Diseases of aquatic organisms最新文献

The 2022 Oder River disaster was one of the most significant harmful events in recent European river history, with an estimated 60% reduction in fish biomass in the lower section of the river. While the prevailing hypothesis attributes associated fish kills to toxins from golden algae Prymnesium parvum, our histopathological study on the gills of 2 common cyprinid fish species, namely vimba bream Vimba vimba (L.) and roach Rutilus rutilus (L.), collected from the lower Oder River at 3, 4, and 6 mo after the disaster, suggests another mechanism. Vimba bream showed damage to the epithelial layer of lamellae and increased mucus production. Roach exhibited interlamellar cell mass (ILCM), lamellar damage, including hypertrophy of epithelial cells, lamellar fusion, as well as significant thickening of the water-blood barrier compared to controls. These findings suggest that adverse factors, most likely the increase in toxin concentrations resulting from reduced water levels together with elevated temperatures and low precipitation, triggered the formation of ILCM, increasing the susceptibility of fish to hypoxia. Fish species with a capacity for adaptive interlamellar hyperplasia, such as common bream Abramis brama, roach, and common perch Perca fluviatilis, accounted for the largest number of deaths during the disaster. Vimba bream, which showed no ILCM, were observed only sporadically, with mortality confined to a single area of the Oder. In conclusion, fish capable of adaptive hyperplasia, whereby the gills attempt to protect themselves by developing ILCM, appear to be particularly vulnerable in conditions of aquatic hypoxia.

Cyvirus cyprinidallo 2 (CyHV-2) is the pathogen of herpesviral hematopoietic necrosis (HVHN) that mainly infects goldfish Carassius auratus and crucian carp C. carassius and is characterized by high infectivity and pathogenicity. The availability of rapid and convenient detection methods is essential for early detection of CyHV-2. A colloidal gold immunochromatographic strip using 2 specific anti-CyHV-2 monoclonal antibodies (MAbs) has been developed and validated for rapid detection of CyHV-2. The test results can be viewed within 10min. The detection limit of test strip was 2.08 × 102TCID50 ml-1, and it showed no cross-reactivity with other freshwater fish viral pathogen except KHV (koi herpesvirus). The specificity of the strip was 100% when spleen and kidney tissues of CyHV-2 infected and healthy crucian carp were assayed following an experimental challenge. The colloidal gold immunochromatographic strip will be an effective device for the rapid detection of CyHV-2 in the future.

The present study evaluated the immunomodulatory and disease resistance-enhancing effects of dietary supplementation of Withania somnifera root powder in Labeo rohita (22.10 ± 3.30 g, 12.35 ± 1.15 cm), a commercially important freshwater fish species, against Aphanomyces invadans infection under the agro-climatic conditions of Tripura, Northeast India. Four isonitrogenous and isocaloric experimental diets were formulated with varying levels of W. somnifera root powder: control (0%), D1 (0.1%), D2 (0.2%), and D3 (0.3%). After a 21-d feeding period, the fish were challenged with A. invadans zoospores (1 × 104 spores ml-1; 0.1 ml fish-1) and observed for mortality and blood parameter assessment according to standard protocols. The survival rate was markedly higher at 83.33% in the 0.2% W. somnifera group compared to 31.11% in the control group 14 d post-infection. Dietary W. somnifera supplementation improved serum protein, enzymatic, and hematological parameters. Immunological parameters, including nitroblue tetrazolium activity, serum lysozyme activity, and bactericidal activity, were also significantly higher in W. somnifera-fed fish. The findings suggest that W. somnifera root powder at 0.1-0.3% inclusion levels, with 0.2% being the optimal dose, can enhance disease resistance against A. invadans in L. rohita by modulating innate immune mechanisms. Given the growing concerns over antimicrobial resistance and the need for sustainable aquaculture practices, the use of natural immunostimulants such as W. somnifera offers a promising alternative for disease management, particularly in regions prone to epizootic ulcerative syndrome outbreaks.

This work was performed to generate the data needed to set epidemiological cut-off values for minimal inhibitory concentrations (MICs) of 10 antimicrobial agents against Vibrio parahaemolyticus determined using standardised broth microdilution protocols. Eight laboratories performed broth microdilution tests with incubation at 35°C for 16 to 20 h, and 7 also performed tests on the same isolates with incubation at 28°C for 24 to 28 h. Data were analysed by the ECOFFinder and normalised resistance interpretation algorithms. The cut-off values calculated for ceftazidime, florfenicol and trimethoprim/sulfamethoxazole, 1, 1 and 0.25/4.75 µg ml-1, respectively, were the same when calculated from data obtained at both temperatures. The cut-off values calculated from data obtained at 35°C and from data obtained at 28°C were 0.25 and 0.5 µg ml-1 for enrofloxacin, 2 and 4 µg ml-1 for gentamicin, 0.5 and 1 µg ml-1 for oxolinic acid and 2 and 1 µg ml-1 for oxytetracycline, respectively. The influence of incubation temperature on MIC values was investigated by comparing MICs obtained at 35 and 28°C for a specific antimicrobial agent with a particular isolate by an individual laboratory. Results showed that 56% of 1473 of these paired MIC values were identical, while 38% differed from one another by not more than 1 dilution step. The data generated in this work will be submitted to the Clinical and Laboratory Standards Institute for consideration in their setting of internationally agreed epidemiological cut-off values for V. parahaemolyticus that are essential for interpreting antimicrobial susceptibility testing data of this species.

Thermal acclimation effects on locomotory performance have been widely documented for macroscopic organisms, but such responses remain largely unexplored in microorganisms. Metabolic theory of ecology (MTE) predicts faster responses in smaller organisms, with potential consequences for host-parasite interactions in variable temperature environments. We investigated thermal acclimation effects on zoospores of the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd), quantifying (1) thermal performance for maximum zoospore velocity and (2) high temperatures needed to immobilize 50% (CT50max) or 100% (CT100max) of zoospores. We obtained measurements within 18 min following a temperature shift. We found significant curvilinear acclimation effects on maximum zoospore velocity and CT50max, although the latter pattern might have been driven by confoundment with zoospore density. We also observed a significant positive effect of the trial start temperature on CT50max, consistent with a rapid acclimation response to the start temperature on a time scale of ~1-6 min (i.e. too rapid for our experimental acclimation treatments to detect), implying that zoospores either have constitutive heat tolerance (i.e. no acclimation) or fully acclimate CTmax to new temperatures within ~10 min. To explore the plausibility of such a rapid response, we analyzed published CTmax acclimation times for macroscopic eukaryotes, resulting in a predicted interquartile range of 3.11-25.98 min when mass-scaled to the size of a Bd zoospore. Taken together, these results suggest that Bd zoospores do exhibit thermal acclimation response on the rapid time scale predicted by MTE, possibly giving Bd an advantage over slower-acclimating hosts in variable-temperature environments.

Considerable attention has been directed to studying the infection dynamics of the fungal pathogen Batrachochytrium dendrobatidis (Bd) affecting amphibians in the high elevations of the Neotropics. However, lowland forests of the same realm remain comparatively understudied in this context. Herein, we attempt to bridge this gap by measuring the prevalence of Bd via quantitative polymerase chain reaction (qPCR) in several anuran taxa inhabiting the Amazonian lowlands in the northeast of Ecuador. To this end, we sampled 207 anurans from 10 different families, 25 different genera, and 55 distinct host species originally collected in 2008. Taxonomy (at the family level), morphology (i.e. weight and snout-vent length), and life-long aquatic dependency of hosts (i.e. aquatic index) were also compiled to serve as potential predictors of Bd infection status. Our findings revealed a relatively high Bd prevalence of 58%, with 88% of sampled anuran families testing positive for the fungus at varying proportions. Model selection involving fitting and testing several different linear models, including mixed linear models, revealed a significant negative relationship between host weight and Bd infection status (p < 0.01). However, no significant associations were observed between taxonomy, aquatic dependency, snout-vent length, and Bd infections. In addition, we only detected the global panzootic lineage of Bd (Bd-GPL) and not the Bd-Asia-2/Bd-Brazil lineage via qPCR single nucleotide polymorphism (SNP) genotyping. Our findings contribute to the understanding of Bd dynamics in the Neotropical lowlands and emphasize the need for future research on the ecological factors influencing Bd in the Amazon and their implications for amphibian conservation.

Intentional harm to marine mammals refers to deliberate human actions that cause injury, suffering, or death, and it is illegal in many countries. These actions often result from direct human attacks and are motivated by various reasons, with retaliation by fishermen being the most common. Such attacks cause severe tissue damage, frequently leading to the debilitation or death of the targeted animal. In this report, we document 13 cases of intentionally harmed marine mammals: 12 bottlenose dolphins Tursiops truncatus and 1 Mediterranean monk seal Monachus monachus found in the Croatian part of the Adriatic Sea between 1990 and 2023. Our analysis includes the life history data of the attacked specimens, post-mortem findings, and the weaponry involved. Among 311 post-mortem examinations conducted, 4.2% revealed intentional harm. Adult male bottlenose dolphins were most frequently targeted (46.2%), with a majority (53.8%) succumbing immediately due to exsanguination. Shotgun pellets, bullets, and underwater speargun spearheads were recovered from their carcasses. The attacks occurred with no discernible seasonal pattern; however, 61.5% of the cases were recorded from Istria County. Our findings underscore the inadequacy of current surveillance and enforcement in protecting marine mammals from deliberate harm. We advocate for the implementation of educational initiatives targeting relevant groups, intensive sea patrols, and routine inspection of weapons with high penalties for illegal possession and misuse, all reinforced by media campaigns to combat this malicious human behaviour.

Gas-bubble disease (GBD)-a non-infectious disease in aquatic organisms caused by supersaturated levels of total dissolved gases (oxygen and nitrogen) in water-is well known in various species, including fish and amphibians, but has not previously been reported in giant salamanders. In the present study, macroscopic and histopathological examinations of 2 mature Andrias spp. (kept with 293 fish in an aquarium) were performed to characterize GBD pathology. Bubbles developed on the body surfaces of the salamanders and fish, with erythema specifically noted in the salamanders. Within 3 d of the bubbles appearing, both salamanders and more than 270 fish had died. On Days 1 and 2, dissolved oxygen levels were 75.5 and 86.9%, respectively, while dissolved nitrogen gas levels were 90.6 and 103.1%, respectively. The 2 salamanders exhibited identical lesions characterized by erythema, congestion, and numerous bubbles in the major veins of the body cavity. Histopathologically, congestion and gas embolism-like dilatations were observed in the small vessels and capillaries. These lesions were found in the parenchymal and gastrointestinal organs, skin, eyeballs, and surrounding stromal tissue. Based on these findings and that GBD occurs at dissolved nitrogen gas and oxygen levels above 120 and 200%, respectively, the salamanders were diagnosed with nitrogen GBD. The exact etiology of this disease remains unconfirmed but likely involves circulatory system dysfunction within the aquarium environment, highlighting the importance of routine inspections and maintenance of equipment.

Cold stress is the leading cause of mortality in West Indian manatees Trichechus manatus in the northcentral Gulf of Mexico. This report describes an adult male manatee that stranded alive with signs of cold stress in Alabama (USA) waters in January 2022 and died during the rescue intervention. Postmortem examination and histopathologic review revealed multiple contributors to death. While the animal had evidence of cold stress syndrome, there was aortic stenosis and concentric left ventricular hypertrophy as well as an esophageal foreign body (plastic bag). Main findings from blood analysis indicated systemic inflammation and possible disseminated intravascular coagulation. Histopathologic findings from the cardiovascular system included aortic fibromuscular dysplasia, mitral and tricuspid valve endocardiosis, left ventricular myocardial hypertrophy, and right myocardial atrophy. A cause of the cardiovascular findings was not determined. This report is the first to document a case of cold stress syndrome complicated by aortic stenosis and esophageal occlusion in this species.

Between September and December 2023, Uruguay experienced unusually high pinniped mortality due to an HPAI-H5N1 virus outbreak. We examined and compared the temporal distribution of strandings and swab results. Data on pinniped strandings was compiled from the Stranding Network project and governmental institutions, and the number of positive and total swabs conducted was obtained through government public information requests. A total of 2713 stranded pinnipeds were recorded; 92.4% were dead, including 80 aborted fetuses. Live stranded animals showed clinical signs such as tremors, convulsions, and extreme weakness. Strandings peaked from mid-September to early November. Species was identified in 1121 cases: 56.1% were South American sea lions (SASL), and 42.6% were South American fur seals (SAFS). Out of 159 swabs, 22.6% tested positive for HPAI-H5N1. Most positive cases were unidentified pinnipeds, 33% in SASL and 22% in SAFS. The estimated mortality reached 1465 SASL, about 15% of the population, significantly affecting the declining population and its reproductive stock. The outbreak response revealed weaknesses in disease surveillance, poor institutional coordination, and delayed swabbing efforts. Improved management strategies are necessary to protect vulnerable species from emerging diseases and catastrophic events.