No description available.

Furunculosis is a disease of great economic importance to the salmon fanning industry. The aetiological agent of the disease is Aeromonas salmonicida, probably the most studied pathogen of non mammalian hosts. Little information exists however on the most fundamental aspects of the infection process or the basis of acquired immunity. Although oral vaccination is an ideal solution to the problems of immunising fanned salmonids, poor immunogenicity has always limited the use of this route of administration. In mammals oral vaccination with live auxotrophic mutants has been shown to elicit both humoral and cellular immunity and provide protection against challenge. The recent development of an aroA mutant of A. salmonicida has enabled investigation into the response of rainbow trout to a live oral vaccine. Initially, the role of gastric acidity in the destruction of the live bacteria was investigated in vitro. Aeromonas salmonicida, Yersinia ruckeri and Escherichia coli were compared for acid resistance. Using a system of low pH buffers appropriate to the acidity found in the gut of rainbow trout it was found that A. salmonicida was readily killed by a pH of 4.0 or less. Resistance to low pH increased during stationary phase and 0.002% of bacteria grown for 72 hours were able to survive at least six hours exposure to pH 3.0, compared with 90% of Yersinia ruckeri exposed to the same conditions. The effect of culture medium, oxygen availability, and the pH of the culture medium were also investigated. Whilst growth in BHIB or in a shaking incubator did not alter the resistance of Aeromonas salmonicida to pH 3.0 growth in TSB adjusted to pH 5.5 increased survival of the bacteria by ten fold. It was apparent that the bacteria would probably require protection from the gastric acidity. The uptake and localisation of the bacteria was investigated by recovery and enumeration of viable bacteria from the stomach and intestinal mucus as well as the kidney, spleen and liver of fish vaccinated orally, anally and by IP injection. The presence of the bacteria was monitored between 5 minutes and 72 hours. Bacteria were found in the organs within 5 minutes of delivery regardless of route. The largest numbers were found following IP injection and the lowest following oral intubation. Oral administration of the vaccine protected by prior administration of sodium bicarbonate increased the number of bacteria found in the fish and increased the persistence within the tissues. The effect of growth conditions on the uptake and localisation was also investigated and no increase in uptake was found. Oral delivery of the bacteria in TSB increased the number of bacteria found within the organs to levels above that found following IP injection in TSB. Poor uptake has been reported for killed oral vaccines suggesting that the bacterium was able to invade the host via the gut mucosae. The interaction between trout intestine and A . salmonicida was investigated using TEM and SEM and the ability of the vaccine strain to invade cell monolayers was compared with that of an A-layer deficient strain and Y. rukeri. Infection of the trout intestine in vitro and in vivo led to pathological damage to the epithelium. There was also evidence of phagocyte infiltration and it was apparent that these cells were destroyed by contact with the bacteria. Invasion of tissue culture cells was assessed by acridine orange staining and enumeration of viable internalised bacteria. Aeromonas salmonicida appears to be invasive but its cytotoxic ECPs appear to kill most of the cells it enters. The specific and non-specific humoral immune response to vaccination was investigated. There was evidence of a limited effect on various nonspecific immune response parameters but there was no detectable antibody response to the vaccine. There is evidence that cellular immunity is preferentially stimulated by live vaccines and any future work should involve an investigation of the systemic and mucosal cellular response.

No description available.

The pathogen Piscirickettsia salmonis, has been isolated from all species of salmonid and has been found in Chile, Canada, Ireland, Norway and Scotland. Rickettsia-like organisms from European sea bass (Dicentrarchus labrax) were found to share common antigens with the P. salmonis type-strain, LF-89 using the indirect fluorescent antibody test (IFAT) and immunohistochemistry (IHC). In addition, the DNA sequences of the 16S rDNA and 16S-23S internal transcribed spacer region (ITS) were compared with those published for P. salmonis strains and showed that the sea bass piscirickettsia-like organism (SBPLO) was another strain of P. salmonis, closely related to the salmonid pathogens. The ability of P. salmonis to survive and replicate within head kidney (HK) macrophages of rainbow trout infected in vitro was demonstrated using transmission electron microscopy (TEM) at various times post-infection (p.i.). However, macrophages derived from fish vaccinated against P. salmonis appeared to clear in vitro infection more rapidly than macrophages from naive fish. Polymerisation of filamentous actin within the cytoplasm of the host cell is used by some mammalian rickettsiae to achieve intercellular spread by actin-based motility (ABM). Both TEM and confocal microscopy were used to investigate possible actin tail formation by P. salmonis. No evidence of tail formation was found. Respiratory burst (RB) by P. salmonis was measured following exposure of rainbow trout HK macrophages to the organisms in vitro. Because of background stimulation of the RB by growth media and debris from the CHSE-214 cells used to culture P. salmonis, it was not possible to detect any effect of the pathogen on the burst. Schering Plough Aquaculture has developed a recombinant vaccine against P. salmonis. The ability of the vaccine to elicit a memory response against P. salmonis was investigated by measuring three different immune responses: a) the expression of iNOS was measured by reverse transcription polymerase chain reaction (RT-PCR) to detect mRNA levels or by the Greiss reaction to quantify the end-products of nitric oxide metabolism in the serum. Increased iNOS expression was not detected in rainbow trout kidney or serum following vaccination/challenge with P. salmonis. However, iNOS expression was detected in gill tissue from naive trout which suggests that expression may be constitutive in this tissue. b) the production of macrophage activating factor (MAF) by lymphocytes from vaccinated trout, following stimulation in vitro with P. salmonis, was measured by the ability of supernatants from these cells to prime elevated RB in naive macrophages. No difference in priming ability between supernatants from vaccinated and non-vaccinated fish was detected. However, macrophages among the immune leukocytes used to produce the MAF supernatants did exhibit elevated RB compared with macrophages from non-immune fish, suggesting that vaccination had produced a population of lymphocytes capable of priming activation of macrophages. c) by screening individual sera concurrently against the rickettsial and CHSE antigen preparations, the antibody response to P. salmonis could be detected specifically and was found to increase significantly in immunised fish by 6 weeks post-vaccination. Specificity of the response was demonstrated by screening the sera against Aeromonas salmonicida.

Thesis (doctoral)--Jena, 1935.

Thesis (doctoral)--Jena, 1935.

Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

This project investigated several factors that influence the virulence of the fish pathogen <I>Aeromonas salmonicida</I> subspecies <I>salmonicida</I>. In this study the effect of iron supplementation was investigated on whole cell bacterin used as a vaccine. It was shown that A-layer negative strains grown under iron supplementation do not confer high protection. A-layer positive strains though, do provide protection at levels similar to the A-layer negative iron restricted bacterin. Use of a combined vaccine appeared to compound the protection. Cells grown under iron normal and iron restricted conditions have previously been shown to produce, respectively, ferric superoxide dismutase (SOD) and manganese SOD to protect against superoxide anions. Analysis here followed the transfer from iron restricted culture to iron supplemented culture to investigate the change in superoxide dismutase (SOD) induction. It appeared that both ferric and manganese SOD were expressed even though only one form was active in either iron condition. This implies post-translational control of activity. Catalase in another enzyme with a protective role and is induced by hydrogen peroxide. Cells grown without the addition of hydrogen peroxide do not appear to express a functional catalase. Analysis of catalase induction has shown that iron normal and iron supplemented growth using hydrogen peroxide induces expression of a catalase enzyme. Iron restricted bacteria show sensitivity to normal induction doses of hydrogen peroxide. Lowering the induction concentration allows expression of the catalase. This suggests that the catalase is heme co-factored. The relationship between iron levels and catalase induction suggests that catalase has a high priority for any available iron. The <I>in vivo</I> expression of the serine proteinase and iron regulated outer membrane proteins (IROMP's) was investigated. Whilst the serine proteinase was induced <I>in vivo</I> in a normal virulent strain, a proteinase-negative strain did not appear to produce the proteinase. This suggests that the serine proteinase is not essential for virulence. The expression of IROMP's <I>in vivo</I> indicates an iron restricted environment. <I>A. salmonicada</I> secretes a glycerophospholipid: cholesterol acyl transferase (GCAT) that is often complexed with LPS and believed to be a major toxin of the ECP. Analysis of culture supernatants has identified a secreted extracellular polysaccharide that may also complex with GCAT.

A climate change impact assessment was conducted to examine the spread of furunculosis found in the fish species of Ouje-Bougoumou; and subsequently to examine the resulting impacts on the health of the community. A past assessment was performed to assess whether there was a temporal relationship between increased temperatures and past incidences of furunculosis using observed climate data and traditional ecological knowledge (TEK) data. To project future impacts of climate change, climate models, lake models and TEK were used. Findings show that the rise in air mean temperature coincides with the timeline of past incidences of furunculosis. It is predicted that the lake temperatures will remain suitable for the presence of A. salmonicida; thus, it is likely that the disease will persist throughout the twenty-first century. To conclude, climate change is not eliminated as a plausible factor to the onset of furunculosis.

A climate change impact assessment was conducted to examine the spread of furunculosis found in the fish species of Ouje-Bougoumou; and subsequently to examine the resulting impacts on the health of the community. A past assessment was performed to assess whether there was a temporal relationship between increased temperatures and past incidences of furunculosis using observed climate data and traditional ecological knowledge (TEK) data. To project future impacts of climate change, climate models, lake models and TEK were used. Findings show that the rise in air mean temperature coincides with the timeline of past incidences of furunculosis. It is predicted that the lake temperatures will remain suitable for the presence of A. salmonicida; thus, it is likely that the disease will persist throughout the twenty-first century. To conclude, climate change is not eliminated as a plausible factor to the onset of furunculosis.