Journal of aquatic animal health最新文献

Objective: Fish disease in aquaculture is a major risk to food safety. The identification of infected fish and disease categories present in fish farms remains difficult to determine at an early stage. Detecting infected fish in time is an essential step in preventing the spread of disease. The aim of this work was to detect fish infected with epizootic ulcerative syndrome and fish lice Argulus spp.

Methods: An improved YOLO (You Only Look Once) version 5 (YOLOV5) model was developed. In the context of transfer learning, our improved model used a pretrained model on binary images. The improved model was deployed and integrated into a Raspberry Pi board.

Results: The experimental results showed that it is more effective than a simple YOLOV5 model.

Conclusions: Using the evaluation metrics of precision, recall, mAP50 (mean average precision at an intersection over union threshold of 0.50), and mAP50-95 (average of the mAP values calculated for intersection over union thresholds ranging from 0.50 to 0.95 in steps of 0.05), our new model achieved accuracy rates of 0.944, 0.969, 0.989, and 0.954, respectively.

Objective: Piscine lactococcosis associated with Lactococcus petauri is a serious emerging threat to fish populations in the Americas. This bacterial disease commonly presents as a hemorrhagic septicemia, resulting in high mortality rates and substantial financial losses. There are no commercial vaccines in the United States, and treatment options are limited and understudied. Florfenicol (Aquaflor) is a broad-spectrum antibiotic approved for finfish aquaculture, and erythromycin (Aquamycin 100) is an investigational new animal drug. This study aimed to compare the effectiveness of florfenicol- and erythromycin-medicated feed against lactococcosis through cohabitation challenges in Rainbow Trout Oncorhynchus mykiss.

Methods: Shedder fish were intracoelomically injected with L. petauri (∼1.5 × 104 CFU) and introduced to naïve populations at 13°C or 18°C. Treatments were initiated immediately after observation of mortality, with fish receiving florfenicol at 15 mg/kg for 10 d, erythromycin at 100 mg/kg for 21 d, or the control diet.

Results: At 18°C, cohabitant survival was significantly higher in florfenicol-treated (100%) and erythromycin-treated (93%) tanks compared to untreated positive controls (60%). There were no mortalities at 13°C or in the negative control tanks. In sampled survivors, L. petauri was detected by quantitative PCR in 29% of positive control fish, 14% of erythromycin-treated fish, and 14% of florfenicol-treated fish at 18°C compared to 21, 7, and 0%, respectively, at 13°C. Culturable bacteria were only recovered from 14% of positive control fish at both temperatures.

Conclusions: These results indicate that early intervention with florfenicol or erythromycin can limit the spread of L. petauri and that lower water temperatures reduce disease onset, improving options for managing lactococcosis in aquaculture.

Objective: Propranolol is a beta-blocker psychoactive drug used for the management of high blood pressure, tremors, atrial fibrillation, and migraine headaches. This study investigated the effect of propranolol on behavior, acetylcholinesterase, lipid peroxidation, superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase in the brain of African Sharptooth Catfish Clarias gariepinus juveniles.

Methods: A total of 180 African Sharptooth Catfish were exposed to 7.00-, 9.00-, 11.00-, 13.00-, and 15.00-mg/L acute propranolol concentrations and a control (0.00 mg/L) for 24, 48, 72, and 96 h, and the 96-h LC50 value was 9.48 mg/L. For sublethal study, 120 juvenile African Sharptooth Catfish were divided into four groups of 30 fish each and exposed to 1.90-, 0.95-, and 0.47-mg/L propranolol concentrations and a control for 21 d and allowed to recover for 7 d. All the treatment groups and control were set in triplicates, with 10 fish in each. The behavioral changes due to propranolol exposure were monitored by direct observation and scoring during the exposure and withdrawal period. The brains of fish were sampled every week for 4 weeks in order to evaluate the effects of propranolol on acetylcholinesterase, lipid peroxidation, and oxidative stress parameters.

Results: Behavioral changes were evidenced by alterations in swimming rates, air gulping activities, and opercula beats in the propranolol-exposed fish during the acute exposure. Sublethal exposure resulted in a significant decrease in superoxide dismutase and catalase but increase in glutathione peroxidase and reductase values. Significant increase in lipid peroxidation and acetylcholinesterase enzyme levels were observed as exposure duration increased from day 7 compared with the control. The effects of propranolol on the observed parameters appeared to wane after fish withdrawal from the drug for 7 d.

Conclusions: The drug propranolol, as demonstrated by these alterations, may negatively impact nontarget aquatic species and may have ecological consequences.

Objective: Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish, causes substantial economic losses to Channel Catfish Ictalurus punctatus producers in the United States. This study evaluates three E. ictaluri strains, each carrying a markerless deletion mutation in a type III or type VI secretion system gene, as candidates for a live attenuated vaccine against enteric septicemia of catfish in Channel Catfish. Replication in Channel Catfish cells, in vivo invasion and persistence, virulence, and the ability to provide single-dose protection against a wild-type E. ictaluri strain were evaluated for each mutant.

Methods: In this study, three isogenic mutants were constructed that introduced deletions in esrC, eseG, and evpC. EsrC is a T3SS-encoded protein that regulates expression of multiple virulence genes, including the T3SS effector EseG and the T6SS structural protein EvpC. Each mutant strain was evaluated for its ability to replicate in Channel Catfish ovary cells and head-kidney-derived macrophage cells. Channel Catfish were also challenged with the mutant strains to evaluate if mutation affected invasion, colonization, or persistence within the head kidney, attenuated mortalities in Channel Catfish, or induced protection against disease following subsequent wild-type E. ictaluri exposure.

Results: Each mutant maintained the ability to replicate within head-kidney-derived macrophage cells and Channel Catfish ovary cells, as well as invade and colonize the head kidney. Although able to replicate intracellularly and successfully colonize catfish tissue, all three mutants were significantly attenuated in their ability to persist in tissues and cause mortality. A single immersion in mutant strains 28 d prior to exposure to wild-type E. ictaluri resulted in significantly lower mortality than fish immersed in sterile broth, with relative percent survival ranging from 95% to 100%.

Conclusions: The findings demonstrate the potential for the development of live attenuated E. ictaluri vaccine strains through the targeted mutation of one or more E. ictaluri T3SS and T6SS genes.

Objective: Thiamine deficiency is a widespread issue in salmonine species and has been reported to induce changes in cardiac morphology and cardiac dysfunction in Lake Trout Salvelinus namaycush. Here, we assess the effects of thiamine concentration on the ventricular morphology of three reproductive life histories (jack males, hooknose males, and females) of wild spawning Chinook Salmon Oncorhynchus tshawytscha.

Methods: Fish were sampled from the Credit River (a Lake Ontario tributary), and skeletal muscle, ventricle, and liver thiamine concentrations were quantified using high-performance liquid chromatography. A subset of ventricles was retained for histological analyses. Hematoxylin and eosin-stained slides were used to measure cardiomyocyte width and compact myocardium thickness, and Masson's trichrome-stained slides were used to measure levels of cardiac fibrosis. Level of spawning senescence was quantified based on a qualitative score.

Results: Thiamine levels did not differ significantly among life histories, except that hooknose males had significantly greater skeletal muscle thiamine concentrations than females. Thiamine concentrations in skeletal muscle and the ventricle were positively correlated. Across all life histories, lower concentrations of thiamine in skeletal muscle were associated with increased levels of cardiomyocyte hypertrophy and cardiac fibrosis, independent of their relationships with ventricle mass and level of spawning senescence. No significant relationships were observed with compact myocardium thickness.

Conclusions: Low thiamine concentrations are associated with pathological alterations in cardiac morphology across reproductive life histories in spawning Chinook Salmon.

Objective: In aquaculture, the trend is shifting towards using plant-derived alternatives that are abundant in phytochemicals as effective replacements for traditional antibiotics and synthetic feed additives. In the present study, the effects of tulsi Ocimum sanctum extract on growth performance, hemato-biochemical indices, serum immune parameters, and antioxidant parameters in Common Carp Cyprinus carpio were investigated.

Methods: Common Carp (mean body weight ± SD = 10.6 ± 0.13 g) were fed experimental diets that contained tulsi leaf extract at 0.0 (control), 0.5, 1.0, and 1.5% for 60 d (25 fish/treatment).

Results: The findings revealed a considerable enhancement in growth performance and a decreased feed conversion ratio, especially for the 1.0% tulsi-based diet. Additionally, weight gain and feed conversion ratio exhibited significance at both the linear and quadratic levels, as indicated by polynomial contrasts. The hematological and biochemical profiles exhibited improvements in groups receiving tulsi-enriched diets. The antioxidant status of fish serum exhibited a notable increase, as evidenced by elevated activities of total antioxidant capacity, superoxide dismutase, and catalase in fish that received the 1.0% and 1.5% tulsi-based diets. Tulsi-supplemented diets led to remarkable enhancements in serum lysozyme activity, alternative complement activity, and total immunoglobulin content. Moreover, tulsi supplementation at 1.0% and 1.5% showcased a significant reduction in serum glucose and cortisol levels compared to the other groups.

Conclusions: In conclusion, tulsi extract emerged as a valuable asset, positively influencing growth, blood parameters, antioxidant balance, and serum immune response in Common Carp, particularly at supplementation levels ranging from 1.0% to 1.5% in the diet.

Objective: The Blue Catfish Ictalurus furcatus is commonly raised in warmwater aquaculture in the United States to produce Channel Catfish I. punctatus × Blue Catfish hybrids. It is also a prominent aquatic invasive species of concern in the mid-Atlantic region of the United States. Here, Yersina ruckeri was isolated from moribund Blue Catfish and hybrid catfish from disparate regions of the USA. The goal of the research here was to compare these Y. ruckeri strains to each other and other known strains for which adequate sequence data was available. In addition, we sought to determine if the strain from Blue Catfish was pathogenic to Rainbow Trout Oncorhynchus mykiss.

Methods: Moribund hybrid catfish from culture ponds in Mississippi were processed for diagnostic evaluation in March 2016. In April 2022, a moribund Blue Catfish specimen was collected from a tributary of the Nanticoke River in Maryland. Bacterial isolates were identified and characterized using biochemical tests, antimicrobial sensitivity screening, serotyping, and complete or partial genome sequencing. Disease pathology was described via histology. The isolate from Blue Catfish was used in challenge experiments to determine if it was pathogenic to Rainbow Trout. Multilocus sequencing typing was conducted using the PubMLST database.

Results: Biochemical testing was consistent with Y. ruckeri. A draft genome of the Y. ruckeri isolate was assembled based on Oxford Nanopore Technology sequencing and identified a single genomic replicon (3,791,418 bp) consistent in size to other Y. ruckeri genomes and a pLT plasmid (60, 933 bp). The challenge study demonstrated no significant virulence of this isolate for Rainbow Trout (Y. ruckeri). This isolate was most similar to other strains isolated from ictalurids. Notably, the gyrase B gene from this isolate was identical to that of archived strains isolated from moribund Mississippi hybrid catfish aquaculture during 2016 and these isolates share identical PubMLST sequence type profiles. Similarly, they shared a pLT plasmid that differed by only 6 bp. This plasmid has never been reported from trout isolates and appears to be unique to ictalurids.

Conclusions: Analyses here provide preliminary genetic evidence that geographically distant (Maryland and Mississippi, USA) isolates of Y. ruckeri from ictalurids are genetically similar to each other and Y. ruckeri (strain SC09) that infects ictalurids in China. This strain is not a biothreat to Rainbow Trout at typical culture temperatures.

Objective: Aquaculture has faced significant challenges due to the emergence of various pathogens affecting fish species. One such species, the Obscure Pufferfish Takifugu obscurus, has experienced high mortality rates due to an outbreak of disease on a fishery farm in Shanghai.

Methods: The pathogen responsible for this outbreak was isolated and identified as Vibrio anguillarum (GA strain) using a combination of morphological, biochemical, and whole-genome single-nucleotide polymorphism-based phylogenetic analyses. Pathogenicity tests confirmed that the GA strain could cause disease in healthy Obscure Pufferfish, inducing overt hemorrhagic symptoms. Histopathological analysis was performed to assess whether tissue damage had occurred. Whole-genome sequencing revealed that the GA strain possessed 235 virulence genes and two drug resistance-related genes: cyclic AMP receptor protein (CRP) and regulator of secondary metabolites A (rsmA). Testing via PCR further confirmed the presence of 10 common virulence genes.

Results: Antibiotic susceptibility testing showed that the GA strain was highly sensitive to antibiotics such as tetracycline, doxycycline, minocycline, and compound sulfamethoxazole and was resistant to cefradine, cefazolin, penicillin, and vancomycin.

Conclusions: To the best of our knowledge, this is the first study to report V. anguillarum as the pathogen responsible for this disease in Obscure Pufferfish. The isolate exhibited strong virulence and multidrug resistance. The findings lay the foundation for further disease control in Obscure Pufferfish and the investigation of the epidemiological mechanisms of V. anguillarum.

Objective: Pyrimidine has a broad range of biological actions and may be an eco-friendly substitute for health management.

Methods: To explore bioefficiency in fish, different concentrations (10 fg/mL to 1 mg/mL) of a pyrimidine analog (4,6-dimethyl-2-hydroxypyrimidine hydrochloride) were prepared from stock solution in water with Stinging Catfish Heteropneustes fossilis for 24 h to determine the effective concentration based on hematological parameters. The effective concentration of pyrimidine (10 pg/mL) was further examined for a study of duration effects (1, 5, and 21 d), followed by a 1-week recovery period (in only water).

Results: The pyrimidine analog improved health-supportive hematological parameters and moderated antioxidative stress. Pyrimidine treatment significantly increased red blood cell count and hemoglobin in Stinging Catfish. It also significantly decreased the white blood cell count, myeloperoxidase activity, and nitroblue tetrazolium in a time-dependent manner, thus helping to manage stress. Nutrient levels (protein, carbohydrate, and lipid) also were improved in pyrimidine-treated fish compared to control fish without treatment.

Conclusions: Results supported the stimulatory effect of pyrimidine on fish immunity, nutrient level, and health parameters. During the recovery period, the levels of the analyzed parameters remained close to those measured at 21 d of treatment compared to the control fish. A reduction in health-supportive parameters 1 week after pyrimidine treatment supported the metabolized nature of the pyrimidine analog compared to other contemporary bioaccumulative drugs. There was no side effect of the effective concentration of the pyrimidine analog, and it did not cause any change in body weight and growth after treatment.

Objective: This study engaged representative native freshwater mussel propagation biologists in focus group discussions to learn their views and priorities related to the development and adoption of freshwater mussel health metrics. It provides a case study on how early consultation with practitioners can better inform research questions and improve imperiled species conservation.

Methods: Two focus group discussions were conducted with freshwater mussel propagation biologists from across the United States to understand the needs of conducting mussel health assessments, current approaches, technical capacity, and where advances may be most beneficial.

Results: Propagation biologists identified how they currently measure freshwater mussel health, listed the largest threats to health, explained similarities among approaches, and made recommendations for future research.

Conclusions: Propagation biologists called for quantitative metrics that complement current procedures that could be measured nonlethally and were reflective of health and resilience rather than presence or absence of disease. Further conservation research could benefit from early engagement with propagation biologists to better ensure adoption of research products and tools.