Immersion vaccination of rainbow trout (Oncorhynchus mykiss) against Flavobacterium psychrophilum

نویسندگان

  • Bjørn Brudeseth
  • David Gauthier
  • Krister Sundell
  • Tom Wiklund
چکیده

Flavobacterium psychrophilum is the causal agent of rainbow trout fry syndrome (RTFS), which seriously affects rainbow trout aquaculture. The disease affects fish at early life stage and can cause high mortality. Within trout aquaculture several procedures have been implemented in order to reduce the disease problem. Use of ”Flavo free” broodstock and disinfection of eggs can reduce probability of introducing the disease to the farm, however, the bacterium has shown to be resistant against several of the disinfection procedures performed today. Other factors such as minimum handling of fish (less skin abrasions) and keeping an optimal fish density and water flow are prophylactic measures that can prevent development of disease [1]. If disease outbreak occurs antibiotic treatment is the most effective measure to stop infections in the early phase. Vaccination has shown to be vital for controlling disease and reducing use of antibiotics in Norwegian salmon and trout farming. Dip and bath vaccination of fry can be a method for reducing outbreaks of RTFS in trout aquaculture. A study was performed to evaluate the efficacy of an inactivated whole-cell based immersion vaccine. Rainbow trout fry with a mean initial weight of 3 g were dip vaccinated for one minute with a 1/10 dilution of a suspension of inactivated F. psychrophilum. At 6 weeks (~5.0 g) post-immunization the fish were challenged by intraperitoneal injection with 5.2 × 10 7 CFU/fish of a highly virulent strain of F. psychrophilum (Serotype Th isolate, isolated in Finland). The relative percent survival (RPS) was calculated by relating the number of diseased fish in the vaccinated groups with the corresponding number in the control group. To reduce tank effects, the trial was performed in duplicates (identical groups in two tanks). The results from the challenge showed a difference in mortality between the vaccinated groups and the mock-vaccinated (PBS dip) group in both tanks, with an RPS of 50.0% and 56.3% (Tab. 1). Table 1. Relative percent survival of vaccinated trout fry challenged 6 weeks post vaccination by intraperitoneal injection challenge with highly virulent live F. psychrophilum. Tank Vaccination No. of fish Dead fish % Mortality RPS 1 Dip vaccinated 40 7 17.5 56.3 Mock vaccinated 40 16 40.0 0 2 Dip vaccinated 40 8 20.0 50.0 Mock vaccinated 40 16 40.0 0 Although the results in this experiment showed good protection of the vaccine, earlier trials using the same vaccine have resulted in lower RPS levels. However, it should be emphasized that inactivated whole-cell vaccines do induce protection by injection vaccination [2]. Development of a challenge model by infection through natural pathways such as bath or cohabitant (disease carriers) is important for a better interpretation of vaccine efficacy. There are few published studies on successful bath challenge models. A trial was initiated to investigate the significance of exposure time on mortality of naïve rainbow trout. Fry 3–5g (n=50) were challenged by bath using a highly virulent Norwegian F. psychrophilum strain with an exposure time of 2, 4, 7 hours or 7 hours on two repeated days. The study showed that exposure time did not influence the level of mortality and a two-hour challenge was enough for inducing mortality above 50% (Fig. 2). The results showed that it is possible, under experimental conditions, to induce mortality in rainbow trout by immersion exposure to F. psychrophilum. However, further studies should be performed to verify the reproducibility of the bath challenge method. Figure 1. Cumulative per cent mortality in rainbow trout (3–5 g) challenged by bath using a Norwegian F. psychrophilum strain. The fish were exposed for 2, 4, 7 and 2 × 7 hours. One of the major challenges for the development of a protective vaccine regime is the fact that the disease affects fry at early life stages prior to reaching an immunocompetent size. Studies indicate that fry should reach a size of at least 1–2 g to achieve an immune response after dip vaccination and that the onset of immunity is usually obtained after 450 day degrees (Non published PHARMAQ studies). Only healthy fish should be vaccinated to avoid that handling and stress involved in vaccination trigger latent infections causing outbreaks shortly after vaccination. Studies to evaluate the duration of protection are essential for developing an optimal vaccine regime securing a long lasting protection until harvest. Dip vaccination trials (not published) performed by PHARMAQ using inactivated Yersinia ruckeri dip vaccine indicated that a double vaccination procedure should be performed in order to obtain long term protection (15 weeks). Further studies will be initiated to investigate the optimal vaccination regime for long term protection against F. psychrophilum infections The Finnish authorities (Fimea) decided to make a monovalent dip vaccine with inactivated F. psychrophilum antigens from PHARMAQ against RTFS available in Finland on a special license due to the severe situation. A field trial experiment from dip vaccination with inactivated F. psychrophilum indicated that the vaccine reduces mortality after double vaccination. However, mortality also occurred in vaccinated fish groups. Further information will be collected from fish farms for evaluation of the vaccine efficacy.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Characterization of serum and mucosal antibody responses and relative per cent survival in rainbow trout, Oncorhynchus mykiss (Walbaum), following immunization and challenge with Flavobacterium psychrophilum

Serum and mucosal antibody responses of juvenile rainbow trout, Oncorhynchus mykiss, were characterized by enzyme-linked immunosorbent assay (ELISA) following immunization with various preparations of formalin-killed Flavobacterium psychrophilum cells. The protective nature of these preparations was then determined by immunizing rainbow trout fry and challenging with the bacterium. Juvenile rai...

متن کامل

Effect of Hydrogen Peroxide on Immersion Challenge of Rainbow Trout Fry with Flavobacterium psychrophilum

An experimental model for immersion challenge of rainbow trout fry (Oncorhynchus mykiss) with Flavobacterium psychrophilum, the causative agent of rainbow trout fry syndrome and bacterial cold water disease was established in the present study. Although injection-based infection models are reliable and produce high levels of mortality attempts to establish a reproducible immersion model have be...

متن کامل

Complete Genome Sequence of Flavobacterium psychrophilum Strain CSF259-93, Used To Select Rainbow Trout for Increased Genetic Resistance against Bacterial Cold Water Disease

The genome sequence of Flavobacterium psychrophilum strain CSF259-93, isolated from rainbow trout (Oncorhynchus mykiss), consists of a single circular genome of 2,900,735 bp and 2,701 predicted open reading frames (ORFs). Strain CSF259-93 has been used to select a line of rainbow trout with increased genetic resistance against bacterial cold water disease.

متن کامل

Hydrogen peroxide as pre-treatment stressor in experimental immersion challenge of rainbow trout (Oncorhynchus mykiss) fry with Flavobacterium psychrophilum

Flavobacterium psychrophilum is the causative agent of rainbow trout fry syndrome (RTFS), also called bacterial cold water disease (BCWD) in USA. Since being discovered in USA in the 1940s, the disease has spread to aquacultures worldwide [1]. Mortality rates as high as 90% have been reported in fry, although the mortality rate in Danish outbreaks average around 30–40%. Rainbow trout (Oncorhync...

متن کامل

Efficacy of a polyvalent immersion vaccine against Flavobacterium psychrophilum and evaluation of immune response to vaccination in rainbow trout fry (Onchorynchus mykiss L.)

Rainbow trout fry syndrome (RTFS) is a disease caused by the Gram-negative bacterium Flavobacterium psychrophilum, responsible for significant economic losses in salmonid aquaculture worldwide. The diversity of F. psychrophilum isolates and the inherent difficulties in vaccinating juvenile fish has hampered the development of a vaccine for RTFS. Disease episodes tend to occur between 10-14 °C w...

متن کامل

Dataset of proinflammatory cytokine and cytokine receptor gene expression in rainbow trout (Oncorhynchus mykiss) measured using a novel GeXP multiplex, RT-PCR assay

A GeXP multiplex, RT-PCR assay was developed and optimized that simultaneously measures expression of a suite of immune-relevant genes in rainbow trout (Oncorhynchus mykiss), concentrating on tumor necrosis factor and interleukin-1 ligand/receptor systems and acute phase response genes. The dataset includes expression values for drpt, il11a, il1b1, il1b2, il1b3, il1r-like-1(e3-5), il1r-like-1(e...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2012