JPWO2015080198A1 - Methods for controlling crustacean infections - Google Patents

Abstract

An object of the present invention is to provide a method for suppressing an infection that has no effective countermeasures among crustacean infections and that may cause annihilation once it occurs in a farm. The crustacean infection control method according to the present invention is characterized by including a step of ingesting 0.001 g / kg body weight or more of Parachlorella algae per se to the crustacean.

Description

  The present invention relates to a method for suppressing crustacean infections by effectively enhancing the immunity of the crustaceans themselves.

  Edible crustaceans are sometimes collected from nature, but are often cultivated for stable supply and efficiency. Recently, “growing fisheries” are also flourishing, where shellfish are raised to the larval stage, and then fully grown after being released.

  However, in shellfish farming, it is raised in a high density state, and once an infection occurs, it can be annihilated or nearly annihilated. Therefore, antibiotics are sometimes used in shellfish farming, but antibiotics have problems such as adverse effects on the environment and the appearance of resistant bacteria in addition to the problem of remaining in shellfish. In addition, general antibiotics are mainly effective against bacteria unless they are resistant bacteria, but they have the disadvantage of not being effective against viruses and fungi, and it is necessary to use special antibiotics for viruses and fungi . There are very few drugs that are particularly effective against viruses.

  Therefore, it is preferable to increase the immunity of the crustacea itself, and to impart resistance to infectious diseases and natural healing power.

  Examples of feeds for enhancing the immunity of crustaceans include peptidoglycan (Patent Documents 1 and 2), yeast-derived protein components (Patent Documents 3 and 4), lipopolysaccharide (Patent Document 5), and bacterial cells themselves ( Patent Document 6), phospholipid-containing protein and the like (Patent Document 7).

  Moreover, the polysaccharide contained in marine chlorella is known as an immunostimulatory action component which has the tumor growth inhibitory effect in a mouse | mouth (patent document 8). Patent Document 9 discloses a poultry feed to which chlorella containing lutein, which is a kind of carotenoid, is added, and the components contained in chlorella have an effect of enhancing biological defense, an effect of enhancing resistance to bacterial infection, and the like. It is described.

JP-A-6-22705 Japanese Patent Laid-Open No. 10-229831 JP-A-8-113539 JP-A-8-283175 International Publication No. 00/57719 Pamphlet JP 2001-342140 A JP 2004-97006 A JP-A-61-78729 JP 2004-298062 A

  As described above, various methods are known for enhancing the immunity of not only crustaceans but also other organisms.

  However, the conventional technology for improving the immunity of crustaceans is effective against actual infectious diseases, such as the fact that even though the immunity is enhanced, the test to prove it is very simple. There were places where it was unknown. Similar immunity mechanisms have been found not only in vertebrates but also in plants, and crustacean immune mechanisms have found humoral and cellular immunity as in vertebrates. There are many differences. Thus, among vertebrates, especially for humans, so-called health foods that enhance immunity have been widely developed, but immunostimulatory substances effective for vertebrates are not always effective for crustaceans.

  Under the above circumstances, an object of the present invention is to provide a method for suppressing an infection that has no effective countermeasures among crustacean infections and can cause annihilation once it occurs in a farm.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, it was found that Parachlorella algae itself, which is closely related to Chlorella algae but different from Chlorella algae, can enhance the immunity of crustaceans and remarkably suppress their infectious diseases, thereby completing the present invention. did.

  Hereinafter, the present invention will be described.

  [1] A method for suppressing crustacean infectious diseases, comprising a step of ingesting 0.001 g / kg body weight or more of Parachlorella algae per se against a crustacean.

  [2] The method for suppressing crustacean infections according to [1] above, wherein the parachlorella algae are ingested for 4 weeks or more. If parachlorella algae are ingested by crustaceans over 4 weeks, infection can be more reliably suppressed.

  [3] The method for suppressing crustacean infections according to the above [1] or [2], wherein a parachlorella algae is ingested at a dose of 5.0 g / kg body weight or less per day. Similar to general immunostimulants, parachlorella algae may not be improved in a dose-dependent manner if the intake is too large, and the improvement effect may begin to decrease. However, if the daily intake is 0.001 g / kg body weight or more and 5.0 g / kg body weight or less, the effect of improving immunity against crustaceans is sufficiently high.

  [4] The method for suppressing crustacean infections according to any one of the above [1] to [3], wherein Parachlorella kessleri species are used as Parachlorella algae.

  [5] The method for suppressing crustacean infectious disease according to [4] above, wherein KNK-A001 strain (Accession Number: FERM BP-22256) is used as the Parachlorella quercerii algae.

[6] Crustacean infection according to any one of [1] to [5] above, wherein a parachlorella algae having 18S rRNA having any one of the following base sequences (1) to (3) is used: To control the disease.
(1) Base sequence of SEQ ID NO: 1 (2) In the base sequence defined in (1) above, a base sequence in which 1 to 31 bases have been deleted, substituted and / or added (3) (1) ) Base sequence having a sequence identity of 98.5% or more with respect to the base sequence defined in

  [7] The method for suppressing crustacean infections according to any one of [1] to [3] above, wherein Parachlorella beyerinckii species are used as Parachlorella algae.

  [8] The method for suppressing crustacean infections according to any one of [1] to [7], which is for suppressing infections caused by viruses.

  [9] The method for suppressing crustacean infections according to any one of [1] to [8] above, wherein heterotrophic cultured Parachlorella algae are used.

  [10] Parachlorella algae for controlling crustacean infectious diseases, characterized by feeding the crustacean with 0.001 g / kg body weight or more of Parachlorella algae per day use.

  According to the present invention, the immunity of crustaceans can be improved and the infectious disease can be effectively suppressed even under high density breeding conditions such as aquaculture. In addition, as for the Parachlorella algae used in the method of the present invention, its living cells may be used, but even if it is a dry body, the effect can be similarly exerted, so that stable supply is possible. . Therefore, the method for suppressing crustacean infections according to the present invention can effectively suppress crustacean infections that have not had effective countermeasures so far, for example, enabling efficient and stable aquaculture of crustaceans. As a thing, it is very useful in industry.

FIG. 1 is a graph showing changes in the survival rate of virus-infected tiger prawns when fed with or without normal feed containing Parachlorella algae according to the present invention. FIG. 2 is a graph showing changes in the survival rate of virus-infected tiger shrimp when fed with or without a normal feed containing Parachlorella algae according to the present invention. FIG. 3 is a graph showing changes in the survival rate of virus-infected tiger prawns when a feed containing or not containing Parachlorella algae according to the present invention is given. FIG. 4 is a graph for comparing the number of cells contained in the hemolymph of virus-infected tiger shrimp when a feed containing Parachlorella algae according to the present invention or a normal feed not containing it is given. FIG. 5 shows a case of the virus-infected vaname shrimp in the case where the feed containing Parachlorella algae according to the present invention is given, and in the case where the feed containing the normal antibiotic alone is given as the negative control or the commercial antibiotic substitute is given as the positive control. It is a graph which shows the change of a survival rate. FIG. 6 shows the vibrio-infected Banamei shrimp in the case where a feed containing Parachlorella algae according to the present invention is given, and in the case where a feed containing only a normal feed or a commercially available antibiotic substitute is given as a negative control. It is a graph which shows the change of survival rate.

  The crustacean infection control method according to the present invention is characterized by including a step of ingesting 0.001 g / kg body weight or more of Parachlorella algae per se to the crustacean.

  The genus Parachlorella belongs to the Treboxya algae among the genus Chlorella that straddle the Treboxyphyceae and Chlorophyceae, but it depends on the molecular phylogenetic analysis using 18S rDNA and 16S rDNA. For example, it forms a different group from other genus Chlorella.

  Parachlorella algae do not have a strong cell wall structure like Chlorella algae, but instead are covered with a thick membrane mainly composed of polysaccharides. This is considered to be the reason why Parachlorella algae are more easily digested and absorbed by crustaceans than Chlorella algae, and the resistance to infection can be improved efficiently.

  In general, Parachlorella algae can be obtained by isolating colonies from freshwater samples collected in the field by subculture using a general medium, and finally identifying the genus species by molecular phylogenetic analysis. Can be obtained. Moreover, what is necessary is just to acquire and use if there exists a commercially available thing.

  Parachlorella algae can grow in aerobic and anaerobic conditions in common media such as freshwater and LB media, but proliferate particularly well at room temperature to 30 ° C. under bright and aerobic conditions. .

  The para Chlorella algae, for example, Parachlorella kessleri, Parachlorella beyerinckii, Parachlorella marinichlorella, Parachlorella dictyoshaerium, Parachlorella mucidosphaerium, Parachlorella closteriopsis, Parachlorella dicloster, include Parachlorella beijerinck. Among these, Parachlorella kessleri and beyerinckii are particularly preferable.

Of the Parachlorella kessleri seed algae, a particularly suitable KNK-A001 strain (accession number: FERM BP-22256) is deposited with the depository as follows.
(I) Name and address of depositary institution Name: National Institute of Technology and Evaluation Patent Biological Depositary Center Address: 2-5-8-1 Kazusa Kamashi, Kisarazu City, Chiba Prefecture, Japan Room 120 (ii) Date of accession: 2013 September 3 (iii) Accession Number: FERM BP-22256
The morphological characteristics of the KNK-A001 strain according to the present invention are as follows.

  The partial base sequence of 18S rRNA of KNK-A001 strain is shown in SEQ ID NO: 1 (SEQ ID NO: 1).

  In addition, when the 18S rRNA has the following base sequence (2) or (3) with respect to the base sequence (1) corresponding to SEQ ID NO: 1, Parachlorella algae as in the case of the KNK-A001 strain It is considered that crustacean infections can be effectively suppressed as in the case of KNK-A001 strain.

(2) A base sequence in which one or more and 31 or less bases are deleted, substituted and / or added in the base sequence defined in (1) above (3) For the base sequence defined in (1) above In addition, even when the number of bases of the 18S rRNA base sequence changes due to the introduction of mutation such as deletion, the number of mutations is 1 or more and 31 or less as described above. If the percentage of sequence identity is within the range of 98.5% or more as described above, it is possible to specify a position corresponding to a specific position before mutagenesis in the sequence after mutagenesis. Easy for those skilled in the art. Specifically, the sequences to be compared can be aligned and the position determined by a program for multiple alignment of base sequences. In addition, the identity of the base sequence can be easily determined by a program for multiple alignment.

  In the base sequence (2), the number of mutations such as deletion is preferably 30 or less, 20 or less, or 10 or less, more preferably 9 or less, 8 or less, 6 or less, or 5 or less, and further preferably 4 or less, 3 or less. Two or less or one is more preferable.

  In the base sequence (3), the percentage of base sequence identity is preferably 99.0% or more, 99.2% or more, or 99.4% or more, more preferably 99.5% or more, 99.6. % Or more or 99.7% or more is more preferable, and 99.8% or more or 99.9% or more is more preferable.

  Parachlorella algae used in the present invention are preferably heterotrophic cultured at least in the final culture stage. Parachlorella algae may differ in the composition of cells and the components contained in cells when autotrophic culture and heterotrophic culture are performed, but at least the crustaceans by heterotrophic cultured Parachlorella algae The inhibitory effect of infectious diseases has been confirmed.

  Parachlorella algae according to the present invention include mutants of which the dry body exhibits an excellent inhibitory effect on crustacean infections. Here, the “mutant” means a parachlorella algae improved by artificial selection, hybridization, mutation, genetic recombination and the like.

  The Parachlorella algae according to the present invention may use living cells, but may also use dry matter. As in the examples described later, it is possible to effectively suppress crustacean infections even when a dried body of Parachlorella algae is used, and if it is a dried body, it can be used under simpler conditions than live cells. It can be stored and can be supplied stably.

  A dried body of Parachlorella algae itself can be obtained by drying a living cell of Parachlorella algae or a culture solution containing the living cells. That is, the living cells may be separated from the culture solution of Parachlorella algae by filtration or centrifugation, and dried, or the culture solution may be dried as it is. Parachlorella algae release secretions into the culture solution, and this secretion may be one of the effective components for the growth of aquatic organisms. When the culture solution is dried as it is, the dried product contains such secretions.

  The living cells of Parachlorella algae and the culture solution containing the living cells can be dried according to a conventional method. For example, the living cells or the culture solution may be dried at 50 ° C. or higher and 200 ° C. or lower for 10 seconds or longer and 10 hours or shorter. The pressure may be reduced during drying. It should be noted that drying time can be shortened by drying the culture solution while flowing it into a thin film. Moreover, you may freeze-dry. Specific drying conditions can be appropriately adjusted according to the amount of Parachlorella algae to be dried, the amount of the culture solution, the equipment to be used, and the like. Moreover, since the obtained dried body is generally aggregated, it may be further pulverized. The degree of pulverization may be adjusted to such an extent that the crustaceans to be fed are easily ingested.

  The “dried body” in the present invention is not particularly limited, and the water content is not limited as long as the Parachlorella algae are not living cells and are not in a clearly wet state. For example, the moisture content of the dried product can be 30% by mass or less. As the water content, the lower the value, the higher the storage stability of the feed and the easier the transportation, so 20% by mass or less is preferable, 15% by mass or less is more preferable, and 10% by mass or less is more preferable. 8% by mass or less is even more preferable. On the other hand, since it is not necessary to dry excessively, the water content is preferably 1% by mass or more, more preferably 2% by mass or more, and further preferably 5% by mass or more. In addition, since said drying is performed in order to kill a cell and improve storage stability, the water content in the feed at the time of an actual feeding or a feed product does not become a problem. For example, the dried body of Parachlorella algae may be fed after being dispersed in aquaculture water or the like. Further, the moisture content in the dried product can be easily measured by the Karl Fischer method.

  In the method of the present invention, the crustacean is fed 0.001 g / kg body weight or more of Parachlorella algae per day. In the method of the present invention, as described above, either live cells or dry bodies of Parachlorella algae may be fed, but such intake is based on the mass of Parachlorella algae in the dry state.

  The intake of Parachlorella algae may be adjusted as appropriate according to the degree of crustacean growth. For example, the daily intake is preferably 0.002 g / kg body weight or more, 0.003 g / kg body weight or more, or 0.005 g / kg body weight or more, 0.01 g / kg body weight or more, 0.02 g / More preferably kg body weight or more or 0.05 g / kg body weight or more. On the other hand, if the intake is too large, there may be a shortage of nutritional components not contained in Parachlorella algae or nutritional components with a low content, so the intake is preferably 20 g / kg body weight or less, 10 g / kg body weight or less is more preferable. Furthermore, in order to exhibit the effect of improving immunity against crustaceans more reliably, the intake is particularly preferably 5.0 g / kg body weight or less. Furthermore, if the stimulation is too strong, the immunosuppressive effect may be reduced. From this point of view, the daily intake is preferably 1.0 g / kg body weight or less, more preferably 0.5 g / kg body weight or less, and further preferably 0.4 g / kg body weight or less. .

  Parachlorella algae may be fed alone, but in that case, crustaceans may not be ingested, and nutritional components not included in Parachlorella algae may be insufficient. In such a case, it is preferable to mix parachlorella algae with common crustacean feed. In such a case, the proportion of Parachlorella algae in the entire feed is preferably 0.001% by mass or more and 10% by mass or less. The proportion is more preferably 0.002% by mass or more, further preferably 0.005% by mass or more, particularly preferably 0.01% by mass or more, more preferably 8% by mass or less, and 6% by mass or less. More preferred is 5% by mass or less.

  The object of the present invention is to improve the resistance of crustaceans to infections caused by viruses and the like. However, since the immune function does not improve immediately, the Parachlorella algae according to the present invention are preferably ingested continuously by the crustacea, for example, for at least one week. The intake period is preferably 2 weeks or more, more preferably 4 weeks or more, and particularly preferably 5 weeks or more. The upper limit is not particularly limited, and may be from the start of crustacean breeding to sufficient growth, for example, until shipment as a product.

  The number of intakes of Parachlorella algae may be adjusted as appropriate. For example, it can be adjusted to 1 to 3 times per day together with other feeds.

  When parachlorella algae are mixed with feed and ingested by crustaceans, the form is not particularly limited, and may be determined as appropriate according to the type of shellfish to be fed and the degree of growth. For example, in general, the entire feed is in a powder state, and it is 50 μm or more and 100 μm or less for larvae, and can be about 500 μm or more and 800 μm or less in a fully grown stage. Can be adjusted step by step.

  Examples of the crustaceans to be subjected to the method of the present invention include shrimp such as tiger prawn, bovine shrimp, Taisho shrimp, white shrimp, blue shrimp, brown shrimp, tiger shrimp, lobster, lobster, lobster, southern shrimp, crayfish; , Crabs such as king crab, pine crab, crabs, crayfish, and the like, but the method of the present invention can be applied without particular limitation as long as it is a crustacean to be cultured or seeded.

  According to the method of the present invention, it is possible to effectively suppress crustacean infections. Note that “suppression” in the present invention includes both the concepts of suppression of onset of an infectious disease, that is, “prevention”, and reduction of infectious disease that has developed, that is, “treatment”. Therefore, the method of the present invention may be carried out prophylactically prior to the onset of crustacean infections, or may be used to treat while symptoms are relatively mild or to inhibit the progression of symptoms. It may be used to relieve severe symptoms.

  This application is based on Japanese Patent Application No. 2013-245986 filed on November 28, 2013, and Japanese Patent Application No. 2013-254192 filed on December 9, 2013. It is what I insist. The entire contents of the specifications of Japanese Patent Application No. 2013-245986 filed on November 28, 2013 and Japanese Patent Application No. 2013-254192 filed on December 9, 2013 are incorporated herein by reference. Incorporated for reference.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1: Culture experiment of prawn prawns (1) Preparation of feed After sterilized liquid medium was inoculated with Parachlorella kessleri strain KNK-A001 (accession number: FERM BP-22256) and light-shielded with aluminum foil And pre-cultured at 30 ° C. for 72 hours. Next, a preculture medium was added to a larger-capacity sterilized liquid medium, light-shielded with aluminum foil, and then cultured for 143 hours at an internal temperature of 30 ° C., an aeration rate of 2 L / min, a stirring speed of 450 rpm, and a pH of 6-7.

  Subsequently, the culture solution was dried with a double drum dryer, and the obtained dried aggregate was pulverized with a feather mill to obtain a dried cell product of KNK-A001 strain.

  In addition, Parachlorella beyerinckii seed algae (product name “Bayerink”, purchased from Mitsui & Co., Ltd.) was subjected to the same experiment as the Parachlorella algae.

  In a commercially available shrimp feed (manufactured by Higashimaru, product name “Shrimp Star”), 0.1% by mass (1,000 ppm) or 1% by mass (10,000 ppm) of the above KNK-A001 strain, or the above-mentioned Baylink algae The feed was prepared by adding 0.1 mass% (1,000 ppm) and mixing well. For comparison, only the shrimp feed was used as a control.

(2) Aquaculture Experiment Four 200 L water tanks were prepared, each containing the same amount of sand, and seawater heated to about 24 ° C. was always poured with the same amount of water to make it flow. Fifteen fish shrimp weighing 3-5 g were housed in each aquarium, and the feed was fed once a day after sunset. The next morning, the amount of food remaining in each tank was observed, and the amount of feed was adjusted. Daily feeding was approximately 300-600 g / kg / day per shrimp body weight.

  Separately, by homogenizing the muscle of drowned prawns by infecting white spot syndrome virus, the causative virus of prawn white spot disease, and diluting the supernatant obtained by centrifugation with phosphate buffer A virus solution was prepared. Four weeks after the start of breeding, 0.1 mL of the virus solution was injected into the muscles of the third abdominal node of shrimp in each group of aquariums to infect the virus. Survival rate was calculated from the number of shrimps surviving daily from virus infection. The results are shown in FIG.

  As shown in FIG. 1, in the control group that was fed only with the commercial feed, the survival rate decreased rapidly from the virus infection, and the survival rate decreased to 7% on the 8th day after the virus infection. On the other hand, in the other three groups fed with the feed containing Parachlorella algae, the survival rate was clearly maintained compared to the control group even after virus infection. From these results, it was clarified that parachlorella algae improve crustacean immunity, improve resistance to viral infection, and suppress infection. For several days after the virus infection, the survival rates of the Parachlorella querseri KNK-A001 strain 0.1% intake group and the Bayerink strain 0.1% intake group are lower than those of the control group. In these groups, the amount of virus in two prawns killed on the third day after virus infection was measured by PCR, and it was revealed that the cause of death was not virus infection. The cause of death can be a shock caused by the injection process. Therefore, if there is no death due to other than viral infection in these groups, the survival rate after 14 days may have been higher.

Example 2: Shrimp culture experiment In the same manner as in Example 1 (1), 0.02% by mass (200 ppm) of Parachlorella kessleri strain KNK-A001 (accession number: FERM BP-22256) or A feed containing 0.05% by mass (500 ppm) was prepared. For comparison, only the shrimp feed was used as a control.

  Further, a culture experiment was conducted in the same manner as in Example 1 (2). The results are shown in FIG. In FIG. 2, “*” indicates that there is a significant difference at p <0.05 in the t-test regarding the survival rate of the prawns on the 14th day after virus infection, and “**” is significant at p <0.01. Indicates that there is a difference.

  As shown in the results of FIG. 2, in the group fed with the feed containing Parachlorella algae, the survival rate was significantly improved compared to the group fed the normal feed, and the virus infection was effectively suppressed. It was proved that.

Example 3: Shrimp farming experiment In Example 1, a similar experiment was conducted using smaller shrimp. That is, in the same manner as in Example 1 (1), 0.01% by mass (100 ppm), 0.02% by mass of Parachlorella kessleri KNK-A001 strain (accession number: FERM BP-22256) A feed containing 200 ppm) or 0.05 mass% (500 ppm) was prepared. For comparison, only the shrimp feed was used as a control. Further, in Example 1 (2), aquaculture experiment was conducted in the same manner except that the prawn having a weight of about 1.5 g was used and the number of prawns in each water tank was 25. The results are shown in FIG.

  As shown in FIG. 3, even when the amount of the inoculated virus solution relative to the body weight is larger, the survival rate of the three groups fed with the feed containing Parachlorella algae is the control group fed only with the commercial feed. It was clearly higher than The amount of virus was measured by PCR in the same manner as in Example 1 for each of the prawns killed in the 200 ppm and 500 ppm Parachlorella algae combination groups, but it was revealed that the cause of death was not virus infection.

  Further, 14 days after infection with white spot syndrome virus, hemolymph was collected from surviving prawns, and the number of cells contained in the collected hemolymph was counted.

  Specifically, 0.5 mL of a sufficiently ice-cooled K-199 medium was placed in a 1 mL syringe, a 26 G injection needle was attached to the syringe, and 0.5 mL of hemolymph was collected from prawns. Separately, 2 mL of K-199 medium was added to a 15 mL tube, and the hemolymph was added and gently stirred. Subsequently, the hemolymph was poured onto a hemocytometer and the number of cells was counted. The results are shown in FIG.

  As shown in FIG. 4, the number of haemolymph cells in the three groups of prawns fed with the feed containing Parachlorella algae was clearly higher than that in the control group fed only with commercial data. Since the cells contained in the hemolymph are involved in immunity, this result demonstrates that feeding a diet containing Parachlorella algae increases the immunity of the crustacea and strengthens the infection. It was.

Example 4: Culture of shrimp shrimp In the same manner as in Example 1 (1), 0.005% by mass (50 ppm), 0.01% by mass of the above KNK-A001 strain was added to a commercially available shrimp feed (manufactured by Yue Hai). % (100 ppm) or 0.02 mass% (200 ppm) containing feed was prepared. For comparison, only the shrimp feed was used as a negative control, and a feed having the composition shown in Table 2 was used as a positive control. In addition, the positive control sample includes “BioPlus (registered trademark)” manufactured by HANSEN, which is a bacterial spore mixture and is an antibiotic substitute.

  Four 200 L water tanks were prepared for each group, the same amount of sand was added to each group, and seawater heated to about 24 ° C. was constantly poured with the same amount of water and allowed to run. Each fish tank contained 15 lobster shrimp with a body weight of 1 to 2 g, and the feed was fed once a day after sunset. The next morning, the amount of food remaining in each tank was observed, and the amount of feed was adjusted. Daily feed was approximately 30-60 g / kg / day per shrimp body weight.

  Separately, a white spot syndrome virus solution was prepared in the same manner as in Example 1 (2), and after 40 days from the start of breeding, 0.1 mL of the virus solution was added to the muscles of the third abdominal node of shrimp in each group of aquariums. The virus was infected by squeezing inside. The survival rate was calculated from the number of surviving shrimps every day from the virus infection to the 13th day. The results are shown in FIG.

  As the results shown in FIG. 5, the survival rate of the three groups fed with the feed containing Parachlorella algae was clearly higher than that of the control group fed with the commercial feed alone. Thus, it was revealed that Parachlorella algae enhance the immunity of crustaceans.

Example 5: Culture of shrimp shrimp In the same manner as in Example 1 (1), 0.005 mass% (50 ppm), 0.01 mass of the KNK-A001 strain was added to a commercially available shrimp feed (manufactured by Yue Hai). % (100 ppm), 0.02% by mass (200 ppm) or 0.05% by mass (500 ppm) of feed was prepared. Further, as in Example 4, a negative control feed and a positive control feed were used.

Separately, Vibrio alginolyticus possessed by the Southern Seawater Research Institute is 1.5 × 10 ⁶ CFU (Colony Forming Unit), 40 days after the start of breeding, the third abdominal node of shrimp in each group's aquarium Infection was performed by squeezing into the muscle. The survival rate was calculated from the number of shrimps surviving every day until the 12th day after infection. Vibrio alginolyticus is a resident bacteria in seawater, and contact with seawater causes otitis media, skin ulcers and wound infections, and bacteremia in humans. The results are shown in FIG.

  As shown in FIG. 6, the survival rate of the three groups fed with the diet containing Parachlorella algae was also clearly higher than that of the control group fed only with the commercial feed against Vibrio infections. It was. As described above, it has been clarified that Parachlorella algae enhances the immunity of crustaceans and has an effect on crustacean bacterial infections.

Claims (10)

  A method for suppressing crustacean infections, comprising a step of ingesting 0.001 g / kg body weight or more of Parachlorella genus algae per se to crustaceans.   The method for suppressing crustacean infections according to claim 1, wherein the parachlorella algae is ingested over 4 weeks.   The method for suppressing crustacean infections according to claim 1 or 2, wherein a parachlorella algae is ingested at a dose of 5.0 g / kg body weight or less per day.   The method for suppressing crustacean infectious diseases according to any one of claims 1 to 3, wherein Parachlorella kessellii species are used as Parachlorella algae.   The method for suppressing crustacean infectious diseases according to claim 4, wherein the KNK-A001 strain (accession number: FERM BP-22256) is used as the Parachlorella querserie species. The method for suppressing crustacean infections according to any one of claims 1 to 5, wherein a parachlorella algae having 18S rRNA having any one of the following base sequences (1) to (3) is used.
(1) Base sequence of SEQ ID NO: 1 (2) In the base sequence defined in (1) above, a base sequence in which 1 to 31 bases have been deleted, substituted and / or added (3) (1) ) Base sequence having a sequence identity of 98.5% or more with respect to the base sequence defined in   The method for suppressing an infection of a crustacean according to any one of claims 1 to 3, wherein a Parachlorella beyerinckii species algae is used as the Parachlorella algae.   The method for suppressing crustacean infections according to any one of claims 1 to 7, wherein the method is for suppressing infections caused by viruses.   The method for suppressing crustacean infections according to any one of claims 1 to 8, wherein heterotrophic cultured Parachlorella algae are used.   Use of Parachlorella algae for controlling crustacean infections, characterized in that the Parachlorella algae itself is ingested by 0.001 g / kg body weight or more per day for crustaceans.