Skin ulcers in fish: Pfiesteria and other etiologies

Molecular phylogeny by Bayesian analysis and description of a new species of Henneguya, a parasitic cnidarian from Astyanax bimaculatus (Linnaeus, 1758) (Characiformes: Acestrorhamphidae) in Caatinga: A biome with neglected biodiversity data

Myxozoans are cnidarian parasites with a worldwide distribution and represent some of the most spectacular examples of parasite radiation. Based on an integrative taxonomic approach that includes spore morphology and molecular data, as well as other phenotypic characters such as host specificity, a new myxozoan, Henneguya caraubensis n. sp., is described from the gills of Astyanax bimaculatus (Linnaeus, 1758). Plasmodia were located within the gill lamellar epithelium, without connective tissue surrounding them. Mature myxospores were ellipsoidal in the frontal view, measuring 27.2 ± 2.6 μm in total length, 10.3 ± 0.7 μm in body length of spore, and 3.9 ± 0.2 μm in width. Two polar capsules elongated pyriform in shape, equal in size, measuring 3.4 ± 0.3 μm in length and 1.2 ± 0.1 μm in width. Polar tubules had 5 to 6 coils. Histopathological analysis showed large intralamellar polysporic plasmodia associated with displacement, deformation, and fusion of the nearest gill lamellae and with the adjacent lamellae being pushed laterally. Bayesian inference SSU rDNA-based phylogenetic analyses showed a strong tendency of Henneguya/Myxobolus species to form clusters mainly based on the order and/or family of the host, despite having different geographic origins. Phylogenetically, the novel species grouped within a clade containing Henneguya/Myxobolus spp. and appears in a well-supported subclade of Henneguya species parasites of Astyanax fishes. Our study reinforces highly endemic diversity still hidden that inhabits the Caatinga biome and points out the need to improve the strategies of protection and conservation of this threatened ecoregion with neglected biodiversity data.

In vivo verification of fish keratocyte explant culture for use as innate immunotoxicity screening assay: 2,4-Dicholorphenoxyacetic acid effects in fathead minnow (Pimephales promelas) keratocyte cell sheet migration

2,4-Dichlorphenoxyacetic acid (2,4-D) is the active ingredient in selective herbicides commonly used worldwide to control non-native aquatic plants. Limited research on the impacts of 2,4-D exposure on teleost innate immunity, such as barrier defense provided by epidermis, has been conducted. Fish keratocyte explant culture serves as a rapid, low-cost, cutaneous wound healing in vitro model of cell differentiation and migration. To test the hypothesis that this assay can serve as an innate immunotoxicity screening tool, scales containing keratocyte sheets were non-lethally extracted from adult male fathead minnows (Pimephales promelas), incubated in culture medium with increasing concentrations of 2,4-D (0-2,560 ppm), and cell sheet migration was measured. At 24h post scale pull, keratocyte cell sheet farthest migration distance significantly increased upon exposure to 0.04 ppm and significantly decreased upon exposure to ≥160 ppm 2,4-D as compared to controls. A punch biopsy on adult male fathead minnows was performed at the start of a 24h exposure to environmental application concentrations of 2,4-D (0, 0.04, 0.4, 4 ppm), followed by a dye penetration assay to observe keratocyte cell sheet migration in vivo. At 6h post biopsy, keratocytes migrated significantly farther across the wound bed in fish exposed to 0.04 and 0.4 ppm 2,4-D as compared to controls. Results suggest that keratocyte explant culture can model environmentally relevant in vivo scenarios and that 0.04-4 ppm 2,4-D does not negatively impact keratocyte migration rate. Future studies using other environmental toxicants or fish species may continue to explore the value of this assay as a practical screening tool for toxicological effects on cutaneous wound healing.

Food Safety: Pathological and Biochemical Responses of Nile Tilapia (Oreochromis niloticus) to Parasitological Infestation and Heavy Metals Pollution in Aquaculture System, Jeddah, Saudi Arabia

OBJECTIVE

The study aims to assess the overall safety of cultured tilapias in Jeddah City, Saudi Arabia by assessing the impact of infection and anthropogenic pollution on farmed tilapias based on fish sex, body weight, length, and heavy metals contamination.

MATERIALS AND METHODS

A total of 111 fish were collected from an aquaculture farm in Hada Al-Sham, Jeddah, Saudi Arabia. Physicochemical parameters of water from the culture system were evaluated. Both ecto- and endoparasites were checked. Haematological, biochemical and histopathological investigations were evaluated. In addition, heavy metals, namely, cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) were evaluated in different fish tissues and water samples from the aquaculture system.

RESULTS

The study revealed stressed aquaculture system. Tilapias were infested by both ectoparasites including Trichodina, Icthyophthirius multifiliis, Dactylogrus, and Cichlidogyrus, and endoparasites as Icthyophonus hoferi, the nematode Capillaria and coccidian protozoa. The study showed that male tilapias had greater infestation rates than females and longer and heavier male fish tended to be more susceptible to Dactylogyrus infection. Infected fish showed altered biochemical markers with subsequent increases in inflammatory and oxidative stress markers. The post-mortem lesion in the skin, gill lamellae, intestine, spleen, and liver showed significant pathological remarks. All investigated fish tissues revealed higher rates of heavy metals bioaccumulation compared to the surrounding waters. On the other hand, infected Nile tilapia tissues showed higher rate of metals accumulation compared to non-infected ones. Metals accumulated at a higher rate in the liver followed by kidney, intestine, gills, and muscles, respectively.

CONCLUSIONS

This study is recognized as the first to address the food safety of farmed tilapias in Jeddah, Saudi Arabia. The results emphasized a significant relation between parasites and heavy metal in disrupting fish defense systems and harming fish's physiological homeostasis and the histological state of tissues. The parasitized and polluted farmed fish pose health risk to humans due to possible zoonosis from parasitic infections and its subsequent bacterial infections with long-term exposure to toxic chemicals. Addressing the need for a combination of improved aquaculture practices, and stringent regulatory oversight.

The Importance of Baseline Health Surveillance Efforts in Freshwater Fish Conservation Using the Threatened Iberian Leuciscids as an Example

Freshwater fish species are experiencing the highest decline among vertebrates in this century. Although a great effort has been made to identify and tackle threats to the conservation of this taxa, several knowledge gaps still exist particularly for noncommercial endangered species, including considerations regarding fish health status. These species face deteriorating environmental conditions in their natural habitats that may lead to stress and increased risk for infectious disease outbreaks. Establishing health surveillance is crucial to identify and predict physiologic disruption in fish populations. Additionally, information retrieved may be used to direct targeted efforts to contribute to improving the conservation status of these species. We used threatened Iberian leuciscids as a case study to discuss the current knowledge regarding their health surveillance and to suggest recommendations for the establishment of practical health assessments that can benefit conservation plans for these species and be implemented in threatened or endangered freshwater fish species plans globally.

Mass Spectrometry Analysis of Shark Skin Proteins

The mucus layer covering the skin of fish has several roles, including protection against pathogens and mechanical damage in which proteins play a key role. While proteins in the skin mucus layer of various common bony fish species have been explored, the proteins of shark skin mucus remain unexplored. In this pilot study, we examine the protein composition of the skin mucus in spiny dogfish sharks and chain catsharks through mass spectrometry (NanoLC-MS/MS). Overall, we identified 206 and 72 proteins in spiny dogfish (Squalus acanthias) and chain catsharks (Scyliorhinus retifer), respectively. Categorization showed that the proteins belonged to diverse biological processes and that most proteins were cellular albeit a significant minority were secreted, indicative of mucosal immune roles. The secreted proteins are reviewed in detail with emphasis on their immune potentials. Moreover, STRING protein-protein association network analysis showed that proteins of closely related shark species were more similar as compared to a more distantly related shark and a bony fish, although there were also significant overlaps. This study contributes to the growing field of molecular shark studies and provides a foundation for further research into the functional roles and potential human biomedical implications of shark skin mucus proteins.

Identification of Novel Glycans in the Mucus Layer of Shark and Skate Skin

The mucus layer covering the skin of fish has several roles, including protection against pathogens and mechanical damage. While the mucus layers of various bony fish species have been investigated, the composition and glycan profiles of shark skin mucus remain relatively unexplored. In this pilot study, we aimed to explore the structure and composition of shark skin mucus through histological analysis and glycan profiling. Histological examination of skin samples from Atlantic spiny dogfish (Squalus acanthias) sharks and chain catsharks (Scyliorhinus retifer) revealed distinct mucin-producing cells and a mucus layer, indicating the presence of a functional mucus layer similar to bony fish mucus albeit thinner. Glycan profiling using liquid chromatography-electrospray ionization tandem mass spectrometry unveiled a diverse repertoire of mostly O-glycans in the mucus of the two sharks as well as little skate (Leucoraja erinacea). Elasmobranch glycans differ significantly from bony fish, especially in being more sulfated, and some bear resemblance to human glycans, such as gastric mucin O-glycans and H blood group-type glycans. This study contributes to the concept of shark skin having unique properties and provides a foundation for further research into the functional roles and potential biomedical implications of shark skin mucus glycans.

The feasibility of skin mucus replacing exosome as a pool for bacteria-infected markers development via comparative proteomic screening in teleost

In fish, skin mucus forms a protective barrier between the body surface and the external water environment, thus providing the most direct and intuitive clues to monitor the subject's health condition. To explore the impact of the Vibrio harveyi pathogen on teleost, the proteome of epidermal mucus from control and sick Cynoglossus semilaevis were screened through iTRAQ followed with LC-MS/MS. 1531 credible proteins were obtained relating to structural, metabolic and immunological functions. 335 different expressed proteins (DEPs) were identified, with 166 up-regulated and 169 down-regulated in MS. 62 proteins were characterized, including 22 up-regulated proteins and 40 down-regulated proteins. Integrated analysis of DE-miRNAs and DEPs from miRomics and proteomics were conducted to show the indirect regulatory relationship. Comparative analysis of DEPs between mucus and exosomes demonstrated that exosomes contributed the most DEPs of all mucus DEPs. 125 proteins are DEPs only in exosomes, which presented minor difference in total mucus. Expression of Aminopeptidase (anpep), Calcium-transporting ATPase, Histone H2B and H2A confirmed implied fine discriminative power with infected C. semilaevis, among which Calcium-transporting ATPase and H2B also appeared in list of exosomal markers. This study might shed the light on effective biomarker digging at other extended screening scenarios.

Community Structure and Functional Annotations of the Skin Microbiome in Healthy and Diseased Catfish, Heteropneustes fossilis

The skin mucosa of fish serves as a primary barrier against pathogens. In lesion sites in diseased fish, the mucosal barrier is expected to be compromised, with a substantial presence of potential pathogens. An understanding of the skin microbiome and its functional repertoire would provide important insights into host-microbe interactions, which has important implications for prophylactic measures in aquaculture. This study revealed the skin microbiomes and their functional annotations from healthy and diseased stinging catfish (Heteropneustes fossilis) based on 16S rRNA metagenomics. The OTUs consisted of four major phyla, Proteobacteria, Bacteroidota, Actinobacteriota and Firmicutes. Among members of the predominant phyla, Proteobacteria were rich in healthy fishes, but Bacteroidota and Firmicutes were significantly differentiated in healthy and diseased fish. The diversified microbiome was high in the skin of healthy fishes and did not significantly differ from that of the diseased groups. At the genus level, Pseudomonas showed the highest abundance in healthy fish but was nearly absent in diseased fish, whereas Flavobacterium showed the highest abundance in diseased fish. Linear discriminant analysis identified two phyla (Bacteroidota, Firmicutes) and two genera (Flavobacterium, Allorhizobium) that were consistently identified in diseased fishes. Functional prediction analysis specified that the genes related to physiological functions such as metabolism, immune and digestive systems and environmental adaptations could be highly expressed in diseased fishes. The present study indicates that the compositions, richness and functions of the bacterial community could influence the health status of cultured stinging catfish. Aquaculture-associated pathogenic bacteria may be identified, and preventive measures can be taken for the surveillance of fish health.

Mannan Oligosaccharides Application: Multipath Restriction From Aeromonas hydrophila Infection in the Skin Barrier of Grass Carp (Ctenopharyngodon idella)

The objective of this study was to evaluate the efficacy of dietary Mannan oligosaccharides (MOS) supplementation on skin barrier function and the mechanism of on-growing grass carp (Ctenopharyngodon idella). Five hundred forty grass carp were fed for 60 days from the growing stage with six different levels of MOS diets (0, 200, 400, 600, 800, and 1,000 mg kg^-1). At the end of the growth trial, the 14-day Aeromonas hydrophila challenge experiment has proceeded. The obtained data indicate that MOS could (1) decline skin lesion morbidity after being challenged by the pathogenic bacteria; (2) maintain physical barrier function via improving antioxidant ability, inhibiting excessive apoptosis, and strengthening the tight junction between the epithelial cell and the related signaling pathway (Nrf2/Keap1, p38MAPK, and MLCK); and (3) regulate immune barrier function by modulating the production of antimicrobial compound and expression of involved cytokines and the related signaling pathway (TOR and NFκB). Finally, we concluded that MOS supplementation reinforced the disease resistance and protected the fish skin barrier function from Aeromonas hydrophila infection.

An integrative review of lateral line depigmentation in marine and freshwater fish

OBJECTIVE

To qualitatively review reports on lateral line depigmentation (LLD) in marine and freshwater fish.

SAMPLE

English-language publications concerning LLD published before March 1, 2020.

PROCEDURES

Electronic searches of CAB abstracts, PubMed, and Web of Science databases and the proceedings of the International Association of Aquatic Animal Medicine were performed. Records were systematically screened and selected for inclusion in an integrative review. Bibliographies of records included in the review were examined to identify other records to be screened. Included records were qualitatively reviewed. Evidence level and quality were graded according to previously described criteria. Information pertinent to epidemiological factors, etiopathogenesis, clinical and histopathologic findings, treatment, and prevention of LLD was collected.

RESULTS

401 records were screened, and 24 unique publications (16 peer-reviewed articles, 1 textbook, and 7 abstracts) were included in the study; 12 (50%), 1 (4%), 6 (25%), and 5 (21%) were classified as evidence level I (experimental), II (quasi-experimental), III (nonexperimental), and V (clinical reports or clinician experience), respectively. Seventeen (71%) and 7 (29%) reports were classified as high quality and good quality, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

LLD should be considered a clinical observation indicative of a dermatologic response of fish to suboptimal conditions; LLD should continue to be adopted as the preferred term to describe the classic signs. Whereas gross findings are similar among species, histologic findings can vary. Evidence-based treatment of LLD for individual fish consists of source control (changing tanks or systems), topical treatment with 0.01% becaplermin gel, supportive care, and antimicrobial treatment when warranted. For schools of fish, treatment and prevention of LLD should be focused on improving suboptimal environmental and physiologic conditions.

Molecular Epidemiology, Virulence Traits and Antimicrobial Resistance Signatures of Aeromonas spp. in the Critically Endangered Iberochondrostoma lusitanicum Follow Geographical and Seasonal Patterns

Despite the fact that freshwater fish populations are experiencing severe declines worldwide, our knowledge on the interaction between endangered populations and pathogenic agents remains scarce. In this study, we investigated the prevalence and structure of Aeromonas communities isolated from the critically endangered Iberochondrostoma lusitanicum, a model species for threatened Iberian leuciscids, as well as health parameters in this species. Additionally, we evaluated the virulence profiles, antimicrobial resistance signatures and genomic relationships of the Aeromonas isolates. Lesion prevalence, extension and body condition were deeply affected by location and seasonality, with poorer performances in the dry season. Aeromonas composition shifted among seasons and was also different across river streams. The pathogenic potential of the isolates significantly increased during the dry season. Additionally, isolates displaying clinically relevant antimicrobial resistance phenotypes (carbapenem and fluroquinolone resistance) were detected. As it inhabits intermittent rivers, often reduced to disconnected pools during the summer, the dry season is a critical period for I. lusitanicum, with lower general health status and a higher potential of infection by Aeromonas spp. Habitat quality seems a determining factor on the sustainable development of this fish species. Also, these individuals act as reservoirs of important antimicrobial resistant bacteria with potential implications for public health.

Alteration of the Immune Response and the Microbiota of the Skin during a Natural Infection by Vibrio harveyi in European Seabass (Dicentrarchus labrax)

Disease outbreaks continue to represent one of the main bottlenecks for the sustainable development of the aquaculture industry. In marine aquaculture, many species from the Vibrio genus are serious opportunistic pathogens responsible for significant losses to producers. In this study, the effects on the immune response and the skin microbiota of European sea bass (Dicentrarchus labrax) were studied after a natural disease outbreak caused by V. harveyi. Data obtained from infected and non-infected fish were studied and compared. Regarding the local immune response (skin mucus) a decrease in the protease activity was observed in infected fish. Meanwhile, at a systemic level, a decrease in protease and lysozyme activity was reported while peroxidase activity showed a significant increase in serum from infected fish. A clear dysbiosis was observed in the skin mucus microbiota of infected fish in comparison with non-infected fish. Moreover, V. harveyi, was identified as a biomarker for the infected group and Rubritalea for healthy fish. This study highlights the importance of characterizing the mucosal surfaces and microbial composition of the skin mucus (as a non-invasive technique) to detect potential disease outbreaks in fish farms.

Sea lice Lepeophtheirus spinifer, Tuxophorus sp. and Caligus sp. infections on wild-caught queenfish Scomberoides commersonnianus from northern Australia

Studies of ectoparasites of wild-caught queenfish Scomberoides commersonnianus from several areas in northern Australia were reviewed to investigate relationships between parasite burdens, environmental conditions and external lesions. A sample of 27 queenfish captured near a dredge spoil disposal site in Gladstone Harbour, Queensland, Australia, in January 2012 was anomalous, with a high percentage of fish (66.6%) exhibiting grossly visible skin lesions including foci of erythema and petechial haemorrhages, particularly on the pectoral girdle and ventrolateral surfaces. Microscopically, lesions comprised acute epidermal erosion, ulceration and/or perivascular dermatitis with dermal oedema and depigmentation. Skin lesions were associated with high prevalence (100%) and intensity (mean = 21.2 copepods fish-1, range 4-46) of infection by sea lice Lepeophtheirus spinifer. Only queenfish infected with >10 L. spinifer presented with skin lesions. This is the first record of L. spinifer from Australia. In contrast, grossly visible skin lesions were not reported from queenfish (n = 152) sampled from other sites in the Northern Territory and Queensland, where the sampled fish had a much lower prevalence (51.3%) and intensity (mean = 3.54, range 0-26) of copepod (L. spinifer, Caligus spp. and Tuxophorus sp.) infections. Copepods from queenfish in studies undertaken outside Gladstone Harbour exhibited an over-dispersed pattern of infection, with the vast majority (n = 137, or 90.1%) of fish infected with <5 copepods. These data demonstrate that heavy L. spinifer infections, combined with poor water quality and/or direct exposure to contaminated dredge spoil and blooms of the cyanobacterium Lyngbya majuscula, can be associated with cutaneous disease in wild-caught queenfish.

Alterations in the epidermis of the carp, Labeo rohita (Cyprinidae: Cypriniformes), infected by the bacteria, Aeromonas hydrophila: A scanning electron microscopic, histopathological and immunohistochemical investigation

This study was carried out to comprehend the pathogenicity of the bacteria in the epidermis of Labeo rohita inoculated with Aeromonas hydrophila. Alterations in the histopathology of the epidermis were examined using scanning electron microscopy, light microscopy and the localization of iNOS and caspase 3 + ve cells by means of immunohistochemical methods. Skin samples obtained from infected fish at different intervals 2, 4, 6, 8 and 10 days showed significant changes in the cellular components of the epidermis. Epithelial cells often appeared hypertrophied with fragmented and loosely arranged microridges, and in the process of exfoliation. Mucous goblet cells increased significantly in density. Club cells showed degenerative changes, often with simultaneous confluence of adjacent cells and release of their contents. Increase in density of iNOS and caspase 3 + ve cells indicates inflammatory response and apoptosis. This study could provide valuable information on the pathogenesis of the disease, and disease outbreaks in farmed fish. Further, it could provide useful guidelines for fish farmers to take preventive measures for the control of the disease.

Could mycotoxigenic Fusarium sp. play a role in ulcerative dermal necrosis (UDN) of brown trout (Salmo trutta morpha trutta)?

Fusarium infections have been reported in aquatic animals, but are still poorly investigated in wild salmonids. The aim of the study was to determine the impact of the fungi and their toxins on the health status of brown trout (Salmo trutta morpha trutta) migrating from the Baltic Sea to the freshwater. Individuals from the wild brown trout population exhibiting ulcerative skin lesions were collected from the Słupia River in Poland and subjected to microbiological, histopathological, and hematological examinations, as well as toxicological analysis for a presence of mycotoxins. The results of microflora isolation from the brown trout skin samples revealed the presence of conditionally pathogenic bacteria and fungi classified by molecular techniques as Fusarium spp. Toxicological analysis allowed for detection of zearalenone (ZEN) in the liver, kidney, and gastrointestinal tract of the fish. In several cases, there was α-zearalenone (α-ZEL) identified at trace levels in the liver, as well as sterigmatocystin and enniatin B at low levels in the kidney and the liver. Histopathological examination revealed the presence of fungal hyphae disrupting the epidermis and penetrating into the necrotic dermis and hypodermis. The decreased values of the blood parameters, i.e., hemoglobin concentration (HGB), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and white blood cell count (WBC), were indicative of osmoregulation failure being a consequence of the skin damage. The results of the study provide new information regarding Fusarium sp. infection in brown trout and serve as the basis for further research on the potential impact of the fungi and their mycotoxins on the Baltic salmonid population, including their role in ulcerative dermal necrosis.

Pinpointing the role of Aeromonas salmonicida in the development of skin ulcerations in common dab (Limanda limanda)

Aeromonas salmonicida was isolated from ulcerations in common dab (Limanda limanda). An experiment was performed to pinpoint its role in ulceration development, considering the importance of the skin barrier and the pigmented and non-pigmented sides. The skin of dab was treated in three zones, one where scales and epidermis were removed, one where mucus was discarded and one non-treated zone. Fish were tagged to allow individual identification and challenged with A. salmonicida. Mortality and severity of the developing lesions were recorded for 21 days post-inoculation. Starting 12 days post-inoculation, mortality occurred gradually in challenged fish; however, no direct cause could be established. Both control fish and challenged fish developed ulcerations containing A. salmonicida. Sequencing of vapA gene revealed that isolates retrieved from both groups were distinct, suggesting the presence of A. salmonicida prior to the trial. Most ulcerations developed in zones where skin was removed, suggesting that abrasion might be a predisposing factor in ulceration development. Ulcerations were also observed at the insertion site of the tag, where exposed muscle tissue might have favoured the development of ulcerations. In conclusion, A. salmonicida seems to be involved in the development of skin ulcerations in dab, although the exact pathogenesis needs to be elucidated.

Hole-in-the-head disease in discus fish, Symphysodon (Heckel, 1840): Is it a consequence of a dietary Ca/P imbalance?

Hole-in-the-head (HITH) disease-affected fish develop characteristic lesions in the skin above sensory pores of the head and the trunk. This study investigated whether an unfavourable Ca/P ratio in the diet could provoke lesions consistent with HITH disease in discus fish Symphysodon (Heckel, 1840) as a comparable condition to secondary hyperparathyroidism of tetrapod species. Two groups of five fish were fed a plain beef heart diet (Ca/P of 0.03), whereas two other groups were kept on commercial discus feed (Ca/P of 2.73). Each feeding group was submitted to two different water hardness regimes (35.66-71.39 mg/L CaCO₃ and 124.94-196.33 mg/L CaCO₃ , respectively). All fish were observed for the development of the characteristic lesions for 16 weeks. At the end of the study, histological, bacteriological and parasitological examinations were conducted and plasma Ca, P and Mg values were determined. Diplomonad flagellates were detected in two fish. Isolated bacteria of all groups mostly belonged to Aeromonadales and Pseudomonadales. No significant difference of plasma mineral values between the groups was observed. Compared to the results of other authors, Ca stayed mainly in the range and P exceeded the reference values. Histological examinations did not indicate HITH disease, and no fish developed signs of the disease during the study. Clinical trial registration number GZ 68.205/0135-WF/V/36/2014.

Scrutinizing the triad of Vibrio tapetis, the skin barrier and pigmentation as determining factors in the development of skin ulcerations in wild common dab (Limanda limanda)

Recently, Vibrio tapetis was isolated for the first time from skin ulcerations in wild-caught common dab (Limanda limanda). To further examine its role in the development of these skin lesions, an in vivo experiment was performed. The significance of the skin barrier and in addition the difference between pigmented and non-pigmented side were investigated. Hence, the skin of common dab was treated in three different ways on both the pigmented and non-pigmented side. On a first “treatment zone”, the scales and overlying epidermal tissue were removed whereas in a second zone only the mucus was discarded. The third zone served as a non-treated zone. Thereafter, fish were challenged with V. tapetis. The control group was sham treated. Mortality, clinical signs, severity and size of the developing lesions were recorded. All animals were sacrificed and sampled 21 days post-inoculation. Significantly more fish of the group challenged with V. tapetis died compared to the control group with the highest incidence occurring 4 days post-inoculation. Fish challenged with V. tapetis developed more severe skin ulcerations. In zones where scales and epidermal tissue were removed, the ulcerations were more severe compared to zones where only mucus was eliminated. Ulcerations occurred more frequently, were more severe and larger on the pigmented side. Our data represents prove of V. tapetis as causative agent of ulcerative skin lesions although prior damage of the skin seems to be a major contributing factor. Furthermore, the pigmented side seemed predisposed to the development of skin ulcerations.

El Niño drives a widespread ulcerative skin disease outbreak in Galapagos marine fishes

Climate change increases local climatic variation and unpredictability, which can alter ecological interactions and trigger wildlife disease outbreaks. Here we describe an unprecedented multi-species outbreak of wild fish disease driven by a climate perturbation. The 2015–16 El Niño generated a +2.5 °C sea surface temperature anomaly in the Galapagos Islands lasting six months. This coincided with a novel ulcerative skin disease affecting 18 teleost species from 13 different families. Disease signs included scale loss and hemorrhagic ulcerated patches of skin, fin deterioration, lethargy, and erratic behavior. A bacterial culture isolated from skin lesions of two of the affected fish species was identified by sequencing of the 16S rRNA gene as a Rahnella spp. Disease prevalence rates were linearly correlated with density in three fish species. In January 2016, disease prevalence reached 51.1% in the ring-tailed damselfish Stegastes beebei (n = 570) and 18.7% in the king angelfish Holacanthus passer (n = 318), corresponding to 78% and 86% decreases in their populations relative to a 4.5-year baseline, respectively. We hypothesize that this outbreak was precipitated by the persistent warm temperatures and lack of planktonic productivity that characterize extreme El Niño events, which are predicted to increase in frequency with global warming.

Healing and mucosal immunity in the skin of experimentally wounded gilthead seabream (Sparus aurata L)

Skin lesions are very common in fisheries, increasing the risk of pathogens entering through the wounded skin of the fish. In the present assay, the progression of wound healing was studied over a 7 day period in gilthead seabream (Sparus aurata L.) after making experimental wounds in two different locations: above (group A) or below (group B) the lateral line. Macroscopic observation confirmed faster wound healing of the wounds of fish from group B. Furthermore, several immune-related components were studied in the skin mucus of wounded fish to ascertain whether wounding altered the mucus composition compared with the values obtained from non-wounded fish (group C, control). Significant variations were detected depending on both the site of the wound and the studied parameter. At the same time, the gene expression profile of several immune-relevant genes, including pro-inflammatory (il1b,il6, tnfa), anti-inflamamtory (tgfb, il10), immunoglobulins (ighm, ight), involved in oxidative stress (sod, cat) and in skin regeneration (krt1and grhl1) were studied in the three groups of fish (A, B and C). The results throw further light on the complex process of skin wound healing in fish, since substantial changes in the skin mucus and in the skin gene expression originated by the presence of wounds were observed. This work underline some important differences depending on the place of the fish body where the wound is located. Of particular note was the fact that such changes depended on the site of the wound.

Silver nanoparticles enhance wound healing in zebrafish (Danio rerio)

Silver nanoparticles (AgNPs) were successfully synthesized by a chemical reduction method, physico-chemically characterized and their effect on wound-healing activity in zebrafish was investigated. The prepared AgNPs were circular-shaped, water soluble with average diameter and zeta potential of 72.66 nm and -0.45 mv, respectively. Following the creation of a laser skin wound on zebrafish, the effect of AgNPs on wound-healing activity was tested by two methods, direct skin application (2 μg/wound) and immersion in a solution of AgNPs and water (50 μg/L). The zebrafish were followed for 20 days post-wounding (dpw) by visual observation of wound size, calculating wound healing percentage (WHP), and histological examination. Visually, both direct skin application and immersion AgNPs treatments displayed clear and faster wound closure at 5, 10 and 20 dpw compared to the controls, which was confirmed by 5 dpw histology data. At 5 dpw, WHP was highest in the AgNPs immersion group (36.6%) > AgNPs direct application group (23.7%) > controls (18.2%), showing that WHP was most effective in fish immersed in AgNPs solution. In general, exposure to AgNPs induced gene expression of selected wound-healing-related genes, namely, transforming growth factor (TGF-β), matrix metalloproteinase (MMP) -9 and -13, pro-inflammatory cytokines (IL-1β and TNF-α) and antioxidant enzymes (superoxide dismutase and catalase), which observed differentiation at 12 and 24 h against the control; but the results were not consistently significant, and many either reached basal levels or were down regulated at 5 dpw in the wounded muscle. These results suggest that AgNPs are effective in acceleration of wound healing and altered the expression of some wound-healing-related genes. However, the detailed mechanism of enhanced wound healing remains to be investigated in fish.

Saddleback syndrome in European sea bass Dicentrarchus labrax (Linnaeus, 1758): anatomy, ontogeny and correlation with lateral-line, anal and pelvic fin abnormalities

This study focused on the anatomy and ontogeny of saddleback syndrome (SBS) in reared European sea bass. The abnormality was detected at an unusually high frequency (12-94%) during a routine quality control in a commercial hatchery. Anatomically the abnormality was mainly characterized by the loss of 1-5 hard spines and severe abnormalities of the proximal pterygiophores (anterior dorsal fin), size reduction of a few lepidotrichia, missing lepidotrichia and/or lepidotrichia of poor ossification (posterior dorsal fin). SBS was significantly correlated with abnormalities of the anal and pelvic fins in all the examined populations. Moreover, in juvenile fish, SBS was significantly correlated with an abnormal lack of sectors of the lateral line. The examination of early larval samples revealed that SBS was ontogenetically associated with severe abnormalities of the primordial marginal finfold, which developed at the flexion stage (ca 8.5-11.0 mm SL). Histologically, these abnormalities were associated with extensive epidermal erosion. The results are discussed in respect of the critical ontogenetic period and the possible causative factors of SBS in European sea bass. It is suggested that causative factors acted during a wide ontogenetic period including flexion and metamorphosis phases.

Pathology of finfish and mud crabs Scylla serrata during a mortality event associated with a harbour development project in Port Curtis, Australia

The objective of this study was to assess the extent and describe the nature of a multi-species marine finfish and crustacean disease event that occurred in Gladstone Harbour, Australia, 2011-2012. Finfish were examined for this study in January to April 2012 from sites where diseased animals were previously observed by the public. Gross abnormalities, including excessive skin and gill mucus, erythema, heavy ecto-parasitism, cutaneous ulceration, corneal opacity, and exophthalmos, were higher (25.5%) in finfish from Gladstone Harbour (n = 435) than in those from an undeveloped reference site, 250 km to the north (5.5%, n = 146, p < 0.0001). Microscopic abnormalities, especially non-infectious erosive to ulcerative dermatitis and internal parasitism, were more prevalent in fish from Gladstone Harbour (n = 34 of 36, prevalence = 94.4%) than in fish from the reference site (3 of 23, prevalence = 13.0% p < 0.0001). The prevalence of shell lesions was higher in mud crabs Scylla serrata sampled from Gladstone Harbour (270 of 718, prevalence = 37.5%) than from the reference site (21 of 153, prevalence = 13.7%; p < 0.0001). The significantly higher prevalence of ulcerative skin disease and parasitism in a range of species suggests affected animals were subjected to influences in Gladstone Harbour that were not present in the control sites. The disease epidemic coincided temporally and spatially with water quality changes caused by a harbour development project. The unique hydrology, geology, and industrial history of the harbour, the scope of the development of the project, and the failure of a bund wall built to retain dredge spoil sediment were important factors contributing to this epidemic.

Histopathology investigation on the Vardar chub (Squalius vardarensis) populations captured from the rivers impacted by mining activities

Many natural freshwater ecosystems, especially in the north eastern Macedonia, are polluted with heavy metals, which are released by active mines. Long-term exposure to high levels of dissolved metals might result in increased metal bioaccumulation in organs of aquatic organisms, and consequently might cause various sub-toxic and toxic effects. The aim of this study was to assess the health of Vardar chub (Squalius vardarensis) inhabiting mining impacted rivers Zletovska and Kriva, in comparison with chub from the reference Bregalnica River. It was done by use of indicators of tissue damage (histopathology of liver and gonads) and general indicators of exposure to environmental stressors (condition factor, organo-somatic indices and external/internal macroscopic lesions). Histological assessment of gonads revealed good reproductive health in all three rivers, indicating high tolerance of gonads to contaminant exposure. Contrary, several external/internal lesions were more pronounced in chub from severely metal contaminated Zletovska River. Prevalence of hepatic lesions was also higher in mining impacted rivers (in Kriva, 70%; in Zletovska, 59%) compared to Bregalnica River (38%). The spectrum of histological lesions observed in chub liver varied from non-specific minor degenerative conditions, such as lymphocyte infiltration, fibrosis, parasites, granulomas and lipidosis, to extensive and/or more severe changes such as bile duct proliferation, necrosis, megalocytosis, light-dark hepatocytes and hepatocytes regeneration. The results of histopathological investigation for all three rivers showed clear signs of water contamination, especially prominent in mining influenced rivers. More research efforts should be devoted to study of environmental conditions and metal contamination in the mining impacted rivers worldwide, especially of their effects on health of local ichthyofauna.

Endocrine effects of real-life mixtures of persistent organic pollutants (POP) in experimental models and wild fish

A series of studies have assessed the occurrence, levels, and potential adverse effects of persistent organic pollutants (POP) in fish from Lake Mjøsa. In this lake, high levels of various POP were detected in biota. Fish from the nearby Lake Losna contain background levels of POP and served as reference (controls) in these studies. Significantly higher prevalence of mycobacteriosis and pathological changes were documented in burbot (Lota lota) from Mjøsa compared to burbot from Losna. Further, transcriptional profiling identified changes in gene expression in burbot from Mjøsa compared to burbot from Losna associated with drug metabolism enzymes and oxidative stress. POP extracted from burbot liver oil from the two lakes was used to expose zebrafish (Danio rerio) during two consecutive generations. During both generations, POP mixtures from both lakes increased the rate of mortality, induced earlier onset of puberty, and skewed sex ratio toward males. However, opposite effects on weight gain were found in exposure groups compared to controls during the two generations. Exposure to POP from both lakes was associated with suppression of ovarian follicle development. Analyses of genome-wide transcription profiling identified functional networks of genes associated with weight homeostasis, steroid hormone functions, and insulin signaling. In human cell studies using adrenocortical H295R and primary porcine theca and granulosa cells, exposure to lake extracts from both populations modulated steroid hormone production with significant difference from controls. The results suggest that POP from both lakes may possess the potential to induce endocrine disruption and may adversely affect health in wild fish.

Experimental Infection of the Mayan Cichlid Cichlasoma urophthalmus with the Oomycete Aphanomyces invadans

This study aimed to determine the susceptibility of the Mayan cichlid Cichlasoma urophthalmus to infection with the fungus Aphanomyces invadans (also known as epizootic ulcerative syndrome [EUS]). A total of 27 C. urophthalmus were exposed to the original A. Invadans 2006/86/EC strain by intramuscularly injecting the fish with 25,000 zoospores/ml or exposing the fish to a suspension of 25,000 zoospores/ml in 6-L aquaria for 30 days. To assess the infectious capacity of A. invadans, 3 golden barbs (Puntius semifasciolatus) were infected intramuscularly with 200,000 zoospores/ml. A second experiment using 100 C. urophthalmus was performed for 60 days with 50 fish in each treatment group. A polymerase chain reaction (PCR)-based diagnostic method was used; muscle and gills were the target tissues. In the first experiment, none of the exposed C. urophthalmus developed skin lesions related to A. invadans infection. However, PCR analysis revealed that infection had occurred. For the intramuscular treatment, there were significant differences between the controls and the muscle samples (Fisher's exact test; P < 0.05) but not between the controls and the gill samples (P > 0.05). All golden barbs became infected, as indicated by PCR, and developed skin lesions typical of A. invadans infection. We concluded that C. urophthalmus was infected with A. invadans but was an asymptomatic carrier because skin lesions did not develop. In the second experiment, all fish were negative, suggesting that the fish had cleared the infection by the end of the experiment.

Carp head kidney leukocytes display different patterns of oxygen radical production after stimulation with PAMPs and DAMPs

Wound healing and tissue regeneration are essential mechanisms to ensure the survival and health of any organism. Despite this, only a few studies have been devoted to study tissue regeneration during wound healing in fish. Reactive oxygen species (ROS), in particular hydrogen peroxide, play an important dual role both for promoting tissue repair, but also for eradication of pathogens. This study aims at dissecting the contribution of PAMPs (using β-glucan) and DAMPs in the respiratory burst response of carp head kidney-derived leukocytes, and address their contribution to wound healing processes. Consistent with a pathogen eradication strategy, ROS responses to PAMP stimulation (β-glucan) was fast, vigorous and highly dominated by production of superoxide anion. In contrast, stimulation with DAMPs led to a slow, subtle but long-lasting production of oxygen radicals dominated by hydrogen peroxide. Using an in vitro model of scratch-wounded CCB fibroblast cell cultures and a novel PhotoID proliferation assay, stimulation with low and continuous levels of hydrogen peroxide (5 μM) led to a slight increase in the percentage of wound recovery and thus promoted wound closure. In contrast, high doses of hydrogen peroxide (300 μM) impaired fibroblast scratch-wound recovery and caused cell death. These results elucidate the capacity of hydrogen peroxide to influence the fate of tissue regeneration through the establishment of environments suitable for promoting either tissue regeneration or oxidative stress and thereby potential tissue damage. Direct in vitro stimulation with β-glucans did not impact fibroblast scratch-wound recovery, which further suggests that interaction with tissue-resident leukocytes or other components of the fish immune system are required to induce fibroblast proliferation and thus for the accelerated wound healing promoted by β-glucan stimulation.

Environmental hazard of yperite released at sea: sublethal toxic effects on fish

The aim of this study was to evaluate the potential toxicological effects on fish related to the leakage of yperite from rusted bomb shells dumped at sea. Both in vivo and field studies have been performed. As for the in vivo experiment, specimen of European eel were subcutaneously injected with 0.015, 0.15 and 1.5mg/kg of yperite and sacrificed after 24 and 48 h. In the field study, specimen of Conger eel were collected from a dumping site in the Southern Adriatic Sea. The presence/absence of yperite in tissues, genotoxicity, detoxification enzymes, histological alterations and gross abnormalities were investigated. Results of the in vivo experiment showed a significant increase of EROD activity at both 24h and 48 h. UGT activity increased significantly at 48 h post injection. An acute inflammatory response after 24h in skin layers and muscle was observed, associated to cell degeneration and necrosis after 48 h at the highest dose. On field, comet assay revealed genotoxicity in gills of fish from the dumping site. Specimen from the dumping site showed significantly higher EROD activities compared to controls, deep ulcers and papules on skin together with liver and spleen histopathological lesions.

Immunological impacts of oil sands-affected waters on rainbow trout evaluated using an in situ exposure

Rainbow trout were exposed in situ to oil sands-affected waters for 21 d, either with or without an immune stimulation using inactivated Aeromonas salmonicida. Three aquatic systems were utilized for the experiment: a pond containing oil sands tailings capped with approximately 3 m of natural surface water, a second pond where unextracted oil sands materials were deposited in the watershed, and a reservoir receiving Athabasca River water as a reference caging location. The three systems showed a gradient of oil sands-related compounds, most notably, total naphthenic acids were highest in the system containing tailings (13 mg/L), followed by the system influenced by unextracted oil sands (4 mg/L), followed by the reference cage location (1 mg/L). Biochemical and chemical measures of exposure in rainbow trout showed the same trend, with the tailings-influenced system having the highest hepatic EROD activity and elevated bile fluorescence measured at phenanthrene wavelengths. Trout caged in the tailings-influenced location had significantly fewer leukocytes and smaller spleens as compared to the reference fish, though liver size and condition factor were unaffected. Fish in the tailings-influenced waters also demonstrated increased fin erosion, indicative of opportunistic infection. The trout exposed to tailing-influenced waters also showed a significantly decreased ability to produce antibodies to the inactivated A. salmonicida. Given the complexity of the exposure conditions, exact causative agents could not be determined, however, naphthenic acids, polycyclic aromatic hydrocarbons and pH correlate with the immunotoxic effects while elevated salinity or metals seem unlikely causes.

Morphopathological features of a severe ulcerative disease outbreak associated with Tenacibaculum maritimum in cultivated sole, Solea senegalensis (L.)

This study describes morphopathologic changes in naturally infected farmed Senegalese sole affected by tenacibaculosis caused by Tenacibaculum maritimum. Macroscopic observation, in addition to light microscopy and scanning electron microscopy, was used to study the lesions. Main lesions were characterized by complete loss of epidermis and dermis, as well as extensive necrosis of muscle layers. Mild-to-moderate inflammatory response with the presence of macrophages was noted around hyaline degenerated muscle cells. Gram-negative filamentous bacteria could be detected only at the dermis. Under scanning electron microscopy, filamentous bacteria located over the scales without epithelium could be observed. These findings together with the isolation and PCR detection of the bacteria in kidney and skin tissues suggest that once the bacteria reach the dermis, probably through eroded epidermis, they are able to proliferate and produce enzymes that are responsible for the damage in the underlying tissues.

Effects of cumulative stress on fish health near freshwater outlet sluices into the sea: a case study (1988-2005) with evidence for a contributing role of chemical contaminants

Epizootic skin diseases in euryhaline flounder (Platichthys flesus) in the Dutch Wadden Sea were first reported in 1988. Particularly high prevalences of skin ulcers (up to one-third of individual fish being affected) were encountered in the vicinity of sluices draining freshwater from IJsselmeer Lake, in contrast with much lower levels in the freshwater bodies behind the sluices and open sea areas (<2%). It was proposed that salinity stress, high bacterial loads, nutritional deficiencies, and obstruction to fish migration by the sluices could all be involved in disease causation. Results of follow-up surveys at these outlet sluices from 1994 to 2005 further substantiate our preliminary findings. The follow-up data also show a general reduction in disease and improved condition factor during this period, which can be explained by improved habitat conditions for the flounder, partly due to effective sluice gate management. Furthermore, statistical correlations (p<0.05) were demonstrated between flounder ulcer occurrence and chemical contaminant concentrations in liver (Hg, Cd, Cu, Zn) and bile (the metabolite 1-OH pyrene as an indicator of chronic polycyclic aromatic hydrocarbon exposure), and histological liver lesions generally indicative of contaminant exposure (hydropic vacuolization of biliary duct epithelial cells). The findings suggest that a combination of osmotic and contaminant-induced stress also contributed to the observed disease patterns.

Chronic ulcerative dermatopathy in cultured marine fishes. Comparative study in sharpsnout sea bream, Diplodus puntazzo (Walbaum)

Chronic ulcerative dermatopathy (CUD) also known as chronic erosive dermatopathy, hole-in-the-head, head and lateral line erosion syndrome (HLLE) and lateral line depigmentation (LLD) is a chronic disease of unknown aetiology that affects the lateral line canals of the head and the trunk of various fish species. It has been described only in freshwater species although there are reports that it also affects marine fish. Here, we describe the disease in cultured sharpsnout sea bream using histology and scanning electron microscopy and identify several marine species as CUD sensitive. The results of this study correlate the development of the disease with the use of borehole water, indicating that the aetiology is probably associated with water quality rather than nutritional imbalance or infectious agents.

Histopathology of culture-associated skin erosions and papillary hyperplasia of Atlantic halibut, Hippoglossus hippoglossus (L.)

Atlantic halibut, Hippoglossus hippoglossus (L.), that were cultured in tanks with a smooth bottom (gel-coated fibreglass) substrate developed papillary hyperplasia and skin erosions on the blind (ventral) side. No viruses, bacteria or parasites were observed in any sections of affected skin. Comparison of microscopic pathology with that of skin from normal, wild-caught halibut showed severe epidermal proliferation with foci of severe mucous cell hyperplasia. Both epidermal thickness and mucous cell density were significantly greater in fish held on a smooth substrate compared to skin of healthy fish. Spongiosis was present, especially at the base of the papillary, hyperplastic epidermis, and there was a chronic inflammatory infiltrate in the scale pockets composed of lymphocytes, histiocytes and erythrocytes. Skin erosions had various degrees of epidermal loss, in some cases to the basement membrane. A predisposing factor for the epidermal sloughing may have been related to the spongiosis, and the vacuolated, degenerated basal cells. When affected halibut were cultured for an additional 28, 62 or 97 days on a sand substrate, which is conducive to skin lesion healing, there was no apparent change in epidermal thickness over time. However, mucous cell density significantly increased from day 0 to 97 during the healing process.

Effects of bacterial infestation caused by human wastes on the skin structures of Mugil platanus Günther, 1880 (Mugilidae)

Manifestation of infectious pathologies in fishes usually increases in environments where organic wastes are disposed. Specimens of Mugil platanus Günther, 1880 and water samples collected at three points of the Tramandaí river were analyzed during a one year period. The macroscopic observation revealed ulcerations in the caudal peduncle area covered with a mass of amorphous and whitened tissues. Histopathologic analysis showed the presence of negative gram bacteria, probably responsible for alterations of the normal structure of the epidermic tissues. Non-parametric statistical analysis for ammonia concentration showed a significant variation among the three collected spots as well as in the multiple comparison between two spots. In this study, we describe cutaneous lesions observed in Mugil platanus specimens and tested their correlation with environmental ammonia concentration.

Acute hypoxia-reperfusion triggers immunocompromise in Nile tilapia

Inadequate dissolved oxygen in the aquatic environment is a well-established cause of fish morbidity and mortality. The specific effects of hypoxia on immune function in fish, however, are not well characterized. In this study, the effects of acute hypoxia followed by reoxygenation (rapid tissue reperfusion) as a source of immunocompromise in Nile tilapia Oreochromis niloticus were investigated. Using a precision apparatus developed in our laboratory for hypoxia exposures, a series of assays of increasing specificity for immune function were performed on acutely hypoxia-stressed Nile tilapia: tier I consisted of histopathology, tier II of hematology, plasma chemistry, and determining cortisol concentration, and tier III of determining the phagocytic index and analyzing the expression of the cytokines transforming growth factor-beta (TGF-beta) and interleukin-1beta (IL-1beta). Nile tilapia were exposed to 7% oxygen saturation for 96 h, then tank water was rapidly reoxygenated. Sampling intervals were 48 and 96 h during hypoxia and 12 and 84 h during reperfusion. Histopathology showed no remarkable microscopic abnormalities in lymphoid or other tissues. Lymphopenia and neutrophilia were observed in peripheral blood. Plasma total protein, partial pressure of oxygen, and oxygen saturation were decreased in response to hypoxia. Plasma lipase decreased in response to hypoxia but returned to normal during reperfusion. Phagocytic capability and the phagocytic index decreased during hypoxia and 12 h reperfusion, whereas these values were recovered by 84 h reperfusion. The TGF-beta transcription continued to increase during the exposures, the greatest production being at 12 h reperfusion, whereas IL-1beta transcription decreased in response to hypoxia and reperfusion. We conclude that acute hypoxia triggered an overall downregulation of the immune system in the test fish. This suggests a possible factor in the pathogenesis of disease outbreaks in fish in which repeated, sublethal bouts of environmentally induced hypoxia lead to increased disease susceptibility and individual mortalities rather than massive fish kills.

Molecular assays for detecting Aphanomyces invadans in ulcerative mycotic fish lesions

The pathogenic oomycete Aphanomyces invadans is the primary etiological agent in ulcerative mycosis, an ulcerative skin disease caused by a fungus-like agent of wild and cultured fish. We developed sensitive PCR and fluorescent peptide nucleic acid in situ hybridization (FISH) assays to detect A. invadans. Laboratory-challenged killifish (Fundulus heteroclitus) were first tested to optimize and validate the assays. Skin ulcers of Atlantic menhaden (Brevoortia tyrannus) from populations found in the Pamlico and Neuse River estuaries in North Carolina were then surveyed. Results from both assays indicated that all of the lesioned menhaden (n = 50) collected in September 2004 were positive for A. invadans. Neither the FISH assay nor the PCR assay cross-reacted with other closely related oomycetes. These results provided strong evidence that A. invadans is the primary oomycete pathogen in ulcerative mycosis and demonstrated the utility of the assays. The FISH assay is the first molecular assay to provide unambiguous visual confirmation that hyphae in the ulcerated lesions were exclusively A. invadans.

A quantitative real-time RT-PCR assay to measure TGF-beta mRNA and its correlation with hematologic, plasma chemistry and organo-somatic indices responses in triamcinolone-treated Atlantic menhaden, Brevoortia tyrannus

A quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) assay was developed to measure transforming growth factor-beta (TGF-beta) in Atlantic menhaden (Brevoortia tyrannus), an estuarine-dependent species plagued by ulcerative skin lesions in the estuaries along the eastern United States. Atlantic menhaden were acclimated in a closed system for two weeks prior to initiation of the study. The synthetic glucocorticoid, triamcinolone acetonide (10mg/kg body weight) was administered by intracoelomic injection and its effect on the splenic mononuclear cell TGF-beta mRNA transcription, liver-somatic index, spleno-somatic index, hematology, and plasma chemistry were compared to untreated fish at 48 and 96h post-treatment. Triamcinolone-treated Atlantic menhaden showed suppression of TGF-beta mRNA production, neutrophilia, monocytosis, lymphopenia, and an increase in blood glucose concentrations. The health indices used in this study may help us interpret some of the changes observed during the development of ulcerative skin lesions in wild-caught menhaden.

Characterization of ichthyocidal activity of Pfiesteria piscicida: dependence on the dinospore cell density

The ichthyocidal activity of Pfiesteria piscicida dinospores was examined in an aquarium bioassay format by exposing fish to either Pfiesteria-containing environmental sediments or clonal P. piscicida. The presence of Pfiesteria spp. and the complexity of the microbial assemblage in the bioassay were assessed by molecular approaches. Cell-free water from bioassays that yielded significant fish mortality failed to show ichthyocidal activity. Histopathological examination of moribund and dead fish failed to reveal the skin lesions reported elsewhere. Fish larvae within "cages" of variable mesh sizes were killed in those where the pore size exceeded that of Pfiesteria dinospores. In vitro exposure of fish larvae to clonal P. piscicida indicated that fish mortality was directly proportional to the dinospore cell density. Dinospores clustered around the mouth, eyes, and operculi, suggesting that fish health may be affected by their direct interaction with skin, gill epithelia, or mucous surfaces. Molecular fingerprinting revealed the presence of a very diverse microbial community of bacteria, protists, and fungi within bioassay aquaria containing environmental sediments. Some components of the microbial community were identified as potential fish pathogens, preventing the rigorous identification of Pfiesteria spp. as the only cause of fish death. In summary, our results strongly suggest (i) that this aquarium bioassay format, which has been extensively reported in the literature, is unsuitable to accurately assess the ichthyocidal activity of Pfiesteria spp. and (ii) that the ichthyocidal activity of Pfiesteria spp. is mostly due to direct interactions of the zoospores with fish skin and gill epithelia rather than to soluble factors.

Fluorescein: a rapid, sensitive, nonlethal method for detecting skin ulceration in fish

There is a need to develop simple, rapid, and accurate methods for assessing health in fish populations. In this study we demonstrate that use of fluorescein, a nontoxic fluorescent dye, can rapidly and easily detect the presence of skin ulcers in all fish tested, including rainbow trout (Oncorhynchus mykiss), channel catfish (Ictalurus punctatus), goldfish (Carassius auratus), and hybrid striped bass (Morone saxatilis male X M. chrysops female). Exposure of fish to as little as 0.10 mg fluorescein per milliliter of water for 3 minutes was sufficient to identify experimentally induced lesions, even pinpoint ulcerations. Such lesions were not visible to the naked eye but were clearly demarcated with fluorescein treatment. Examination of fish that appeared clinically normal often revealed the presence of focal ulcerations, which might have been a consequence of damage during capture, but it also might suggest that skin ulceration may be common even in "clinically normal" fish. Exposure of either nonulcerated or experimentally ulcerated hybrid striped bass to an excessively high concentration of fluorescein had no apparent effect on health or survival. Our studies suggest that fluorescein may be a highly useful tool for rapid health screening in fish populations.

Evaluation of the tissue reactions in the skin and body wall of koi (Cyprinus carpio) to five suture materials

Five different suture materials (silk, monofilament nylon, polyglyconate, polyglactin 910, and chromic gut) were placed in the skin and body wall of 10 Doitsu (scaleless) koi (Cyprinus carpio). After seven days the sutures were retrieved from five of the fish in 5 mm and 6 mm punch biopsies, and after 14 days they were retrieved in the same way from the other five. The tissue reactions were evaluated by gross visual inspection and by histological examination. The total inflammatory reaction was graded on a scale from 0 (no inflammation) to 5 (severe inflammation). The synthetic suture materials generally induced a moderate inflammatory reaction that decreased after seven days. After 14 days the superficial reaction to monofilament nylon was substantial, and the tissue reactions to the organic suture materials were slightly greater than the reactions to the synthetics. The inflammatory response to silk was greater after 14 days than after seven, and chromic gut induced a moderately severe inflammatory response after seven days; the chromic gut sutures fell out before the biopsies were taken after 14 days. The organic materials induced intense inflammatory reactions which did not subside if the suture remained in the tissue.

Human health effects of exposure to Pfiesteria piscicida: a review

Since its identification, the dinoflagellate Pfiesteria piscicida has been implicated in fish kills and fish disease in the southeastern United States. Adverse health effects have been reported in researchers working with the organism and in watermen following exposure to a fish kill in Maryland. A bioactive secretion is postulated as the cause of these effects but has not yet been isolated and chemically characterized. The biology and toxicology of this organism remain the topic of debate and research.