Journal of aquatic animal health最新文献

The purpose of this study was to determine the optimal imaging protocol for contrast-enhanced computed tomography (CECT) using micro-CT (μ-CT) for the posterior cardinal vein (PCV), dorsal aorta (DA), hepatic portal vein (HPV), kidney, liver, cephalic arteries (CAs), and gills of Cloudy Catsharks Scyliorhinus torazame. Additionally, we examined the availability of CECT screening for the coelomic organs. Different doses of iopamidol (100, 300, 500, and 700 mg iodine [mgI]/kg) were administered intravenously for 20 s in six sharks. The CT scans from the pectoral girdle to the pelvic girdle were performed at 0–600 s after administration. Contrast-enhanced CT imaging of the CAs, gills, and coelomic organs was examined. Assessment of the signal enhancement value revealed that the PCV was easily visualized with all contrast doses at 25 s. The CAs, gills, and DA were visible at a slightly higher dose (CAs and gills: 200 mgI/kg at 40 s; DA: 300 mgI/kg at 50 s). The HPV was obvious at a dose of at least 500 mgI/kg after a 150-s delay. The parenchyma of the kidney had a contrast effect at 300 mgI/kg, 150 s after the contrast effect of the renal portal system disappeared. The liver, which stores a lot of lipids, had poor overall contrast enhancement that was optimized at the highest dose of 700 mgI/kg. Contrast-enhanced CT screening at 700 mgI/kg and 150 s is likely to obtain the optimal imaging of the reproductive organs, such as the ovary, oviducal gland, uterus, and testis. The present findings can be applied not only to clinical practice but also to academic research and education on elasmobranchs in aquariums.

Pseudomonas alcaligenes infection is rare in aquaculture. In this study, we provide the first report on the characterization of P. alcaligenes from koi (a variant of Common Carp Cyprinus carpio) in China. A gram-negative bacterium was isolated from the diseased koi and was named KCP-516. Morphological and biochemical tests as well as phylogenetic tree analyses derived from 16S ribosomal RNA, gyrase subunit A, and gyrase subunit B gene sequencing all strongly indicated that the isolate KCP-516 was P. alcaligenes. In liquid medium, the optimal growth conditions were 25°C, 2.5% NaCl, and pH 8. The pathogenicity of the isolate was demonstrated in koi, with 7.0 × 10⁴ CFU/g fish weight identified as the dose lethal to 50% of test fish. The results will provide a scientific reference for the diagnosis and treatment of P. alcaligenes infection.

Flavobacterium psychrophilum, the causative agent of bacterial coldwater disease (BCWD), causes significant economic losses worldwide, particularly in farmed Rainbow Trout Oncorhynchus mykiss. Over the last decade, multilocus sequence typing has revealed >30 clonal complexes (CCs) globally, comprised of >320 F. psychrophilum sequence types (STs). Despite the large number of CCs worldwide, CC-ST10, which is currently the largest CC affecting Rainbow Trout, has been the primary focus of F. psychrophilum virulence studies, leaving the role of other CCs as primary causes of BCWD epizootics unclear. To this end, fingerling Rainbow Trout were experimentally challenged with F. psychrophilum strains belonging to the CC now recognized as the second largest in the world (CC-ST191) alongside CC-ST10 strains. Cumulative percent mortality was 100% in 7-month-old Rainbow Trout and between 27.8% and 61.1% in 8-month-old Rainbow Trout. All examined F. psychrophilum STs were virulent to Rainbow Trout, and no significant differences in virulence between CC-ST10 and CC-ST191 were detected. Due to their wide distribution and high pathogenic potential, both CC-ST191 and CC-ST10 F. psychrophilum strains are excellent candidates for further research aimed at preventing and controlling BCWD.

The goals of this study were to investigate the potential use of metomidate for one-step euthanasia of ornamental fish species representing commonly sold families in the ornamental fish trade and to determine a baseline euthanasia dose for most species tested. Metomidate hydrochloride, a rapid-acting, water-soluble, nonbarbiturate hypnotic related to etomidate, was tested at various concentrations and durations for euthanasia of species representing the following freshwater and marine aquarium fish families: Apogonidae, Ariidae, Blenniidae, Callichthyidae, Characidae, Cichlidae, Cyprinidae, Gobiidae, Gyrinocheilidae, Loricariidae, Melanotaeniidae, Osphronemidae, Pimelodidae, Poeciliidae, Pomacentridae, and Pseudochromidae. Fish in each trial were euthanized as a group (n = 1). Most groups contained 10–12 fish. Some higher doses required buffering. Euthanasia was considered successful if all fish in each group did not recover after 6 h in unmedicated water. All species immediately lost buoyancy and equilibrium, dropping to the tank bottom within 1 min and ceasing ventilation typically within minutes. However, reactivity to vibration, sound, or touch was noticeable for varying time periods afterward (8–66 min), so an additional 30 min of exposure after cessation of reactivity was included as part of the protocol. Although some species (Neon Tetras Paracheirodon innesi and Australian Rainbowfish Melanotaenia australis) were euthanized at a concentration of 40 mg/L metomidate for a total exposure time of 38 min, most species tested were successfully euthanized with metomidate at a concentration of 100 mg/L, with total exposure times ranging from 35–96 min. A few catfish species (Otocinclus sp. and Bronze Corydoras Corydoras aeneus) were refractory and recovered after 100 mg/L. However, Otocinclus sp. were successfully euthanized at 250 mg/L, and Bronze Corydoras were euthanized at 1,000 mg/L. Further studies are needed to provide additional data for these and other species and families, for different water chemistry conditions, and for various biological factors to fine-tune dosing regimens.

In this case study, phage therapy was applied to treat a multidrug-resistant case of septicemic cutaneous ulcerative disease (SCUD) caused by Citrobacter freundii in a loggerhead sea turtle Caretta caretta. Phages were applied topically, intravenously, into the carapace, and into the exhibit water using various phage cocktails specific to the causative agent over an 8-month period. This was performed in conjunction with antimicrobial therapy. The animal was monitored through weekly cultures, photographs, and complete blood cell counts, as well as immune assays (phagocytosis, plasma lysozyme and superoxide dismutase activity, and plasma electrophoresis profiles). The animal, in comparison to an untreated, unaffected control, had elevated antibody titers to the administered phages, which persisted for at least 35 weeks. Although cultures were clear of C. freundii after phage treatment, the infection did return over time and immune assays confirmed deficiencies when compared to a healthy loggerhead sea turtle. Immune parameters with statistically significant changes over the study period included the following: decreased phagocytosis, increased alpha- and gamma-globulin protein components, and an increased albumin : globulin ratio. When C. freundii appeared again, the multidrug-resistant status had reverted back to normal susceptibility patterns. Although not completely known whether it was another subspecies of bacteria, the therapy did resolve the multidrug-resistant challenge. Phage therapy in combination with antimicrobial agents may be an effective treatment for sea turtles with normally functioning immune systems or less-severe infections. Additional research is needed to better understand and quantify sea turtle immunology.

In August 2018, a series of large fish kills involving only Silver Carp Hypophthalmichthys molitrix occurred on the Mississippi River in northern Louisiana. Clinical signs observed in moribund animals included erratic swimming behavior, such as spiraling and spinning at the surface. A moribund specimen was captured by dip net near the surface at Lake Providence Landing in East Carroll Parish, northern Louisiana, and was submitted for analysis. An aseptic necropsy was performed, and diagnostic procedures, including bacteriology, parasitology, histopathology, virology, and electron microscopy, revealed that a gram-positive coccus was the primary pathogen. Pure cultures of the organism were obtained from the brain, and it was the predominant colony type isolated from the spleen, kidney, and liver. Bacterial sepsis caused by the gram-positive coccus and involving multiple organ systems was diagnosed histologically. Bacterial colonization and necrotic lesions were seen in the spleen, liver, kidney, heart, eye, and brain. Numerous cocci were observed dividing intracellularly in phagocytic cells of the kidney and brain by transmission electron microscopy. The organism was identified as Streptococcus dysgalactiae ssp. dysgalactiae by conventional biochemical methods and subsequently by the API 20 Strep system. The identity of the pathogen was later confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and sequencing of the 16S ribosomal RNA gene. Multilocus sequence analysis clustered this isolate along with two other S. dysgalactiae isolates from fish in a divergent phyletic group that was separate from other S. dysgalactiae ssp. dysgalactiae isolates from terrestrial animals, implying a possible novel clade that is pathogenic for fish.

MicroRNAs (miRNAs) are well-known as powerful regulators of gene expression, with their potential to serve for immunology widely researched in mammals and birds but rarely in fishes. To better understand fish immunology behavior, we herein investigated nine immune-related miRNAs that were reported in other animals, as well as five related cytokine factors and lysozyme (LZM) in the liver, anterior kidney, and spleen of Channel Catfish Ictalurus punctatus after being stimulated by lipopolysaccharides (LPS) and β-glucan. We also predicated the potential targets of these miRNAs via bioinformatics and further investigated nine of them via quantitative real-time PCR. Results showed that expressions of the nine miRNAs were quickly changed in varying extent after stimulation by LPS, especially for miR-122, miR-142a, miR-155, and miR-223, which were significantly changed in spleen, and the same occurred for the LZM and three cytokine factors TNF-α, IFN-γ and TLR2. Compared with LPS, although most of the miRNAs and the cytokine genes were also affected by β-glucan, the extent of the effect was weak. Bioinformatics analysis revealed many immune-related targets of the miRNAs, with some of them reported by previous studies. For the nine investigated target genes, seven targets (77.8%) were significantly upregulated after the stimulation of LPS. It therefore can be inferred that the immune-related miRNAs, LZM, and cytokine factors elicited quick immune responses of Channel Catfish to LPS stimulation as in other animals, but the regulation mechanism of miRNAs might be complex and diverse. This research will contribute to a better understanding will support further immunology research in fishes.

Among the bacterial infections that impair the health status of marine mammals, those caused by Brucella spp. are the most reported worldwide. Brucella infections in marine mammals can result in acute or chronic disease and are associated with variable clinical outcomes, depending on the organ involved during the infectious process, infection route, host immunity, and strain pathogenicity. Asymptomatic infections may also occur. The current study expands the investigation of Brucella infection in northeast Brazil by analyzing 19 dead, stranded cetaceans and 52 Antillean manatees Trichechus manatus manatus. The manatees included 8 dead, captive manatees and 44 live specimens, of which 10 were analyzed only after reintroduction into the wild as part of a rehabilitation program, 9 were analyzed both while in captivity or semi-captivity and after reintroduction, 20 were sampled only in captivity or semi-captivity, and 5 were free-living manatees. Serological tests were used to screen for antibodies against smooth Brucella spp. Whole blood, swabs, and tissue samples were screened for Brucella spp. DNA by PCR. Samples with positive PCR results were cultured for Brucella spp. isolation. All manatees yielded negative results in serological and molecular tests. Brucella spp. DNA was detected in the kidney of one adult Guiana dolphin Sotalia guianensis exhibiting necrosis in the liver. No growth of Brucella spp. was observed via microbiological culturing. This study is the first report of Brucella spp. DNA detection in cetaceans in the state of Pernambuco, and it highlights the importance of conducting systematic monitoring for the presence of Brucella infection in marine mammals along the Brazilian coast, especially in the northeast region, where several cases have been reported.

Tilapia culture is a very promising industry within the aquaculture sector. However, disease outbreaks have continued to threaten the industry, causing serious economic losses among the producers. Streptococcosis has become the major bacterial disease affecting tilapia production in most regions of the world. To combat the disease and minimize its economic impact on fish producers, numerous preventive and control measures have been developed and reported over the years. This paper aims to systematically review the measures that could be used to manage the disease outbreaks and maintain fish health based on previously published scientific studies. Although numerous measures currently available have been highlighted, it is far better for the producers to maximize the preventive measures for management to be economically feasible. Among the currently available preventive measures, the use of vaccines has been shown to have the most promise, while the use of herbs has been demonstrated to be a more sustainable and economically affordable control measure. However, there are still a number of important gaps in existing literature that require further investigation. Overall, significant progress has been made in preventing and controlling streptococcosis in tilapia although, no single effective measure has been identified. Therefore, a combination of these measures may provide a more effective result.

One of the major goals in aquaculture is to protect fish against infectious diseases as disease outbreaks could lead to economic losses if not controlled. Antimicrobial peptides (AMPs), a class of highly conserved peptides known to possess direct antimicrobial activities against invading pathogens, were evaluated for their ability to protect Channel Catfish Ictalurus punctatus and hybrid catfish (female Channel Catfish × male Blue Catfish I. furcatus) against infection caused by the fish pathogen Aeromonas hydrophila ML09-119. To identify effective peptides, the minimum inhibitory concentrations against bacterial pathogens Edwardsiella ictaluri S97-773, Edwardsiella piscicida E22-10, A. hydrophila ML09-119, Aeromonas veronii 03X03876, and Flavobacterium columnare GL-001 were determined in vitro. In general and overall, cathelicidins derived from alligator and sea snake exhibited more potent and rapid antimicrobial activities against the tested catfish pathogens as compared to cecropin and pleurocidin AMPs and ampicillin, the antibiotic control. When the peptides (2.5 µg of peptide/g of fish) were injected into fish and simultaneously challenged with A. hydrophila through immersion, increased survival rates in Channel Catfish and hybrid catfish were observed in both cathelicidin (alligator and sea snake) treatments as compared to other peptides and the infected control (P < 0.001) with alligator cathelicidin being the overall best treatment. Bacterial numbers in the kidney and liver of Channel Catfish and hybrid catfish also decreased (P < 0.05) for cathelicidin-injected groups at 24 and 48 h after challenge infection. These results show the potential of cathelicidin to protect catfish against bacterial infections and suggest that an approach overexpressing the peptide in transgenic fish, which is the long-term goal of this research program, may provide a method of decreasing bacterial disease problems in catfish as delivering the peptides via individual injection or feeding would not be economically feasible.