Gill Necrosis Research Articles

The Short-term Exposure Effect of Chlorpyrifos (20% EC) on Haematological, Biochemical and Histopathological Response of Striped Catfish Pangasianodon hypophthalmus

An experiment of acute toxicity was conducted to find out the lethal concentration 50 (LC50) of chloropyrifos (CPF) for Pangasianodon hypophthalmus. Our findings indicated that the 96-h LC50 value of CPF for P. hypophthalmus was 0.106 mg L-1. Effects of different concentrations of CPF (0.09, 0.1, 0.11, 0.12, and 0.13 mg L-1) for 96-h on hemato-biochemical, enzyme and histological effects were evaluated in this study. Acute exposure induced significant differences in enzymes acid phosphatase, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase and acetylcholine of blood serum of the treated group as compared to control group. However, significant decreases in serum total protein, globulin, albumin, and triglycerides levels while serum glucose enhanced with consequent increasing doses of CPF exposure. Also, CPF induced significant declines in RBC count, haemoglobin and hematocrit level whereas the exposure groups showed significant rises in WBC and blood indices levels as compared to control group. Furthermore, CPF exposure causes gill curling, epithelium lifting, necrosis, and lamellae degeneration. Hemosiderin, sinusoid dilations, necrosis, malanomacrophage, hepatocyte hypertrophy were observed in liver histology. Reduction of lumen tubule, hyperplasia, increased bowman space and degenerations were seen in kidney. Overall findings indicates that the acute CPF exposure to P. hypophthalmus resulted in significant adverse changes in biochemical, hematological, and histopathological response.

Assessment of patho-physiological responses, gill histopathology and SEM analysis in common carp (Cyprinus carpio) exposed to varied doses of chloramine-T: A potent chemotherapeutic agent

Chloramine-T (Cl-T) is a chemo-therapeutant used at aquafarms to control fish mortalities associated with bacterial and parasitic infections in freshwater aquaculture. It is also effective as a disinfectant against a wide range of viruses known to cause disease in fish. However, a very little information is available on the patho-physiological alterations in common carp (Cyprinus carpio) exposed to different doses of Cl-T. Herein, the present study aimed to assess the patho-physiological changes in common carp exposed to different doses of Cl-T (20 mg/L, 100 mg/L, and 200 mg/L) for 15 days followed by a post-exposure assessment for another 15 days. The results indicated a significant decrease in haematological indices viz., Total Erythrocyte Count (TEC), Total Leucocyte Count (TLC), Total Platelet Count (TPC), Haemoglobin (Hb), Haematocrit (Hct), and Mean Corpuscular Haemoglobin Concentration (MCHC) at higher Cl-T concentrations. Whereas, a decrease in some of the immune-biochemical parameters was also noted viz., lysozyme, NBT, Total Ig, phagocytic activity, protein, albumin and globulin in a dose-dependent manner. However, a significant increase in Mean Corpuscular Volume (MCV) and glucose levels was observed during exposure period. Histopathological analysis revealed gill hypertrophy, fusion of secondary lamellae, sloughing of lamellar epithelium and gill necrosis which were more pronounced with increasing concentration of Cl-T. The maximum damage to the gill was noted at a concentration of 200 mg/L. Whereas, scanning electron microscopic (SEM) analysis of gill revealed sloughing of lamellar epithelium, reduced interlamellar space and hypertrophy of secondary lamellae in Cl-T exposed fishes. Together, these results suggest that Cl-T exposure in common carp at 20 mg/L has a mild and acceptable effect on gill and physiology of fish, 100 mg/L has moderate effect, and 200 mg/L causes extensive damage to gills and physiology of fish.

Threat of heavy metal pollutants and parasites to freshwater fish with special reference to their risk of cancer to humans in Egypt

Understanding how pollution and parasite infection work together to stress their hosts' health raises the possibility of a danger to aquatic life and humans. This study examined two freshwater fish species, Clarias gariepinus, and Oreochromis niloticus, at El-Abbasa Fish farm in Sharkia Governorate of Egypt. to determine their heavy metal content, parasite frequency, and potential health risks. Parasitological investigations revealed higher parasite prevalence in C. gariepinus, with trematodes being the most prevalent. Histopathological examinations displayed severe alterations in infected fish, including gill necrosis, intestinal damage, liver degeneration, and muscle necrosis. Moreover, heavy metal analysis. Heavy metals levels in water, Fe, Zn, Pb, Cu, As, and Cd levels were 0.95 ± 0.04, 0.75 ± 0.03, 0.14 ± 0.02, 0.09 ± 0.01, 0.07 ± 0.01, and 0.03 ± 0.01 mg/L, respectively. Sediment samples showed Cd as the lowest (2.38 ± 0.94 μg/g dry wt. basis) and Fe as the highest (241.01 ± 6.39 mg/kg dry wt. basis). The sequence of heavy metal concentrations in both water and sediment was Fe > Zn > Pb > Cu > As > Cd. Significant differences were found among metals in water and sediment (p < 0.05). Heavy metal concentrations in fish tissues followed the order liver > muscles > gills > intestine Iron was the most abundant, while cadmium was the lowest is the order in which bio-accumulation factors (BAF) between water and fish tissues followed a descending order: BAF-Liver < BAF-Gills < BAF-Intestine < BAF-Muscles. The sequence of heavy metal accumulation in tissues was BAF-Fe > BAF-Pb > BAF-Cd > BAF-As > BAF-Cu > BAF-Zn, indicating varying degrees of accumulation across different metals and tissues and bio-sedimentation (BSF) of metals in fish tissues are the order of heavy metal concentration within tissues was BSF-Cd > BSF-As > BSF-Fe > BSF-Zn > BSF-Cu > BSF-Pb. Additionally, data were recoded to reflect histological changes in several fish organs. The estimated daily intake of heavy metals (EDI-HMs) was far lower than the permissible tolerated daily intake (PTDI) limits, which were set by international authorities at 70 kg of body weight. As the hazard index value is below 1, the THQ and HI associated with the consumption muscle of fish demonstrate negligible non-carcinogenic harm to residents' health. Contrarily, As, and Cd pose a cancer threat for kids and adults who eat muscular fish, and it needs to be viewed as a warning sign from the perspective of data indices and human health.

Br - nanoconjugate enhances the antibacterial efficacy of nimboloide against Flavobacterium columnare infection in Labeo rohita: A nanoinformatics approach

BackgroundThe bacterial pathogen, Flavobacterium columnare causes columnaris disease in Labeo rohita globally. Major effects of this bacterial infection include skin rashes and gill necrosis. Nimbolide, the key ingredient of the leaf extract of Azadirachta indica possesses anti-bacterial properties effective against many microorganisms. Nano-informatics plays a promising role in drug development and its delivery against infections caused by multi-drug-resistant bacteria. Currently, studies in the disciplines of dentistry, food safety, bacteriology, mycology, virology, and parasitology are being conducted to learn more about the wide anti-virulence activity of nimbolide. MethodsThe toxicity of nimbolide was predicted to determine its dosage for treating bacterial infection in Labeo rohita. Further, comparative 3-D structure prediction and docking studies are done for nimbolide conjugated nanoparticles with several key target receptors to determine better natural ligands against columnaris disease. The nanoparticle conjugates are being designed using in-silico approaches to study molecular docking interactions with the target receptor. ResultsBromine conjugated nimbolide shows the best molecular interaction with the target receptors of selected species ie L rohita. Nimbolide comes under the class III level of toxic compound so, attempts are made to reduce the dosage of the compound without compromising its efficiency. Further, bromine is also used as a common surfactant and can eliminate heavy metals from wastewater. ConclusionThe dosage of bromine-conjugated nimbolide can be reduced to a non-toxic level and thus the efficiency of the Nimbolide can be increased. Moreover, it can be used to synthesize nanoparticle composites which have potent antibacterial activity towards both gram-positive and gram-negative bacteria. This material also forms a good coating on the surface and kills both airborne and waterborne bacteria.

Histopathological assessment of Atlantic salmon exposed to calcium oxide particles: a controlled clinical study

Particulate calcium oxide (CaO) has been successfully used for the control of sea urchin and starfish populations. Recent studies have proven its efficacy in killing planktonic copepods, making it a promising and cheap option for salmon louse control in the Atlantic salmon (Salmo salar) farming industry. Additionally, preliminary laboratory tests demonstrated that exposure to 0.2 g/L–0.6 g/L of fine CaO particles induced significant mortality of salmon louse (Lepeophtheirus salmonis) in the planktonic stages. The present study investigated the effects of water treatment with fine CaO particles [0.2 g/L or 127.4 g/m2; 0.1 mm–0.3 mm], conducted twice a week for three consecutive weeks at 5°C and 12°C on Atlantic salmon post-smolt in a flow-through system. The study compared mortality rates and histopathology of skin, eyes, gills, and intestines between treated and untreated control salmon. The results indicated that CaO exposure did not induce fish mortality or histopathological damages in the skin, eyes, or intestines. Although there were no significant effects of CaO exposure on gill inflammation or hyperplasia, the exposure did increase the occurrence of gill vascular injuries and necrosis in small portions of the tissue (&amp;lt; 10% of the respiratory gill tissue in most of the samples) by 60% and 35%, respectively. The effect was not modulated by temperature or time. The results indicate that the CaO treatment protocol used in this study is not lethal to Atlantic salmon and is safe for most analyzed tissues. Nonetheless, the induction of vascular damage and necrosis in the gill, albeit in small tissue portions, emphasizes the need for further research. It is crucial to develop a protocol that avoids such lesions, ensuring the secure application of CaO as an antiparasitic treatment in salmon aquaculture.

First detection of Koi herpesvirus disease (KHVD) in Garmian, Kurdistan region of Iraq: A clinical and molecular study.

Koi herpesvirus disease (KHVD) is attributed to cyprinid herpesvirus-3 (CyHV-3) and predominantly affects common carp and ornamental koi carp (Cyprinus carpio). This viral infection leads to substantial morbidity and mortality among these fish species. This study aimed to confirm the presence of KHVD in the Kurdistan region of Iraq by employing clinical and optimized molecular assays on fish populations experiencing high mortality among common carp in carp farms. The present research was conducted in the Kalar district, situated at the heart of Garmian province in Iraqi Kurdistan. four samples from common carp fish farms were received by our laboratory. These samples specifically displaying clinical signs associated with koi herpesvirus (KHV) infection, were subjected to clinical examinations, and PCR assay in addition to sequence analysis. The results of the current study revealed that the observed clinical signs, particularly gill necrosis, skin lesions, and sunken eyes, closely resembled the clinical signs of KHVD in common carp fish. In addition, PCR, nested PCR, and sequence analysis assay detected appropriate DNA fragments of the CyHV-3 major capsid protein gene confirming the first detection of KHVD in common carp fish in the Kurdistan region of Iraq. In this study, the results confirm the detection of KHVD in the Kurdistan region, Iraq, for the first time. This study revealed that CyHV-3 was responsible for KHVD-related signs and symptoms. Based on these results, it is strongly recommended that comprehensive studies be initiated to investigate the prevalence and distribution of CyHV-3.

Study of changes in the histological structure of the gills of carp and zander living in lake Balkhash

The problem of adaptation and reactivity of an organism to various environmental factors is one of the central problems in theoretical and practical biology. At present, the attention of researchers is especially attracted bythe issues of ecological adaptation. Morphological works that shed light on the corresponding structural and functional rearrangements of fish gills in connection with their ecology are still poorly understood. In particular, the issues of comparative morphological assessment of the adaptive responses of gas exchange organs have not been developed. The impact of the enterprises of the metal and mining complex is reflected in the tissues of the organs of fish. Thus, environmental factors, such as the accumulation of heavy metals in water, subject the fish body to a structural and functional rearrangement, thereby changing the normal tissue structure. In this regard, the purpose of the study was to study changes in the histological structures of the gills of carp and zander living in Lake Balkhash. Changes in the tissue structure of the gill arch of fish were in the form of emerging pathologies, the frequency of which was noted using a comparative analysis. For the implementation of this work, a histological, morphometric and statistical study of the tissues of the gills of the studied fish individuals was also carried out. The following pathological processes were observed in the structure of the gills of carp and zander: changes in the shape of secondary lamellae, hyperplasia of the gill epithelium, necrosis and edema of the respiratory epithelium, as well as foci of hemorrhages. The detected changes in the histological structures of fish gills indicate the impact of external environmental factors, one of which, in this article, is the accumulation of heavy metals in water. This study was carried out from a natural ecosystem, thus, literary sources are used to compare the data obtained.

The pathology of Lates calcarifer herpesviral disease-Disseminated intravascular coagulation explains mortality spikes.

Lates calcarifer herpesvirus (LCHV) causes an emerging serious disease in aquaculture. Sudden drops in feed rates and mortality spikes exceeding 40%-50% often accompany LCHV infections in juvenile L. calcarifer, soon after transfer into sea cages. Affected fish have patchy white skin and fins, corneal opacity and frequently hang in surface water column like 'ghost' or 'zombie' fish. Fish have pale gills, fluid-filled intestines with yellowish casts, lipid depleted liver, enlarged spleen and kidney and reddened brain. Epithelial hyperplasia, apoptosis, marginated nuclear chromatin, amphophilic intranuclear inclusion bodies and the occasional multinucleated cells are observed in gills, skin, intestines, liver and kidney. These are often accompanied by lymphocytic-monocytic infiltration and extensive necrosis in gills, skin, kidney and intestines. Martius scarlet blue stains indicate presence of fibrin in vasculature in brain, gills, intestines, kidney and liver, or disseminated intravascular coagulation (DIC). DIC has been reported in human herpesviral infections. Multifocal lifting of intestinal epithelium with proteinaceous exudate and necrosis of several adjacent villi often progress to involve entire gut sections. Atrophied livers with accentuated lobules may progress to marked loss of hepatic acini. Multifocal dilated attenuated renal tubules are often accompanied by casts and marked protein loosing renopathy. This study on LCHV demonstrates that it can cause significant pathology and mortality.

The analysis of a cluster of koi herpesvirus disease outbreaks in intensive carp aquaculture using molecular and conventional epidemiology.

The analysis of a cluster of koi herpesvirus disease outbreaks in intensive carp aquaculture using molecular and conventional epidemiology.

Histopatología de juveniles cultivados de Totoaba macdonaldi asociados con aislamientos bacterianos identificados molecularmente como Vibrio spp. durante un evento de aumento de temperatura

Totoaba macdonaldi is an endangered species of croaker endemic to the Gulf of California, Mexico. This species has been cultured for the repopulation of wild stocks and commercialization at the Wildlife Management and Conservation Unit for the culture of T. macdonaldi at the Universidad Autónoma de Baja California, Mexico. A mortality episode was observed in 50 day-old juveniles, that coincided with an increase of temperature from 16 to 25.5˚C that affected the aquaculture facility. Histopathological and bacteriological analysis of survivor fishes were conducted to investigate the possible causes of mortality. Gill damage including severe congestion in gill filaments, necrosis, and epithelial dissociation of lamellae were observed. Moreover, epidermal, hypodermic necrosis, as well as diffuse bacterial colonization of the dermis was detected. Severe congestion and hemolysis were detected in the heart’s atrium and hepatic portal vessels. From the skin lesions, eight colonies of bacteria were isolated, these corresponded to four species of genus Vibrio, tentatively identified by partial sequence of the 16S rRNA gene as Vibrio harveyi, V. rotiferianus, V. brasilensis and V. shilonii. From them, V. harveyi corresponded to 4 of the 8 isolates and was found in all moribund fishes. Characteristics of the tissue alterations related with these opportunistic Vibrio spp. suggest an acute mortality event favoured by a temperature increase. This is the first record of the histopathology of T. macdonaldi juveniles that suffered an unusual mortality event under an increase of temperature in cultured conditions associated with Vibrio spp.

Status and preventive and curative measures in fish farming in the Western region of Ukraine

An assessment of the epizootic state and the main technological processes with the analysis of hydrochemical and hydrobiological indicators, a clinical examination, and a complete parasitological and pathological examination of carp fish in several fish farms in the Western regions of Ukraine during 2017–2022, was carried out. The analysis of farms in the region showed that carp farming is carried out with significant violations of fish farming requirements and technological norms regarding feeding, feed components, and nutrition. In many farms, reclamation measures and pond fertilization are not carried out, resulting in low fish productivity and increased organic pollution. As a result, the water environment's hydrochemical and hydrobiological indicators are disturbed, with them the veterinary and sanitary state of water bodies, which causes the emergence of infectious and invasive diseases. As a result, there are periodic outbreaks of diseases dangerous for fish, the main of which are the previously known infectious diseases: carp pox, gill necrosis, aeromonosis; fish mycoses: branchiomycosis, saprolegniosis, invasive diseases: ichthyobodosis (costiosis), trypanosomosis, coccidiosis, chylodonellosis, trichodinosis, ichthyophthiriosis, dactylogirosis, hyrodactylosis, diplostomosis, sanguinecolosis, philometroidosis, botryocephalosis, caviosis, caryophyllosis, synergasillosis, lerneosis, argulosis and many others. The mentioned diseases significantly reduce fish productivity and cause the death of fish in fish farms. The unsatisfactory epizootic state and the occurrence of most diseases are associated with violations of the rules of biotechniques of fish farming, non-compliance with veterinary and sanitary requirements, and non-fulfillment of preventive and curative measures.

Sublethal biochemical, histopathological and genotoxicological effects of short-term exposure to ciprofloxacin in catfish Rhamdia quelen

Ciprofloxacin (Cipro) is commonly detected in water worldwide, however, the ecotoxicological effects to aquatic biota is still not fully understood. In this study, using multiple biomarkers, it was investigated sublethal effects of short-term exposure to Cipro concentrations (1, 10 and 100 μg.L−1) in the Neotropical catfish Rhamdia quelen compared to non-exposure treatment (Control). After 96 h of exposure, the fishes were anesthetized for blood collection to hematological and genotoxicity biomarkers analysis. After euthanasia, the brain and muscle were sampled for biochemical biomarkers analyses. Gills, liver and posterior kidney for genotoxicity, biochemical and histopathological biomarkers analysis and anterior intestine for histopathological biomarkers analysis. Genotoxicity was observed in all tissues, regardless of the Cipro concentrations. Hematological alterations, such as reduction of the number of erythrocytes and leucocytes, as well as in hematocrit concentration and histopathological damages, such as reduction of microridges in gill epithelium and necrosis in liver and posterior kidney, occurred mainly at 100 μg.L−1. In addition, at 100 μg.L−1, Cipro increased antioxidant system activity (Catalase in liver and posterior kidney). These results demonstrated that under short-term exposure, Cipro causes toxic effects in R. quelen that demands attention and surveillance of environmental aquatic concentrations of this antibiotic.

MAJOR DISEASES OF STURGEONS IN AQUACULTURE OF THE REPUBLIC OF BELARUS

The article presents the main diseases of sturgeons occurring on fish farms of the Republic of Belarus – diseases of bacterial etiology (pseudomonosis), mycosis (saprolegniosis of fish and caviar), invasive (trichodinosis, argullosis, diplostomiasis), as well as diseases of non-infectious etiology (gill necrosis, gas bubble disease, fatty degeneration of the liver, anomalies in individual development). Up-to-date domestic drugs used in sturgeon aquaculture are also presented: neomycin, ciprofloxacin, enrotim, levofloxacin, Bacto-health, Disol-Na, Leoledum and Diplocid.

Haematological and Histopathological Examinations of African Catfish (Clarias gariepinus) Exposed to Sub-Lethal Concentrations of Paraquat

The study was designed to investigate the sub-lethal effects of paraquat on haematological parameters and histopathology of the gills, skin and liver of Clarias gariepinus juveniles of mean weight (38.26±1.20g) and length (17.50±1.55cm). The fish were exposed to 10, 20, 30, 40 and 50% of the 96hrsLC50 value of 107mg/l estimated from the 96 hours acute toxicity test. Blood samples were collected into heparinized tubes for the analyses of some haematological parameters, while the gills, skin and liver were also removed for histological examinations following standard procedures. The result revealed a significant reduction (P &lt; 0.05) in the values of red blood cells (RBCs), haemoglobin (Hgb), packed cell volume (PCV) and erythrocytes indices from the control. The white blood cells (WBCs) and platelets (Plt) were however increasing significantly (P &lt; 0.05) from those of the control as the test concentrations increased. The histology of the gills revealed some alterations such as epithelial proliferation, vacuolation of the mucus, hyperplasia of epithelial tissue of the gill filament, lifting and necrosis of the secondary lamellae. The exposed skin showed mucous cell proliferation, erosion of the epithelial lining, hypertrophy, necrosis of epithelial cells and widening of the epidermal and dermal layers. The liver exhibited cellular proliferation, sinusoid enlargement, congestion of the central vein, paranchymatous degeneration, vacuolar degeneration, pyknotic nucleic degeneration, legions and necrosis with severity as concentration of paraquat increases. The gills and skin were observed to be the most affected tissues in this study. The study also revealed that paraquat was toxic to C. gariepinus and causes some haematological and histopathological alterations in the fish blood and tissues at concentrations higher than 30mg/l. Therefore, the use of paraquat by farmers should be regulated particularly in area close to the aquatic environment.

Uses of Elaeis guineensis oil for Stress Management during the Transportation of Catfish Fingerlings: A Dose-Dependent Outcome

Cameroonian farmers used Elaeis guineensis oil (EGO) named usually palm oil to reduce stress and mortality during the transportation of catfish fingerlings. The present study is aimed to evaluate the uses of EGO for stress management during the transportation of catfish fingerlings. Antioxidant activities of EGO were assessed in vitro. 1500 fingerlings were transported from Douala (Littoral Region, Cameroon) to Yaoundé (Centre Region Cameroon). The transportation was for 7 h 55 min in black tins of 10 L which contain 8 L of water and 100 fingerlings each. The following treatment was administrated: commercial anti-stress, 2, 4, and 6 drops of EGO. Control received no treatment and all groups were triplicated. After 10 fingerlings were sacrificed by decapitation. Total protein, total bilirubin (TB), triglycerides level, and lactate deshydrogenase (LDH) activity were assessed in the liver as well as oxidant stress parameters. Brain and gills were fixed for histopathological analysis. Results showed that transportation of catfish fingerlings induced a significant increase of TB level and LDH activity in the liver. Indeed, it induced cerebellar and gills necrosis. Moreover, EGO exhibits antioxidant activities in vitro against DPPH, ABTS radicals, and possesses a ferric reducing antioxidant power of 6.31 mEAG/g. This observation was confirmed in vivo by the increase in a dose-dependent manner of GSH and nitrites levels in the liver compared to control. However, the administration of 6 drops of EGO increased significantly (p &lt; 0.05) the activity of LDH in the liver compared to control. Thus, high dose induced anaerobic respiration which was confirmed by alveolar necrosis in gills and neurodegeneration although low dose of EGO (2-4 drops) prevented those alterations compared to control. Hence, low doses of Elaeis guineensis oil can prevent liver, cerebellar and gills impairment during artisanal transportation to reduce the effects of stress.

Isolation of a novel adomavirus from cultured American eels, Anguilla rostrata, with haemorrhagic gill necrosis disease.

Recently, the culture of American eels (Anguilla rostrate) in China has been impacted by emergence of a disease with signs of haemorrhagic gill necrosis. The gills of diseased eels are covered with petecchia and they bleed when the operculum is pressed. In this study, a novel American eel adomavirus (AEAdoV) was isolated from the diseased eels using the eel ovary cell line (EO). The virus proliferated in the EO cells with a maximum TCID50 /ml of 106.29±0.23 at 6days post-infection. The virions were non-enveloped with a diameter of 75-85nm and shown to be a DNA virus upon 5-iodo-2'-deoxyuridine (IDU) treatment. PCR assays showed that AEAdoV encodes a superfamily 3 helicases (S3H) replicase and shared high similarities with Anguilla marmorata adomavirus (MEAdoV). Although no clinical signs or mortality was observed among the eels injected with AEAdoV, the virus was reisolated from livers, kidneys and gills of injected eels at 35days post-injection. Our results suggested that AEAdoV exhibited a latent infection in A.rostrata. The pathogenicity of the AEAdoV needs to be confirmed further.

Resistome characterization of Flavobacterium columnare isolated from freshwater cultured Asian sea bass (Lates calcarifer) revealed diversity of quinolone resistance associated genes

Flavobacterium columnare is a Gram-negative bacterium which causes columnaris disease in freshwater fish species worldwide. Antibiotics, especially quinolone, is a primary therapeutic option to mitigate the economic loss caused by this disease. Phenotypic characterization and susceptibility testing were performed to identify quinolone resistance (QR)-associated genes in F. columnare isolated from freshwater cultured Asian sea bass. A total of 15 F. columnare isolates were collected from moribund fish that exhibited columnaris-like clinical signs and lesions including gill necrosis, saddleback lesion, and fin erosion. Phylogenetic analysis based on 16S rRNA and dnaK revealed that these isolates belonged to genetic group (GG) 2 and 4. Disk diffusion test results indicated that the 15 isolates were susceptible to all tested antibiotics except quinolones. Five and six isolates were resistant to oxolinic (OA) (33.33%) and nalidixic acid (NA) (40%) respectively. Broth microdilution indicated that highest OA, NA and enrofloxacin (ENR) minimum inhibitory concentration (MIC) values were 16, 64 and 1 μg/mL respectively. The MIC level to quinolone of GG 2 was higher for the GG 4 counterparts. Sequence analysis revealed a serine:phenylalanine amino acid substitution at position 83 (S83F) and a glutamine:histidine amino acid substitution at position 458 (Q458H) of quinolone resistance-determining regions (QRDRs) of gyrA and gyrB respectively. The Q458H in gyrB was identified as a novel non-synonymous mutation of the Flavobacteriaceae family. A genome-scale resistome analysis revealed that connections between GG and QR level potentially correlated with the presence or absence of chromosomal antimicrobial resistance genes and accumulated mutations in QRDRs. This study provide a guidance for choosing antibiotics for treatment columnaris disease and point out the important quinolone resistance mechanisms in F. columnare.

Accumulation of paralytic shellfish toxins by Southern Rock lobster Jasus edwardsii causes minimal impact on lobster health

Recurrent dinoflagellate blooms of Alexandrium catenella expose the economically and ecologically important Southern Rock Lobster in Tasmania to paralytic shellfish toxins (PST), and it is unknown if PST accumulation adversely affects lobster performance, health and catchability. In a controlled aquaculture setting, lobsters were fed highly contaminated mussels to accumulate toxin levels in the hepatopancreas (mean of 6.65 mg STX.2HCl equiv. kg−1), comparable to those observed in nature. Physiological impact of PST accumulation was comprehensively assessed by a range of behavioural (vitality score, righting ability and reflex impairment score), health (haemocyte count, bacteriology, gill necrosis and parasite load), nutritional (hepatopancreas index and haemolymph refractive index) and haemolymph biochemical (21 parameters including electrolytes, metabolites, and enzymes) parameters during a 63 day period of uptake and depuration of toxins. Exposure to PST did not result in mortality nor significant changes in the behavioural, health, or nutritional measures suggesting limited gross impact on lobster performance. Furthermore, most haemolymph biochemical parameters measured exhibited no significant difference between control and exposed animals. However, the concentration of potassium in the haemolymph increased with PST, whilst the concentration of lactate and the sodium:potassium ratio decreased with PST. In addition, exposed lobsters showed a hyperglycaemic response to PST exposure, indicative of stress. These findings suggest that PST accumulation results in some measurable indicators of stress for lobsters. However, these changes are likely within the adaptive range for Jasus edwardsii and do not result in a significant impairment of gross performance. Our findings support previous conclusions that crustaceans are relatively tolerant to PST and the implications for the lobster fishery are discussed.

Susceptibility of Koi, Koi×Red Common Carp, and Red Common Carp×Koi to Koi Herpesvirus (KHV).

The disease-causing koi herpes virus (KHV), also known as cyprinid herpesvirus-3 (CyHV-3), causes mass mortality of koi and carp. Koi (Cyprinus carpio) is a host for KHV, one of 12 virus species in the Alloherpesviridae family. We examined the effects of KHV disease koi (KK), and on koi×red common carp (KR) and red common carp×koi (RK) cross, using a virus challenge test. The infected fish had clinical signs that included gill necrosis and skin lesions. The RK and KR were highly more resistant (cumulative mortality: RK; 6% and KR; 8%) to KHV infection than KK fish (cumulative mortality: 28%). KHV DNA was confirmed in the tissues of all dead fish in groups by use of polymerase chain reaction (PCR), and the presence of the KHV protein in kidney was confirmed by immunohistochemistry. Histological analysis showed severe gill lesions and fusion of the lamellae in KK fish, but less severe damage in RK fish. In immunohistochemistry analysis, the KHV protein localized in the cytoplasm of infected kidney cells of KK, but the cross groups had lower levels of KHV antigen. Our data indicate that the cross groups had increased resistance to KHV disease.

Severe damages caused by Malathion exposure in Colossoma macropomum

The increase in pesticide use in response to agricultural demands poses a risk to non-target organisms, including fish. Integrated analysis of biochemical, histopathological and genetic parameters in fish exposed to Malathion insecticide provide information on the toxicity mechanisms of this pesticide, which is classified as a probable carcinogen for humans. The present study assessed the biological responses of Colossoma macropomum after exposure to Malathion. We started determining the lethal concentration, which is the concentration capable of killing 50% of the subjects in an acute toxicity test (LC50-96 h), which was 15.77 ± 3.30 mgL−1. The fish were, then, exposed to Malathion during 96 h at a sublethal concentration, 7.30 mgL−1. Overall, we observed an increased activity of biotransformation and antioxidant enzymes, which reduced production of mitochondrial reactive oxygen species after 96 h exposure, as well as kept constant the mitochondrial respiration, Acetylcholinesterase activity and DNA damage. However, fish exposed to insecticide presented severe gill histopathological damage and increased expression of proto-oncogene ras. Taken together, the results suggest that, after four days of exposure to the Malathion, C. macropomum efficiently activates its defense mechanisms, suggesting that the basal response mechanisms are responsive. On the other hand, histopathologic damages evidenced the adverse effects of Malathion on fish, since it promoted gill necrosis and increased the expression of ras oncogene that is directly related to tumorigenesis events.