Diseases of aquatic organisms最新文献

Nutritional steatitis (yellow fat disease) caused by vitamin E (vitE) deficiency is typically associated with diets high in unsaturated fatty acids or/and low levels of vitE. This work describes, for the first time, an outbreak of nutritional steatitis in cultured silver catfish Rhamdia quelen in Argentina. Necropsy, histopathology, bacteriology and molecular studies of the affected fish were performed. In addition, peroxide level and vitE concentration of the fish feed were measured. Affected specimens had firm, yellowish-brown dermo-hypodermal nodules located in the adipose fin and dorsal region of the body. Histologically, lesions consisted of fat necrosis and multifocal granulomatous lobular steatitis, primarily affecting the subcutaneous and intermuscular adipose tissue, and occasionally, the coelomic fat. Feed analyses revealed a high peroxide value (41.2 mEq kg-1), indicative of rancid feed, and a low concentration of vitE (2.7 IU kg-1). In this case, fish had been fed rancid food with an inadequate value of vitE, leading to the development of nutritional steatitis caused by vitE deficiency.

Bonamiasis, caused by haplosporidian parasites Bonamia spp., is an infectious disease prevalent in 'flat' oysters internationally. Bonamia was first detected in Australian native oysters Ostrea angasi in Victorian waters in the early 1990s and caused mass mortalities in this pilot industry. The species identity of Bonamia at that time was unclear and no attempts were made to unequivocally resolve it. Interest in O. angasi culture was renewed in 2010 alongside a small-scale bonamiasis surveillance programme, given previous experience with the parasite. Basic data on culture methods, epidemiology and pathology are presented from 2011 until the epizootic that destroyed most of the stock at the major aquaculture site in 2015. At that time, a comprehensive phylogenetic analysis of the relationship between the cause of this epizootic and other Bonamia spp. internationally demonstrated >98% homology to B. exitiosa. Moreover, the report on Perkinsus olseni is the first in O. angasi. The presumed incidental finding of the more recently identified P. beihaiensis is the first for any mollusc species in Australia.

Pathological conditions associated with feather ingestion have rarely been reported in any species and not previously in fish. From 2013 to 2024, 87 American shad Alosa sapidissima collected from the wild for display purposes were housed in a multispecies habitat within a zoological facility, alongside various fish, invertebrate and bird species from the St. Lawrence Estuary (Quebec, Canada) ecozone. Since 2013, 81 of the 87 shad either died or were euthanized due to health issues, and macroscopic examinations were performed on 36 of these. Bird feathers were present within the gastric lumen in 12 of the 36 fish and were associated with penetrating perforations of the gastric wall with gross evidence of peritonitis in 11 of the 12 cases. Histopathologic examinations were performed in 7 of the affected fish and in 6 revealed the presence of transmural, focally extensive granulomatous infiltration of the gastric wall, centered on foreign bodies morphologically characteristic of feather shafts and barbs. Significant comorbidities included trauma (n = 18) and systemic Ichthyophonus infection associated with granulomatous reaction, which was considered a potential contributory cause of morbidity and mortality in at least 2 fish, including 1 with gastric feather perforation. Incidental encysted anisakid nematodes within the coelomic cavity, intestines and liver were also observed (n = 3). Eight of the affected fish were underconditioned, suggestive of chronic morbidity. This case series indicates that American shad are prone to ingesting bird feathers and highlights a previously unreported health issue associated with keeping this species in mixed exhibits with birds.

Magellanic penguins Spheniscus magellanicus are seasonal migratory seabirds. During the migratory period, these penguins are observed mainly in the seas of Argentina, Uruguay, and Brazil. Studies on mortality events in the species are limited, particularly those comparing free-ranging and captive penguins. This study describes the causes of death and pathological findings in Magellanic penguins using necropsy records from a retrospective study (2011-2021). Records from 164 penguins were analyzed, comprising 95 in captivity, 68 free-ranging, and 1 of undetermined origin. Non-infectious diseases (n = 104) were predominant in free-ranging penguins and included starvation (n = 49), suspected drowning (n = 27), hypothermia secondary to oil pollution (n = 25), trauma (n = 2), and intestinal obstruction (n = 1). Infectious/inflammatory diseases (n = 23) were most frequent among captive populations, including cases of malaria (n = 9), aspergillosis (n = 7), other mycotic infections (n = 3), bacterial infection (n = 2), protozoal meningoencephalitis (n = 1), and granulomatous air sacculitis of unknown origin (n = 1). Juvenile penguins constituted most cases in both non-infectious and infectious categories. There were 37 cases of undetermined diagnoses. Gastrointestinal parasitosis, cutaneous lesions, and pulmonary edema were the main secondary pathologic findings. These results enhance our understanding of the diseases affecting the Magellanic penguins and provide valuable insights for the conservation and maintenance of free-ranging and captive penguins.

Renibacterium salmoninarum, the cause of bacterial kidney disease (BKD), severely impacts salmonid populations. Much of our understanding of the BKD pathology in salmonids comes from evaluating fatal infections in wild populations or spawning Pacific Northwest salmonids. Our study investigated the histological progression and bacterial load dynamics of R. salmoninarum infection in Chinook salmon following intraperitoneal injection to enhance understanding of the disease's dynamics. Seventy presmolt salmon were injected with the ATCC-33209 isolate of R. salmoninarum and monitored over 10 wk. Histological signs of disease were observed in spleen and liver tissues at 1 wk post-injection and in kidney tissues at 4 wk post-injection, with signs of disease increasing over time. Additionally, histopathological analysis revealed splenic and hepatic capsulitis (coelomitis), individual hepatocyte necrosis, progressive granulomatous hepatitis, splenitis, and nephritis with necrosis. Gram staining confirmed the presence of Gram-positive bacteria within macrophages and extracellularly in infected tissues. Quantitative PCR revealed significant increases in bacterial loads in both kidney and liver tissues over the study period, with higher bacterial loads observed in the kidney tissue. Bacterial load was strongly correlated with disease stage, with peak bacterial burdens coinciding with the most severe histological changes. Our study provides a comprehensive account of R. salmoninarum infection and disease progression in Chinook salmon after intraperitoneal injection.

This study examines acute hepatopancreatic necrosis disease (AHPND) in shrimp farming, caused by specific strains of Vibrio (Vp AHPND+), and evaluates the potential of silver and silver chloride nanoparticles (Ag/AgCl NP) synthesised from marine resources as an antibacterial additive in shrimp feed. Penaeus vannamei juveniles were fed diets supplemented with 0, 10, 100, and 1000 mg Ag/AgCl per kg for 20 d. The highest weight gain (%WG) was observed in individuals consuming the 100 mg Ag kg-1 diet, with a 104.27 ± 4.11% increase. Histopathological analysis revealed that 10 and 100 mg Ag kg-1 improved hepatopancreas (HP) ultrastructure, whereas 1000 mg Ag kg-1 caused severe lesions, including cell necrosis. After infection with Vp AHPND+, survival rates increased from 27% in the control group to 78% in juveniles fed the 100 mg Ag kg-1 diet for 7 d. Microbiome analysis showed no significant changes in alpha diversity due to Ag/AgCl NP doses, although a notable shift was observed during the depuration phase. These findings highlight the potential of Ag/AgCl NP as a dietary supplement to improve growth, health, and disease resistance in shrimp farming, emphasising the importance of precise dosing to maximize benefits while minimising risks.

Disease outbreaks among shellfish cause significant declines in both wild fisheries and aquaculture production globally. In Aotearoa New Zealand, a long history of flat oyster infections by the haplosporidian parasite Bonamia exitiosa has influenced fishery dynamics in the Foveaux Strait. B. ostreae, which causes high host mortality, was detected in both wild and farmed oysters in the Marlborough Sounds in 2015 and at Stewart Island in 2017, prompting the development of rapid diagnostic tests with high sensitivity and specificity that can be used to simultaneously monitor both Bonamia species. Separate molecular diagnostic assays were developed for B. exitiosa and B. ostreae using droplet digital PCR (ddPCR). Analytical tests indicated both assays were specific and had limits of detection below 0.4 copies µl-1. Estimates of diagnostic performance used latent class analysis conducted on comparisons with previously established test methods. Both ddPCR assays had a diagnostic sensitivity and specificity equal to or greater than tests based on qPCR, end-point PCR, histopathology and heart imprints, validating their use for fishery health assessment and biosecurity monitoring. The new ddPCR assays are preferred over other methods in situations where high throughput and analytic and diagnostic performance are essential, as seen in New Zealand where 2 Bonamia species are sympatric in some regions and may co-infect a single host. Furthermore, the new assays could be adapted for eDNA-based surveillance and combined with other pathogen assays for multiplex assays, enabling further research into Bonamia lifecycles.

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.