Redmouth Disease In Rainbow Trout Research Articles

Effects of fish size and route of infection on virulence of a Danish Yersinia ruckeri O1 biotype 2 strain in rainbow trout (Oncorhynchus mykiss)

The comparative virulence of Yersinia ruckeri serotype O1 biotype 2 strain 07111224 from a Danish outbreak of enteric redmouth disease in rainbow trout (Oncorhynchus mykiss) was investigated in different sizes of rainbow trout (5, 19, 25 and 52 g) using a panel of challenge methods (bath, intraperitoneal (IP) injection, anal intubation and cohabitation).The results show that Y. ruckeri 07111224 is virulent enough to successfully cause mortality in 5–52 g rainbow trout through three different infection routes (bath, IP injection and anal intubation), and strongly suggests that susceptibility to Y. ruckeri infection is dependent on fish size. Bath challenge (108 CFU/ml) caused 79% mortality in 5 g fish, while the mortality in 19–52 g fish was approximately 26%. IP injection challenges (105–106 CFU/individual) resulted in high mortalites in fish of all sizes. Anal intubation challenges (109 CFU/individual) induced 82% mortality in 5 g fish and decreased with increasing fish weight. Finally, cohabitation challenges induced 45% mortality in 5 g test fish when test fish were cohabitated 1:1 with shedder fish, while mortalities in test fish of five other challenge groups were lower (5–25%). Statistical models were fit to the data from each challenge model. The model parameter predictions suggests statistically significant effects of fish weight for bath, IP and anal intubation challenges. Furthermore, they highlight the importance of the ratio of shedders to test fish in cohabitation challenges and of the challenge doses, in particular for the IP challenge model.

Several mucosal vaccination routes confer immunity against enteric redmouth disease in rainbow trout, but the protective mechanisms are different

Several mucosal vaccination routes confer immunity against enteric redmouth disease in rainbow trout, but the protective mechanisms are different

Occurrence of enteric redmouth disease in rainbow trout (Oncorhynchus mykiss) on farms in Croatia.

During the spring of 1996 and autumn of 1997 unusual mortality outbreaks among rainbow trout fry and yearlings occurred at two different trout farms, resulting in mortality of 20 and 10 per cent, respectively. Generally, the affected fish, swimming at the water surface, were reluctant to eat and were dark pigmented with visible haemorrhages around and within the oral cavity. Bacterial isolates from moribund fish from both cases were identified as Yersinia ruckeri by standard biochemical tests and API 20E. The isolated strains were found to be sensitive to tetracycline, chloramphenicol, co-trimoxazole, nalidixic acid, flumequine, enrofloxacin, carbenicillin and gentamicin. Microplate agglutination assay confirmed that both isolates belonged to serotype O1. The pathogenicity of the isolated bacteria was confirmed by challenge experiment. Titres of specific antibodies were determined in the sera of survivors. The titre was highest on the 21st day postchallenge and was detectable until the 81st day.

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.

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

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

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

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.

Yersinia ruckeri sp. nov., the Redmouth (RM) Bacterium

Cultures of the redmouth (RM) bacterium, one of the etiological agents of redmouth disease in rainbow trout (Salmo gairdneri) and certain other fishes, were characterized by means of their biochemical reactions, by deoxyribonucleic acid (DNA) hybridization, and by determination of guanine-plus-cytosine (G+C) ratios in DNA. The DNA relatedness studies confirmed the fact that the RM bacteria are members of the family Enterobacteriaceae and that they comprise a single species that is not closely related to any other species of Enterobacteriaceae. They are about 30% related to species of both Serratia and Yersinia. A comparison of the biochemical reactions of RM bacteria and serratiae indicated that there are many differences between these organisms and that biochemically the RM bacteria are most closely related to yersiniae. The G+C ratios of RM bacteria were approximated to be between 47.5 and 48.5%. These values are similar to those of yersiniae but markedly different from those of serratiae. On the basis of their biochemical reactions and their G+C ratios, the RM bacteria are considered to be a new species of Yersinia, for which the name Yersinia ruckeri is proposed. Strain 2396-61 (= ATCC 29473) is designated the type strain of the species.

Establishment of an Asymptomatic Carrier State Infection of Enteric Redmouth Disease in Rainbow Trout (Salmo gairdneri)

The dynamics of establishment, pathogenesis, and continued maintenance of Enteric Redmouth (ERM) disease in rainbow trout (Salmo gairdneri) were examined. Groups were infected by parenteral and oral routes and subsampled at weekly intervals. Both modes of infection were standardized to obtain ID100 levels of infection with an average of 30 bacteria constituting an LD50 dosage when administered parenterally. The clinical course of the disease was monitored up to 102 days postinfection. A clinically asymptomatic carrier state infection was established in the lower intestine of 25% of survivors 45 days postinfection at 14.5 C. Thereafter, regular intestinal shedding of the pathogen, causing recurrent infection and mortality within the population, occurred on acyclic basis of 30–40-day intervals. Clinical recovery, establishment of the asymptomatic condition, and periodicity of intestinal shedding and the clinical course of the disease to convalescence were described.