandi), amberjack (Seriola rivoliana), Seriola carpen
teri, Seriola fasciata, southern amberjack (Seriola hippos), Seriola peruana, and Seriola
The method of treatment according to any one of claims 9 to 11, wherein the treatment method is any one of Iola zonata. The method of treatment according to any one of claims 9 to 12, wherein the administration period of the active ingredient is 1 to 20 days. A treatment method according to any one of claims 9 to 13, in which the administration period of the active ingredient is 3 to 10 days. 15. The method of treatment according to any one of claims 9 to 14, wherein a period of 10 to 17 days during which no administration is performed is provided after administration of the active ingredient. 16. The method of treatment according to any one of claims 9 to 15, characterized in that administration is started 9 to 23 days after the fry are introduced into the cage.

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