Phylogenetic analysis of infectious pancreatic necrosis virus in Ireland reveals the spread of a virulent genogroup 5 subtype previously associated with imports

Peer-reviewed. The final publication is available at Springer via DOI: 10.1007/s00705-014-2307-9Infectious pancreatic necrosis is a significant disease of farmed salmonids resulting in direct economic losses due to high mortality and disease-management costs. Significant outbreaks of the disease occurred in farmed Atlantic salmon in Ireland between 2003 and 2007, associated with imported ova and smolts. As the virus was known to occur in the country since the development of aquaculture in the 1980s, this study examined archived samples to determine whether these older isolates were associated with virulent forms. The study showed that two genotypes of IPNV were present in the 1990s, genotype 3 and genotype 5. A more virulent subtype of the virus first appeared in 2003 associated with clinical outbreaks of IPN, and this subtype is now the most prevalent form of IPNV found in the country. The data also indicated that IPNV in Ireland is more closely related to Scottish and continental European isolates than to Norwegian, Chilean and Australasian genogroup 5 isolates

National Survey of Sea Lice (Lepeophtheirus salmonis Krøyer and Caligus elongatus Nordmann) on Fish Farms in Ireland – 2019

Farmed stocks of Atlantic salmon in Ireland are inspected on 14 occasions throughout the year to monitor sea lice levels as part of a national programme. Sea lice are a naturally occurring parasite found on marine fish, including salmonids. They are small ecto-parasitic copepod crustaceans and there are approximately 559 species. The objectives of the National Sea Lice Monitoring Programme are: To provide an objective measurement of infestation levels on farms. To investigate the nature of infestations. To provide management information to drive the implementation of control and management strategies. To facilitate further development and refinement of this strategy. The sea lice control and management strategy has five principal components: Separation of generations. Annual fallowing of sites. Early harvest of two-sea-winter fish. Targeted treatment regimes, including synchronous treatments. Agreed husbandry practices

Impact of inter-lab variation on the estimation of epidemiological cut-off values for disc diffusion susceptibility test data for Aeromonas salmonicida

Peer-reviewed. Released with a Creative Commons Attribution Non-Commercial No Derivatives LicenseTwo laboratories investigated the susceptibility of 106 Aeromonas salmonicida strains (from Denmark, France, Ireland, Norway and Scotland) to erythromycin, gentamicin, oxytetracycline and oxolinic acid using the disc diffusion protocols (M42-A) published by the Clinical and Laboratory Standards Institute. In studies of susceptibility to florfenicol an additional 15 Canadian strains were included. Comparison of the data generated by the two laboratories demonstrated that for each disc both detected a similar pattern of distribution but that there was a significant numerical difference in the zone sizes they recorded. Analysis of the extent of this lateral shift between the data generated in two laboratories indicated that the application of a single laboratory-independent epidemiological cut-off value for each disc could result in disagreement between the laboratories as to whether a strain should be classified as wild-type or non wild-type. Normalised resistance interpretation was employed to generate epidemiological cut-off values from the data obtained by each laboratory. The use of these laboratory-specific cut-off values resulted in both laboratories achieving complete agreement as to the classification of all strains to all agents

Biofouling of the hydroid Ectopleura larynx on aquaculture nets in Ireland: implications for finfish health

Peer-reviewedThe potential direct health problems posed to marine-farmed salmonids by the biofouling hydroid Ectopleura larynx (Phylum Cnidaria, Class Hydrozoa) and in situ net washing processes to remove the fouling organisms have not yet been addressed. In an attempt to address the possible impacts, the rate of E. larynx growth on aquaculture nets over a net-cleaning cycle was assessed and Atlantic salmon (Salmo salar) smolts were exposed to hydroid-biofouled nets under experimental challenge. After only 1 week of immersion, there was a high settlement of E. larynx on net panels, with the maximum growth observed after 3 week of immersion. For the challenges trials, experimental treatment groups of S. salar were exposed to hydroid net panels or loose hydroid material for 11 hours under controlled conditions. Gills were examined for signs of gross damage and assigned a histopathological gill score. Prior to the experiment, the gills were healthy and did not show signs of damage from any insult. After exposure to E. larynx, focal areas of epithelial sloughing, necrosis and haemorrhage were visible on the gills under histopathology and a maximum gill score of 4 was observed. These results are the first in an investigation of this kind and suggest that E. larynx can damage the gills of S. salar. Further work on this area is vital to develop a better understanding of the pathogenesis of the damage caused by hydroids and their long-term effects on fish health, growth and survival

The advantages of the use of discs containing single agents in disc diffusion testing of the susceptibility of Aeromonas salmonicida to potentiated sulphonamides

Peer-reviewed. Released with a Creative Commons Attribution Non-Commercial No Derivatives LicenseThe susceptibilities of 106 strains of Aeromonas salmonicida to trimethoprim/sulfamethoxazole (SFT) were determined in two laboratories using the Clinical and Laboratory Standards Institute's M42-A disc diffusion protocols. The data generated by the use of discs containing 25 μg SFT (SFT25) allowed the strains to be placed into two groups. Strains in one group (17 strains) generated no inhibition zones and the zones obtained from the other 89 strains were distributed over a wide range but showed no natural division into separate sub-classes. A further investigation performed by one of the participating laboratories, of the susceptibility of 91 of these 106 strains used discs containing 100 μg sulfmethoxazole (SFM100) and 5 μg trimethoprim (TMP5). Application of normalised resistance interpretation to these data allowed the estimation of epidemiological cut-off values for WT strains of ≥ 9 mm for SFM100 and ≥ 21 mm for TMP5. This investigation demonstrated the presence of three distinct phenotypic classes, one containing strains manifesting wild type susceptibility to both agents, another containing strains manifesting non-wild type susceptibility to both and a third containing strains manifesting wild type susceptibility with respect to TMP but non-wild type with respect to SFM. Analysis demonstrated the inability of SFT25 discs to generate data that allowed the separate identification of strains that were fully susceptible to both TMP and SFM from those that were fully susceptible to TMP but were not fully susceptible to SFM. It is recommended that, in investigation of the susceptibility to potentiated sulphonamides of isolates from diseased fish, separate discs, containing the individual components of the mixture, should be employed

Stress and stress disorders in a teleost fish, the common carp Cyprinus carpio L.

Unlike research using mammalian animal models such as rats or mice, experimental fish often come from wild or commercial sources, leading to a lack of well defined experimental animal models. Isogenic carp offer us a well defined fish model for physiological research. The aim of this thesis was to, therefore, investigate the physiological stress response of isogenic strains of carp. Increased levels of stress in intensively reared animals results in large economical losses (due to disease mortalities, poor growth) and an increased understanding of the stress response is therefore relevant to the fish farming industry. Using a standard stressor, we aimed to examine the influence of environmental disturbances (e.g. high densities, restricted feeding levels) on the physiological response of the carp to this stressor. Fish showed a mild response to the period of crowding, although they appeared to recover physiologically, fish reared at a high density were more sensitive to an additional disturbance as seen by the higher levels of stress-hormones in the circulation. In addition, alternate periods of optimal or maintenance feeding levels were also found to affect the response to stress. An alternative method for measuring chronic stress in fish was also established through hormonal measurements in the water. A stress disorder was noted in one strain, these fish appear to suffer from a disorder similar to the 'chronic adrenal hyperplasia' which occurs in mammals. As this has never been described in a lower vertebrate, these fish may prove to be an important model for future studies on fish endocrinology

Measuring cortisol in the water as an indicator of stress caused by increased loading density in common carp (Cyprinus carpio)

The influence of a high loading density for a period of 28 days on growth, water quality and stress parameters in common carp (Cyprinus carpio) was investigated. In addition, cortisol levels in the water were measured during the experiment to investigate if a relationship exists between loading density and cortisol levels. No differences in the relative growth rates and food conversion were found between fish reared at the high (2.6 kg l(-1) min) and low loading rates (0.6 kg l(-1) min). Water quality was reduced in tanks with a higher loading density but not to an extent which was detrimental to the health of the fish. Plasma cortisol levels were only significant between high and low loading densities on day 3. However, cortisol levels in the water were significantly elevated on days 1, 3, 8 and 28 in the highdensity groups compared to the low. Loading densities did not effect plasma glucose and free fatty acid (FFA) levels, although an effect of the initial handling was found for FFA. Results show that carp adapt well to high loading densities and that measuring cortisol levels in the water may prove to be a useful indicator of stress levels in fish without inducing any disturbance. (C) 2003 Elsevier Science B.V. All rights reserved

Stress-induced facilitation of the cortisol response in 17a-hydroxylase deficient XX mas -1/mas -1 carp (Cyprinus carpio)

Facilitation of the stress response results from a reduction of the inhibitory effects of circulating corticosteroids, allowing an animal to respond to a novel stressor. In this study, the existence of a facilitated cortisol stress response in normal (STD) and 17¿-hydroxylase deficient XX mas¿1/mas¿1 (E5) carp was investigated. E5 carp had previously been characterized as having a low cortisol response to stress. Fish were subjected to either cortisol feeding or daily-acute stress, from 45 until 140 days post-hatch (dph) and were then subjected to a novel net-confinement stressor at 141 dph. Growth of E5 fish was reduced in both the daily-acute stress and cortisol-fed groups, but STD fish were only affected by daily-acute stress. Cortisol feeding had no effect on the stress response of STD fish but daily-acute stress significantly inhibited the response to a subsequent novel stressor. In contrast, daily-acute stress facilitated the cortisol stress response of E5 fish to a novel stressor, while cortisol feeding inhibited the cortisol response. Facilitation was accompanied by significant enlargement of the head-kidney tissue (which contains the steroidogenic interrenal tissue) in E5 fish. To our knowledge this is the first report of stress-induced facilitation in a lower vertebrat

Plasma cortisol and metabolite level profiles in two isogenic strains of common carp during confinement

A rapid increase in common carp Cyprinus carpio plasma cortisol levels was noted, in two experiments, after 30 mins of a 3 h net confinement, which was sustained while the fish were held in the nets. After release from the nets, cortisol levels returned to control values in 1 h. Plasma glucose and free fatty acid levels were elevated by the confinement. Glucose was increased after 30 min but returned to basal levels after 22 h of recovery while free fatty acids were not elevated until 3 h of confinement and remained high for the duration of the recovery period. After confinement for 3 h, plasma lactate levels were reduced and remained low for a further 1 h. No change in either plasma triglyceride or cholesterol levels were found during the study. Confinement had no effect on haematocrit levels but blood haemoglobin levels were reduced. In both experiments hypochloraemia occurred in response to confinement. However, values returned to pre-confinement levels 22 h after confinement. These results show that rearing isogenic carp strains, under identical conditions, results in a reproducable response to an acute stressor and that these carp respond in a similar manner to other teleost specie