Diseases of aquatic organisms最新文献

Voriconazole treatment for amphibian chytridiomycosis has emerged as a less toxic alternative to the widely used itraconazole, although its efficacy needs to be validated across different species, particularly for frogs with clinical signs of disease. We assessed the effectiveness of topical voriconazole antifungal treatments for subclinical and clinical chytrid infections after experimental Batrachochytrium dendrobatidis (Bd) exposure. In addition, we looked to validate this treatment for use with multiple age classes of 2 highly susceptible, Critically Endangered Australian myobatrachid frogs: southern corroboree frogs Pseudophryne corroboree and northern corroboree frogs P. pengilleyi. Treatment involved twice daily topical application of a 0.00015% voriconazole solution for 7 d or until clear of Bd. Supportive care was provided for frogs displaying clinical signs of chytridiomycosis. This study was conducted across 2 experiments: experiment 1 (Expt 1) involved only P. corroboree and Expt 2 included P. corroboree and P. pengilleyi. In Expt 1, voriconazole treatment cleared Bd from 78% (N = 21/27) of infected P. corroboree, resulting in 68% survival among the P. corroboree with clinical chytridiomycosis. In Expt 2, 100% of Bd-positive P. pengilleyi (N = 7) cleared and survived infection, including all 4 cases with clinical disease. In Expt 2, none of the P. corroboree (4) tested positive for Bd, and all remained normal throughout treatment. Our results demonstrate that voriconazole is an effective treatment for chytridiomycosis in P. corroboree and P. pengilleyi, and that clinically ill frogs of multiple age classes can recover with the addition of electrolyte therapy and antibiotics.

Cyprinid herpesvirus 3 (CyHV-3) is a highly contagious virus that causes high mortalities in common and koi carp worldwide. The molecular detection of this double-stranded DNA virus has been extensively researched. Nonetheless, there are currently no real-time PCR assays available for detecting CyHV-3 mRNA, which could serve as an indicator of active virus replication, aiding in the evaluation of the susceptibility of non-target species. This study describes a probe-based reverse transcription, real-time PCR (RT-qPCR) assay that was designed to detect CyHV-3 mRNA for efficient, high-throughput detection. The assay is highly specific for CyHV-3 mRNA, with no detection in samples from non-infected fish, closely related viruses or CyHV-3 DNA. The analytical sensitivity of the assay was examined using dilutions of a plasmid control and nucleic acid from a CyHV-3-infected cell line, where the CyHV-3 mRNA limit of detection was approximately 1 copy per reaction. Testing of diluted CyHV-3 mRNA demonstrated comparable sensitivity of the RT-qPCR with an existing reverse transcription PCR assay. Progressive monitoring of positive control samples revealed that the assay had a high level of repeatability. The assay was used to provide further evidence that non-target species silver perch and Murray cod were not susceptible to developing disease when experimentally exposed to CyHV-3. The novel RT-qPCR assay is an invaluable tool for detection of the replication phase of CyHV-3.

Bycatch in fishing gear is one of the main threats to cetaceans globally. It is often immediately fatal, particularly for small cetaceans, but animals sometimes escape with parts of fishing gear still attached to them. Chronic entanglement is well documented in large whales, but less so in small cetaceans. We describe year-round entanglement of an immature common bottlenose dolphin, combining in-field observations and post-mortem investigations. The dolphin survived a full year without deterioration in body condition, but was subsequently fatally entangled in another gear. The 2 entanglements appeared unrelated. Necropsy confirmed good body condition and suggested the chronic entanglement could have resolved on its own. Given the scarcity of published records and its long-term nature, this case provides useful insights into the impacts of chronic entanglement and potential prospects of survival. Finally, we evaluate the appropriateness of potential intervention attempts, with implications for response decisions for small cetaceans.

Green turtles Chelonia mydas are vital components of marine ecosystems and are recognized as indicators of environmental health. Fibropapillomatosis (FP), a debilitating disease associated with a chelonid herpesvirus, disproportionately affects juveniles in coastal foraging areas. This study presents the first analysis of FP dynamics in Babitonga Bay, southern Brazil, an important habitat for the species. Between 2019 and 2023, 171 juvenile green turtles were monitored using capture-mark-recapture and photo-identification techniques. FP prevalence in Babitonga Bay was among the highest reported in Brazil, reaching 53.2%. Tumors were predominantly located in the anterior region of the body, particularly around the flippers and axillary area, and were mostly small, consistent with mild FP. Disease severity was quantified using an FP index, and its association with body condition was examined, revealing no significant association. Data from recaptured individuals revealed both tumor progression and regression, underscoring individual variability and suggesting the influence of environmental and immunological factors. The predominance of FP in juveniles highlights their heightened vulnerability during early developmental stages. These findings enhance our understanding of FP dynamics in green turtles and support the need for continued health assessments and conservation measures. This research contributes to global efforts to safeguard marine biodiversity, aligning with the goals of the United Nations Decade of Ocean Science for Sustainable Development.

We report significant pathological findings from 272 stranding investigations of 20 cetacean species in the Pacific Islands region between 2006 and 2024. Full or partial necropsies of 209 cases (76.8%) resulted in one or more diagnoses associated with death in 137 cases. Natural disease accounted for 62% of stranded animals; approximately half were in poor body condition due to chronic illness. Morbillivirus and Brucella sp. infections caused mortality in 11 species, including striped dolphins and Longman's beaked whales. Toxoplasmosis, of anthropogenic cause in Hawai'i, led to deaths of 2 spinner dolphins and a bottlenose dolphin. Pygmy and dwarf sperm whales, beaked whales and pilot whales showed heavy parasitism by nematodes, cestodes and trematodes. Approximately 12.4% of stranded individuals were perinates/neonates, with 3 cases of dystocia with maternal mortality. Anthropogenic trauma was observed in 29.2% of strandings, including 6 goose-beaked whales with cranial and/or microvascular hemorrhages. Vertebral and skull fractures were attributed to direct vessel strikes for 2 pygmy sperm whales, 2 humpback whale calves, a goose-beaked whale, a spinner dolphin and a striped dolphin. Blast trauma was observed in 3 Fraser's dolphins in an uncommon stranding event. Significant plastic debris and/or fishery debris were found in stomachs of 6 species, with fatal gastric obstruction in a sperm whale and fatal fishhook penetration in a bottlenose dolphin. This study highlights the value of necropsy examinations in a region inhabited by small island-associated populations where carcass recovery rates are low, and cetaceans face an array of natural and anthropogenic threats.

Access to clean water is a fundamental Sustainable Development Goal that is increasingly undermined by emerging microbial contaminants linked to urbanization, pollution, overfishing, and climate change. This paper investigates the rising incidence of mycobacterial infections in aquatic environments, from potable and surface waters to marine and aquaculture systems, with a particular focus on the Mediterranean Sea. The region, a biodiversity hotspot, exemplifies how climate-induced thermal shifts, combined with anthropogenic pressures, enhance pathogen survival and disease transmission in fish, especially in species with limited thermoregulation. The study synthesizes evidence on the global distribution of various Mycobacterium species, their modes of transmission, and their clinical impacts on a wide range of aquatic organisms. It further explores the challenges posed by ineffective water disinfection, biofilm-associated persistence, and regulatory gaps that complicate disease management. The findings underline the critical need for integrated public health strategies and sustainable aquaculture practices to mitigate the dual threats to marine biodiversity and human health posed by these emerging infections.

Mycobacteria infections are sporadically documented in wild sea turtles and are generally regarded as opportunistic pathogens. This case series describes infections by a Mycobacterium ulcerans ecovar in 2 imperiled species of sea turtle, the Kemp's ridley Lepidochelys kempii (n = 5) and loggerhead turtle Caretta caretta (n = 1). Most cases were stranded animals that presented with neurological abnormalities resulting from severe mycobacterial meningoencephalitis. In 4 instances, infected turtles were found in relative proximity to one another and without evident predisposing conditions, suggesting the potential for broader population health significance. Lesions were predominantly heterophilic and histiocytic, and were characterized by extensive leukocytic necrosis, absence of organized granuloma formation within the nervous system, fibrinoid vascular necrosis, and myriad extracellular and intrahistiocytic acid-fast bacilli. Except for one severely bacteremic animal, involvement of visceral organs was relatively mild and often paucibacterial. Multiple genetic loci were 100% identical in all 6 affected turtles and to multiple reported M. ulcerans ecovars; an ITS2 sequence amplified from each turtle was 100% identical only to M. pseudoshottsii, a pathogen of wild and farmed fish. The genetic relatedness of the organism to M. ulcerans ecovars known to produce mycolactones (polyketide toxins) suggests that the distinct pathological features among these cases are the result of a mycolactone-producing species of mycobacteria. This is the first report of M. ulcerans ecovar infection of a reptile. Mycobacterial meningoencephalitis should be considered as a differential etiological diagnosis for neurological disease in wild sea turtles.

Two supersaturation events caused gas bubble disease (GBD) in captive Melibe leonina (lion's mane sea slugs). For the first event (a), supersaturation spikes (114-127% total dissolved gas [TDG]) occurred on Days 1a, 4a, and 23a. On Day 5a, nearly all 77 animals developed grossly visible gas bubbles within vasculature. Two recompression treatments were performed on 2 cohorts: (1) 7 animals were placed at 8.5 m depth (103 kPa) and unmonitored for 5 d, after which they had resolution of gas bubbles; and (2) 12 animals were placed in a hyperbaric chamber (152 kPa) for 5 d and had resolution of gas bubbles within 2 h of treatment initiation. Untreated animals had slow, consistent improvement with complete resolution at Day 12a. Starting on Day 23a (date of a supersaturation spike) through Day 79a, 0-4 animals died per day, totaling 60 deaths (78% mortality), after which no further mortalities occurred. After the first supersaturation event, 17 animals remained, and 16 new animals were added to the tank. Two months later, during the second event (b), supersaturation spikes (106-110% TDG) occurred on Days 1b, 2b, and 6b-15b. On Day 15b, all M. leonina developed grossly visible bubbles and were placed in a hyperbaric chamber for 14 d; gas bubbles resolved, and no mortalities occurred in the second event. Histologically, gas emboli were in the hemolymphatic sinuses and caused soft tissue edema. The cause for GBD was unknown for the first event and, for the second event, was due to cracked plumbing valves.

This work was performed to generate the data needed to set epidemiological cut-off values for inhibition zone data of 8 antimicrobial agents against Vibrio parahaemolyticus determined using standardised disc diffusion protocols with incubation at 35 ± 2°C for 16 to 20 h and at 28 ± 2°C for 24 to 28 h. The zone diameter data aggregated from 3 to 5 laboratories were analysed by the normalised resistance interpretation algorithm. Cut-off values calculated from data obtained at 35 and 28°C were ≥23 and ≥24 mm for ceftazidime, ≥18 and ≥20 mm for enrofloxacin, ≥28 and ≥29 mm for florfenicol, ≥14 and ≥14 mm for gentamicin, ≥29 and ≥32 mm for meropenem, ≥17 and ≥18 mm for oxolinic acid, ≥22 and ≥24 mm for oxytetracycline, as well as ≥19 and ≥21 mm for trimethoprim/sulfamethoxazole. The influence of the incubation temperature on inhibition zone sizes was investigated by calculating the difference between the zones obtained at 35 and 28°C for a specific antimicrobial agent with a particular isolate by an individual laboratory. The mean of the differences calculated for 1314 paired observations was 0.38 mm with a standard deviation of 2.68 mm. The data generated in this work will be submitted to the Clinical and Laboratory Standards Institute and the European Committee on Antimicrobial Susceptibility Testing for consideration in their setting of internationally agreed-upon epidemiological cut-off values for V. parahaemolyticus that are essential for interpreting antimicrobial susceptibility testing data of this species.

Edwardsiella ictaluri is a pathogenic bacterium that poses a significant threat to the economic viability of aquaculture. However, the effects of E. ictaluri infection on the non-specific immune response of hybrid grouper and the regulatory mechanisms of oligochitosan in modulating the infection are poorly understood. We investigated the impact of oligochitosan supplementation on the growth performance, biochemical parameters, immune response, and apoptosis in hybrid grouper infected with E. ictaluri. The results showed that oligochitosan significantly improved the weight and length of hybrid grouper, whereas E. ictaluri infection reduced their growth performance. Histopathological analysis of the head kidney showed no significant differences among the groups. Biochemical analysis revealed that E. ictaluri significantly increased the activity of serum glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT), while decreasing the activities of catalase (CAT) and superoxide dismutase (SOD), with oligochitosan ameliorating these effects. E. ictaluri infection also significantly elevated the GOT activity in the head kidney while reducing CAT and SOD activities. The analysis of inflammatory factor expression revealed that E. ictaluri significantly increased the levels of IL-8, TNF-α, and IKKα, whereas oligochitosan effectively decreased these inflammatory markers. Apoptosis gene expression analysis indicated that E. ictaluri infection significantly upregulated bax, caspase-3, and caspase-8, while supplementation with oligochitosan reduced their expression levels. TdT-mediated dUTP nick-end labeling signals were significantly increased following E. ictaluri infection, while supplementation with oligochitosan notably reduced them. In conclusion, oligochitosan can regulate growth, immune response, and apoptosis, potentially protecting hybrid grouper infected with E. ictaluri.