Diseases of aquatic organisms最新文献

Ranaviruses (RVs) are emerging pathogens that infect amphibians, reptiles, and fish, and have been linked to declines in several anuran species globally. Assessing their prevalence in wild populations is essential for effective monitoring and conservation efforts. This study evaluates the prevalence of RV in anurans from forest fragments in the Atlantic Forest in Brazil. We investigated the presence of RV in tissue samples obtained from 203 anurans, which included metamorphosed individuals and tadpoles of native species and the invasive American bullfrog. Additionally, we collected water from ponds to assess the presence of RV in the environment (using eDNA). We performed quantitative real-time PCR assays targeting the major capsid protein (MCP)-encoding region of RV to evaluate the potential risk posed by RV within these communities. The analysis revealed the presence of viral DNA in 3 of 5 sites and an overall prevalence of 60% in the animals. Our results show that RV is widespread and prevalent among wild amphibians living in fragments of the Atlantic Forest. Our findings highlight the potential threat posed by RVs as an emerging disease.

Decapod hepanhamaparvovirus 1 (DHPV), formerly known as hepatopancreatic parvovirus (HPV), primarily causes stunted growth in juvenile shrimp and, in some cases, mortality in shrimp larvae. DHPV belongs to the genus Hepanhamaparvovirus within the family Parvoviridae and is classified into 5 genotypes (genotypes I-V). Previous studies have reported DHPV infections in various shrimp species; however, no reports have documented co-infection with different DHPV genotypes in shrimp. In this study, we report the first evidence of co-infection by 2 DHPV genotypes-genotype IV (DHPV-GS) and genotype V (DHPV-GJ)-in Penaeus vannamei cultured in South Korea. To discriminate between the 2 genotypes, we established and validated genotype-specific PCR assays, and the assays demonstrated high specificity, with no cross-amplification observed between the 2 genotypes. Using these assays, we screened 38 shrimp from Goseong and 12 shrimp from Geoje, and found co-infection with both DHPV-GS and DHPV-GJ in 36.8% and 100% of the samples, respectively. These findings highlight the importance of genotype-specific diagnosis for accurate surveillance and improved understanding of DHPV epidemiology in aquaculture systems.

Coccidia are protozoal parasites that can cause coccidiosis, a disease linked to high mortality in young, stressed, and overcrowded animals. In the order Urodela, only 21 coccidia species have been registered, and none in the Critically Endangered Ambystoma mexicanum. The present study presents the detection and follow-up of Eimeria in A. mexicanum. The monitoring was conducted at CIBAC (Centro de Investigaciones Biológicas y Acuícolas de Cuemanco), analyzing fecal samples from 90 juveniles using sedimentation, Faust, and modified Zajíček McMaster techniques. An overall prevalence of 65.6% was observed, with median oocyst shedding values of 100 oocysts per gram (opg) from July to September and 27500 opg from October to December, suggesting a seasonal pattern. Nematode eggs from the Kathlaniidae family were also identified in 18.3% of samples, with no observed association with water source, time period, or mortality. Further research is needed to describe the life cycle of this Eimeria species and its potential pathological effects.

Melanoma is a highly aggressive neoplasm of melanocytes, commonly studied in mammals but rarely documented in wild fish populations. This study reports the first confirmed case of malignant melanoma in Terapon jarbua (Forsskål, 1775) from the Parangipettai landing center on the southeastern coast of India. Gross examination revealed superficial raised, hyperpigmented lesions primarily distributed along the dorsal and lateral body surfaces. Wet mount analysis showed extensive melanization within the dermal layers of the affected tissue. Histological examination identified pleomorphic melanocytes with dense melanin deposition, architectural disruption of the skin, and features consistent with superficially spreading melanoma. Scanning electron microscopy of melanotic lesions revealed significant alterations to the epidermal surface, with rounded or angular projections and sharply defined crevices. Transmission electron microscopy showed classical ultrastructural abnormalities such as pleomorphism, irregular melanosome aggregation, binucleation, cytoplasmic vacuolation, and necrotic cells with compromised plasma membranes. The presence of melanosomes at various maturation stages indicated hyperactive melanogenic activity. This novel discovery points to the importance of regular tumour surveillance and research into environmental stressors as possible causative agents, adding to the small but increasing body of evidence of neoplastic disease in Indian marine ecosystems.

Piscine orthoreovirus (PRV) infection is widespread in the global salmonid aquaculture industry. This study aimed to investigate the presence or absence of PRV genotypes in rainbow trout Oncorhynchus mykiss farmed in Peru. The Peruvian National Authority for Fisheries and Aquaculture Health and Safety (SANIPES) carried out a disease surveillance plan between October and December 2023. In this context, 48 fish exhibiting clinical signs of circulatory disorders were screened for PRV genotypes. Quantitative PCR analysis showed that 12.5% of pools (2 out of 16) were positive for PRV-3 but negative for PRV-1 and PRV-2. The CT value was 23.48 for tissue pool no. 14 and 27.03 for tissue pool no. 15, but both pools contained tissues from fish farmed in Lake Titicaca. Concurrently, Weissella ceti was isolated from these fish. PRV-3-positive fish showed mild mononuclear myocarditis in the ventricular spongy layer (2 out of 6). The sequences of the S1 and M2 segments of the Peruvian isolates belonged to the PRV-3 gene group, subgroup PRV-3b. These sequences showed 100% identity with the Danish PRV-3b isolates, suggesting possible European origin. Overall, the results of this study confirm, for the first time, the presence of PRV-3b in the Peruvian rainbow trout farming industry and highlight the need to implement biosecurity measures for the import of embryonic eggs to minimize the risk of pathogen entry and dissemination in the industry, as well as a permanent epidemiological surveillance plan for all PRV genotypes.

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.