Novel edwardsiella ictaluri e-ict-vl33 strain, vaccines thereof, and a method for protecting fishes using said vaccines

a technology of edwardsiella ictaluri and eictvl33, which is applied in the field of new edwardsiella ictaluri eictvl33 strain, can solve the problems of high mortality rate of fishes, septicemia or, ultimately, death, and high mortality rate of bacterial septicemia with a high mortality rate, and achieves the effect of higher survival rate of treated fish than the survival rate of untreated fish

Active Publication Date: 2012-02-02
SBC VIRBAC LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013]Still another object of the invention is to provide a method for improving the immunity of fish against E. ictaluri, and further preventing and protecting fishes from infection of E. ictaluri by using said vaccines.
[0018]An oral vaccine is obtained by using an inactivating agent to inactivate or kill the Edwardsiella ictaluri E-ict-VL33 strain (i.e., an inactivation process). The inactivated bacteria is then suspended in a buffer solution to form a bacterial suspension, and the bacterial suspension is mixed with an adjuvant to form a mixture. The mixture is then homogenously emulsified by a homogenizer with high shear force. This process allows the oral vaccine to be obtained. Said oral vaccine can further be spray coated on the outside of a feed to deliver the oral vaccine to fish. Also, the coated feed can further be sprayed with edible oil, such as plant oil and / or animal oil (in particular, a fish oil), to improve the delivery efficiency of the oral vaccine.
[0025]The term “prevent and protect” is intended to mean that, compared to the immunity of untreated fish, the immunity of treated fish against E. ictaluri is improved and the survival rate of treated fish after infection of E. ictaluri is higher than survival rate of untreated fish. Further inoculation of the amount of inactivated bacteria prevents and protects the fish from the infection of E. ictaluri or disease derived thereto.

Problems solved by technology

Acute Edwardsiella septicemia usually results in typical bacterial septicemia with a high mortality rate for fishes.
Chronic Edwardsiella septicemia can result in Hole-in-the-head syndrome, septicemia or, ultimately, death.
Edwardsiella septicemia occurs worldwide and causes high mortality and considerable economic damage to the catfish industry, especially in Vietnam and the USA.
All catfish species are susceptible to E. ictaluri and the disease causes major damage in Basa Tra fish in the Mekong delta and other places where the fish is cultured in Vietnam.
Many ways of protecting the fish have been tried but none so far have been very successful.
The use of antibiotics to counteract bacterial infections has been successful in some instances but not in others, especially because of widespread resistance as a result of extensive and non-controlled use of many different antibiotics either alone or in various combinations.
Furthermore, the use of antibiotics and chemotherapeutics is discouraged because of both environmental and residual problems, and long-term use of antibiotics is not a sustainable control method for fish diseases.
However, preventing and protecting the fish from Edwardsiella septicemia cannot be achieved by using antibiotics which can only control the spreading of Edwardsiella septicemia.
It has been claimed that an attenuated vaccine is able to help in the control of the disease but, to date, the product has not made major inroads in the field.
However the limitations of this method include lack of immune efficacy [Gudding R, et al.

Method used

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  • Novel edwardsiella ictaluri e-ict-vl33 strain, vaccines thereof, and a method for protecting fishes using said vaccines
  • Novel edwardsiella ictaluri e-ict-vl33 strain, vaccines thereof, and a method for protecting fishes using said vaccines
  • Novel edwardsiella ictaluri e-ict-vl33 strain, vaccines thereof, and a method for protecting fishes using said vaccines

Examples

Experimental program
Comparison scheme
Effect test

example 1

Isolation and Identification of Edwardsiella ictaluri E-ict-VL33 Strain

[0032]An isolated E-ict-VL33 strain was isolated from infected tra catfish (P. hypophthalmus). Bacterial culture grown in Brain Heart Infusion (BHI, the composition of BHI are shown in Table 1) broth for 18 hours at 25-30° C. was used for experimental infection. Bacteria growth on BHI agar for 48 h at 30° C. was used for bacterial identification.

TABLE 1The composition of BHI broth (Difco Laboratories, Sparks, MD)CompositionContentCalf Brains, Infusion from 200 g 7.7 gBeef Heart, Infusion from 250 g 9.8 gProteose Peptone10.0 gDextrose 2.0 gSodium Chloride 5.0 gDisodium Phosphate 2.5 gAdd water up to 1 literTotal  1 liter

[0033]The Characteristics of Edwardsiella ictaluri E-ict-VL33 Strain

[0034]FIG. 1 shows that the isolated E-ict-VL33 strain is a rod bacterium. An analysis of Gram staining shows that the isolated E-ict-VL33 strain is a Gram-negative rod bacterium. Referring to Tables 2 to 4, these tables show the g...

example 2

Preparation of Vaccines

[0039]Step 1 Cultivation and Collection of the Bacteria

[0040]The bacteria (Edwardsiella ictaluri E-ict-VL33 strain) were cultured in Brain Heart Infusion (BHI) broth at 28° C. for 48 hours, then collected in a bacteria suspension.

[0041]Step 2 Inactivated Processes

[0042]Inactivation of bacteria was done by adding 37% formaldehyde at a final concentration of 0.5% (w / v) to the bacteria suspension obtained in Example 1, and incubating (shaking) the bacteria suspension with formaldehyde at 25° C., 70 rpm for a minimum of 24 hours (preferably 48 hours). The bacteria (Edwardsiella ictaluri E-ict-VL33 strain) have to be verified as being completely inactive by a test. The supernatant of the bacteria suspension containing the formaldehyde was separated by using centrifugation at 9000×g to remove the formaldehyde, then suspending the pellet in a buffer solution (such as distilled water, phosphate buffered saline (PBS)). Finally, the vaccine stock containing inactivated ...

example 3

Preparation of Immersion Vaccine of Edwardsiella ictaluri E-ict-VL33

[0043]Vaccine stock obtained in example 2 were prepared as immersion vaccine by suspending the vaccine stock in a buffer solution (such as sterile water or PBS). The content of formaldehyde in the immersion vaccine is lower than 0.2% (v / v).

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Abstract

A novel Edwardsiella ictaluri E-ict-VL33 strain, a vaccine derived from the novel Edwardsiella ictaluri E-ict-VL33 strain, especially in immersion form and oral form, and a method for protecting fishes from the infection of Edwardsiella ictaluri, especially catfish, the method including a primary immersion immunization using immersion vaccine, and after an appropriate period, boosting by oral vaccination, resulting in a strong and long-lasting immunity for fishes.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a divisional application of U.S. patent application Ser. No. 12 / 845,965 filed on Jul. 29, 2010, which is incorporated by reference herein in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to a novel Edwardsiella ictaluri E-ict-VL33 strain, vaccines derived therefrom, and a method for protecting fishes using said vaccines.[0004]2. Brief Description of the Prior Art[0005]Edwardsiella is a type of small Gram-negative rod bacterium. The host of Edwardsiella includes Catfish, Eel, Tilapia and other warm water fishes. Edwardsiella ictaluri is one member of Edwardsiella. E. ictaluri that can infect catfish, thereby causing Edwardsiella septicemia. Acute Edwardsiella septicemia usually results in typical bacterial septicemia with a high mortality rate for fishes. Chronic Edwardsiella septicemia can result in Hole-in-the-head syndrome, septicemia or, ultimately, death.[...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): A61K39/02A61P31/04A61K9/00
CPCA61K39/025A61K2039/552A61K2039/542A61K2039/521A61P3/04A61P31/04
Inventor KUO, TSUN-YUNGCHEN, HSU CHUNG GABRIEL
Owner SBC VIRBAC LTD
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