Diseases of aquatic organisms最新文献

Achlya bisexualis is a notorious oomycete pathogen with the potential to cause emerging disease in fish farms. In this study, we report the first isolation of A. bisexualis from captive-reared golden mahseer Tor putitora, an Endangered fish species. The infected fish showed a cotton-like growth of mycelia at the site of infection. The mycelium when cultured on potato dextrose agar produced radially growing white hyphae. The hyphae were non-septate, and some of them carried matured zoosporangium with dense granular cytoplasmic contents. Spherical gemmae with stout stalks were also observed. All the isolates had 100% identity in internal transcribed spacer (ITS)-rDNA sequence and showed highest similarity to that of A. bisexualis. In molecular phylogeny, all the isolates formed a monophyletic group with A. bisexualis which was supported by a bootstrap value of 99%. Based on the molecular and morphological findings, all the isolates were confirmed as A. bisexualis. Further, the anti-oomycete effect of boric acid, a known antifungal agent, against the isolate was evaluated. The minimum inhibitory concentration and minimum fungicidal concentration were found to be 1.25 and >2.5 g l-1, respectively. Isolation of A. bisexualis from a new fish species indicates its possible occurrence in other unreported hosts. Considering its wide infectivity and the potential to cause disease in farmed fishes, its probable prevalence in a new environment and host needs to be closely monitored to prevent the spread of infection, if any, by adopting suitable control measures.

Two populations of the invasive slipper limpet Crepidula fornicata were sampled in Swansea Bay and Milford Haven, Wales, UK, to determine the presence of putative pathogens and parasites known to affect co-located commercially important shellfish (e.g. oysters). A multi-resource screen, including molecular and histological diagnoses, was used to assess 1800 individuals over 12 mo for microparasites, notably haplosporidians, microsporidians and paramyxids. Although initial PCR-based methods suggested the presence of these microparasites, there was no evidence of infection when assessed histologically, or when all PCR amplicons (n = 294) were sequenced. Whole tissue histology of 305 individuals revealed turbellarians in the lumen of the alimentary canal, in addition to unusual cells of unknown origin in the epithelial lining. In total, 6% of C. fornicata screened histologically harboured turbellarians, and approximately 33% contained the abnormal cells-so named due to their altered cytoplasm and condensed chromatin. A small number of limpets (~1%) also had pathologies in the digestive gland including tubule necrosis, haemocytic infiltration and sloughed cells in the tubule lumen. Overall, these data suggest that C. fornicata are not susceptible to substantive infections by microparasites outside of their native range, which may contribute in part to their invasion success.

Managed care of cephalopods can be complicated by numerous factors including infectious and non-infectious disease, environmental stressors, and anatomic and physiological changes associated with senescence. The current report describes a unique case of nephrolithiasis in a senescent, >2 yr old female Pacific octopus Enteroctopus dofleini housed in a public aquarium. Clinical signs included generalized external pallor, inappetence progressing to anorexia, lethargy, and a slow healing mantle abrasion over a period of a year. Due to the animal's declining condition, humane euthanasia was elected. At necropsy, multiple, small, approximately 1-5 mm diameter crystalline deposits were reported throughout all sections of the renal appendages. Histopathology identified a large crystal expanding and rupturing a focal tubule, causing necrosis, ulceration, and hemocytic infiltration. Crystalline stone analysis revealed that the nephrolith was composed of 100% ammonium acid urate. Additional changes to the digestive gland included marked atrophy with fibrosis correlated to the animal's history of hyporexia/anorexia secondary to senescence. To our knowledge, this is the first report of nephrolithiasis in E. dofleini.

Ranaviruses can cause mass mortality events in amphibians, thereby becoming a threat to populations that are already facing dramatic declines. Ranaviruses affect all life stages and persist in multiple amphibian hosts. The detrimental effects of ranavirus infections to amphibian populations have already been observed in the UK and in North America. In Central and South America, the virus has been reported in several countries, but the presence of the genus Ranavirus (Rv) in Colombia is unknown. To help fill this knowledge gap, we surveyed for Rv in 60 species of frogs (including one invasive species) in Colombia. We also tested for co-infection with Batrachochytrium dendrobatidis (Bd) in a subset of individuals. For Rv, we sampled 274 vouchered liver tissue samples collected between 2014 and 2019 from 41 localities covering lowlands to mountaintop páramo habitat across the country. Using quantitative polymerase chain reaction (qPCR) and end-point PCR, we detected Rv in 14 individuals from 8 localities, representing 6 species, including 5 native frogs of the genera Osornophryne, Pristimantis and Leptodactylus, and the invasive American bullfrog Rana catesbeiana. Bd was detected in 7 of 140 individuals, with 1 co-infection of Rv and Bd in an R. catesbeiana specimen collected in 2018. This constitutes the first report of ranavirus in Colombia and should set off alarms about this new emerging threat to amphibian populations in the country. Our findings provide some preliminary clues about how and when Rv may have spread and contribute to understanding how the pathogen is distributed globally.

The thick-shelled river mussel Unio crassus Philipsson, 1788 is a species native to many European habitats, with declining populations. The impact of parasite communities on health status of this species is poorly understood. In this study, parasites of 30 U. crassus specimens from the Our and Sauer Rivers in Luxembourg were identified morphologically and, in some cases, using molecular genetic methods. The findings were correlated to selected parameters (total length, visceral weight, shell lesions, gonadal stage). The 2 populations did not differ in shell length, visceral weight, number of males and females, gonadal scoring, shell lesions, and the occurrence of glochidia. The prevalence and infestation intensities of detected Trichodina sp., Conchophthirus sp., and freshwater mite larvae did not differ between the 2 populations, whereas the prevalence and infestation intensities of mite eggs, nymphs, and adults were significantly higher in the Sauer River. Rhipidocotyle campanula and European bitterling Rhodeus amarus larvae were only present in the Sauer. Histopathology revealed the destruction of the gonads by R. campanula and tissue damage by the mites. The only significant correlation of the selected parameters was a positive correlation between R. amarus occurrence and total length as well as a negative correlation between R. amarus occurrence and gonadal stage. In the Sauer River, 2 mussels were found to be hermaphrodites.

As grazers, sea urchins are keystone species in tropical marine ecosystems, and their loss can have important ecological ramifications. Die-offs of urchins are frequently described, but their causes are often unclear, in part because systematic examinations of animal tissues at gross and microscopic level are not done. In some areas, urchins are being employed to control invasive marine algae. Here, we describe the pathology of a mortality event in Tripneustes gratilla in Hawai`i where urchins were translocated to control invasive algae. Although we did not determine the cause of the mortality event, our investigation indicates that animals died from inflammation of the test and epidermal ulceration, followed by inability to maintain coelomic fluid volume, colonization of coelomic fluid by opportunists (diatom, algae), and inappetence. Parasites, bacteria, fungi, and viruses were not evident as a primary cause of death. Pathology was suggestive of a toxin or other environmental cause such as lack of food, possibilities that could be pursued in future investigations. These findings highlight the need for caution and additional tools to better assess health when translocating marine invertebrates to ensure maximal biosecurity.

Eastern hellbenders Cryptobranchus alleganiensis alleganiensis, large aquatic salamanders, are declining over most of their range. The amphibian-killing fungus Batrachochytrium dendrobatidis (Bd) has contributed to global amphibian declines and has been detected on eastern hellbenders, but infection intensities were lower than those of species that are more susceptible to Bd. The factors limiting Bd on hellbenders may include antifungal metabolites produced by their skin microbiota. We used a metabolite fingerprinting technique to noninvasively identify the presence, but not identity, of metabolites associated with eastern hellbenders. We surveyed the skin of wild eastern hellbenders to test whether the composition and richness (i.e. number of metabolites) of their metabolites are explained by Bd status or location. Furthermore, we surveyed for metabolites on captive eastern hellbenders to test whether metabolite compositions were different between captive and wild eastern hellbenders. Bd detection was not associated with either metabolite richness or composition. Both metabolite composition and richness differed significantly on hellbenders from different locations (i.e. states). For metabolite composition, there was a statistical interaction between location and Bd status. Metabolite richness was greater on captive eastern hellbenders compared to wild hellbenders, and metabolite compositions differed between wild and captive eastern hellbenders. The methods we employed to detect metabolite profiles effectively grouped individuals by location even though metabolite composition and richness have high levels of intraspecific variation. Understanding the drivers and functional consequences of assemblages of skin metabolites on amphibian health will be an important step toward understanding the mechanisms that result in disease vulnerability.

Coral disease is a major cause of coral reef degradation, yet many diseases remain understudied. Yellow-banded tissue loss disease (YBTLD) has a distinct gross lesion morphology and to date has only been reported from the Arabian/Persian Gulf; little else is known about the ecology of the disease. We report on the first occurrence of YBTLD outside of the Arabian/Persian Gulf at 2 sites (Laku Point, Narara Reef) within the Gulf of Kachchh (GoK) located on the northwest coast of India. At Narara Reef, YBTLD was observed at 12 out of 24 transects with an average prevalence of 4.7 ± 1.3%. At Laku Point, YBTLD was observed at 19 out of 24 transects with an average prevalence of 5.4 ± 1%. Four out of 15 coral genera within transects had signs of YBTLD and included Goniopora, Dipsastraea, Lobophyllia, and Turbinaria. Lobophyllia and Turbinaria had the highest susceptibility to the disease, with prevalence significantly higher than expected based on their abundance on the reefs. The distribution and prevalence of YBTLD in the GoK was higher than in coral reefs in the Arabian/Persian Gulf. The GoK is an extreme environment for coral reefs with both natural stressors (high salinities, strong, seasonal storm activities, and extreme tides) and anthropogenic pollutants from industrial, mining, agricultural, and domestic activities. These poor environmental conditions may help explain the high occurrence of YBTLD on GoK reefs.