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1.
Furunculosis, a septicaemic infection caused by the bacterium Aeromonas salmonicida subsp. salmonicida, currently causes problems in Danish seawater rainbow trout production. Detection has mainly been achieved by bacterial culture, but more rapid and sensitive methods are needed. A previously developed real‐time PCR assay targeting the plasmid encoded aopP gene of A. salmonicida was, in parallel with culturing, used for the examination of five organs of 40 fish from Danish freshwater and seawater farms. Real‐time PCR showed overall a higher frequency of positives than culturing (65% of positive fish by real‐time PCR compared to 30% by a culture approach). Also, no real‐time PCR‐negative samples were found positive by culturing. A. salmonicida was detected by real‐time PCR, though not by culturing, in freshwater fish showing no signs of furunculosis, indicating possible presence of carrier fish. In seawater fish examined after an outbreak and antibiotics treatment, real‐time PCR showed the presence of the bacterium in all examined organs (1–482 genomic units mg?1). With a limit of detection of 40 target copies (1–2 genomic units) per reaction, a high reproducibility and an excellent efficiency, the present real‐time PCR assay provides a sensitive tool for the detection of A. salmonicida.  相似文献   

2.
Vibrio harveyi is a causative agent of the Vibriosis or luminescent bacterial disease in worldwide aquaculture industry. A reliable assay for identification of V. harveyi infection is important to prevent the bacterial spread. In this study, biotinylated loop‐mediated isothermal amplification (LAMP) amplicons were produced by a set of four designed primers that recognized specifically the V. harveyi vhhP2 gene, encoding a putative outer membrane protein with unknown function, followed by hybridization with an fluorescein isothiocyanate (FITC)‐labelled probe and lateral flow dipstick (LFD) detection. A novel set of PCR primer was also designed specifically to vhhP2 gene and appear to be a species‐specific tool for V. harveyi detection. The optimized time and temperature conditions for the LAMP assay were 90 min at 65°C. The LAMP‐LFD and PCR methods accurately identified 22 isolates of V. harveyi but did not detect 16 non‐harveyi Vibrio isolates, and 34 non‐Vibrio bacterial isolates. The sensitivity of LAMP‐LFD for V. harveyi detection in pure culture was 1.1 × 102 CFU mL?1 or equivalent to 0.6 CFU per reaction, while that of PCR was 6 CFU per reaction. For spiked shrimp sample, the sensitivity of LAMP was 1.8 × 103 CFU g?1 or equivalent to 5 CFU per reaction, while that of PCR was 50 CFU per reaction. In conclusion, the established LAMP‐LFD methods provided a valuable tool for rapid identification of V. harveyi and can be used to distinguish V. harveyi from V. campbellii.  相似文献   

3.
This study was conducted to investigate the effects of fructooligosaccharide (FOS) and Bacillus licheniformis (B. licheniformis) on growth performance, body composition, intestinal enzymes activities and gut histology of Megalobrama terminalis. Nine experimental diets were formulated to contain three FOS levels (0, 3 and 6 g kg?1) and three B. licheniformis levels (0, 1 and 5 × 107 CFU g?1) following a 3 × 3 factorial design. Accordingly, diets were named as 0/0, 0/3, 0/6, 1/0, 1/3, 1/6, 5/0, 5/3 and 5/6 (B. licheniformis/FOS). At the end of the 8‐week feeding trial, weight gain (WG) and specific growth rate (SGR) of fish fed 6 g kg?1 FOS were both significantly (P < 0.01 and P < 0.05) higher than that of the other groups in terms of dietary FOS levels. Besides, WG and SGR of fish fed 1 × 107 CFU g?1 B. licheniformis were significantly (P < 0.05) higher than that of the control group in terms of dietary B. licheniformis levels. In addition, a significant interaction (P < 0.05) between dietary FOS and B. licheniformis was observed in finial weight, WG, SGR as well as the survival rate with the highest values all observed in fish fed diet 1/3. Hepatosomatic index, carcass lipid content, lipase activities as well as microvilli length increased significantly (P < 0.05) from 0 to 1 × 107 CFU g?1, but no significant difference (P > 0.05) was observed in terms of dietary FOS levels. In addition, a significant (P < 0.05) interaction of FOS and B. licheniformis was observed in both protease and Na+, K+‐ATPase activities with the highest value obtained in fish fed diet 1/3. The results indicated that the dietary applications of dietary FOS and B. licheniformis alone or in combination can significantly improve the growth performance, survival rate, intestinal enzymes activities as well as microvilli length of triangular bream. In addition, there is a significant interaction between dietary FOS and B. licheniformis. The best combination for this species is 3 g kg?1 FOS with 1 × 107 CFU g?1 B. licheniformis.  相似文献   

4.
Vibrio anguillarum is an aggressive and halophilic bacterial pathogen most commonly originating from seawater. Vibrio anguillarum presence in fisheries and aquaculture facilities causes significant morbidity and mortality among aquaculture species primarily from haemorrhaging of the body and skin of the infected fish that eventually leads to death, collectively recognized as the disease vibriosis. This study served to develop a non‐probe, multiplex real‐time PCR assay to rapidly detect V. anguillarum presence in seawater. Specific primers targeting genes vah1, empA and rpoN of V. anguillarum were selected for multiplex reaction among 11 different primer sets and the extension step was eliminated. Primer concentration, denaturation time as well as annealing time and temperature of DNA amplification were optimized, thus reducing reaction duration. The two‐step, non‐probed multiplex real‐time PCR set forth by this study detects as little as 3 CFU mL?1 of V. anguillarum presence in sea water, without enrichment cultivation, in 70 min with molecular precision and includes melting curve confirmation.  相似文献   

5.
This study evaluated the efficiency of differently prepared vaccines against Aeromonas hydrophila in the hybrid surubim (Pseudoplatystoma corruscans × P. reticulatum). Survival and haemato‐immunological parameters were compared between the treatments: non‐vaccinated fish (C); bacterin‐vaccinated fish (B); bacterin plus oral booster vaccinated fish (B+O); bacterin and toxoid‐vaccinated fish (B+T) and bacterin, toxoid and oral booster‐vaccinated fish (B+T+O). Fourteen‐days vaccinated fish from B+O and B+T+O were fed with an oral booster for 4 days. After 1 week, the fish were intraperitoneally challenged with 2 × 108 CFU mL?1 of A. hydrophila. Fish from the treatment B+T+O showed the lowest cumulative mortality (11.36%) 96 h after challenge, compared with other treatments (22.72–44.04%), and a relative survival of 74%. Serum immunoglobulin in B+T+O fish was higher than in other treatments. All vaccinated fish showed an increased agglutination titre when compared with non‐vaccinated fish, both before and after challenge. Fish fed with oral booster showed an increase in phagocytic percentage before and after challenge. It can be inferred that the oral booster vaccination was efficient in reducing mortality in hybrid surubim by enhancing the response against haemorrhagic septicaemia due to A. hydrophila infection.  相似文献   

6.
To evaluate the possible dietary application of live and heat‐inactivated probiotic Bacillus pumilus SE5 in grouper Epinephelus coioides, juveniles (14.6 ± 0.2 g) were fed either a basal control diet (without probiotic) or the basal diet supplemented with 1.0 × 108 CFU g?1 live (T1) and heat‐inactivated B. pumilus SE5 (T2). The heat‐inactivated probiotic significantly improved the final weight, weight gain (WG) and specific growth rate (SGR) at day 60 and significantly decreased the feed conversion ratio (FCR) at day 30 and 60, while the viable probiotic significantly decreased the FCR at day 60 (P < 0.05). Phagocytic activity, serum complement C3 and IgM levels as well as SOD activity elevated significantly in fish fed the heat‐inactivated probiotic for 60 days (P < 0.05). Furthermore, the heat‐inactivated probiotic remarkably up‐regulated expression of TLR2 and pro‐inflammatory cytokines (IL‐8 and IL‐1β) in head kidney (P < 0.05), but the viable probiotic failed to do so. These results indicated that heat‐inactivated B. pumilus SE5 can effectively improve the growth performance and immune responses of E. coioides.  相似文献   

7.
In spring of 2011, an epidemic outbreak of torafugu with high mortality occurred in an aquafarm with marine industrial recirculation aquaculture system (MIRAS) in Yantai, Shandong Province, China. The diseased fish showed anorexia, haemorrhaging and festering fin and skin and swelling internal organs. Forty‐five dominant bacterial isolates were obtained from the diseased fish, and were found to belong to 12 species according to 16S rRNA gene sequences. One strain from each species was selected to test the pathogenicity, and five strains were showed to be virulent to zebrafish. Whereas Enterovibrio nigricans Fr42 was highly virulent with the LD50 of 7.8 × 104 CFU g?1, Photobacterium swingsii Fr23, Vibrio owensii Fr40, V. harveyi Fr51 and V. rotiferianus Fr71 were moderately virulent with the LD50 of 1.7 × 106 to 8.4 × 106 CFU g?1. Both the bacteria and their extracellular products of the five strains were found to show phospholipase, caseinase, gelatinase, amylase and/or lipase activities. The production of N‐acyl homoserine lactones (AHLs) of the five strains was detected by three different AHLs biosensors, and three of them were found to produce AHLs by at least one kind of biosensor. This is the first study describing various opportunistic bacterial pathogens of fish cultured in MIRAS in China.  相似文献   

8.
This study was carried out to establish the effects of a 6 week treatment with the diet supplemented with L. rhamnosus in concentrations of 107 CFU g?1 (G1 group) and 108 CFU g?1 (G2 group) on the condition expressed by condition factors (Fulton's, Clark's and B), intestinal microbiology, haematological, histological and selected antioxidative parameters of rainbow trout. A significantly higher condition factors were found in G1 group indicating that higher concentration of probiotic (108 CFU g?1) did not result in the better condition. Cholesterol and urea levels were significantly higher in both G1 and G2 groups, albumin in G1 and creatinine in G2 group with respect to control. A significantly higher liver TBARS level was observed in G2 group. The feeding with supplemented probiont apparently changed the resident microbiota. Three weeks after withdrawal of the supplemented feed, the microflora mostly reverted to the control composition, although L. rhamnosus in faecal matter of fish remained inherent. The epithelial structure of the proximal and distal intestine revealed the increased absorptive area in both treated groups, as well as the increase in the mucin‐secreting goblet cells. The L. rhamnosus‐treated groups demonstrated the capacity for the augmentation of the innate host defence.  相似文献   

9.
Aeromonas salmonicida is the causative agent of furunculosis, a disease that affects both salmonid and non‐salmonid fish. Detection of A. salmonicida can be labour intensive and time consuming because of the difficulties in distinguishing the bacterium from other species given the wide variety of existing biochemical profiles and the slow growth characteristics which allow other organisms to overgrow the A. salmonicida. Herein, we report the development of a specific immunoassay using gold‐conjugated polyclonal antibodies for the rapid detection of A. salmonicida in fish tissues. Monodispersible 13‐nm gold nanoparticles were coated with polyclonal antibodies specific to A. salmonicida. Reddish purple agglutination of gold particles indicated the presence of A. salmonicida in samples. Positive reactions were detected visually with the naked eye. No agglutination was observed when A. salmonicida antibody‐coated gold nanoparticles were tested with other common bacterial fish pathogens, thereby verifying the specificity of the assay. The assay could detect A. salmonicida in fish tissues down to 1 × 104 CFU mL?1, and results were obtained within 45 min. The antibody‐coated gold nanoparticles were stable for at least 2 months at 4°C. The immunoassay using antibody‐coated gold nanoparticles represents a promising tool for the rapid and specific detection of A. salmonicida in fish tissues.  相似文献   

10.
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11.
Different laboratory synthesized metal nanoparticles viz. Copper oxide (CuO), Zinc oxide (ZnO) and silver doped titanium dioxide (Ag‐TiO2) were studied for their effect on hatching and survival of larvae and fry of Indian major carp, rohu, Labeo rohita both in direct application in tank water & coated onto tanks. Among these nanoparticles, CuO and ZnO nanoparticles exhibited highest percentage of hatching in both direct addition (78.0 ± 3.1% and 78.05 ± 4.2%, respectively) and coating onto tanks (58.6 ± 2.1% and 61.2 ± 2.7%, respectively) at 1 mg mL?1 while least percentage of hatching was recorded in Ag‐TiO2 nanoparticles irrespective of its concentration & mode of supplementation. Highest survival of L. rohita fry (50.13 ± 2.2%) was observed after 15 days post hatching in CuO coated tanks followed by ZnO coated tanks (38.6 ± 2.8%) while least was recorded in Ag‐TiO2 coated tanks (22.53 ± 3.0%). However in control tanks coated with Poly‐Urethane base with hardener and uncoated control tanks, the survival was 42.4 ± 1.2% and 41.36 ± 1.8% respectively. Further, significantly lower microbial load of water was recorded in CuO nanoparticles coated tanks (1.5 × 1010 CFU L?1) as compared to uncoated control tanks (1.1 × 1016 CFU L?1) without affecting water quality parameters. On the other hand, in Ag‐TiO2 coated tanks, significantly lower microbial load (1.0 × 106 CFU L?1) as compared to uncoated control tanks at 15 days post hatching was recorded. However, Ag‐TiO2 was toxic to L. rohita larvae & fry both in direct application and coating onto tanks. Considering the beneficial effects of CuO nanoparticle application, it has the scope of being used in a more eco‐friendly way in hatchery operations.  相似文献   

12.
This work describes a primer pair and a high‐throughput SYBR Green I‐based real‐time PCR protocol combined with melting curve analysis for identification and quantification of Vagococcus salmoninarum in bacterial cultures and infected fish tissues. The 16S rRNA gene was selected for the design of the primer pair (SalF and SalR). The sensitivity and specificity of this primer pair were compared with other previously designed for conventional PCR. Although both primer pairs showed 100% specificity using pure bacterial cultures or DNA extracted from bacteria or fish tissues, the primer pairs designed in this study showed the highest sensitivity with a detection limit of 0.034 × 100 amplicon copies per assay (equivalent to 2 × 10?11 ng/µl, Cq value of 30.49 ± 1.71). The developed qPCR protocol allowed the detection of V. salmoninarum in non‐lethal and lethal fish samples with detection levels of 0.17 × 100 gene copies in tissues artificially infected and 0.02 × 100 in tissues of fish experimentally infected with V. salmoninarum. The high sensitivity of the developed method suggests that it could be considered as a useful tool for diagnosis of vagococcosis and the detection of V. salmoninarum in asymptomatic or carrier fish.  相似文献   

13.
The present feeding trial examined the effect of synbiotic use of Bacillus mycoides and organic selenium (OS) as Sel‐Plex on marron immunity, growth and survival. The marron were cultured in recirculated tanks and fed test diets consisting of a basal diet; basal diet supplemented with B. mycoides (108 CFU g?1 of feed); basal diet supplemented with OS (Sel‐Plex) (0.2 g kg ? 1 of feed) and basal diet supplemented with synbiotic (B. mycoides at 108 CFU g?1 and OS 0.2 g kg ? 1 feed) diet, in triplicate. The effect of the prebiotic OS (Sel‐Plex) on the growth rate of B. mycoides was also studied in vitro. The results suggested that synbiotic use of B. mycoides and OS significantly improved some immune parameters of marron, particularly the glutathione peroxidase, and to some extent total haemocyte counts. However, the synbiotic feed did not synergistically improve marron growth, in fact the use of B. mycoides‐supplemented diet alone demonstrated significantly higher growth in marron compared with the growth of marron fed on other test diets. Supplementation of the basal diet with host origin B. mycoides significantly increased the intestinal bacterial population (3.399 ± 825 CFU g ? 1 of gut) in marron compared with other diets. Organic selenium as Sel‐Plex in Trypticase Soya Broth also confirmed that OS did not increase the amount of growth of B. mycoides and resulted in a lower intestinal bacterial population in the synbiotic diet‐fed marron. In conclusion, synbiotic of OS and B. mycoides may improve a particular immune parameters of marron and to a lesser extent their growth.  相似文献   

14.
This study was aimed to address the promising evaluation of Cissus quadrangularis plant (stem) and lipopolysaccharide (LPS from bacteria) supplemented diets on innate immune response in Lates calcarifer fingerlings against Aeromonas hydrophila infection. Fingerlings were fed supplemented diets containing four different concentrations of C. quadrangularis (0.5, 1.0, 1.5 and 2.0 g kg?1 feed), LPS (25, 50, 75 and 100 mg kg?1 feed) and control (normal formulated diet) for 60 days. The fish fingerlings fed supplemented diet displayed significant differences (P < 0.05) in specific growth rate (SGR) and relative percentage survival compared to the control group fed without C. quadrangularis and LPS‐supplemented diet. Fingerlings were injected intraperitoneally with 100 μL lethal dose of A. hydrophila containing 1 × 106 CFU g?1. Supplementation of C. quadrangularis and LPS diet significantly increased biochemical profile such as protein, lipid and carbohydrate content, haematological parameters of L. calcarifer fingerlings in different experimental periods when compared with the control group. Dietary doses of C. quadrangularis and LPS‐supplemented diet significantly influenced growth performance and increased survival rate in L. calcarifer fingerlings against A. hydrophila infection.  相似文献   

15.
Probiotic administration is associated with the enhancement of host resistance to environmental and nutritional stressors, improving survival and growth rates. This study was carried out to evaluate the effects of dietary supplementation of Bacillus subtilis and Bacillus cereus toyoi on growth performance, innate immune responses and gut morphology of two trout species feeding a commercial diet high in soybean meal. A commercial probiotic (4.2 × 109 CFU g?1 of additive) was supplemented to the experimental diets at 0% (control), 0.03% (P1; 6 × 103 CFU g?1 of diet) or 0.06% (P2; 1.5 × 106 CFU g?1 of diet) and fed to brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) for 9 and 20 weeks respectively. Rainbow trout showed significantly better growth performance than brown trout, regardless of the dietary treatment. No effect of dietary probiotic supplementation was detected on growth performance, body composition or innate immune parameters (plasma lysozyme, alternative complement and peroxidase activities). In both species, after 9 weeks, intestinal lamina propria and submucosa were widened, with increased presence of inflammatory cells, significantly higher in groups fed probiotics. This inflammatory process, with villi and enterocytes noticeably damaged compared with the control group, was more pronounced in brown trout. Under the current trial conditions, the B. subtilis + B. cereus toyoi had no positive impact in either trout species, on the contrary a harmful effect was observed.  相似文献   

16.
Fish are always susceptible to a wide variety of deadly pathogens which cause a huge loss in aquaculture industries. In this investigation, we have demonstrated the in vivo probiotic efficiency of Bacillus sp. MVF1 (GenBank Acc. No. KP256503) in Labeo rohita challenged with pathogenic strain of Aeromonas hydrophila (MTCC 1739). To check the probiotic potential of the selected bacterial strain, fish were divided into four groups: control, D1, D2 and D3. A total of 100 days (70 days probiotic feeding + 71th day sampling and 28 days challenged test + 29th day sampling) of feeding trial was conducted. To establish the probiotic potential of Bacillus sp. MVF1, certain haematological parameters (haemoglobin, total erythrocyte and leucocyte count), serum biochemical parameters (total protein, albumin and globulin), immune parameters (serum lysozyme and total IgM levels) and hepatic stress profile (malondialdehyde production, superoxide dismutase and catalase activity) have been measured. Our results demonstrated that red blood cell number, white blood cell number and haemoglobin content were much higher in D2 group fish compared to other groups and control fish. Similarly, total protein contents, albumin concentration, globulin concentration, lysozyme activity and IgM production were also recorded to be highest in D2 group fish. This finding clearly indicated the probiotic potential of Bacillus sp. MVF1 in L. rohita. Furthermore, our results also demonstrated that 1 × 107 CFU g?1 feed (D2) provides better immunity compared to 1 × 105 (D1) and 1 × 109 (D3). Due to beneficial effects, the bacterium Bacillus sp. MVF1 might be useful in aquaculture industries to reduce the disease susceptibility.  相似文献   

17.
Due to increasing resistance to chemical therapeutants, the use of ‘cleaner fish’ (primarily wrasse, Labridae, species) has become popular in European salmon farming for biocontrol of the salmon louse, Lepeophtheirus salmonis (Krøyer). While being efficient de‐licers, cleaner fish mortality levels in salmon cages are commonly high, and systemic bacterial infections constitute a major problem. Atypical furunculosis, caused by Aeromonas salmonicida A‐layer types V and VI, is among the most common diagnoses reached in clinical investigations. A previously described real‐time PCR (qPCR), targeting the A. salmonicida A‐layer gene (vapA), was modified and validated for specific and sensitive detection of all presently recognized A‐layer types of this bacterium. Before stocking and during episodes of increased mortality in salmon cages, cleaner fish (primarily wild‐caught wrasse) were sampled and screened for A. salmonicida by qPCR and culture. Culture indicated that systemic bacterial infections are mainly contracted after salmon farm stocking, and qPCR revealed A. salmonicida prevalences of approximately 4% and 68% in pre‐ and post‐stocked cleaner fish, respectively. This underpins A. salmonicida's relevance as a contributing factor to cleaner fish mortality and emphasizes the need for implementation of preventive measures (e.g. vaccination) if current levels of cleaner fish use are to be continued or expanded.  相似文献   

18.
Enteric septicaemia of catfish (ESC) caused by Edwardsiella ictaluri is becoming an increasing problem in aquaculture and has been reported worldwide in a variety of fish species. This study reports ESC in hybrid catfish, Clarias macrocephalus (Günther) × Clarias gariepinus (Burchell), cultured in southern Thailand. The bacteria were identified as E. ictaluri by conventional and rapid identification systems, as well as by genetic and phylogenetic characterization. Analysis of 16S rRNA indicated 100% homology to the 16S rRNA sequence of several E. ictaluri strains in GenBank. Plasmid profiles demonstrated 4.0‐ and 5.6‐kb plasmids, compared with the 4.8‐ and 5.6‐kb plasmids in the US isolates, and representative genes of three of the four known pathogenicity islands of US isolates were present. Serologically, lipopolysaccharide (LPS) purified from the Thai isolates was not recognized by a monoclonal antibody against the LPS of US isolates. Fish experimentally infected with E. ictaluri showed 23–100% mortality within 14 days with a 168‐h LD50 of 6.92 × 107 CFU mL?1 by immersion and a 96‐h LD50 of 1.58 × 106 CFU fish?1 by intraperitoneal injection. Examination of tissue sections obtained from both naturally and experimentally infected fish indicated that infection of hybrid catfish with E. ictaluri produced lesions in several organs including liver, kidney, spleen, heart and brain. Histopathology findings included cellular necrosis, focal haemorrhage, infiltration of lymphocytes and multifocal granulomatous inflammation in the infected organs.  相似文献   

19.
A feeding trial was carried out to determine effects of dietary supplements of inactivated Pediococcus pentosaceus (PP) on growth, feed utilization and blood characteristics of red sea bream. Five diets containing different concentrations [0 (PP0), 1.6 × 1010 (PPI), 1.6 × 1011 (PPII), 1.6 × 1012 (PPIII) and 3.2 × 1012 (PPIV) cells g?1] of PP were fed to fish for 56 days. At the end of the feeding trial, the obtained results revealed a significant increase (P < 0.05) in weight gain, specific growth rate and skin mucus secretion in all PP‐supplemented groups when compared with control group. Moreover, fish fed PPIII and PPIV diets resulted in significantly higher final body weight, feed efficiency ratio and bactericidal activity than those of fish fed PP0 diet (P < 0.05). Further, fish fed the PPIII diet also had a higher feed intake, protein efficiency retention, haematocrit, mucus lysozyme activity (LA), plasma and serum proteins than those of PP0 fed group (P < 0.05). Similarly, fish fed PPIV diet resulted in a significant increase in serum LA, peroxidase activity and tolerance against low‐salinity stress test (P < 0.05). Considering these promising results, we suggest that the supplementation of PP Prep improves growth and health conditions of Pagrus major.  相似文献   

20.
A bacteria–parasite challenge model was used to study the role of sea lice, Lepeophtheirus salmonis (Copepoda), as a vector of Aeromonas salmonicida subsp. salmonicida. Three hypotheses were tested: (i) L. salmonis can acquire A. salmonicida subsp. salmonicida via water bath exposure; (ii) L. salmonis can acquire the bacteria via parasitizing infected Atlantic salmon, Salmo salar; and (iii) L. salmonis can transmit the bacteria to naïve Atlantic salmon via parasitism. Adult L. salmonis exposed to varying A. salmonicida subsp. salmonicida suspensions (101–107 cells mL?1) for 1.0, 3.0 or 6.0 h acquired the bacteria externally (12.5–100%) and internally (10.0–100%), with higher prevalences associated with the highest concentrations and exposures. After exposure to 107 cells mL?1, viable A. salmonicida subsp. salmonicida could be isolated from the external carapace of L. salmonis for 120 h. Lepeophtheirus salmonis also acquired the bacteria externally and internally from parasitizing infected fish. Bacterial transmission was observed only when L. salmonis had acquired the pathogen internally via feeding on ‘donor fish’ and then by parasitizing smaller (<50 g) ‘naive’ fish. Under specific experimental conditions, L. salmonis can transfer A. salmonicida subsp. salmonicida via parasitism; however, its role as a mechanical or biological vector was not defined.  相似文献   

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