KR102242408B1 - Method for preventing viral hemorrhagic septicemia against fish and method for producing fish resistant to infection against viral hemorrhagic septicemia virus - Google Patents

Abstract

Since the method for preventing viral hemorrhagic sepsis of the present invention can effectively prevent viral hemorrhagic sepsis occurring in flounder, it can be usefully used in the aquaculture industry of flounder. In addition, because it exhibits a protective effect against viral hemorrhagic sepsis similar to injection-based vaccines through immersion, viral hemorrhagic sepsis can be easily prevented not only in adult fish but also in fry, and through this, it has disease resistance against viral hemorrhagic sepsis virus. You can produce halibut.

Description

TECHNICAL FIELD [Method for preventing viral hemorrhagic septicemia against fish and method for producing fish resistant to infection against viral hemorrhagic septicemia virus}

The present invention relates to a method for preventing viral hemorrhagic sepsis in fish and a method for producing fish having infection resistance to viral hemorrhagic sepsis virus.

Viral hemorrhagic septicemia (VHS), a representative viral disease that causes mass mortality in farmed fish in low temperature, is one of the fish infectious diseases that cause very serious economic losses to the flounder farming industry in Korea.

The causative virus of VHS, which has been called Egtved disease from the past, is a viral hemorrhagic septicemia virus (VHSV) belonging to the rhhabdovirus family characterized by a nucleic acid type of negative strand RNA. . VHSV has been known to be highly susceptible to freshwater salmon family fish, but by the 2000s it is known to cause disease in more than 90 species of freshwater or seawater fish. As a disease subject to quarantine, it has been designated as a legally infectious disease of aquatic organisms in Korea.

VHS is known to be mainly caused by horizontal infection, so it is thought that water-borne virus transmission is possible, but the overall mechanism for water-borne horizontal infection is unknown. There are no studies related to the distribution of VHSV in the aquatic environment and the distribution of the virus according to season or region.

At the halibut farming site in Korea, VHS is known to occur during the winter, which is the low water temperature, and the mortality rate tends to decrease when the water temperature exceeds 15℃, and then it is known to end with the passage of time.

The occurrence of VHS in flounder farming is a disease that needs to be established as soon as possible because it is widely seen from fry to adult fish, and has a high mortality rate.

VHSV structural proteins and antigenic proteins, inactivated vaccines, recombinant vaccines, and vaccine development studies such as attenuated vaccines or DNA vaccines are being conducted, but there are no commercially available vaccines. In the case of an attenuated vaccine, it is reported to be effective under laboratory conditions, but it is difficult to obtain permission due to the risk of recovery of the pathogenicity of the virus and the risk of spreading it to nature.

Injection immunity induces stress on small fish, and injection stress alone can lead to death. Therefore, it is difficult to apply to flatfish of 15 cm or less. In addition, injections are required for each individual, requiring a lot of labor and additional costs for vaccination. Therefore, the need to replace the vaccine delivery route with a mucosal (immersion/oral) route that does not stress the body has been raised in order to overcome the limitations of the injection immunological method. Vaccine delivery by immersion/oral route can be applied to fish of very small size without causing stress on fish, but it has the disadvantage of being very low in terms of efficacy by injection vaccine.

The present inventors have tried to develop an effective immunization method for the defense of VHSV infection in fish. As a result, the present invention was completed by confirming the water temperature at which VHSV infection does not occur, and finding that VHS disease-resistant flounder having resistance to VHS can be produced by applying a method of pre-soaking the flounder with VHSV in a certain period and condition. .

Accordingly, an object of the present invention is to provide a method for preventing viral hemorrhagic sepsis in fish.

Another object of the present invention is to provide a method for producing fish having infection resistance to viral hemorrhagic sepsis virus.

According to one aspect of the present invention, the present invention provides viral hemorrhagic activity for fish, comprising immersing the fish in a water tank at a water temperature of 17 to 23°C containing a viral hemorrhagic septicemia virus (VHSV). It is about how to prevent sepsis.

The present inventors have tried to develop an effective immunization method for preventing VHSV infection in fish, and as a result, confirming the water temperature at which VHSV infection does not occur, and applying a method of pre-soaking VHSV in flounder in a certain period and conditions. It was found that it can produce VHS disease-resistant flounder with resistance to

As used herein, the term'Viral hemorrhagic septicemia (VHS)' is a viral disease that causes great damage to more than 70 species of freshwater and marine fish throughout Europe, the United States and Southeast Asia. In Korea, since it first occurred in 2001, it has been causing huge economic losses due to frequent occurrence. It occurs mainly in spring from late winter, and shows a high mortality rate of 50-70% in all age groups (from fry to adult) of flounder at a water temperature of 8-15℃.

The virus that causes viral hemorrhagic sepsis (VHSV) is a negative single-stranded RNA virus and belongs to the family rhabdovirus. VHSV causes mortality not only in young fry, but also in large adult fish at the time of shipment.Infected fish are body color blackened, transparent ascites retention in the peritoneum and abdominal cavity, liver congestion, spleen enlargement, kidney enlargement, necrosis and gills in the liver, kidney, spleen and skeletal muscles. It has been reported that internal symptoms such as thickening of the liver, hepatic concentration, and accumulation of skeletal muscle blood cells appear, and the virus enters the fish through the skin epithelial layer or gill endothelial cells and travels rapidly to the internal organs such as the hematopoietic tissue of the kidney and spleen through the bloodstream have.

In the present invention, the term "prevention" means any action that suppresses or delays the onset of VHS.

The method for preventing VHS in fish of the present invention will be described in detail step by step as follows:

(a) Fish immersion in a water tank of appropriate water temperature containing VHSV

The water temperature of the water tank containing VHSV is adjusted to 17 to 23°C, and fish are immersed in the water tank.

According to the present invention, the water temperature of the tank for immersing fish is 17 to 23°C, 17 to 22°C, 17 to 21°C, 17 to 20°C, 17 to 19°C or 17 to 18°C, for example, 17°C. to be.

The most important factor in the VHS prevention method of the present invention is the water temperature of the water immersed in fish. VHSV is a viral infectious disease that occurs mainly during low water temperature. If the breeding temperature of fish is controlled above the onset temperature, mortality by VHSV does not occur at all or death is reduced. In the present invention, the water temperature at which VHSV infection does not occur was confirmed, and VHSV was pre-immersed in fish under this temperature condition to induce immunity to VHSV.

The tank is 10 ⁴ TCID ₅₀ /mL to 10 ⁸ TCID ₅₀ /mL, 10 ⁴ TCID ₅₀ /mL to 10 ^7.5 TCID ₅₀ /mL, 10 ⁴ TCID ₅₀ /mL to 10 ⁷ TCID ₅₀ /mL, 10 ⁴ TCID ₅₀ / mL to 10 ^6.5 TCID ₅₀ /mL, 10 ⁴ TCID ₅₀ /mL to 10 ⁶ TCID ₅₀ /mL, 10 ^4.5 TCID ₅₀ /mL to 10 ⁸ TCID ₅₀ /mL, 10 ^4.5 TCID ₅₀ /mL to 10 ^7.5 TCID ₅₀ /mL , 10 ^4.5 TCID ₅₀ /mL to 10 ⁷ TCID ₅₀ /mL, 10 ^4.5 TCID ₅₀ /mL to 10 ^6.5 TCID ₅₀ /mL, 10 ^4.5 TCID ₅₀ /mL to 10 ⁶ TCID ₅₀ /mL, 10 ⁵ TCID ₅₀ /mL to 10 ⁸ TCID ₅₀ /mL, 10 ⁵ TCID ₅₀ /mL to 10 ^7.5 TCID ₅₀ /mL, 10 ⁵ TCID ₅₀ /mL to 10 ⁷ TCID ₅₀ /mL, 10 ⁵ TCID ₅₀ /mL to 10 ^6.5 TCID ₅₀ /mL or 10 ^{Including VHSV at a concentration of 5} TCID ₅₀ / mL to 10 ⁶ TCID ₅₀ / mL, for example, including VHSV at a concentration of 10 ^5.5 TCID ₅₀ / mL, but the concentration of VHSV may vary depending on the type of individual, and the It is not limited to the base concentration.

According to the present invention, the VHSV used in fish immersion may be a virus that has not been subjected to inactivation treatment.

If a virus that has not been inactivated is directly used as an immunogen, it is necessary to verify its safety because of the risk that the virus can recover its pathogenicity and act as an infectious agent if it spreads to nature. As demonstrated in the following examples, as a result of mixed breeding of halibut treated with VHSV and non-infected halibut at the water temperature, no death was observed in both the group treated with VHSV and the experimental group of uninfected halibut. This indicates that there was no release of VHSV, which causes horizontal infection from flounder treated with VHSV at the water temperature. Therefore, the method of the present invention has safety as a method of preventing VHS for fish.

The immersion is carried out for 30 minutes to 6 hours, 30 minutes to 5 hours, 30 minutes to 4 hours, 30 minutes to 3 hours, 30 minutes to 2 hours or 30 minutes to 1 hour 30 minutes, for example, 1 hour. I can.

The fish may be halibut fish, for example, halibut, more preferably halibut fry, but is not limited thereto.

(b) induction of immune response

After immersion, fish are reared for 3 to 5 weeks in a water bath at a water temperature of 5 to 25°C that does not contain VHSV to induce an immune response against VHSV.

The step of inducing the immune response may be carried out by breeding the fish for 3 to 5 weeks, for example, 4 weeks in a tank that does not contain VHSV.

The fish after the immersion in step (a) survives without dying even if the water temperature decreases under the temperature conditions capable of infecting VHSV. Therefore, the step of inducing the immune response is possible even under a temperature condition where VHSV infection is possible.

According to an embodiment of the present invention, the induction of the immune response is 5 to 25°C, 5 to 23°C, 5 to 21°C, 5 to 20°C, 5 to 19°C, 5 to 18°C, 10 to 25°C, 10 To 23°C, 10 to 21°C, 10 to 20°C, 10 to 19°C, 10 to 18°C, 15 to 25°C, 15 to 23°C, 15 to 21°C, 15 to 20°C, 15 to 19°C or 15 It can be carried out at a temperature condition of to 18°C, for example, it can be carried out at 17°C.

According to another aspect of the present invention, the present invention relates to a method for producing fish having infection resistance to viral hemorrhagic sepsis virus comprising the following steps:

Immersing fish in a water bath at a water temperature of 17 to 23° C. containing viral hemorrhagic septicemia virus (VHSV);

Inducing an immune response against viral hemorrhagic sepsis virus by rearing the fish for 3 to 5 weeks in a water bath at a water temperature of 17 to 23°C; And

Obtaining a fish having resistance to viral hemorrhagic sepsis virus infection.

The production method of fish having infection resistance to VHSV of the present invention relates to a method of obtaining fish subjected to the above VHS prophylaxis, and overlapping content between them is omitted in consideration of the complexity of the present specification.

Fish with infection resistance to VHSV produced by this method do not release VHSV, which causes horizontal infection. Therefore, through the production method of fish having infection resistance to VHSV of the present invention, it is possible to produce a safe flounder fry that has strong disease resistance to VHS and does not have a horizontal source of infection.

Since the method for preventing viral hemorrhagic sepsis of the present invention can effectively prevent viral hemorrhagic sepsis occurring in flounder, it can be usefully used in the aquaculture industry of flounder. In addition, because it exhibits a protective effect against viral hemorrhagic sepsis similar to injection-based vaccines through immersion, it is possible to easily prevent viral hemorrhagic sepsis not only in adult fish but also in fry, and through this, flounder, which has disease resistance against viral hemorrhagic sepsis. Can produce.

1 is a schematic diagram of treatment with viral hemorrhagic sepsis virus live immersion vaccine. (a) exposing the viral hemorrhagic virus to the flounder fry cultured at a water temperature of 17° C. at a concentration of ^{10 5.5} TCID _{50 /mL for about 1 hour;} (b) maintaining the water temperature at 17° C. for about 30 days and inducing immunity of flounder fry; (c) the production of halibut resistant to viral hemorrhagic sepsis infection; (d) producing a resistant flounder fry against viral hemorrhagic sepsis virus infection by adjusting the water temperature to 10°C, which is the temperature of viral hemorrhagic sepsis infection.
2 is a graph comparing the cumulative mortality rate according to the viral hemorrhagic sepsis virus concentration of flounder fry infected by the immersion method.
3 is a graph comparing the cumulative mortality rate according to the water temperature of viral hemorrhagic sepsis virus infection of flounder fry infected by the immersion method.
Figure 4a is a graph comparing the relative survival rate after viral hemorrhagic sepsis virus artificial infection of flounder fry treated with live virus immersion vaccine at a water temperature of 17°C.
Figure 4b is a graph comparing the relative survival rate after viral hemorrhagic sepsis virus artificial infection of flounder fry treated with a live virus immersion vaccine at a water temperature of 20°C.
FIG. 5A is a graph comparing virus infection rates by organs of flounder over time after viral hemorrhagic sepsis virus immersion infection of flounder fry under a water temperature of 10°C.
FIG. 5B is a graph comparing virus infection rates by organs of flounder over time after viral hemorrhagic sepsis virus immersion infection of flounder fry under a water temperature of 17°C.
6 is a graph comparing the relative survival rate of flounder fry treated with live virus immersion vaccine when moving from a water temperature of 17°C to a water temperature of 10°C.
7 is a graph comparing the cumulative mortality rate of flounder treated with a viral hemorrhagic sepsis virus immersion vaccine after a viral hemorrhagic sepsis virus artificial infection.
8 is a graph comparing the relative survival rate after viral hemorrhagic sepsis virus artificial infection at a water temperature of 10° C. after treatment with a live virus immersion vaccine according to the virus concentration at a water temperature of 17°C.
FIG. 9 is a graph comparing the safety of horizontal infection of vaccine-treated flounder after viral hemorrhagic sepsis virus artificial infection during mixed breeding of vaccine-treated flounder and non-vaccinated flounder. (a) infected halibut (naive) and co-breed halibut (naive); (b) infected halibut (naive) and co-breed fish (vaccinated); (c) Infected fish (vaccinated) and co-breed fish (naive).

Hereinafter, the present invention will be described in more detail through examples. These examples are only for describing the present invention in more detail, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by these examples according to the gist of the present invention. .

Example

Throughout this specification, “%” used to indicate the concentration of a specific substance means solid/solid (weight/weight) %, solid/liquid (weight/volume) %, and liquid unless otherwise stated. /Liquid (volume/volume) is %.

Example 1. VHSV immersion immune treatment method

1-1. Preparation of viral hemorrhagic sepsis virus antigen

VHSV reference antigen used to measure viral hemorrhagic septicemia virus (VHSV) viral infection value and to detect RNA was cultured and identified from viruses isolated from VHS-infected flounder at Yeosu farm in 2005, and electrophoresis using PCR method. The isolates (hereinafter VHSV FY05 isolates) identified by this method were used. VHSV was inoculated into FHM, a fathead minnow cell line, and the virus was cultured.FHM was DMEM (DMEM10) containing 10% (v/v) fetal calf serum, 150 UI/mL of penicillin G, and 100 μg/mL of streptomycin. And cultured. The cultured VHSV was centrifuged at 8,000 rpm for 15 minutes at 4°C to remove cell debris, and then the supernatant was collected and stored at -80°C until use.

1.2. Determination of breeding temperature during immersion treatment of VHSV-free flounder fry

2 is a graph showing the cumulative mortality according to the VHSV concentration when VHSV was infected with VHSV-free flounder fry.

VHSV was immersed in flounder fry using the immersion method. VHSV adjusted to infection values of 10 ^3.5 , 10 ^5.5 and 10 ^7.5 TCID ₅₀ / mL was subjected to immersion infection for 1 hour at 10° C. known as the optimal VHS incidence temperature, and then the cumulative mortality was observed for about 15 days.

As a result, as shown in Fig. 2, ^{the cumulative mortality rates according to the infection rates 10 3.5} , 10 ^5.5 and 10 ^7.5 TCID ₅₀ /mL were 0%, 50% and 70%, respectively.

3 is a graph showing the cumulative mortality according to the breeding water temperature when viral infection by the immersion method in VSHV-free flounder fry.

As a result of measuring the cumulative mortality rate while rearing for about 20 days after immersing ^{10 5.5} TCID ₅₀ /mL virus in flounder fry whose breeding water temperature was adjusted to 10°C, 17°C, 20°C and 23°C for 1 hour, cumulative The mortality rates were 80%, 20%, 25% and 30%, respectively.

VHSV is known as a viral infectious disease that occurs mainly during low water temperature. In this case, when the temperature of the breeding water is adjusted above the onset temperature, mortality is not reduced or death does not occur.

Based on the results of FIGS. 2 and 3, the VHSV immersion vaccine-treated virus infection concentration was set to ^{10 5.5} TCID _{50 /mL under a water temperature condition of 17°C or higher.}

Example 2. Infection resistance to VHS of flounder fry treated with VHSV immersion vaccine

2.1. Determination of breeding temperature during immunization with VHSV immersion vaccine in uninfected flounder fry

In order to induce immunity and produce halibut fry showing disease resistance to VHS by treating fish raised in water temperature conditions outside the range of VHS incidence, the appropriate breeding water temperature conditions were reviewed.

Figures 4a and 4b is lowered to the water temperature halibut subjected to VHSV immersion vaccination in terms of VHSV unattended 17 ℃ VHSV uninfected temperature infection halibut fry and 20 ℃ to 10 ℃ of VHSV infections temperature VHSV 10 ^4.5 TCID _50/100 This is the result of observing the relative survival rate while breeding by performing artificial infection in the muscle of flounder so that it becomes µl/fish. Relative survival rates were observed as 90% and 80% at water temperatures of 17°C and 2C°C, respectively, and there was no significant difference in the relative survival rates at water temperatures of 17°C and 20°C. Based on this result, it was judged that the concentration ^{of 10 5.5} TCID ₅₀ /mL at a water temperature of 17°C was most suitable for VHSV immersion vaccine treatment.

Example 3. Safety verification of flounder treated with VHSV immersion vaccine

3.1. Changes in viral infection value in fish after VHSV immersion vaccine treatment

When a virus that has not been inactivated is directly used as an immunogen, safety verification is required for the risk of recovery of the pathogenicity of the virus and the risk that it may act as an infectious agent when spreading to nature.

Figure 5a is a graph measuring the virus infection value of flounder per organ after VHSV virus immersion in flounder fry at 10°C, which is a VHSV infection water temperature, at 10 ^5.5 TCID _{50 /mL.}

Figure 5b is a graph measuring the virus infection value of flounder organs after VHSV virus immersion at a water temperature of 17°C, which is a VHSV immersion vaccine treatment condition, at 10 ^5.5 TCID _{50 /mL in the present invention.}

As a result of conducting VHSV artificial infection to flounder fry under the condition of water temperature of 10°C, virus infection rate began to be measured about 5 days after infection, and high infection rate ^{of 10 5} to 10 ⁹ TCID _{50 /mL in all test institutes on the 7th day of infection.} Was measured. In addition, from the 5th day of infection to the 10th day, the end of the experiment, the viral infection value in the halibut was steadily increased. However, in the case of halibut fry treated with VHSV at a water temperature of 17℃, the proliferation of VHSV in the halibut and an increase in infectious value were not observed.

From the above results, it was confirmed that the VHSV live virus immersion vaccine treatment condition of the present invention at a water temperature of 17°C and 10 ^5.5 TCID ₅₀ /mL virus infection was not recognized in the halibut fish body by VHSV infection under the immersion treatment condition.

3.2. Infection safety evaluation under fluctuating water temperature conditions of VHSV immersion vaccine-treated fish

6 is a result of an experiment conducted to confirm the safety of the vaccine-treated flounder as a horizontal source of infection when the water temperature is adjusted to 10°C, which is a condition of VHSV infection after VHSV immersion vaccine treatment.

After treatment with VHSV immersion vaccine at a water temperature of 17°C, the relative survival rate was observed by breeding at 10°C, which is a water temperature of VHSV infection, for 30 days. The relative survival rate was confirmed to be 100% after the water temperature of flounder treated with VHSV immersion vaccine was changed to 10°C at a water temperature of 17°C.

Through the above results, it was confirmed that the flounder treated with VHSV immersion vaccine survived even when the water temperature decreased due to VHSV infection conditions, and the immersion-treated virus did not act as a horizontal source of infection in water during the breeding period.

FIG. 7 is a result of confirming the acquisition of disease resistance against VHSV infection after performing an artificial infection by intramuscular injection in the immersion vaccine-treated flounder of FIG. 6 at a water temperature of VHSV infection.

10 ^4.5 TCID ₅₀ /100 µl/fish After artificial infection through intramuscular injection, the relative survival rates of flounder fry without VHSV infection were compared. The relative survival rate after intramuscular injection was observed to be about 80% in the case of flounder treated with VHSV immersion vaccine, but 100% mortality was observed in the case of uninfected flatfish, resulting in a relative survival rate of 0%.

^{Figure 8 shows the VHSV concentration of 10 2.5} , 10 ^5.5 , 10 ^7.5 TCID ₅₀ / mL for 30 days under the condition of water temperature of 17° C. After immersion vaccine treatment was performed, the breeding water temperature was adjusted at 10° C., the VHS infection water temperature, and 10 ^4.5 TCID ₅₀ / This is the result of comparing the relative survival rate with VHSV-free flounder fry after artificial infection through intramuscular injection under the condition of 100 µl/fish. ^{In the case of halibut fry treated with 10 2.5} , 10 ^5.5 TCID ₅₀ /mL after artificial infection, a relative survival rate of about 80% was observed, and in ^{the case of halibut fry treated with 10 7.5} TCID ₅₀ /mL, a relative survival rate of about 70% Indicated.

From these results, it was confirmed that the flounder treated with VHSV immersion vaccine strongly resisted VHSV re-infection and showed a very high survival rate. From the results, it was confirmed that strong resistance to VHS was obtained in fish immunized with VHSV immersion.

9 is a result of testing the safety of flounder treated with VHSV immersion vaccine as a horizontal source of infection. VHSV immersion vaccine-treated flounder and VHSV-free flounder were mixed in different combinations and reared for 30 days to observe the cumulative mortality rate.

9A is a result of comparing cumulative mortality due to horizontal infection in halibut fry of VHSV by mixing and breeding halibut with artificial infection of VHSV and halibut without artificial infection with respect to non-infected halibut. A cumulative mortality rate of about 70% was observed in the experimental group of halibut infected with VHSV, and a cumulative mortality rate of about 40% was observed in the case of the uninfected halibut that was mixed with them. VHSV produced and released from was transmitted horizontally, confirming that infection occurred in uninfected flounder.

In the case of FIG. 9B, the results of comparing the cumulative mortality due to horizontal infection of the halibut treated with VHSV artificial infection and the halibut treated with the VHSV immersion vaccine and the experimental group subjected to mixed breeding. In the case of uninfected flounder artificially infected with VHSV, a cumulative mortality rate of about 60% was observed during the experiment, but no mortality was observed in flounder treated with VHSV immersion vaccine.

Through this result, it was confirmed that the VHSV immersion vaccine-treated flounder was not infected at all despite the conditions under which VHSV horizontal infection was established, so that the VHSV immersion vaccine treatment method of the present invention obtained disease resistance to VHS.

9C is a graph showing experimental results of mixed breeding of halibut treated with VHSV immersion vaccine and uninfected halibut. That is, if the release of VHSV occurs from the halibut treated with the VHSV immersion vaccine, it is confirmed whether horizontal infection occurs with the uninfected halibut that has been mixed and raised, and the possibility of the horizontal infection of the disease-resistant fish obtained through the treatment with the VHSV immersion vaccine of the present invention is verified. This is the result of confirming the safety of As a result of the experiment, no mortality was observed in both the VHSV immersion vaccine treatment group and the uninfected flounder test group.

This result means that the immersion vaccine-treated flounder acquired disease resistance to VHS through the VHSV immersion vaccine treatment method, as well as proving that there was no release of VHSV, which causes horizontal infection from the fish. It was confirmed that the proposed VHSV immersion vaccine treatment method can produce safe flounder fry with strong disease resistance and no horizontal infectious agent.

Claims (7)

A method for preventing viral hemorrhagic septicemia for fish, comprising immersing the fish in a water bath at a water temperature of 17 to 23° C. containing a viral hemorrhagic septicemia virus (VHSV) that is not inactivated.
The method of claim 1, wherein the water tank contains a viral hemorrhagic sepsis virus at a concentration of ^{10 4} TCID ₅₀ /mL to 10 ⁸ TCID _{50 /mL.}
delete The method of claim 1, wherein the fish is a fish belonging to the family Paralichthyidae.
The method of claim 1, wherein the immersion is performed for 30 minutes to 6 hours.
The fish according to claim 1, further comprising the step of inducing an immune response against the viral hemorrhagic sepsis virus by rearing the fish in a water bath at a water temperature of 5 to 25°C for 3 to 5 weeks after the immersion. How to prevent viral hemorrhagic sepsis for.
A method for producing fish with infection resistance to viral hemorrhagic sepsis virus comprising the following steps:
Immersing fish in a water bath at a water temperature of 17 to 23° C. containing viral hemorrhagic septicemia virus (VHSV) that is not inactivated;
Inducing an immune response against the viral hemorrhagic sepsis virus by rearing the fish for 3 to 5 weeks in a water bath at a water temperature of 5 to 25°C; And
Obtaining a fish having resistance to viral hemorrhagic sepsis virus infection.

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