Diseases of aquatic organisms最新文献

Biomarkers in blood are useful for assessing health and welfare in animals. This study evaluated the agreement among 3 point-of-care testing (POCT) instruments (Seamaty SMT-120VP, Mnchip Pointcare V2/V3, and Zoetis Vetscan VS2 analyzer) on Atlantic salmon Salmo salar. A repeatability study investigated internal measurement variation. In total, 60 plasma samples from adult fish were analyzed simultaneously using different rotors with multiple biomarkers. A comparison between blood and plasma was conducted on 35 blood samples. Lin's concordance correlation coefficient was <0.9 for all analyte comparisons between the 3 POCT except for bile acids; therefore, the McBride strength of agreement was generally poor and was moderate for bile acids. Internal measurement showed a low coefficient of variation for most analytes, except for aspartate aminotransferase (Pointcare V2/V3), alanine transaminase (Pointcare V2/V3), blood urea nitrogen (Pointcare V2/V3), and creatinine (Pointcare V2/V3, SMT-120VP). There was high concordance between whole blood and plasma samples for most analytes on both SMT-120VP and Pointcare V2/V3 systems, except for sodium, total bilirubin, and total CO2. This study underscores the necessity for system-specific calibration and validation of POCT systems like the Seamaty SMT-120VP and Mnchip Pointcare V2/V3 when used in aquaculture for clinical assessment of Atlantic salmon. The reproducibility study demonstrated that the precision of analysis was acceptable for most analytes. The comparison between whole blood and plasma suggests that whole blood can be used on-site to reduce the complexity of analysis. In summary, these systems offer promising tools for rapid on-site health monitoring in salmonid aquaculture but they require validation against gold-standard methods.

Agricultural practices have a profound impact on watershed dynamics, water quality, and the well-being of aquatic life. One major concern is agricultural pollution, particularly the excess of nutrients, which can elevate disease risks in various host-pathogen relationships. However, the exact mechanisms driving this effect remain uncertain. Elevated nutrient levels are believed to significantly influence populations of aquatic environmental bacteria, potentially reshaping the microbiomes of aquatic organisms and affecting their vulnerability to disease. Despite this, the impact of nutrient enrichment on host microbiomes as a link to diseases in aquatic organisms has been largely overlooked. In this study, we investigated the impact of nutrient enrichment on the skin-associated microbial communities of the American bullfrog Lithobates catesbeianus. We observed a significant shift in bacterial richness and community composition in nutrient-enriched ponds compared with reference ponds. Although the proportion of the community inhibitory towards Batrachochytrium dendrobatidis (Bd) did not change significantly, Bd loads were markedly higher in nutrient-enriched ponds. Nutrient enrichment significantly altered carbon utilization patterns as measured by Biolog EcoPlates, and antibiotic resistance was prevalent across all ponds and samples, with resistance to trimethoprim, sulfamethazine, and chloramphenicol significantly higher in nutrient-enriched ponds. Our findings indicate that nutrient enrichment affects the structure and function of skin-associated microbial communities in American bullfrogs, influencing both Bd load and antibiotic resistance.

The incidence of Ecytonucleospora hepatopenaei (EHP) infections in farmed shrimp has increased markedly in recent years, resulting in significant economic losses for the global shrimp farming industry. The lack of an efficacious drug for EHP infection has led to the development of a strategy based on the timely screening and elimination of EHP-carrying shrimp seeds as a means of preventing financial loss. This strategy requires portable, accurate and rapid detection methods for EHP, especially when applied to sites such as farms. However, the current lack of user-friendly devices capable of real-time detection under field conditions represents a significant challenge in the implementation of this strategy. In this study, an isothermal amplification nucleic acid biosensor for EHP detection was developed. The biosensor targeted the spore wall protein gene of EHP and amplified the target gene by recombinase polymerase amplification (RPA) combined with strand displacement reaction (SDR). The amplified products were applied on gold nanoparticle-based lateral flow nucleic acid strips (LFNAS) for visual signal conversion. The limit of detection of the SDR-RPA-LFNAS assay was 7 copies reaction-1, and the entire process could be completed in 30 min without cross-reaction. In contrast to existing conventional RPA-related detection methods, the introduction of SDR, which is used to eliminate the background signal produced by long primers, avoids the use of endonucleases and reduces costs. Moreover, the biosensor is straightforward to operate and does not require the use of expensive machinery, rendering it more suitable for the in situ detection of EHP in shrimp farms or aquaculture facilities.

Invasive non-native species (INNS) are expanding their geographic range due to climate change, maritime traffic (primary route) and aquaculture (secondary route), resulting in the potential spread of microbes associated with them. Few studies have investigated the INNS-pathogen phenomenon. In this study, marine invertebrate species (native and INNS) were sampled monthly over 3 mo and screened by PCR for the ostreid herpesvirus-1 microvariant (OsHV-1 μVar) and Vibrio bacteria. Both pathogens are negatively associated with bivalve aquaculture. Sample sites included a shipping port, an oyster farm, a marsh nature reserve and a riverine site. Crustacea, Mollusca, Polychaeta, Tunicata and Porifera were sampled. Vibrio spp. were detected in 54.3% (n = 319/588) across all taxa and sample sites. The first detection of V. salmonicida associated with Atlantic salmon Salmo salar was detected in the INNS beaked barnacle Austrominius modestus. OsHV-1 μVar (7.7%, 45/588) was detected in Crustacea, Mollusca and Polychaeta at non-culture sites and in mussels Mytilus spp. at a much lower temperature (average sea surface temperature, SST, 11.25°C) than previously recorded. The shipping port had the highest Vibrio diversity and OsHV-1 μVar detection. Over half (51.1%) of 'recently dead' shore crabs Carcinus maenas had either pathogen detected compared to 29.4% of living crabs. OsHV-1 μVar detection was significantly higher in dead crabs (24.4%) compared to living crabs (5.9%). Findings from this study contribute a better understanding of the role of estuarine native and INNS as vectors/carriers of pathogens and of how the spread of INNS might facilitate the spread of pathogens.

The invasive species Anguillicola crassus is a nematode that infects the swimbladders of anguillid eels. Heavy, repeated infections cause the swimbladder to become thickened and scarred, which can alter swimbladder gas volume, increase energy demands of buoyancy regulation, and influence normal function. Silver-phase (sexually maturing) eels migrate up to thousands of kilometers to the Sargasso Sea to reproduce, and increased energetic requirements may be detrimental to migration and breeding success. Currently, the best practice to confirm A. crassus infection is to dissect an eel and examine the swimbladder. We used a portable digital X-ray system to determine the presence of A. crassus in American eels Anguilla rostrata. Silver-phase eels were anesthetized and radiographed. Post-imaging, individuals were dissected to compare the contents of the swimbladder to the radiographs. Infections appeared opaque on radiographs. Results showed no false positives and an accuracy of 74.8%. Out of 193 X-rayed eels, 107 contained parasites; 27 infections were undetectable on radiographs (false negatives). Detection was influenced by the intensity, size, and location of parasites within the swimbladder. This digital X-ray method is a quick and non-lethal process that could be incorporated into existing monitoring programs.

In this study, we used a dataset including 42 individual bottlenose dolphins (Tursiops spp.) to determine the reliability of lung function testing as a method for assessing respiratory health. Each dolphin was trained to beach voluntarily, allowing researchers to measure respiratory flow in a controlled, beached state. From the collected respiratory flow data, alongside timing parameters, we extracted 18 specific variables, supplemented by additional factors such as body mass, age, and sex. These variables were hypothesized to serve as potential variables for identifying respiratory compromise. A model was developed that reduced the number of predictive variables, showing that 4 specific variables were particularly effective, yielding an accuracy of 88.4% in determining whether a dolphin was free from respiratory disease. This high level of accuracy underscores the potential of lung function testing as a diagnostic tool in the context of stranded dolphins, where rapid, non-invasive methods are crucial for assessing health status. These results suggest that lung function testing provides a non-invasive and efficient method for evaluating respiratory health in stranded dolphins and supports the use of lung function assessments in wildlife management and conservation. By enabling early detection of respiratory issues, this approach can enhance the success of rehabilitation efforts, potentially improving the survival rates of dolphins that have stranded, which is often a critical concern in marine conservation initiatives.

A 33 yr old female grey seal Halichoerus grypus presented with inappetence and progressive weight loss. Medical management included blood analysis, imaging, and fecal evaluation, along with multimodal supportive therapy, which periodically improved the overall medical condition. Six months after the initial presentation, the clinical condition deteriorated significantly, including severe hyporexia, hematemesis, and marked neutrophilic leukocytosis, which led to the decision to euthanise based on welfare grounds. Necropsy findings included severe thickening of the distal esophagus, cardia, and proximal gastric fundus, as well as multiple nodular to cystic structures over the stomach's serosa, omentum, and mesentery. Histologically, a mucinous gastric adenocarcinoma was diagnosed, with metastasis to the gastric lymph nodes and prominent carcinomatosis involving the omentum, mesentery, and diaphragm. Immunohistochemically, the gastric adenocarcinoma was positive for cytokeratin AE1/AE3, weakly positive for COX-2 and E-cadherin, and negative for vimentin. The Ki-67 proliferative index was low (0.8). Although rare, this case offers further insights into the clinical presentation, histopathology, and immunohistochemical profile of gastric tumors in pinnipeds.

A trematode was identified in the gastropod Euspira gilva in the East China Sea. The intensity of infection in individual snails ranged from light to heavy, with an overall prevalence of 83.1% (n = 219). Given the observed decline in the E. gilva population, a series of diagnostic techniques were employed to identify the trematode and investigate the damage caused. These included smear observation, histopathological observation and molecular analysis. The results of the smear observation and histological sections indicated that this trematode only infected the gonad, and the presence of the larval rediae stage in the parasitized tissue was observed. The 28S rDNA sequence was used for molecular identification, which revealed a homology of 92.1-95.8% with the Echinostomatoidea superfamily and a genetic distance of 0.042-0.093 with existing genera within the superfamily. The considerable genetic distance between this trematode and other genera of the superfamily indicates that it cannot be clustered into any genus at present. The phylogenetic tree also demonstrated that this trematode constituted a discrete branch, albeit one that was closely related to Himasthla and Acanthoparyphium spp. within the family Himasthlidae. Based on the aforementioned data and in consideration of the observed decline in wild populations, we postulate that this echinostomatoid trematode represents a potential threat to E. gilva. This is the first report on trematodes in E. gilva.

In the River Traun in Austria, diseased European chub Squalius cephalus were observed for several years. In 2019, an investigation of the condition revealed the presence of several myxozoan species in different tissues, without evidence of other pathogens. The most prevalent and abundant myxozoan parasite in the different organs was Myxobolus ellipsoides ex S. cephalus, a parasite formerly only reported to infect the fin of European chub. To further investigate tissue tropism and molecular data of this parasite, samples from 11 different organs of 13 European chub were collected 1 yr later and examined with various methods. Myxospore morphology was assessed by microscopy and compared to the literature. A specific PCR protocol targeting the 18S rRNA gene of M. ellipsoides ex S. cephalus and subsequent sequence analyses detected 11 different 18S variants clustering into 2 groups. To differentiate M. ellipsoides ex S. cephalus unambiguously from other myxozoan parasites in the tissues, histological methods and in situ hybridization with a species-specific probe targeting the 18S rRNA of the parasite were applied. DNA of M. ellipsoides ex S. cephalus could be detected by PCR in each of the examined fish in at least 2 of the sampled organs, but not in any blood sample. In 2 fish, M. ellipsoides ex S. cephalus myxospores were detected in plasmodia in the kidney. Our findings present new data regarding tissue tropism and molecular diversity of M. ellipsoides ex S. cephalus in European chub and provide a basis for further studies investigating possible health impacts by this parasite.

The host specificity of Marteilia pararefringens is under discussion after its suggested reseparation from the flat oyster pathogen M. refringens in 2018. In Norway, M. pararefringens has been detected in mussels Mytilus spp. sampled from several isolated, small heliothermic ponds (polls) that, at least on the western coast, inhabit some of the last reproducing flat oyster populations. M. refringens has never been detected in Norway. The polls have a limited water exchange, and their uniquely warm temperature can result in high M. pararefringens prevalence and infection intensities, representing unique sites to study the susceptibility of flat oysters to this parasite. We have sampled flat oysters and mussels from all known M. pararefringens sites along the Norwegian coast. All flat oysters and mussels were screened by histology and PCR. Furthermore, to study the potential effect of natural resistance breeding of local flat oysters subjected to repetetive M. pararefringens cycles, we deployed naïve flat oysters from a known Marteilia-free poll to Agapollen, where the parasite has had consistent infection cycles since its discovery in 2016. Naïve mussels were deployed simultaneously in 2 separate years to verify that the flat oysters were subjected to at least 2 transmission cycles. M. pararefringens was not detected in any flat oysters in any poll, local or naïve, despite presence in the mussel populations. Our results show that the European flat oyster Ostrea edulis is not a susceptible host for M. pararefringens.