Enteric Redmouth Research Articles

An epizootic in chinook salmon (Oncorhynchus tshawytscha) caused by a sorbitol-positive serovar 2 strain of Yersinia ruckeri.

Enteric redmouth disease is described in chinook salmon (Oncorhynchus tshawytscha) at a state hatchery in Sand Ridge, Illinois. Biochemical, isoenzyme, and serological data indicated that the epizootic was caused by a sorbitol-fermenting Serovar 2 strain of Yersinia ruckeri. In laboratory experiments the isolate was pathogenic for both brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar).

Monoclonal antibody‐based enzyme‐linked immunosorbent assays for the rapid diagnosis of clinical cases of enteric redmouth and furunculosis in fish farms

Monoclonal antibody‐based enzyme‐linked immunosorbent assays for the rapid diagnosis of clinical cases of enteric redmouth and furunculosis in fish farms

Occurrence of Yersinia ruckeri infection in farmed whitefish, Coregonus peled Gmelin and Coregonus muksun Pallas, and Atlantic salmon, Salmo salar L., in northern Finland

Yersinia ruckeri, the aetiological agent of enteric redmouth disease (ERM), is now generally recognized to be distributed worldwide. The pathology and epizootiology of the disease was first described by Rucker (1966) and although rainbow trout, Salmo gairdneri Richardson, has been the most frequently affected species, all salmonids are now considered to be potential hosts for the organism (McDaniel 1979). The present paper reports the first confirmed occurrence of Y. ruckeri infection in farmed whitefish and Atlantic salmon, Salmo salar L., in Finland, with the known host range being extended to include the whitefish Coregonus peled Gmelin and Coregonus muksun Pallas . The outbreaks of infection involved two fish farms on the Oulujoki and Iijoki rivers in northern Finland (Fig. 1). Infection in whitefish Yersinia ruckeri infection was first identified in July 1982 in a mixed population of 3500 C. peled and C. muksun broodstock fish held in a single 1000-m 2 earthen pond at farm A. The organism was isolated from only one of four diseased C. muksun examined bacteriologically at this time and mortalities during the summer months were light (0 .5-1 .0%) for both species. The following year Y. ruckeri was isolated from the internal organs of both C. peled and-C. muksun on a number of occasions during the period from June to August, but again mortalities remained at a low level (0 .5—F5%) throughout. In 1984 infection was confirmed in C. peled but not C. muksun broodstock (Fig. 2). The low levels of mortality associated with the Y. ruckeri infection are similar to those recorded for diseased brook trout, Salvelinus fontinalis (Mitchill), and landlocked Atlantic salmon in Australia where a Y. ruckeri-like organism was isolated (Llewellyn 1980) and in an ERM outbreak in rainbow trout in Canada (Wobeser 1973). Diseased whitefish showed loss of scales, haemorrhages on the body surface and paired fin bases, and petechiation in the peritoneum and visceral fat. Some affected fish. also exhibited severe inflammation of the distal portion of the intestine and vent. Saprolegnia

Enteric redmouth disease: outbreak in rainbow trout in Switzerland

Enteric redmouth disease: outbreak in rainbow trout in Switzerland

Protection against enteric redmouth disease in rainbow trout, Salmo gairdneri Richardson, after vaccination with Yersinia ruckeri bacterin

Abstract. Rainbow trout, Salmo gairdneri Richardson, (average weight 100g) were vaccinated intraperitoneally (i.p.) with Yersinia ruckeri bacterin in saline or in oily adjuvant. Agglutinating antibody kinetics were followed during 445 days before challenge (1.2×107 bacteria i.p.). Fourteen days after challenge 88.5% of the control fish had died while few mortalities were observed with vaccinated fish regardless of their agglutinating titre. Protection against Y. ruckeri does not seem to be due to antibodies.

Indirect enzyme-linked immunosorbent assay (ELISA) to titrate rainbow trout serum antibodies against two pathogens: Yersinia ruckeri and Egtved virus

Two indirect ELISAs were developed to quantify specific antibodies in rainbow trout. One was against Yersinia ruckeri, agent of the ‘enteric redmouth disease’, in which a soluble antigen extract containing a high level of lipopolysaccharide (LPS) was used to coat microplates. The other was against Egtved virus, agent of viral haemorrhagic septicaemia, for which the virus was purified on sucrose gradients. In both cases the conjugate was a peroxidase-conjugated rabbit anti-trout immunoglobulin. The sensitivity and specificity of each ELISA were compared with agglutination and seroneutralization.

Antimicrobial susceptibility patterns and R plasmid-mediated resistance of the fish pathogen Yersinia ruckeri

Fifty strains of Yersinia ruckeri, the causative agent of enteric redmouth disease of salmonid fish, were tested for susceptibility to 23 antimicrobial agents by using an agar dilution procedure. The MICs were generally uniform for all serological varieties. Two of the 50 strains carried a 36-megadalton plasmid which determined resistance to tetracyclines and sulfonamides and was transferable to both Escherichia coli and Y. ruckeri recipients. The serovars did differ in their response to polymyxin B. Strains of serovars II, III, and V were highly resistant (MICs of 128 to 512 micrograms/ml), whereas most serovar I strains were susceptible to less than or equal to 2.0 micrograms/ml. Of 33 serovar I strains, 6 were highly resistant to polymyxin B, which is a characteristic that may divide serovar I (Hagerman) strains into two distinct subgroups.

Remarks on an increasing resistance of fishpathogenic and facultative-fishpathogenic bacteria in lower saxony (FRG).

Increasing resistance of specific-fishpathogenic and facultative-fishpathogenic bacteria against the main drugs licensed in Germany.With an average of yearly 600 examined cases-including the whole range of additional virological-, bacteriological-, histological-, water quality and residual. tests-the Fish Health Service (FHS) of Hannover of the Northern Federal State of LOWER SAXONY reached within the last years some representative experience dealing with the control and therapy of fish diseases in aquaculture. The control of the three notifiable viral epidemics of freshwater fish presently included in the pertinentlegislation (Animal Epidemics Act) of the FRG-VHS, IPN and SVC-is the competence of the STATE FISH EPIDEMICS CONTROL SERVICE OF LOWER SAXONY from which the FHS mentioned above is a part. The therapy of bacterial diseases-essentially Aeromonas salmonicida infections (Furunculosis/Salmonids; Erythrodermatits/Cyprinids), vibriosis, from 1981 on increasingly Enteric Redmouth Disease/ERM (with an unexpected peak in late winter-, spring and summer 1984) as well asthe mainly environment dependent-sometimes with septicemic development of the whole range of ubiquitous facultative-fishpathogenic bacteria from the aquatic environment-developed rather unprob lematic and successful in Lower Saxony for many years. From 1981 on a change in this situation with concomitant increasing resistance of specific-fishpathogenic as well as facultative-fishpathogenic bacteria. against the main drugs licensed in the FRG and used in the control of freshwater fish diseases mainly through medicated feed is observed. The bacterological examination with antibiogramme proved indispensable. In the FRG the presently licensed drugs for treatment of bacterial infections in fish are Chloramphenicol, Chlor- and Oxitetracycline, Furazolidone, Trimethoprim/Sulfadimethoxine and Nifurpracine. In the FRG Chloramphenicol was forbidden for use in domestic animals (homoeotherms) for human consumption in April 1984. It is to assume that Chloramphenicol will be withdrawn for use in fish soon. Only in few individual cases and strictly controlled by the veterinary authorities some otherdrugs can be experimentally tested under prescription and strict supervision of a veterinarian specialized in fish diseases and aquaculture. Besides the substances mentioned above antibiogrammes are routinely carried out with Oxolinic acid, “Lincospectin” (Lincomycine + Spectinomycine 1 : 2), Ampicilline, Erythromycine and very recently Flumequine.The results of 596 FHS-cases from which in 289 the bacteriological examination proceed necessaryfrom them in 162 cases the antibiogramme was feasible-carried out within the frame of the work of the FHS from January 1983 to May 1984 are discussed-, the increased resistance showed-, the effectivity and/or uselessness of some of the drugs presented. Flumequine, Oxolinic acid, Lincospectine (not yet licensed in the FRG) and last but not least the tetracyclines showed promising. The finding of few Aeromonas salmonicida subsp. salmonicida isolates completely resistant against the drugs licensed in the FRG may involve further serious problems as well as cases of total failure of therapy carried out in strict accordance with the antibiogramme if a chronic viral infection is present in the background-as e.g. observed with ERM concomitant to VHS. The results of a first field trial with Oxolinic acid in a rainbow trout population during summer of 1984 are shown. As a main result of this trials it is recommended to 86 enlarge the presently narrow frame of drugs licensed for fish in the FRG by at least two of the compounds tested: Oxolinic acid and Flumequine, or Oxolinic acid and Lincospectin; and to delete Ampicilline which was included in a pertinent priority list in 1982.

Serological variation among Yersinia ruckeri strains

Abstract. Strains of Yersinia ruckeri, the enteric redmouth (ERM) bacterium, show greater serological diversity than previously supposed. A distinct sub–group of the otherwise homogeneous serovar I (Hagerman) strains includes the salmonid blood spot (SBS) bacterium. Two other new serological varieties, serovars IV and V, have been designated.

Vaccination of fish: a practical view.

Commercial vaccines giving protection against three important bacterial fish diseases (enteric redmouth, furunculosis and vibriosis) became available in the United Kingdom in 1983. The degree of protection obtained and the cost effectiveness vary according to the method of presentation (injection, dipping or spraying and oral dosing). These methods and the optimum time for vaccination are described.

Isolation of Yersinia ruckeri Bacteriophages

Eight bacteriophages effective against Yersinia ruckeri, the enteric redmouth disease bacterium, were isolated. Phage YerA41, a tailed icosahedral virus isolated from sewage enrichments, lysed 34 of 35 strains of Y. ruckeri serovar I, but was inactive against 15 strains belonging to three other serological groups. Six other phages lysed strains of serovars II, V, and I', a subgroup of serovar I. YerL62, a phage obtained by mitomycin C induction, was specific for one of three serovar V strains. These bacteriophages, particularly YerA41, have potential value for fish disease diagnostic work.

The identification of Yersinia ruckeri and its relationship to other representatives of the Enterobacteriaceae

From a study of the phenotypic and serological characters of representative strains of Yersinia ruckeri and other Enterobacteriaceae taxa, it was determined that the causal agent of enteric redmouth ( Y. ruckeri) in salmonid fish was related to the type strain of Salmonella arizonae (NCTC 8397). This similarity suggested that the organisms were not sufficiently distinct to warrant their inclusion in two genera.

Outbreak of enteric redmouth disease in rainbow trout, Salmo gairdneri Richardson, in France

Outbreak of enteric redmouth disease in rainbow trout, <i>Salmo gairdneri</i> Richardson, in France

An outbreak of enteric redmouth disease in West Germany

An outbreak of enteric redmouth disease in West Germany

Oxolinic acid for control of enteric redmouth disease in rainbow trout.

Oxolinic acid for control of enteric redmouth disease in rainbow trout.

Potentiated Sulfonamide Therapy of Enteric Redmouth Disease

Effective control of enteric redmouth disease was obtained during artificial infection of rainbow trout (Salmo gairdneri) and in natural outbreaks in rainbow trout and chinook salmon (Oncorhynchus tshawytscha) with a potentiated sulfonamide, Ro5-O037, a combination of five parts sulfadimethoxine and one part ormetoprim. Treatment was given at the rate of 50 mg/kg of fish for 5 d.Key words: potentiated sulfonamide, enteric redmouth, therapy, salmonids

Tribrissen® and tiamulin for control of enteric redmouth disease

Abstract. Fifteen drugs were tested for in vitro control of Yersinia ruckeri. Those drugs yielding in vitro control were subsequently tested for in vivo control of induced enteric redmouth disease in rainbow trout. Two of the drugs, Tribrissen®v and tiamulin, controlled Y. nickeri in vivo under laboratory conditions. The effective doses used in this study were 1–0 mg of Tribrissen/kg fish/day and 5–0 mg of tiamulin/kg fish/day, when the compounds were administered orally for 14 days. No toxic effects were noted at these dose levels, or from Tribrissen given at 15 times the above effective dose.

A serotypic survey and cross‐protection test of North American field isolates of Yersinia ruckeri

Abstract. A serological study of 23 North American strains of Yersinia ruckeri showed that they were comprised essentially of one serotype–the classical ‘Hager‐man’ serotype. Cross‐protection tests showed that rainbow trout could be protected from challenge with various strains. Continuous surveillance of enteric redmouth disease and further work including DNA binding studies is necessary to determine the precise significance of the other related serotypes.

Biochemical and Serological Characteristics of Ontario Isolates of Yersinia ruckeri

During testing hatchery and wild fish from Ontario sources, we isolated bacteria that had sufficient characteristics in common with Yersinia ruckeri to suggest they were strains of this organism. Three isolates from brook trout (Salvelinus fontinalis), rainbow trout (Salmo gairdneri), and cisco (Coregonus artedii) biochemically resembled the sorbitol-fermenting Serovar II strain of Y. ruckeri, but gave cross reactions with antiserum to the Hagerman strain, Serovar I. A fourth isolate from brown trout (Salmo trutta) appeared to be different from the three previously described serovars. A fifth isolate previously obtained from muskrat (Ondatra zibethica) intestine biochemically and serologically corresponded to the Hagerman serovar. We suggest that the geographic range of Y. ruckeri and variations in its biochemical and serological properties are greater than previously believed. These findings are of significance in diagnosis and regulation of enteric redmouth disease of salmonids.Key words: Yersinia ruckeri, enteric redmouth, ERM, bacterial disease, fish health protection

Morphological diversity among strains of Yersinia ruckeri

There are morphological variations in strains of Yersinia ruckeri, the causal agent of enteric redmouth in salmonid fish. Those variations include subtle differences in cell size and shape, as recorded from growth on a range of bacteriological media. Moreover, from a critical re-evaluation of the phenotypic traits, it appears that these organisms are more closely related to Salmonella than Yersinia.