Diseases of aquatic organisms最新文献

Infections by Erysipelothrix rhusiopathiae occur in domestic animals and cause the disease known as 'erysipelas'. The ubiquity of Erysipelothrix spp. makes infection possible in a wide range of vertebrates and invertebrates. Cetaceans are highly susceptible to erysipelas, especially those under human care. The number of cases documented in wild cetaceans is low, the pathogenesis is incompletely understood, and the full spectrum of lesions is not well defined. The possible serotypes and species of the genus that can cause disease are unknown. In October 2022, a common bottlenose dolphin Tursiops truncatus stranded in Vilassar de Mar (Catalonia) showing skin lesions consistent with 'diamond skin disease', a characteristic lesion of erysipelas shared by swine and cetaceans. Necropsy was performed following standardized procedures, and multiple samples were taken for histopathology and bacteriology. Erysipelothrix sp. grew in pure culture in many tissue samples. Genetic characterization by multi-locus sequence analysis identified the species as E. rhusiopathiae. Histologically, the main lesions were an intense suppurative vasculitis of leptomeningeal arteries and veins with abundant intramural Gram-positive bacilli and meningeal hemorrhages. Meningeal lesions were considered the cause of death. The affected skin showed moderate suppurative dermatitis. Herein we document a case of erysipelas in a Mediterranean common bottlenose dolphin with unusual lesions in the leptomeningeal vessels and marked skin tropism. To our knowledge, this is the first case of severe brain involvement in erysipelas in a cetacean. We also provide a review of available cases in wild cetaceans, to highlight the characteristics of the disease and improve future diagnosis.

Wolffish are regularly housed in aquaria, but little data on their husbandry and health is available for caretakers. High occurrence rates of nephrocalcinosis and urolithiasis have been observed in Atlantic Anarhichas lupus and spotted A. minor wolffish housed at 2 Canadian zoological institutions. To explore the effect of diet on nephrocalcinosis and urolithiasis development, a 16 mo prospective study was conducted. A total of 32 juvenile spotted wolffish were randomly assigned to one of 4 experimental groups fed exclusively with the following diet: (1) Skretting® Europa 18 pellets; (2) Mazuri® LS Aquatic Carni-Blend Diet Formula; (3) vitamin-supplemented fish-based diet, and (4) vitamin-supplemented invertebrate-based diet. Urinalysis, radiographs, and complete necropsies were performed at the end of the study. None of the wolffish developed uroliths during the study period. All specimens fed with the fish-based and invertebrate-based diets developed nephrocalcinosis, whereas this condition was seen in 12.5 and 0% of the fish in the Skretting® and Mazuri® groups, respectively. Affected wolffish often presented with oxalate crystalluria and increased radiodensity of the posterior kidneys. Urinalysis and radiographic study were considered useful in the antemortem diagnosis of nephrocalcinosis. None of the previously published risk factors for the development of nephrocalcinosis in fish were supported by the results of this study. However, nutritional analyses of the 4 diets suggest that high dietary levels of gelatin or vitamin C or low levels of vitamin E could be potential risk factors for the development of nephrocalcinosis in spotted wolffish and thus warrant further study.

Odontocetes are difficult to study in the wild, making tagging and remote tracking a valuable practice. However, evaluations of host responses at tagging sites have been primarily limited to visual observations in the field. Here we explore the macro- and microscopic pathology of dorsal fin tag attachments in 13 stranded and released short-beaked common dolphins Delphinus delphis from Cape Cod, MA that later re-stranded and died or were euthanized 1-28 d post-tagging. Tags were attached to stranded dolphins' dorsal fins using 2 methods: core biopsy or piercing. Grossly, the piercing method resulted in epidermal compression into the dermis. One tag site had a necrotic border 28 d after application. Grossly, the biopsy method resulted in minimal to no tissue reaction. Two tag sites had granulation tissue accumulation 4 and 12 d after tagging. Histopathologic findings for all tag types and animals consisted of focal epithelial loss, dermal edema, perivascular edema, inflammation and hyperplasia, and inter- and extracellular edema in the adjacent epidermis. Minor expected pathological changes given the procedure were also observed: superficial epidermal necrosis in 3 cases, and superficial bacterial colonization in 2 cases. There was no evidence of sepsis and tagging was not related to cause of re-stranding or death in any case. These gross and histopathologic findings support previous observational conclusions in small delphinids that with appropriate sterile technique, the impacts of single pin dorsal fin tagging on the animal can be minimal and localized. Of the 2 methods, core biopsy may be a better tagging method.

Lymphomas are malignant neoplasms of the hematopoietic system arising from lymphocytes with highly variable biologic behavior. B-cell small lymphocytic lymphoma (B-SLL) is a non-Hodgkin lymphoma infrequently described in domestic and wild animals. The present study describes a case of B-SLL in a free-ranging adult male Arctocephalus australis in Brazil. The main necropsy findings included poor body condition, generalized lymphadenomegaly, severe and diffuse splenomegaly, and multiple, white to yellow nodules in the kidneys and small intestine. Histologically, these organs were partially or totally effaced by neoplastic small lymphocytes arranged in sheets, with moderate anisocytosis and anisokaryosis and a low mitotic count. These cells diffusely immunolabeled for CD79α and CD20, and were negative for CD3. A diagnosis of multicentric B-SLL was established and to the authors' knowledge, it has not been previously described in this genus.

A huge, unprecedented mortality of cockle Cerastoderma edule caused by the protist Marteilia cochillia, which had never before been detected in Galicia (NW Spain), brought on a cockle fishery collapse in the Ría de Arousa (Galicia) in 2012. Since then, the disease dynamic pattern in the shellfish bed of Lombos do Ulla (at the inner area of that ria) involved an overwhelming annual wave of infections and subsequent cockle mass mortality that caused the near extinction of every cohort recruited to that bed. However, a pattern shift was detected among wild cohorts recruiting since 2016, with progressive declines of marteiliosis prevalence and increments in cockle survival. This suggested 2 non-exclusive hypotheses: increasing marteiliosis resistance through natural selection, and reduced abundance and/or virulence of the parasite. A field experiment was performed to assess these hypotheses by comparing marteiliosis prevalence and severity, as well as mortality, in cockles that naturally recruited to this bed in 2017 and 2018 with those of naïve cockles collected from a marteiliosis-free area and transplanted into Lombos do Ulla in 2017 and 2018. Marteiliosis prevalence and cumulative cockle mortality quickly reached very high values among the transplanted cockles, demonstrating that the parasite remained present and virulent in the area. Conversely, marteiliosis prevalence and cockle mortality were much lower in the cockles that recruited to Lombos do Ulla, suggesting increased resistance that may have been driven by natural selection. The young age at which cockles start reproduction and the very high mortality caused by marteiliosis may have enhanced natural selection.

Gastritis and gastric ulcers are well-recognized conditions in cetaceans; bacteria of the genus Helicobacter are considered the primary cause of these diseases. Dolphins have been shown to be susceptible to infection by at least 2 gastric species of Helicobacter, H. cetorum and H. delphinicola, both of which are closely related to the human pathogen H. pylori. In the present study, we evaluated the carriage rate and relationship to gastric disease of H. cetorum and H. delphinicola, based on a study population of 82 dolphins maintained at 21 facilities in Japan. Of these 82 dolphins, 79 (96.3%) and 45 (54.9%) were positive for H. cetorum and H. delphinicola, respectively; H. delphinicola infection was significantly associated with chronic gastric diseases (odds rate: 5.9; 95% CI: 2.1-16.9), but no such association was detected for H. cetorum. Of the 21 facilities, 20 (95%) and 11 (55%) housed H. cetorum- and H. delphinicola-positive dolphins, respectively, and our study suggested that the transmission between dolphins occurs quickly within pools. These findings indicate that methods will need to be established to prevent the transmission of Helicobacter infections within facilities housing dolphins.

Perkinsus olseni (Perkinsidae) is a molluscan parasite notifiable to the World Organisation for Animal Health that is reported in several shellfish hosts in New Zealand, including the native green-lipped mussel Perna canaliculus. Green-lipped mussels comprise over half of New Zealand's aquaculture export value and have historically been considered free of serious diseases based on extensive histology-based surveillance. The discovery of P. olseni in green-lipped mussels has raised questions about future disease threats to green-lipped mussels, particularly under changing ocean climatic conditions. Using mussels collected from farmed (n = 358) and wild (n = 236) populations, we aimed to determine the distribution and prevalence of P. olseni in green-lipped mussels around New Zealand, and assess the performance of diagnostic tests, including real-time PCR, conventional PCR, and culture using Ray's fluid thioglycolate medium (RFTM). Prevalence and diagnostic test performance was evaluated using Bayesian latent class analysis with informative priors. The prevalence of P. olseni was 0-3%, except for 1 wild population from a harbour where prevalence was 22%. Real-time PCR had the highest diagnostic sensitivity (87%) compared to 62 and 21% for conventional PCR and RFTM, respectively. Diagnostic specificity was similar among all methods (96-98%). No mortality was observed during the study. Our results suggest that real-time PCR is the diagnostic test best suited for surveillance of P. olseni in subclinically infected green-lipped mussels under New Zealand conditions.

The pathogenic fungus Batrachochytrium dendrobatidis (Bd) is associated with drastic global amphibian declines. Prophylactic exposure to killed zoospores and the soluble chemicals they produce (Bd metabolites) can induce acquired resistance to Bd in adult Cuban treefrogs Osteopilus septentrionalis. Here, we exposed metamorphic frogs of a second species, the Pacific chorus frog Pseudacris regilla, to one of 2 prophylactic treatments prior to live Bd exposures: killed Bd zoospores with metabolites, killed zoospores alone, or a water control. Prior exposure to killed Bd zoospores with metabolites reduced Bd infection intensity in metamorphic Pacific chorus frogs by 60.4% compared to control frogs. Interestingly, Bd intensity in metamorphs previously exposed to killed zoospores alone did not differ in magnitude relative to the control metamorphs, nor to those treated with killed zoospores plus metabolites. Previous work indicated that Bd metabolites alone can induce acquired resistance in tadpoles, and so these findings together indicate that it is possible that the soluble Bd metabolites may contain immunomodulatory components that drive this resistance phenotype. Our results expand the generality of this prophylaxis work by identifying a second amphibian species (Pacific chorus frog) and an additional amphibian life stage (metamorphic frog) that can acquire resistance to Bd after metabolite exposure. This work increases hopes that a Bd-metabolite prophylaxis might be widely effective across amphibian species and life stages.

The emerging fungal pathogen Batrachochytrium dendrobatidis (Bd) threatens hundreds of amphibian species globally. During laboratory-based experiments it is often essential to quantify live Bd cells, but a comparison of the effectiveness of methods for counting and assessing the viability of the infectious zoospore life stage has not been done. A direct comparison of staining methods that assess viability will ensure that the most accurate and efficient method is used. Here, we compared the use of 2 relatively cheap common stains, trypan blue and methylene blue, and assessed their accuracy and precision for estimating the viability of Bd zoospores during both manual counting and colorimetric assays. We stained known proportions of killed Bd zoospores (0, 0.25, 0.50, 0.75, and 1.00) with each stain and estimated the proportion of stained (dead) and unstained (viable) cells in each sample using both manual counting and colorimetric assays. Trypan blue was found to be a much more effective stain than methylene blue for both microscopy and colorimetric assays. Additionally, counting zoospores via microscopy was both a more accurate and precise technique. We recommend using manual counts via microscopy using the trypan blue stain for assessing Bd zoospore viability.