Diseases of aquatic organisms最新文献

A total of 4193 specimens with everted tentacles of the trypanorhynch cestode Mixonybelinia lepturi obtained from Gempylus serpens and Trichiurus lepturus were examined in order to identify abnormalities in hook shape and armature pattern. The abnormality rate of the tentacular hooks and armature was 0.09%, ranging from changed hook direction and slight changes of single hook shapes to completely altered hooks and armature patterns. In a single case, the armature pattern could not be assigned to any existing trypanorhynch family. The observed malformations were classified in 5 categories and 9 types, a categorization also to be used as a standard for other trypanorhynchs. The low abnormality rate demonstrates high reliability of tentacular hooks and armature patterns as taxonomic characters in trypanorhynch systematics, confirming that trypanorhynch larvae have identical tentacular armatures compared with their adults. Considering the low rate of abnormality, the role of environmental factors in causing the unsymmetrical changes on originally symmetrical tentacles is probably weak. Therefore, a genetic origin seems to be more probable. Such phenotypic armature variations may cause transfer of worms to new attachment sites within the same host or into a new host species, where new tentacular armatures with increased fitness are eventually formed by natural selection under the model of micro-allopatric speciation. The finding of an abnormal tentacle that unites hollow and solid hooks together with completely altered hook shapes and armature patterns is good evidence in demonstrating the ancient origin of different hook shapes and the evolutionary changes of armature patterns.

Erysipelothrix is a genus of opportunistic bacteria of humans and animals. In 2019, a marked increase in infections by the zoonotic bacterium Erysipelothrix in Cook Inlet (Alaska, USA) beluga whales Delphinapterus leucas (CIBs) was detected through routine surveillance. A retrospective study was performed using archival records from 1998 to the present; archived samples from 2006 to the present; colleague interviews; and a literature review. Erysipelothrix was detected in 18 of 63 (28.6%) CIBs necropsied between 2006 and 2023, and when present after 2017, it was the primary cause of death. Erysipelothrix was rarely detected in other species of wildlife, domestic animals or in the environment in and around Cook Inlet during the same period. Sequencing of isolates demonstrated several different lineages, negating the possibility of infection from a common source or single strain. The lack of documented previous occurrence of Erysipelothrix in or near Cook Inlet indicates that this is likely an emerging phenomenon.

The Franciscana dolphin Pontoporia blainvillei is one of the most endangered cetaceans in the South Atlantic Ocean, primarily threatened due to bycatch. Knowledge regarding the natural causes of mortality and morbidity in this species is still limited. An adult female P. blainvillei that died as a result of bycatch was found stranded on the north coast of São Paulo, Brazil. At necropsy, a multi-cavitary tumor (~10.8 × 10.1 cm, 431 g) was found on the left adrenal gland, and on cut section, the tumor was hemorrhagic and necrotic. On histopathology, the tumor presented anaplastic characteristics including moderate anisocytosis and anisokaryosis, homogeneous and finely stippled chromatin, and nucleoli sometimes evident. Occasional binucleations and atypical giant cells were observed. The tumor was immunoreactive for chromogranin A and negative/not immunoreactive for Factor VIII, CD31, pan-cytokeratin AE1/AE3, vimentin, CD56, and synaptophysin, suggesting a poorly differentiated neuroendocrine tumor (NET). A moderate deviation of the lumbar spine (lordosis), lumbar ankylosing spondylosis, and thoracolumbar and caudal spine discopathy were confirmed via post-mortem radiographs. The vertebral anomalies and NET contribute to the knowledge of natural diseases of this endangered dolphin species.

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.