Diseases of aquatic organisms最新文献

This study analysed published data on the distributions of minimum inhibitory concentrations of a group of freshwater isolates classified as Aeromonas spp. with the aim of establishing whether they provided any evidence that epidemiological cut-off values set from these data would be unreliable. This group contained 233 isolates and included members of at least 11 species. The standard deviations (SDs) of the wild-type distributions for 10 antimicrobial agents were calculated for this multi-species group using the ECOFFinder and normalised resistance interpretation (NRI) algorithms. These were compared to the SDs of 110 distributions established for individual species published by the European Committee on Antimicrobial Susceptibility Testing. Fifty-one of these distributions had been generated by multiple laboratories and 59 by single laboratories. When the ECOFFinder algorithm was used to calculate the SDs, the mean for the multi-species group was 0.63 log2 µg ml-1, and the 51 individual species and multiple-laboratory groups were 0.68 and 0.65 log2 µg ml-1, respectively. When the NRI algorithm was used, the mean for the multi-species group was 0.79 log2 µg ml-1, and the 51 individual species and multiple-laboratory groups were 0.79 and 0.76 log2 µg ml-1, respectively. These comparisons indicate that the heterogeneity in the susceptibility to antimicrobial agents within the multi-species group of Aeromonas is not significantly different from that recorded for individual species. This analysis, therefore, suggests that epidemiological cut-off values designed to be applied to all members of the genus Aeromonas would not be inherently unreliable.

This report describes a severely emaciated adult female bottlenose dolphin Tursiops truncatus found dead in September 2021 with numerous traumatic injuries. The animal stranded in coastal Alabama, USA, a hotspot in the Gulf of Mexico for trauma-related marine mammal strandings. A combination of traditional and advanced diagnostic techniques including postmortem examination, histopathology, and computed tomography revealed trauma from multiple events, including rib and vertebral fractures of varying chronicity and a more recent catfish barb penetrating the diaphragm with associated tissue necrosis. Tooth growth layer group analysis indicated this individual was ~40 yr old, despite a total straight length notably less than is typically reported for an adult female T. truncatus in the region. Advanced age was also supported by tooth wear, evidence of multiple pregnancies, fusion of sternal bones, and age-related changes in the heart and liver. This case illustrates a multifactorial cause of death in a coastal bottlenose dolphin and highlights the value of combining traditional postmortem examination with advanced imaging techniques to more accurately determine cause of death in the presence of multiple traumatic injuries.

Shellfish fisheries and aquaculture within the Chesapeake Bay (hereafter 'the Bay') and its tributaries have been historically impacted by disease and climate events. Climate-driven shifts in temperature and salinity can alter host-parasite dynamics, influencing outbreaks. Here, we explore the relationship between temperature, salinity and parasite distribution and abundance in the eastern oyster Crassostrea virginica-Perkinsus marinus system. We use long-term (30 yr) environmental data and P. marinus surveys in the Bay to identify (1) how climate affects P. marinus prevalence and intensity, (2) seasonal and climate-driven infection patterns, and (3) regional environmental influences on disease. We found significant relationships between P. marinus infection intensity, prevalence, increasing temperature and decreasing salinity. Our results indicated that there is an overall decreased abundance of P. marinus prevalence and intensity throughout the Bay driven by decreases in salinity over time, most prominently from 2003-2020. However, these temporal trends in prevalence and intensity vary largely by region, with some regions still experiencing high disease burden. Examining monthly environmental parameters reinforced the dominant role of salinity in driving disease patterns. Salinity had significant relationships with prevalence and intensity year-round, with the largest effects in late spring/early summer. Monthly temperatures had fewer significant relationships to prevalence and intensity, but the largest significant effects were seen in late winter/early spring. Notably, this study is the first to document that winter salinity influences fall parasite prevalence, sometimes exerting a greater effect than temperature. Continued and expanded monitoring of marine disease is crucial to understand how the changing climate is impacting disease.

Emerging infectious diseases (EIDs) pose a major threat to global amphibian populations, contributing to widespread mortality and species extinctions. Among EIDs, those caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal), and viruses in the genus Ranavirus (Rv), represent the most significant threats to amphibian biodiversity. Here, we tested for occurrence of Rv in 3 different locations in southeastern Sweden. Using a quantitative PCR assay, complemented by a secondary PCR-based validation method targeting the viral major capsid protein gene and additional 5 partial sequences, we detected Rv in 2 of 3 locations and in 5 out of 43 individuals tested. This is the first record of Rv occurrence reported at such high latitudes in northern Europe and the first from the Scandinavian peninsula, contributing important insights into infection prevalence in northern amphibian populations. These findings establish a basis for the conservation of vulnerable populations.

We tested the antiviral activity of aqueous extract of star anise Illicium verum (AEIV) against striped jack nervous necrosis virus (SJNNV) in vitro as well as in vivo using the Sahul Indian Seabass Spleen (SISS) cell line and Asian seabass Lates calcarifer. Preliminary results from GC-MS profiling and polyphenol content estimation of AEIV revealed the antiviral potential of the extract. Before testing the compound, the extract was assessed for its toxic potential in an in vitro model (SISS cell line) using 4 different concentrations (50, 75, 100 and 200 µg ml-1) of AEIV through MTT and neutral red assays. The tested concentrations were not toxic (≥90% survival). Subsequently, the same concentrations of AEIV were tested for their antiviral potential against SJNNV in SISS cells. The results showed that AEIV at higher concentration (100 and 200 µg ml-1) effectively inhibited SJNNV replication in the SISS cells. RT-PCR and qPCR confirmed the inhibition of the virus. The same concentrations were then used to evaluate their antiviral efficacy in vivo by intraperitoneal injection in Asian seabass. We observed 100% mortality only in the fish injected with SJNNV (control), which confirms that AEIV possesses the potency to control the replication of SJNNV under both in vitro and in vivo conditions. The present study indicates that medication with plant extracts having antiviral activity could be a potentially beneficial alternative to the usage of chemotherapeutics in aquaculture.

Microcystis spp. blooms in fish ponds can lead to fluctuations in water parameters, and the microcystin-LR (MC-LR) toxin they produce may pose health risks for fish, as well as consumers. Hydrogen peroxide (H2O2) treatment has been demonstrated to reduce populations of Microcystis spp. in aquaculture ponds. This study conducted 2 trials to investigate whether these treatments result in the release of MC-LR under laboratory conditions. We applied 7 mg l-1 of H2O2 to a Microcystis sp. culture and assessed the MC-LR level post-treatment. In the first trial, no MC-LR was detected in the H2O2 treatment group nor the negative control group, while 0.933 ± 0.381 ppb of MC-LR was extracted from 2344230 Microcystis sp. cells in 5 ml of media stock in our positive control group (where all cells were destroyed). In our second trial, where we added almost 30 times more Microcystis sp. to the culture media (i.e. 64125000 cells in 5 ml of stock), 19.333 ± 0.742 ppb of MC-LR were detected in the positive control on average. At this concentration of algae, our negative control (no treatment) and our H2O2 treatment group had 16.933 ± 0.303 ppb and 16.933 ± 0.109 ppb of MC-LR, respectively. The toxin levels were similar between the treated and untreated groups, but significantly less than the positive control group (p = 0.003). The results suggest that 7 mg l-1 H2O2 treatment to Microcystis sp. did not increase the level of MC-LR in the solution, but MC-LR was also not removed by the treatment. The low-dose 7 mg l-1 H2O2 treatment against Microcystis sp. bloom is unlikely to cause extra toxin (MC-LR) release to the medium.

A novel dinoflagellate is described from bluegill Lepomis macrochirus, rock bass Ambloplites rupestris, largemouth bass Micropterus nigricans, and yellow perch Perca flavescens collected from Lundgren Lake and Townsend Flowage, Wisconsin, USA. A new genus, Dermisichthinium gen. nov., is established for this species, D. pseudosporum sp. nov., which produces white spots grossly similar to those caused by Ichthyophthirius multifiliis. Microscopically, however, the vegetative cysts of D. pseudosporum closely resemble Haidadinium ichthyophilum, a parasite of threespine stickleback Gasterosteus aculeatus. Haidadinium ichthyophilum was collected from Haida Gwaii, British Columbia, Canada, for morphological and molecular comparison. Molecular analysis of the small subunit (18S), large subunit (28S), and internal transcribed spacer rDNA regions supports the novel species description and erection of a new genus. Pairwise comparisons of partial 18S and 28S sequences revealed divergence levels approximately 3 times greater than those among congeneric suessiacean dinoflagellates. Dermisichthinium pseudosporum sp. nov. lacks a 25 bp insertion in 28S unique to H. ichthyophilum, providing a molecular character for distinguishing the 2 species and supporting their placement in separate genera. Phylogenetic analyses consistently place D. pseudosporum sp. nov. and H. ichthyophilum in distinct clades. This study enhances our understanding of parasitic dinoflagellate diversity, underscores the importance of integrating morphological, molecular, and other diagnostic characteristics in their taxonomic classification, and offers valuable diagnostic insight for fish health professionals and parasitologists encountering this unusual group of cyst-forming dinoflagellates.

Infectious pancreatic necrosis virus (IPNV) poses a significant economic threat to aquaculture, yet understanding of the host-virus interaction remains limited. This study investigates the impact of IPNV on proteasomal response within rainbow trout kidneys during both subclinical (5 days post-infection, dpi) and clinical (10 dpi) stages of infection. Our results reveal a biphasic response: an initial stimulation of proteasomal activity at 5 dpi followed by inhibition at 10 dpi. Transcript analysis of proteasomal subunits in individual fish shows predominantly a correlation between their expression and proteasomal activity at 5 dpi, but this correlation was not seen by 10 dpi. Additionally, it was observed that the upregulation of immunoproteasome subunits by gamma interferon (γIFN) did not consistently cause a rise in proteasomal activity. Notably, a significant increase in free ubiquitin and ubiquitinated proteins was detected at 5 dpi, followed by a decrease at 10 dpi, indicative of dynamic changes in protein degradation, which agrees with proteasomal activity. The biphasic proteasome response suggests that early activation aids viral protein clearance, while later inhibition triggers cellular stress, potentially driving symptom development. Overall, this study underscores the significant impact of IPNV on proteasome activity in rainbow trout.

Ergasilids are an important group of parasitic copepods that occur globally in some coastal, estuarine, and freshwater habitats, including the south coast of the island of Newfoundland, Canada. Generally, males and developing females are not parasitic and remain in plankton. Adult females, however, become parasitic and seek a host following mating. Few studies have focused on detection and/or quantification of planktonic stages, and of those, all have utilized microscopic techniques. This method is time consuming and dependent on a specific parasitological skill set. In recent years, quantitative PCR (qPCR) techniques have become common in the detection and relative quantification of various invertebrate larval stages within plankton, including many metazoan parasites. In the present study, a qPCR assay using TaqMan™ minor groove binder probe technology, based on the Ergasilus labracis mitochondrial cytochrome c oxidase subunit I sequence, was developed for the first time to detect this parasite in mixed plankton samples taken near active salmonid aquaculture sites in a Northwest Atlantic coastal estuary. Ultimately, the technique can be used for tracking seasonal variability and abundance of planktonic stages of this parasite and thus illustrate patterns of seasonal infestation for both wild and cultured species in this region.

Protozoan parasites Perkinsus marinus (dermo) and Haplosporidium nelsoni (MSX) are associated with extensive epizootic mortality in eastern oyster Crassostrea virginica populations along the coastlines of the Atlantic Ocean and Gulf of Mexico. For decades, both diseases have resulted in substantial losses to ecological functioning of natural oyster habitat and have undermined the economic stability of wild oyster fisheries and mariculture industries in the USA. Both pathogens are widespread in coastal Georgia and are established regionally within native oyster populations, yet a clear timeline of transmission is not defined. Here, high frequency sampling was used to investigate when disease transmission is most probable relative to oyster lifecycle stage based in a localized region of the South Atlantic Bight (SAB). Dermo was present in the water column throughout the year with peaks in abundance concurrent with spawning activity, resulting in significant positive correlations among P. marinus concentration and the number of spawning females, egg yield, and shell height per spawning female. Detection of MSX in water samples appeared during 3 punctuated periods throughout the year but was not significantly associated with any environmental or life cycle metric. Overall, this research indicates that spawning events may be a mechanism for P. marinus transmission in oyster populations of the SAB.