The short-beaked common dolphin Delphinus delphis is the most frequently stranded cetacean species around the 700 km coastline of Cornwall, southwest England, with over 100 animals stranding each year. Between January 2018 and December 2024, 867 stranded common dolphins were reported, of which 175 (20%) individuals were necropsied. The most common cause of death was bycatch, accounting for 39% (n = 68; interannual range: 29-44%). Observed pathology and available fishing effort data suggest that smaller vessels engaged in static (and potentially drift net) fishing were the most probable cause of the majority of diagnosed bycatch mortality. Infectious disease was the probable cause of death in 25% of cases (n = 43), with severe parasitism being implicated in 32 of these cases. Live stranding of animals in relatively good health and nutritional status accounted for 10% (n = 17) of cases, where the only significant pathological changes found were lesions that could be attributed to the stranding event itself. Non-bycatch related trauma (n = 14) and starvation (n = 13) represented 8 and 7% of cases, respectively. Other causes of death included gastric impaction (n = 5), peritonitis (n = 3), intestinal impaction (n = 2), non-bycatch related asphyxia (n = 2) and gas embolism (n = 2). In 5 cases, the cause of death could not be established. Necropsies of common dolphins carried out in Cornwall make a substantial contribution to our knowledge of the threats faced by this species in UK waters and the wider region. This includes the continued impact of fisheries-related mortality, with Cornwall being the hotspot for bycatch of this species in the UK.
White spot syndrome virus (WSSV) causes catastrophic losses in shrimp aquaculture, yet no antiviral interventions are available once infection has begun. In this study, we evaluated the stage-dependent efficacy of RNA interference (RNAi) by administering long double-stranded RNA (dsRNA) targeting the WSSV ribonucleotide reductase 2 (rr2) gene at defined time points following viral challenge in Penaeus vannamei. Delivery of dsRNA during the peri-infection period (0-12 h post-infection, hpi) resulted in near-complete protection, consistent with interference prior to extensive viral establishment. Importantly, administration during the early post-infection phase (24-48 hpi) significantly reduced mortality and viral loads, demonstrating that RNAi retains therapeutic relevance after viral replication has begun. In contrast, treatment during the late post-infection phase (72 hpi) provided only limited protection, indicating a sharp decline in efficacy once high viral burdens were established. Increasing dsRNA dosage enhanced viral suppression but did not proportionally improve survival, whereas higher viral challenge doses delayed rr2 transcript suppression and reduced therapeutic outcomes. Together, these results define a biologically constrained early post-infection therapeutic window for RNAi-based intervention against WSSV, determined by both infection stage and viral burden at the time of treatment. Although injection-based delivery limits immediate field application, this study provides a realistic framework for developing post-exposure RNAi strategies for disease management in shrimp aquaculture.
Plants possess an impressive range of chemical traits to defend themselves against pathogens. Describing and interpreting these traits can provide insights into plant resistance to infection and disease progression. To examine one potentially responsive chemical trait, we measured polyphenolic content of green and lesioned tissue from Labyrinthula-infected eelgrass shoots growing in both the field and a long-term common garden. Infection of eelgrass Zostera marina with wasting disease (Labyrinthula zosterae) leads to the formation of necrotic lesions on host tissue and is known to alter host photobiology and secondary metabolite production. It is common to quantify total polyphenolics as a potential measure of eelgrass defense against infection, yet there is no clear evidence that polyphenolics are a reliable indicator of host response or immunity. We found that polyphenolic concentrations in lesion tissue fell predictably as lesion cover increased, while polyphenolic concentrations in green tissue were more variable and increased only across large ranges of lesion cover. We hypothesize that while polyphenolic induction may be a part of the host plant response to L. zosterae infection, total polyphenolic concentrations in both green and lesioned tissue may also be influenced by genetic variability and localized metabolic processes. Further research is necessary to assess a causative relationship between plant defenses and disease severity in this system and may benefit from looking beyond phenolics.
Red abalone Haliotis rufescens is a gastropod species that has historically been used for purposes including food, currency, and curio trade. Research into gastropod diseases often focuses on their potential as intermediate hosts of bacteria, viruses, or parasites due to their consumption by humans; neoplasms are rarely reported. The red abalone presented in the present case had multiple masses that were diagnosed histologically as mesenchymal neoplasms composed of spindle cells within lacunae embedded in abundant basophilic matrix resembling the cartilage of vertebrates. Some histochemical staining properties of the matrix were also similar to the chondroid matrix of vertebrate cartilage. In abalones, the sole cartilaginous or ‘cartilage-like’ structure is the odontophore, a mass of tissue that surrounds the radula, a structure used to prehend food. This paper categorizes the histochemical staining characteristics of the abalone odontophore and compares it to the neoplasm in this animal. The similarities in morphology and histochemical staining between the neoplasm and the odontophore, and the lack of other cartilaginous structures in this species, support that this tumor arose from the odontophore, consistent with a diagnosis of an odontophoroma. The odontophore is an anatomic structure unique to the phylum Mollusca, and this mesenchymal neoplasm has not been previously reported in any species within this phylum.
This study investigated the immunomodulatory effects of dietary pineapple peel powder (PPP) supplementation in Labeo rohita fingerlings (15.2 ± 0.3 g) through a 60 d feeding trial followed by a 15 d Aeromonas veronii infection challenge. Processing 1 kg of pineapple fruit generates approximately 30-35% waste, primarily peels, containing bioactive compounds including bromelain enzyme. Using a completely randomized design, 300 fingerlings were distributed into 5 treatment groups in triplicate: Control (0%), T1 (2%), T2 (4%), T3 (6%), and T4 (8%) PPP supplementation. Immunological, haematological, biochemical, and antioxidant parameters were assessed at 0, 15, 30, and 60 d, with bacterial challenge conducted on Day 61 and post-infection (PI) sampling at 7 and 15 d PI. Fish fed 6% PPP (T3) exhibited significantly enhanced immunological parameters, with serum lysozyme activity reaching 185.6 ± 8.4 unit ml-1 compared to 112.3 ± 5.7 unit ml-1 in control. Significant improvements occurred in haematological indices (red blood cells, white blood cells, hemoglobin, hematocrit), serum proteins (total protein, albumin, globulin), and antioxidant enzyme activities (superoxide dismutase, catalase, glutathione peroxidase). Following A. veronii challenge (1×107 CFU ml-1; 0.1 ml fish-1), T3 demonstrated the highest survival rate (82.5 ± 3.4%) compared to control (45.6 ± 2.7%). Growth performance also improved significantly, with specific growth rate (2.84 ± 0.12% vs. 2.15 ± 0.09% d-1) and feed conversion ratio (1.42 ± 0.06 vs. 1.85 ± 0.08) both enhanced in T3 compared to control. These results demonstrate that 6% PPP supplementation optimally enhances immunophysiological parameters, disease resistance, and growth performance in L. rohita, highlighting its potential as a natural immunostimulant in sustainable aquaculture health management.
Chelonid alphaherpesvirus 5 (ChHV5) is the putative pathogen of fibropapillomatosis, a tumor-forming sea turtle disease. Quantitative polymerase chain reaction (qPCR) techniques are commonly applied to evaluate the presence and quantity of ChHV5 in blood and tissue samples. However, samples can have little or no virus present despite coming from infected individuals. In addition, sample age and storage may further impact ChHV5 detection. This creates uncertainty in the interpretation of ChHV5 qPCR results for archived (>1 yr old) blood and skin because a negative sample does not imply an individual was free of ChHV5 infection, but rather that the sample itself was free of viable ChHV5 DNA. To assess the ability of qPCR to detect ChHV5 infections from archived samples, we tested blood, skin, and tumor samples collected from juvenile green turtles Chelonia mydas captured in the Indian River Lagoon, Florida, USA, between 1995 and 2018. Sample ages ranged from 1 to 24 yr old at the time of molecular analyses. We found very low overall prevalence of ChHV5 in blood (1.4% positive, n = 513) and skin (6.5% positive, n = 123) samples, and high prevalence in tumor samples (89.7% positive, n = 39). These results suggest that qPCR of archived blood and/or skin samples provides little inference on individual-level infection status.
Blood analyte data are limited for California sea lion Zalophus californianus pups despite frequent admission to rehabilitation facilities. The objectives of this study were to establish blood analyte reference intervals for rehabilitated California sea lion pups (n = 58) deemed clinically normal for release and for free-ranging California sea lion pups (n = 37) during routine health assessment on San Miguel Island, California, USA; to compare manual white blood cell (WBC) differentials to an in-house hematology analyzer (ProCyte Dx); and to evaluate paired blood analyte data of pups affected by malnutrition at time of intake compared to release and in comparison to free-ranging conspecifics. From 2020 to 2022, all stranded pups were thin or emaciated with various additional health concerns at admission (e.g. pneumonia, abscesses, ocular injuries). Average time in rehabilitation was 101 ± 27 d. Reference intervals were established for successfully rehabilitated and free-ranging pups. WBC differential counts evaluated by the analyzer compared to manual blood film review were inconsistent. Blood analytes of pups differed between intake and release, and with free-ranging conspecifics. These findings provide evidence for systemic inflammation, nutritional imbalances, and metabolic derangements in stranded malnourished pups and elucidate physiological changes undergone by growing pups during rehabilitation, particularly as they differ from free-ranging conspecifics. Moreover, the results herein underscore the importance of blood film review for obtaining accurate data for the establishment of reference intervals. These data aim to support clinical assessments of sea lion pups at intake and at release in context of other clinically relevant release criteria.
An unusual mortality event (UME) was declared from December 2020 to April 2022 after increased deaths of emaciated Florida (FL) manatees Trichechus manatus latirostris occurred in the Indian River Lagoon (FL, USA) following seagrass reduction. While thyroid hormones are known to fluctuate with fasting, stress, and disease in pinnipeds and cetaceans, investigations in sirenians are limited. Serum from clinically normal free-ranging FL manatees (n = 35) and individuals affected by the UME (n = 20) was analyzed via radioimmunoassay and chemiluminescent immunoassays for total triiodothyronine (TT3), total thyroxine (TT4), and free thyroxine (fT4) quantification after assay validation. Total iodine (TI) and inorganic iodine (INORG-I) were measured using inductively coupled plasma mass spectrometry; organic iodine (ORG-I) was calculated from these values. Reference intervals for TT3 and TT4 were generated for clinically normal manatees. There were no differences in TT3, TT4, TI, or INORG-I between groups. Body condition index weight difference expressed as a percentage of the population mean (BCI%) and fT4 were significantly lower in UME manatees, most consistent with chronic starvation. However, BCI% and fT4 were not significantly different between UME manatees who survived rehabilitation versus those who died, suggesting these are unreliable prognostic markers. Serum ORG-I was significantly higher in UME manatees. High thyroid tissue iodine in necropsied UME manatees (n = 6), associated with follicular cysts in a subset (n = 3), suggests a potential impact on thyroid gland metabolism. These data expand the current understanding of pathophysiological aspects of the UME due to chronic malnutrition and may help guide supportive care for FL manatees undergoing rehabilitation.
Ulcerative granulomatous disease in farmed snubnose pompano Trachinotus blochii (Lacepede, 1801) in the Philippines was documented in 2019 by the Bureau of Fisheries and Aquatic Resources and has since become an annual problem for fish farmers, with outbreaks occurring between September and October. Three apparently healthy adults and 5 diseased adults displaying ulcerated skin were subjected to diagnosis. During postmortem examination, multiple nodules were present in all kidneys and the spleen in the 5 diseased fish. Histopathology revealed severe granulomatous formations at different stages. Bacterial pathogens were isolated from diseased fish using modified Lowenstein-Jensen medium, producing wrinkled, cream-colored colonies. Staining revealed Gram-positive, acid-fast, branching, beaded, long rod filamentous bacteria. Identification at the species level and taxonomic positioning of the isolate was achieved through a specific Nocardia seriolae PCR and by sequencing the 16S rRNA gene using pure cultures and tissue sample DNA. PCR amplification of 13 virulence genes resulted in the detection of mce, mce1A, gapA, fbpA, nirD, nirB, narI, narJ, narH, and katG, which are important in N. seriolae invasion, infection, and intracellular survival in macrophages. Two tetracycline resistance genes, namely tetB and tetC, were also found, which might contribute to oxytetracycline resistance, rendering the farm's prophylactic strategy of using oxytetracycline ineffective. To our knowledge, this is the first confirmed report of nocardiosis in farmed snubnose pompano in the Philippines.
Proteus mirabilis is a Gram-negative opportunistic pathogen increasingly reported in aquatic animals; however, its pathogenic potential and genomic features in ornamental fish remain unclear. This study isolated 3 strains (WSY-112, WSY-113, and WSY-114) from diseased Asian arowana Scleropages formosus displaying hemorrhagic and ulcerative lesions. All 3 isolates were identified as P. mirabilis through physiological and biochemical characterization as well as 16S rRNA and gyrB sequencing. Strain WSY-114 was selected for further analyses, including whole-genome sequencing, antimicrobial susceptibility testing, and experimental infection. Genomic annotation identified multiple virulence-related genes for flagellar assembly, adhesion, toxin production, iron acquisition, and type III/IV/VI secretion systems. Experimental infection in zebrafish Danio rerio showed dose-dependent mortality (LD50 = 6.6 × 104 CFU g-1) and clinical signs mirroring natural infections in the arowana. The strain exhibited resistance to multiple tested antibiotics, including tetracyclines (tetracycline, minocycline, and doxycycline), macrolides (erythromycin and azithromycin), and ampicillin, consistent with antibiotic-resistance genes detected in its genome. These results indicate that P. mirabilis exhibits pathogenic potential under experimental conditions and may represent a potential risk factor in ornamental fish.
The parasitic dinoflagellate Hematodinium perezi is known to harm and kill marine crustaceans worldwide. It is unclear, however, how the phenology of host infections differs from that of in-water life stages of H. perezi, and how these cycles may vary regionally. Across the US East Coast, including in South Carolina (SC), H. perezi is a parasite of the economically important Atlantic blue crab Callinectes sapidus. The aim of this study was to determine and compare the seasonal presence of H. perezi in C. sapidus and benthic water of the Charleston Harbor estuary, SC, USA, using real-time PCR (RT-PCR). Hemolymph of 322 blue crabs was sampled over 21 mo beginning in September 2022, with concurrent benthic water eDNA sampling beginning in April 2023. DNA from H. perezi was detected in a total of 11 blue crab samples collected in the spring, fall, and winter of 2023. Positive environmental detections of DNA occurred every sampling season, including when H. perezi was reported absent in C. sapidus. Although other unknown factors likely contributed to the observed prevalence, our results suggest a seasonal pattern of the presence of H. perezi in the estuary largely driven by both water temperature and salinity. Altogether, our findings provide foundational information on the phenology of this parasite, critical for understanding disease dynamics in blue crabs in the southeast USA.
Flatworms are widespread in the marine realm, but only a few species parasitize corals. Several of these are considered pests in the aquarium trade, and the invasive potential of these species is a concern. In the Caribbean there are no records to date of flatworms naturally occurring in coral nurseries and/or parasitizing corals in the wild. Here we report, for the first time, a flatworm identified as Convolutriloba longifissura affecting a Caribbean coral and include a phylogenetic and histological analyses. Flatworms were collected from nursery corals and artificial recruitment units (bioballs) suspended in the water column at Punta Cana reef. Sequencing and morphology of individuals from both indicate that C. longifissura is present in the wild as well as the nursery. Experiments were conducted to investigate the effect of flatworm exposure on signs of macroscopic stress (i.e. mucus production, paleness, bleaching, and tissue loss) on microfragments of Pseudodiploria clivosa. Standard histopathological techniques were applied to describe microscopic alterations of the coral exposed to C. longifissura. We found corals exposed to 30 individuals of C. longifissura had a 2.5-fold increased probability of developing macroscopic stress signs compared to controls after 14 d of exposure to different flatworm densities. While the actual impacts of these flatworms on coral restoration and microfragmentation programs or wild corals in the Caribbean remain to be determined, our results indicate that flatworms are no longer an exclusive problem of Indo-Pacific corals.
White spot syndrome virus (WSSV) causes severe economic losses globally. Although RNA interference (RNAi) is a key antiviral defense in crustaceans, the co-existence of WSSV mRNA and siRNA observed in Fenneropenaeus chinensis during acute infection suggests dysfunction of the RNA-induced silencing complex. This led us to investigate whether WSSV encodes viral suppressors of RNAi (VSRs) to counteract host RNAi pathways at this stage. Through an integrated computational and experimental approach, we identified a hypothetical protein of WSSV, GP017 (YP_009220491.1), as a potential VSR. Computational docking revealed a potential interaction between GP017 and shrimp Argonaute 2 (AGO2), a core RNAi component. A mammalian cell-based reversal-of-silencing assay demonstrated that GP017 restored GFP expression by suppressing RNAi-mediated silencing in HEK293T cells, with an efficacy comparable to that of the well-characterized VSR P19. Furthermore, yeast 2-hybrid and bimolecular fluorescence complementation assays confirmed an interaction between GP017 and shrimp AGO2, supporting its role as a VSR. Bioinformatic analyses suggest a coordinated regulatory model for gp017, in which viral proteins WSV500 and WSV083 may interact with high-potential promoter regions. These findings provide the initial evidence of a WSSV-encoded VSR, offering insights into viral immune evasion and potential targets for antiviral strategies in shrimp aquaculture.
Infectious diseases, particularly those caused by members of the genus Ranavirus (Iridoviridae), have caused mass mortality events in amphibian populations worldwide. Frog virus 3 (FV3) infects a wide range of amphibian hosts and results in high mortality. Despite the global prevalence of FV3, its origin and routes of spread remain unclear, largely because of limited genetic data from limited geographic regions. This study aimed to classify the ranaviruses isolated in the Republic of Korea through whole-genome sequencing. We collected amphibian carcasses and both symptomatic and asymptomatic live amphibians. The asymptomatic amphibians were collected from locations with previous infections. Among the 278 amphibian samples collected from 24 locations, 44 were positive for ranavirus according to quantitative PCR (qPCR) analysis. We obtained whole-genome sequences from 5 isolates, all of which were identified as FV3-like ranaviruses and belonged to the Asian FV3 clade in the maximum likelihood phylogenetic tree. By comparative analysis of open reading frames (ORFs) and phylogenomic trees, the Korean isolates were further divided into 2 strains: FV3-Kor_MT (mountain lineage) and FV3-Kor_LL (lowland lineage). Our findings highlight the importance of surveillance of a wide range of amphibian species and facilitate phylogenetic analyses of global FV3-like strains, including newly verified Korean strains.
The relationship between the anisakid nematode Anisakis simplex and red vent syndrome (RVS) was investigated through parasitological, clinical and pathological examinations of 124 wild adult Atlantic salmon Salmo salar, sampled from the River Dee, Wales, River Tyne, England, and River Tyne estuary between 2009 to 2013. All S. salar were infected with A. simplex, but those exhibiting RVS lesions displayed significantly higher infection intensities of A. simplex than unaffected individuals. S. salar exhibiting RVS lesions also displayed significantly higher infection intensities of A. simplex in the discrete location of the vent than unaffected fish. Up to 95% of total A. simplex infection intensities were found within the vent, with up to 83.6% localised within the outer ~5-10 mm of vent tissue. This suggests that the vent is a discrete and potentially favoured site of A. simplex. Intensity of infection of A. simplex in the vent did not always correlate with vent pathology. Moreover, internal inflammation and marked fibrogranulomatous changes were observed in the absence of associated haemorrhage, suggesting that visual reddening of the vent may not always occur in spite of significant A. simplex infections. Whilst fish exhibiting clinical RVS displayed significantly higher vent infection intensities, no correlation was identified between the severity of symptoms and A. simplex intensity.
