Academic literature on the topic 'Cardicola'

Melanomacrophage centres (MMCs) are aggregates of macrophages accumulating various pigments. They have been proposed as an indicator of fish immune response. Blood flukes are common parasites in farmed fish. Two cohorts of wild Southern Bluefin Tuna (Thunnus maccoyi) were examined at transfer, before treatment against blood flukes (pre-treatment) and at harvest. MMCs were assessed in histological sections using image analysis, while Cardicola forsteri and Cardicola orientalis infection severity was determined using qPCR, count of adult flukes in heart flushes and count of eggs in gill filaments. Fish from both cohorts showed the same pattern in the changes in the surface area of MMCs. The surface area of splenic MMCs increased over the ranching duration and was positively correlated to the PCR determined copy numbers of Cardicola forsteri ITS2 rDNA in the gills of those fish. However, the infection with blood fluke was more variable, both between cohorts and individuals within the same cohort. Eggs of blood fluke were detected in renal MMCs using histology. Cardicola forsteri had a higher prevalence than Cardicola orientalis. This study contributes to our understanding of blood fluke infections in Southern Bluefin Tuna and their interactions with MMCs.

A survey of Pacific coral reef fishes for sanguinicolids revealed that two species of Lutjanidae (Lutjanus argentimaculatus, L. bohar), six species of Siganidae (Siganus corallinus, S. fuscescens, S. lineatus, S. margaritiferus, S. punctatus, S. vulpinus), seven species of Chaetodontidae (Chaetodon aureofasciatus, C. citrinellus, C. flavirostris, C. lineolatus, C. reticulatus, C. ulietensis, C. unimaculatus), three species of Scombridae (Euthynnus affinis, Scomberomorus commerson, S. munroi) and three species of Scaridae (Chlorurus microrhinos, Scarus frenatus, S. ghobban) were infected with morphologically similar sanguinicolids. These flukes have a flat elliptical body, a vestigial oral sucker, a single testis, separate genital pores and a post-ovarian uterus. However, these species clearly belong in two genera based on the position of the testis and genital pores. Sanguinicolids from Lutjanidae, Siganidae, Chaetodontidae and Scombridae belong in Cardicola Short, 1953; the testis originates anteriorly to, or at the anterior end of, the intercaecal field and does not extend posteriorly to it, the male genital pore opens laterally to the sinistral lateral nerve chord and the female pore opens near the level of the oötype (may be anterior, lateral or posterior to it) antero-dextral to the male pore. Those from Scaridae are placed in a new genus, Braya; the testis originates near the posterior end of the intercaecal field and extends posteriorly to it, the male pore opens medially at the posterior end of the body and the female pore opens posterior to the oötype, antero-sinistral to the male pore. The second internal transcribed spacer (ITS2) of ribosomal DNA from these sanguinicolids and a known species, Cardicola forsteri Cribb, Daintith & Munday, 2000, were sequenced, aligned and analysed to test the distinctness of the putative new species. Results from morphological comparisons and molecular analyses suggest the presence of 18 putative species; 11 are described on the basis of combined morphological and molecular data and seven are not because they are characterised solely by molecular sequences or to few morphological specimens (n=one). There was usually a correlation between levels of morphological and genetic distinction in that pairs of species with the greatest genetic separation were also the least morphologically similar. The exception in this regard was the combination of Cardicola tantabiddii n. sp. from S. fuscescens from Ningaloo Reef (Western Australia) and Cardicola sp. 2 from the same host from Heron Island (Great Barrier Reef). These two parasite/host/location combinations had identical ITS2 sequences but appeared to differ morphologically (however, this could simply be due to a lack of morphological material for Cardicola sp. 2). Only one putative species (Cardicola sp. 1) was found in more than one location; most host species harboured distinct species in each geographical location surveyed (for example, S. corallinus from Heron and Lizard Islands) and some (for example, S. punctatus, S. fuscescens and Chlorurus microrhinos) harboured two species at a single location. Distance analysis of ITS2 showed that nine species from siganids, three from scombrids and five from scarids formed monophyletic clades to the exclusion of sanguinicolids from the other host families. Cardicola milleri n. sp. and C. chaetodontis Yamaguti, 1970 from lutjanids and chaetodontids, respectively, were the only representatives from those families that were sequenced. Within the clade formed by sanguinicolids from Siganidae there was a further division of species; species from the morphologically similar S. fuscescens and S. margaritiferus formed a monophyletic group to the exclusion of sanguinicolids from all other siganid species.

The parasitic blood flukes Cardicola forsteri and C. orientalis are an ongoing health concern for Southern Bluefin Tuna Thunnus maccoyii (SBT) ranched in Australia. In this study we compared the effect of treatment, company, and ranching year on blood fluke infections in ranched SBT. SBT were sampled during the 2018 and 2019 ranching seasons from praziquantel (PZQ) treated pontoons and untreated pontoons managed by two companies. Severity of infection was diagnosed by several criteria including adult fluke counts from hearts, egg counts from gill filaments and the use of specific quantitative polymerase chain reaction (qPCR) for detection of C. forsteri and C. orientalis ITS-2 DNA in SBT hearts and gills. PZQ treatment remains highly effective against C. forsteri infection. Prevalence and intensity of Cardicola spp. infection was lower in 2019 than 2018 for Company A in treated pontoons at week 12 and week 17 of ranching, and lower for Company A than Company B in untreated pontoons at month 5 of ranching. Results indicate re-infection may be less likely in the environment near Company A pontoons, and consistent years of treatment may have lowered the parasite load in the environment. qPCR demonstrated higher sensitivity when comparing diagnostic methods for C. forsteri in heart, and higher specificity when comparing diagnostic methods for Cardicola spp. in gills. Continuing to monitor blood fluke infections in ranched SBT can help to detect changes in drug efficacy over time and help industry to develop a best practice for treatment.

The blood fluke Cardicola forsteri (Trematoda: Aporocotylidae) is a pathogen of ranched bluefin tuna in Japan and Australia. Genomics of Cardicola spp. have thus far been limited to molecular phylogenetics of select gene sequences. In this study, sequencing of the C. forsteri genome was performed using Illumina short-read and Oxford Nanopore long-read technologies. The sequences were assembled de novo using a hybrid of short and long reads, which produced a high-quality contig-level assembly (N50 > 430 kb and L50 = 138). The assembly was also relatively complete and unfragmented, comprising 66% and 7.2% complete and fragmented metazoan Benchmarking Universal Single-Copy Orthologs (BUSCOs), respectively. A large portion (> 55%) of the genome was made up of intergenic repetitive elements, primarily long interspersed nuclear elements (LINEs), while protein-coding regions cover > 6%. Gene prediction identified 8,564 hypothetical polypeptides, > 77% of which are homologous to published sequences of other species. The identification of select putative proteins, including cathepsins, calpains, tetraspanins, and glycosyltransferases is discussed. This is the first genome assembly of any aporocotylid, a major step toward understanding of the biology of this family of fish blood flukes and their interactions within hosts.

Introducción. Un porcentaje elevado de pacientes intervenidos de cirugía cardíaca son tributarios de la realización de transfusiones durante el periodo perioperatorio. Son numerosos los trabajos que a partir de análisis uni y multivariantes han relacionado la práctica de transfusiones con variables relacionadas con las características de los pacientes y de las intervenciones realizadas. Objetivo. El objetivo del presente estudio es analizar diferentes variables relacionadas con la realización de transfusiones durante el periodo perioperatorio en pacientes tratados con una cirugía cardíaca mediante un método de partición recursiva. Material y métodos. Se evaluaron de forma ambispectiva un total de 2.122 procedimientos quirúrgicos de cirugía cardiaca realizados de forma consecutiva durante el periodo 2009-2013 en el Hospital de Sant Pau de Barcelona. Se consideró la relación entre una serie de variables clínicas y perioperatorias y la realización de transfusiones durante el periodo perioperatorio. Se analizó la relación entre las variables consideradas y la práctica transfusional mediante diferentes técnicas de partición recursiva, incluyendo los modelos CHAID (Chi-Square Automatic Interaction Detection) y CRT (Classification and Regression Trees). Resultados. El porcentaje de pacientes intervenidos de cirugía cardiaca y que recibieron algún tipo de transfusión durante el periodo perioperatorio fue del 69.9%. El análisis de partición recursiva clasificó a los pacientes en relación al uso de transfusiones en función de los valores de la hemoglobina preoperatoria, el aclaramiento de creatina y la morbilidad medida de acuerdo con el índice Euroscore. Para los pacientes del sexo masculino la variable más relacionada con la realización de transfusiones fue el nivel de hemoglobina preoperatoria, y para las pacientes del sexo femenino lo fue el aclaramiento de creatinina. Otras variables que se vieron asociadas a la realización de transfusiones durante el periodo perioperatorio fueron el tipo y el grado de prioridad de la cirugía realizada, el antecedente en el uso de antiagregantes, el tiempo de circulación extracorpórea, y el volumen obtenido de los drenajes torácicos postoperatorios. Apareció una relación significativa entre la realización de transfusiones durante el periodo perioperatorio, la mortalidad hospitalaria y el periodo de ingreso. El análisis de partición recursiva permitió definir grupos de pacientes con un mayor riesgo de requerir una transfusión masiva. Se propone un modelo predictivo de los requerimientos transfusionales a partir de los resultados obtenidos con el método de partición recursiva. Se comprobó que este modelo contaba con una eficacia pronóstica semejante a la obtenida con otros modelos propuestos. Conclusiones. La metodología de partición recursiva permite una clasificación pronóstica de los pacientes tratados con una cirugía cardíaca en relación a los requerimientos transfusionales.
Introduction. A high percentage of patients treated with a cardiac surgery are candidates to hematic transfusion during the perioperative period. There are many studies evaluating the relationship between transfusions and variables associated with the characteristics of the patients or of the surgery with uni or multivariate analysis. Objective. The objective of our study is to analyze several variables related to the transfusion during the perioperative period in patients treated with a cardiac surgery with a recursive partitioning analysis approach. Material and methods. We evaluated ambispectively 2.122 cardiac surgery interventions carried out consecutively during the period 2009-2013 in the Hospital de Sant Pau of Barcelona. It was considered the relationship between several clinical and perioperative variables and transfusion with recursive partitioning analysis techniques, including the models CHAID (Chi-Square Automatic Interaction Detection) and CRT (Classification and Regression Trees). Results. The frequency of patients treated with a cardiac surgery that received some transfusion during the perioperative period was 69.9%.The recursive partitioning analysis classified the patients according to the preoperative hemoglobin values, the creatinine clearance and the general health status measured with the Euroscore index. For male patients the variable most related to practice of transfusions was the preoperative hemoglobin values, and for female patients it was the creatinine clearance. Other variable that appeared related to transfusion during the perioperatice period were the type of surgery and the priority of the surgery, the antiaggregation therapy, the extracorporeal circulation time, and the volume obtained from the thoracic drainages. There was a significant relationship between transfusion during the perioperative period and the hospital mortality and the duration of the hospital stays. The recursive partitioning analysis identified patients with a greater risk of massive transfusion. We propose a predictive model of transfusion necessities from data of the recursive partitioning analysis method. It was checked that this precictive model had a prognosis efficiency similar to other proposed models. Concussion. The recursive partitioning analysis methodology allows a prognostic classification of the patients treated with a cardiac surgery in relation to the transfusion necessities.

L'un des problèmes fondamentaux de l'imagerie cardiaque par résonance magnétique du tenseur de diffusion (IRM-TD) est sa faible résolution spatiale, à cause des limitations matérielles des scanners IRM actuels. L'objectif principal de ce travail de thèse est de développer de nouvelles approches pour améliorer la résolution des données d'IRM-TD afin de mieux représenter l'architecture myocardique du coeur humain et de la comparer avec des résultats issus d'autres techniques d'investigation telles que l'imagerie par lumière polarisée. Dans ce cadre, le travail porte sur trois parties principales. La première concerne le développement d'une nouvelle approche pour l'interpolation des champs de vecteurs propres principaux issus de l'IRM-TD cardiaque humaine. Cette approche consiste d'abord à supprimer les vecteurs corrompus par le bruit au lieu de débruiter de manière uniforme le champ entier de vecteurs, et ensuite à interpoler le champ de vecteurs en utilisant la modèle Thin-Plate-Spline (TPS) afin d'exploiter la corrélation entre les composantes du vecteur. La deuxième partie concerne une nouvelle famille de méthodes d'interpolation pour les champs de tenseurs, basée soit sur les angles d'Euler soit sur le quaternion. Ces méthodes exploitent les caractéristiques du tenseur et préservent les paramètres de tenseurs, tels que le déterminant du tenseur, l'anisotropie fractionnelle (FA) et la diffusivité moyenne (MD). En outre, cette partie compare les principales approches d'interpolation au niveau des images pondérées en diffusion et des champs de tenseurs, et les résultats montrent qu'il serait préférable d'effectuer l'interpolation des données d'IRM-TD au niveau des champs de tenseurs. La troisième partie étudie le changement des paramètres MD et FA après un infarctus du myocarde chez les cochons, et l'influence des méthodes d'interpolation sur ces paramètres dans la zone infarctus et la zone distante. Les résultats montrent que la zone infarctus présente une diminution significative de FA et une augmentation significative de MD, comparée avec la zone distante, et que les méthodes d'interpolations du tenseur ont plus d'influence sur FA que sur MD, ce qui suggère que l'interprétation de ces paramètres cliniques après l'interpolation doive être prise avec précaution.

Cardicola forsteri Cribb, Daintith and Munday, 2000 (Digenea: Sanguinicolidae), is a digenean parasite of southern bluefin tuna, Thunnus maccoyii (Castelnau) that can cause disease in an aquaculture environment. The aim of this research was to gain information about factors affecting the epidemiology of blood fluke, C. forsteri, infection in farmed southern bluefin tuna in South Australia. Comparative analysis of blood fluke of other bluefin tunas was undertaken to determine the host range of C. forsteri. We found, through comparisons of ITS2 and partial 28S rDNA, C. forsteri from multiple hosts and localities: southern bluefin tuna (T maccoyii) from South Australia and northern bluefin tuna (T. thynnus) from two localities in the Mediterranean (Spain and Croatia). Host migration seems likely to be responsible for the widespread occurrence of C. forsteri, although it is also possible that C. forsteri was translocated recently by the spread of infected intermediate hosts in international shipping, either as biofouling attached to hulls, or in ballast waters. C. forsteri, was examined in cultured southern bluefin tuna, T. maccoyii, over a six month growout season in Port Lincoln, South Australia. C. forsteri infections declined after an initial peak two months after transfer from the wild and no effect was observed on tuna condition index despite high intensities being recorded. It is concluded that T maccoyii may be able to control blood fluke infection. Stochastic models were developed to describe the infection pattern of Cardicola forsteri in farmed southern bluefin tuna, T maccoyii. Observed field data on the lengths of flukes over a growout season were used as the basis for the models. An estimated time of infection was produced from the models and it was shown that infections mostly occurred after introduction to sea-cages from the wild indicating the presence of the intermediate host in the farming environment. Factors influencing blood fluke intensity, abundance and prevalence were investigated by examining southern bluefin tuna collected from commercial harvests over a three-year period. Blood fluke prevalence was observed to be approximately 60% in tuna over a growout season. Annual means of intensity were fixed around six fluke per infected host and annual means of abundance between three and five fluke per host. A universal factor in explaining variation in C. forsteri intensity, abundance and prevalence was company. Year did not influence intensity or abundance although a decrease in prevalence in 2005 was evident. Tuna harvested in winter had a significantly greater abundance and prevalence of blood fluke than harvest in autumn. Interestingly, the period of time that tuna are in captivity does not significantly influence intensity of infection even though it does affect blood fluke abundance and prevalence. Intensity or abundance did not affect the condition of tuna. An adaptive immune response was investigated by developing an ELISA to detect and quantify an antibody response against the blood fluke in southern bluefin tuna serum. Antibody titres and seroprevalence increased during the growout period. Parasitological and serological values from were compared from a cohort introduced to the tuna farming zone in 2005 to a cohort introduced in 2006 to determine if prior infection in the 2005 cohort elicited any protection against infection in 2006. Although significant differences were not observed in intensities between cohorts it was shown that the cohort that had a history of infection had significantly lower abundances and prevalences of blood fluke infection than the naïve cohort demonstrating the development of acquired resistance against C. forsteri. The accuracies of a gross gill pathology test and a histopathological test for detecting C. forsteri were evaluated. The sensitivity of gross gill pathology was the only high estimate of diagnostic accuracy. Although the other estimates of diagnostic accuracy were low, the high sensitivity of gross gill pathology suggests that this may be a useful tool for future epidemiology studies. A Bayesian approach to the estimation of prevalence was carried out using two populations of tuna and two different diagnostic tests, an ELISA and parasitological examination. The prevalence of infection was shown to be higher than previously thought. ELISA was shown to have poor estimates of accuracy whereas a high sensitivity for parasitological examination was demonstrated. Parasitological examination is probably the best current method for detecting blood fluke infections.

Within the Australian fish production industry the ranching of Southern bluefin tuna (Thunnus maccoyii) (SBT) continues to be one of the most profitable. As culture practices become more efficient, the requirement for efficient methods of pathogen detection and quantification are also of increasing importance. In an effort to better understand the impact of ranching on pathogen prevalence, as well as provide tools for rapid detection, this research aimed to elucidate variability in pathogen prevalence in wild versus ranched SBT through the development of quantitative PCR methods and application of 16S rRNA amplicon sequencing. The first three research chapters focus on the detection of blood flukes (Digena: Aporocotylidae) from genus Cardicola, specifically C. forsteri, C. orientalis and C. opisthorchis; including development and application of a qPCR assay to quantify each species from organ and environmental samples. The final research chapter details the bacterial diversity in SBT spleen using universal bacterial 16S rRNA primers to amplify the V1-3 region and amplicon pyrosequencing. The 2013 SBT ranching season marked the introduction of the anthelmintic called praziquantel (PZQ), which has also been used to mitigate C. orientalis and C. opisthorchis infections in juvenile Pacific bluefin tuna in Japanese culture systems. Both wild and ranched SBT (at harvest) were sampled annually for three consecutive years starting in July 2013. A hydrolysis probe-based qPCR assay was designed and validated to detect and quantify C. forsteri, C. orientalis, and C. opisthorchis ITS2 rDNA. The assay was applied to quantify C. forsteri and C. orientalis DNA in heart and gill, which documented a significant annual variability of C. forsteri infection in ranched SBT hearts. No C. orientalis was detected in 2014 and 2015 ranched SBT, whereas C. forsteri was found in at least 95% of fish examined in all three years. This was an important yet unexpected finding given C. orientalis was significantly more prevalent than C. forsteri in 2011/12 harvests. Lastly, this chapter reports the first detection of C. orientalis in wild SBT. The newly developed hydrolysis probe-based qPCR assay was utilized to examine the prevalence of C. forsteri and C. orientalis ITS2 rDNA in 1995 and 2004 archival formalin-fixed paraffin embedded (FFPE) SBT heart samples. Prior to the examination of archival samples, five FFPE DNA extraction methods were compared, consisting of with and without xylene deparaffinization, application of 1 h 90°C incubation post proteinase K incubation, a QIAamp DNA mini kit® (Qiagen) and a TRIzol reagent based protocol. In addition, extended proteinase K incubation at 37°C, 72 h instead of 24 h, was examined and resulted in a significant increase in C. forsteri ITS2 rDNA. The inclusion of a 90°C h sample incubation step post proteinase K incubation resulted in a 100-fold increase in DNA yield compared to without and was significantly higher than when using a Qiagen QIAamp FFPE kit. This retrospective examination documented the presence of C. orientalis in 1995 FFPE SBT heart, preceding previous published presence in SBT in 2008 samples. C. forsteri and C. orientalis ITS2 rDNA was detected in sea water samples from sea cages alongside commercial harvest and control locations north and south of the cages. Real-time qPCR methods using SYBR green nucleic acid dye was used in the first year, and the hydrolysis probe-based qPCR assay in the second two years. Of three consecutive sampling years, C. forsteri and C. orientalis ITS2 rDNA was only detected in the first, despite qPCR examination of SBT organs documenting the presence of both blood fluke species in the all the years examined. Samples from the control North location (3.5 km North of cages containing SBT) had significantly lower levels of C. forsteri and C. orientalis ITS2 rDNA in the water compared to cages and control South location (2 km South of cages containing SBT). Significantly more C. orientalis ITS2 rDNA (M = 4885.08, SD = 7328.71) was detected compared to C. forsteri (M = 232.67, SD = 337.82) in samples collected on 29th and 30th of August, 2012. Culture independent PCR was applied to spleen of wild (n = 10) and ranched (n = 10) SBT as part of sample preparation for an evaluation of bacterial diversity using 16S rDNA tag-encoded pyrosequencing. The most abundant phylum among wild and ranched fish was Proteobacteria (94.41% ±0.041) followed by Acidobacteria (4.71% ±0.035), Cyanobacteria (0.49% ±0.007), and Firmicutes (0.24% ±0.005). Both Acidobacteria and Cyanobacteria were significantly more abundant in ranched compared to wild SBT (p< 0.05) spleen. Bacteroidetes was significantly more abundant in wild SBT (p < 0.0001) and it was not detected in samples from ranched SBT. The top 18 most abundant genera constituted 99.2% of the spleen microbiota. These included Bosea (66.99%), Phyllobacterium (22.73%), Edaphobacter (2.74%), Methylobacterium (2.03%), Propionibacterium (2%), Bradyrhyzobium 0.69%), Ochrobactrum 0.52%), Mesorhizobium (0.31%), Pseudoalteromonas (0.21%), Corynebacterium (0.19%), Acinetobacter (0.19%), Chelatococcus (0.14%), Burkholderia (0.1%), Staphylococcus (0.1%), Psychrobacter (0.08%), Yersinia (0.06%), Enterobacter (0.06%), and Pseudomonas (0.05%). Although Edaphobacter and Pseudoalteromonas were present in both groups, they were significantly more abundant in ranched SBT spleen (p < 0.05). On average the SBT spleen microbiota had 148.9 (±35.4) operational taxonomic units (OTUs) (min = 109; max = 252) at 97% sequence similarity. No significant difference in alpha diversity indices was found. PCoA plot based on weighted UniFrac distance as a measure of beta diversity showed no visual difference between wild and ranched SBT spleen in the community structure. No distinct difference in bacterial communities between wild and ranched fish may suggest that the documented diversity described in this thesis represents the baseline for SBT. The molecular detection methods described and applied in this thesis as well as the insight to bacterial diversity in SBT spleen have given a unique understanding of the presence of pathogens and will play a significant role in the sustainable ranching and management of this critically endangered bluefin tuna species.

In Australia, the Southern Bluefin Tuna (SBT) industry is regarded as one of the most profitable sectors of aquaculture. Even though SBT are relatively unaffected by infectious diseases, few still have an impact in SBT production, leading to economic losses. Two of the main diseases affecting ranched SBT are infections by blood flukes (Cardicola forsteri and C. orientalis) and swimmer syndrome. Until now, lethal sampling has been used for the detection of C. forsteri and C. orientalis, and in combination with conventional diagnostic methods, they are used as the “gold standard” for the diagnosis of Cardicola and Scuticociliates. Therefore, in an attempt to improve sampling and diagnostic tools for health management of SBT, the focus of this thesis was to: • Compare different lethal and non-lethal sampling methods used with conventional and molecular diagnoses for the detection of C. forsteri and C. orientalis • Determine the presence and identify Scuticociliates in samples from SBT showing swimmer syndrome • Determine the presence of C. forsteri and C. orientalis in biofouling samples near SBT pontoons • Identify the potential relationship between the substrate, the age of the biofouling sample, type of biofouling organisms and depth, with the presence of C. forsteri, and C. orientalis DNA in the biofouling To provide a better understanding of the diseases affecting ranched Bluefin Tuna, a review is presented in Chapter 2. In Chapter 3, lethal sampling and non-lethal sampling techniques as well as, conventional and molecular methods used for the diagnosis of C. forsteri and C. orientalis are compared. Lethal and non-lethal samples from SBT were collected over the course of three years. Results showed differences between lethal sampling used along with conventional diagnosis and non-lethal sampling and molecular diagnosis. Only 37% of the heart flushes were positive and 66% of gill filaments had egg counts, identification of Cardicola species proved to be too challenging. For the same SBT, real-time qPCR along with species specific primers and probes were used for the detection of C. forsteri and C. orientalis. Not all PCR-based techniques allowed the detection of animals positive for adult blood flukes of eggs, such is the case for serum samples where only 3% were real-time qPCR-positive for C. forsteri and 1% to C. orientalis. Gill mucus samples showed similar results to heart flushes (38% of the samples positive for C. forsteri and 28% to C. orientalis), nevertheless, the use of gill mucus and realtime qPCR presents the advantage of allowing the identification of Cardicola species. Gill snips, gill biopsies and gill filaments samples, all presented high sensitivity when compared to conventional diagnostic techniques, where 100% of gill snips and gill biopsies were positive for C. forsteri, 86% of the gill filaments were also positive for C. forsteri and 4% of gill filaments were positive for C. orientalis. All molecular techniques allowed differentiation between species of Cardicola. In Chapter 4, 16 olfactory rosettes from wild SBT and 23 cerebrospinal fluid (CSF) samples from ranched SBT which exhibited swimmer syndrome, were collected. CSF samples positive for Scuticociliates were identified firstly using microscopy methods observing motile cells with a pyriform shape and granular appearance. All samples were tested using end point PCR combined with primers amplifying fragments of the small subunit rDNA (SSU rDNA) and the mitochondrial cytochrome c oxidase subunit 1 (cox1), all the amplifications obtained were sequenced and compared against published data. Olfactory rosettes were considered negative for Scuticociliates as neither of them showed amplification using the SSU rDNA and cox1 primers. Sequencing of the PCR products of the CSF samples, evidenced presence of M. avidus, being 100% identical to sequences of M. avidus previously reported. This means that those swimmer syndrome cases investigated here were associated with M. avidus. In an attempt to identify possible sources of infection of C. forsteri, C. orientalis and M. avidus, and as a result of the data obtained from Chapter 3 and 4, biofouling samples plates and mesh for biofouling were placed at different depths near the tuna pontoons. Samples were placed at one and four metres of depth and collected after one and three months. Organisms were separated according to their taxonomic group and identified by molecular techniques species-specific primers and probes for real-time qPCR. The presence of C. forsteri and C. orientalis was detected in 4 samples, each one of them. C. forsteri was only detected in samples collected at a depth of four metres, while 75% of the positive samples collected at 1 metre depth were positive for C. orientalis. M. avidus prevalence showed an increase from 38% during the first month to 89% of the samples during the third month with no significant differences between depths. The results of this thesis identify different non-lethal sampling techniques that could be used along with molecular analysis as a monitoring and diagnostic tool for the detection of Cardicola in ranched tuna. Further studies need to be performed to evaluate the use and limitation of gill mucus as a non-lethal sample. The findings from this thesis also provide evidence of the advantages PCR and real-time qPCR have over conventional diagnostic methods, allowing the identification for the first time of M. avidus in ranched SBT, and associating M. avidus to swimmer syndrome. Finally, this work contributes to the understanding of the probable reservoirs of infection of Cardicola and U. nigricans in ranched SBT.

The Australian southern bluefin tuna (SBT) industry is continually looking for ways to improve fish health within the ranching environment, both for increased profitability and concern for animal welfare. This thesis utilized current and newly acquired knowledge about southern bluefin tuna health to make educated manipulations of their ranching environment and/or husbandry practices. SBT health, parasites and performance where then monitored as a measurement of success. Five major projects were completed, all projects completed on the commercial scale. Three projects focused on environmental and/or husbandry manipulations: (chapter 2) dietary supplementation of immunostimulants and vitamins; (chapter 4) moving cages further offshore; (chapter 6) an assessment of two management strategies for blood fluke, Cardicola forsteri, infection. While two projects aimed to gain more information about ranched SBT health: (chapter 3) a detailed description of the first two months of ranching; (chapter 5) correlation of SBT humoral immune response with infection stage of C. forsteri. Greater knowledge was obtained relating to the effects of ranching. Over the first two months, weight, length, condition index, hemaoglobin concentration, and immune response were all found to change significantly. Ranched SBT were found to acclimate to ranching within one month post transfer and were relatively healthy prior to an acute mortality event from week five to seven of ranching, which resulted in a cumulative mortality of 8.5%. The mortality event was associated with decreased hemaoglobin concentrations and changes in immune response. Additional information was also gained on one of the most common and significant infections during ranching, blood fluke Cardicola forsteri. The timeline for C. forsteri infection was validated using natural infections in SBT. Humoral immune response (i.e. lysozyme, alternative complement and specific antibody activity) was correlated to infection and was found to develop concurrently with C. forsteri. The majority of physiological response coincided with commencing egg production, at approximately 5 to 7 weeks of ranching. New and previous knowledge regarding C. forsteri infection in SBT were merged, resulting in a inclusive infection, physiological response and diagnosis timeline. Further enhancement of ranched SBT health and performance was also obtained within this thesis utilizing dietary supplementation, adjustments in ranching location, and chemotherapeutics. Supplementing the diet of ranched SBT for the first twelve weeks with Vitamins E and C resulted in 1.5 times higher lysozyme activity at 8 weeks of ranching. Vitamin supplementation was also associated with tow specific improvements in performance, including enhanced survival, decreased Cardicola forsteri prevalence and intensity, and enhanced alternative complement activity. No changes in health, immune response, and performance were associated with immunostimulant supplementation. Examination of the feasibility of offshore ranching yielded significant effects on the health and performance of ranched SBT. Compared to SBT ranched in the traditional near shore environment, SBT ranched further offshore had enhanced survival, increased condition index at 6 weeks of ranching, and superior health. The offshore cohort had no C.forsteri and a 5% prevalence of Caligus spp. compared to a prevalence of 85% for C. forsteri and 55% prevalence for Caligus spp. near shore at 6 weeks of ranching. In addition, offshore ranched SBT had elevated hemaoglobin concentration and lysozyme activity. Finally, management of C. forsteri infection was examined utilizing two management strategies: (1) chemotherapeutic treatment with Praziquantel and (2) temporary offshore ranching. Both management strategies successfully reduced infection as well as mortality, yet evidence of reinfection and/or delayed infection suggest further research needs to be completed to optimize these strategies.