Gill Lesions Research Articles

Biochemical and Molecular Detection of Aeromonas Hydrophila Isolated from Infected Cyprinus Carpio in Salah Al-Din Governorate

This study aimed to identify the presence of Aeromonas hydrophila bacteria in diseased common carp (Cyprinus carpio) fish collected from Salah al-Din Governorate in Iraq. For this purpose, 128 swabs were obtained from skin, gill and fin lesions of 70 fish showing symptoms of hemorrhagic sepsis, skin ulcers and boils, and fin and gill rot. Through different biochemical tests, the isolates showed negative results for Gram stain, methyl red, lactose fermentation, H2S, and string test, while positive results were recorded for glucose fermentation, oxidase, motility test, catalase, Voges-Proskauer, indole, citrate utilization, and gelatin hydrolysis. Eleven isolates were confirmed as A. hydrophila by amplification of the hemolysin gene fragment (hlyA) by conventional PCR. This study represents the first comprehensive study to characterize A. hydrophila bacteria from infected common carp fish in Salah al-Din Governorate. The findings of this study provide valuable insights for developing genetic diagnostic strategies for A. hydrophila infections in this region.

Copper and Temperature Interaction Induced Gill and Liver Lesions and Behaviour Alterations in Mozambique Tilapia (Oreochromis mossambicus)

Climate changes linked to extreme events pose a threat to freshwater biodiversity, impacting organs, behaviour, and reproduction. Moreover, these changes can be amplified by pollution. Copper sulphate (CuSO4) is used in agriculture and aquaculture, so the copper can reach streams, rivers, and lakes impacting fish. This study evaluated the combined effects of temperature and copper on gills and liver histology biomarkers and in the behaviour of Mozambique tilapia over 28 days. Tilapias were exposed to different water temperatures (25 °C and 32 °C) and CuSO4 concentrations (1.1 and 3.6 mg/L). Fish from the control group were exposed to water without copper sulphate and at 25 °C (within their optimum range). Histopathological analysis revealed significant tissue lesions, namely aneurysms and bending of gill lamellae, and hyalinization and vacuolization in the liver at the higher temperature and CuSO4 level. Moreover, behavioural observations revealed increased stress changes under the same conditions. These findings highlight the effects of fast climate change, and rising temperatures on copper toxicity, underlining the necessity for strict monitoring and regulation of copper use due to future climate change scenarios to protect aquatic ecosystems, ichthyofauna population and trophic web dynamics. This data also alerts for similar problems with other toxic metals or chemicals, at short term, in streams and rivers, under rapid climate changes and more frequent extreme events.

Screening for White Spot Syndrome Virus (WSSV) in pink shrimp (Penaeus paulensis) from Rocha Lagoon, Uruguay

Penaeus paulensis (pink shrimp) is an important resource for small-scale fisheries in the brackish coastal lagoons of Uruguay. No viral diseases have been detected in shrimp populations in the Uruguayan territory. The presence of viral pathogens, such as White Spot Syndrome Virus (WSSV) and Infectious Hypodermal Haematopoietic Necrosis Virus (IHHNV) in wild shrimp populations has been previously reported in Brazil and Argentina.We investigated the presence of WSSV in wild populations of penaeid shrimp from Rocha Lagoon, Uruguay. We sampled 70 specimens of juvenile P. paulensis and assessed the presence of these viral pathogens using nested PCR and histology. Gill tissue from the 70 samples was divided into 14 pools of 5 individuals for DNA extraction and PCR analysis. We also retested each pooled sample individually. The nested PCR procedure described in the WOAH aquatic animal manual was used. A subset of 20 individual specimens were also processed using standard histological techniques.The results showed that WSSV was not detected in the pooled or individually tested samples. We found no evidence of the presence of the viral genome or gill lesions in the samples analysed. This indicates that the fishery is still likely to be free of WSSV infection. The procedures and information generated can be used as a baseline study for future implementation of surveillance programmes in the country.

Sub-Lethal Responses of Delta Smelt to Contaminants Under Different Flow Conditions

The Delta Smelt is a largely zooplank­tivorous, endangered fish endemic to the San Francisco Estuary (the estuary). High flows increase the availability of fresh and brackish water habitat for Delta Smelt, but also may mobilize contaminants, potentially increasing toxicological stress. Here, we examine the association between contaminants and Delta Smelt health across contrasting water year types and flow-related management actions. Our study spanned the fall season of three years: 1 dry year (2018) bracketed by 2 wet years (2017 and 2019) and coincided with several management actions meant to benefit Delta Smelt. We collected field water from six sites in the estuary that encompass the freshwater and low-salinity habitat of Delta Smelt and analyzed the water for contaminant concentrations. After a 96-hour exposure to the field water, we assessed cultured Delta Smelt survival and the histopathological condition of the gill and liver. Insecticides, particularly fipronil metabolites, were the most prevalent contaminants detected in 2017 and 2018, and a variety of contaminants associated with the rice harvest were detected in 2019. No acute toxicity was observed during any exposure, but we observed negative effects in the livers of Delta Smelt exposed to agricultural water from the Toe Drain and Cache Slough during a 2019 pulse flow action, which coincided with elevated detections and concentrations of organic pesticides. Other noteworthy sub-lethal effects, likely occurring in response to contaminant mixtures, included severe gill lesions in Delta Smelt exposed to Decker Island water in 2019. In the drier year of 2018, lesions were generally mild or absent. Thus, the trade-offs between increased habitat availability and contaminant loading may provide one explanation for why Delta Smelt abundance does not consistently respond positively to outflow.

Comparative subchronic toxicity of copper and a tertiary copper mixture to early life stage rainbow trout (Oncorhynchus mykiss): impacts on growth, development, and histopathology.

This research aimed to characterize and compare the subchronic impacts of Cu to a Cu, Cd, and Zn mixture in early life stages of rainbow trout (Oncorhynchus mykiss) by examining uptake, survival, growth, development, and histopathology parameters. To accomplish this, rainbow trout were exposed for 31 days from eyed embryos to the swim-up fry life stage to waterborne Cu (31, 47, 70, and 104 μg/L) individually or as mixture containing Cd (4.1, 6.2, 9.3, and 14 μg/L) and Zn (385, 578, 867, and 1300 μg/L). Exposures elicited pronounced effects on survival when Cu was administered as a mixture (LC25 = 32.9 μg/L Cu) versus individually (LC25 = 46.3 μg/L Cu). Mixtures of Cu, Cd, and Zn also elicited more pronounced sublethal toxicity relative to equivalent Cu treatments with respect to reduced yolk sac resorption and increased incidence and/or severity of gill, liver, and kidney lesions. Our findings of reduced body weight (EC10, Cu = 55.0 μg/L Cu; EC10, Cu+Cd+Zn = 58.9 μg/L Cu), yolk sac resorption (LOECCu = 70 μg/L Cu; LOECCu+Cd+Zn = 70 μg/L Cu), coelomic fat (LOECCu = 47 μg/L Cu; LOECCu+Cd+Zn = 70 μg/L Cu), and increased hepatocellular cytoplasmic vacuolation (LOECCu = 70 μg/L Cu; LOECCu+Cd+Zn = 47 μg/L Cu) collectively indicate a complicated metabolic interference by metals in exposed fish. These lethal and sublethal effects observed in the laboratory could translate to reduced survival and fitness of wild salmonid populations inhabiting waterbodies receiving wastewater or runoff containing multiple metals at elevated concentrations.

Condition and postrelease mortality of angled Northern Pike temporarily retained on stringers

AbstractObjectiveAnglers typically use stringers to keep fish intended for harvest from spoiling or for high‐grading purposes (i.e., culling). However, relatively few studies have examined the effects of temporary stringer retention on the physical condition and postrelease mortality of fish. In this study, our objective was to investigate the lethal and sublethal effects of temporarily retaining Northern Pike Esox lucius on stringers.MethodsWe evaluated the blood physiology, reflex impairment, injury, and fate of 168 Northern Pike that were exposed for 2 h on one of five treatments: (1) cord stringer through the operculum, (2) cord stringer through the lower jaw, (3) metal stringer through the operculum, (4) metal stringer through the lower jaw, and (5) aerated tank control.ResultImmediately after retention, blood lactate concentrations of stringer treatments were on average 42% greater relative to controls. Fish from the stringer treatments exhibited injuries of varying severity, most of which (e.g., gill lesions, expanded puncture wounds, swelling) were still present on surviving fish 48 h later. Reflexes were impaired for all stringer fish, whereas control fish tended to have all reflexes intact. No fish died during the treatment period. The highest occurrence of mortality was within the first 8 h following retention for the cord–operculum (48%), metal–jaw (15%), and metal–operculum (19%) treatments. Stringers placed through the operculum had a higher mortality rate (37%) compared with stringers placed through the lower jaw (17%), regardless of stringer type. Overall, 27% of fish placed on stringers died and 68% of the remaining fish showed injuries related to stringers, while control fish showed low mortality (7%) and no meaningful injuries.ConclusionOur results suggest that holding fish on stringers causes stress and injury levels that can result in postrelease mortality. As such, fisheries managers should consider restricting the release of fish placed on stringers, and once placed on a stringer, fish should be regarded as part of the daily harvest limit for a given angler.

Acetylcholinesterase activity, histopathological changes, lipid peroxidation and stress-related genes expression in Nile tilapia (Oreochromis niloticus) exposed to waterborne methidathion

The safety of aquatic system has been threatened due to extensive and inappropriate application of organophosphorus pesticide methidathion (MD). Hence, a 12-day stress trial was carried out to explore the impacts of waterborne MD on acetylcholinesterase (AChE) activity, histopathology, antioxidant status and stress-related genes expression in Nile tilapia (Oreochromis niloticus). Fish (initial mean weight 60 ± 2 g) were placed in 18 tanks (volume 460 L, 30 fish/tank), with triplicate treatment groups being exposed to diverse concentrations of MD (0, 0.8, 1.67, 5.34, 7.49 and 15.83 µg/L). The results showed that AChE activities in serum and liver were inhibited by MD. After the 12-day stress trial, malonaldehyde (MDA) content in serum and liver was higher than that of 0 µg/L group when MD concentration exceeded 0.8 and 5.34 µg/L, respectively. Catalase (CAT) and total superoxide dismutase (T-SOD) activity in serum and liver revealed irregular variations. In addition, MD (＞0.8 µg/L) caused lesions in gills and liver tissues. MD also down-regulated expression of cytochrome P450 1B1, heat shock protein 70 and cytochrome c oxidase subunit 7B, which contradicted the trend of phospholipase A2 and cytochrome P450 1 A (except in the 15.83 µg/L group). In a word, waterborne MD suppressed AChE activities, induced oxidative stress and harmed the liver and gills. Additionally, it may negatively influence resistance to stress, oxidative phosphorylation, detoxification and anti-inflammatory response in Nile tilapia.

Adverse effects of ozonation on the animal welfare of tilapia Oreochromis niloticus in recirculation aquaculture

Ozone is often used to disinfect process water in recirculating aquaculture systems. Here, ozone rapidly leads to the formation of secondary oxidants, called ozone produced oxidants (OPO). We studied the impact of OPO on juvenile tilapia Oreochromis niloticus in brackish water at 0, 0.05, 0.1 and 0.15 mg/L chlorine equivalents after 2 d, 9 d and 21 d of exposure, assessing gill histopathology and lesions of the mitochondrial DNA. Damage of the gills was already observed after 2 d, comprising an increased occurrence of lamellar lifting, fusion of the lamellae and edema at 0.15 mg/L. After 21 d, occurrence of lamellar fusion and edema was elevated at 0.15 mg/L. Increased incidence of hyperplasia was already observed at 0.05 mg/L after 9 d. DNA fragmentation increased to 3.92 lesions per 10 kb at 0.15 mg/L compared to 2.62 lesions per 10 kb in the control. In conclusion, first adverse effects were observed at 0.05 mg/L and severe impact is subsequently recorded at 0.1 mg/L chlorine equivalents. Therefore, OPO concentrations need to be kept below 0.05 mg/L chlorine equivalents to avoid adverse effects on animal welfare.

Acute toxicity of palm oil mill effluent on zebrafish (Danio rerio Hamilton-Buchanan, 1822): Growth performance, behavioral responses and histopathological lesions

Evaluating the toxicity of Palm Oil Mill Effluent (POME) is critical as part of the effort to develop waste management regulations for the palm oil industry. In this study, we investigated the acute toxicity of POME on growth performance, behavioral response, and histopathology of gill and liver tissues of zebrafish (Danio rerio). In total, 550 adult male zebrafish were used for the toxicity experiment including range finding test, acute toxicity test, growth performance and behaviour test. Static non-renewal acute toxicity bioassays were conducted by exposing fish to POME (1.584–9.968 mL/L) for 96 h. Growth performance, behavior response, and histopathological lesions in untreated and POME treated (96-h LC50: 5.156 mL/L) fish were measured at 24, 48, 72 and 96 h. Time-dependent significant decline in body length and body weight of POME-exposed zebrafish was observed. Furthermore, several behavioral changes were recorded, including hyperactivity, loss of balance, excessive mucus secretion, and depigmentation. Decreasing operculum movement and oxygen consumption rate as well as alterations in gill tissues (i.e. hyperplasia, hypertrophy, hemorrhage, and necrosis) of POME-exposed zebrafish were observed, suggesting a dysfunction in respiratory performance. On the other hand, liver tissue alterations (congestion, hemorrhage, hyperplasia, shrinkage of hepatocytes, hydrophilic degeneration, and necrosis) indicated a disruption in detoxification performance. We conclude that exposure to POME at acute concentration caused histopathological lesions both in gill and liver tissue along with changes in fish behaviors which disrupted respiratory and detoxification performance, resulting in mortality and reduced growth of zebrafish. These findings might provide valuable information for guiding POME management and regulation.

Toxicopathic effects of waterborne Cd in sole juveniles, a prospective pollution monitoring sentinel for estuarine ecosystems

IntroductionEstuarine ecosystems are under high anthropogenic pressure and receive a wide Q7 variety of contaminants, including metals. They can remain trapped in estuarine sediments at high concentrations for long periods but eventually they can be released to the overlying water and become toxic for the resident benthic biota. As a consequence, biomonitoring programs surveying the health status of estuaries and coastal areas count with benthic species for the assessment of health disturbances in these specific ecosystems. The present investigation aims at recognizing toxicopathic effects elicited in estuarine life stages of the benthic fish Solea senegalensis on exposure to waterborne Cd, a model compound for metal contamination.MethodsBiological responses to metal exposure were assessed based on the application of a “biomarker + histopathology” approach. Two-year old sole juveniles were exposed to various concentrations of waterborne Cd for 3 and 7 days (Control; Low Cd: 1 µg/l; Mid Cd: 10 µg/l and High Cd: 1000 µg/l). Liver samples were collected for chemical analysis at day 7. Biological samples were collected at days 3 and 7 for biochemical (brain and liver), histochemical (liver) and histopathological analysis (liver, gills and gonad).ResultsBrain acetyl cholinesterase was inhibited after 7 days exposure, indicating neurotoxic effects on exposure to 1000 µg Cd/l. Hepatic catalase and glutathione-Stransferase were induced at day 3 and inhibited at day 7, which suggests a bell-shaped response. A dose-dependent lysosomal membrane destabilization in hepatocytes was recorded at day 7. In parallel, histopathological lesions in gills, liver and gonad were more frequent at day 7 in soles exposed to high Cd concentrations.DiscussionOverall, the “biomarker + histopathology” approach revealed that waterborne Cd causes toxicopathic effects in sole juveniles upon exposure to environmentally relevant concentrations (10 µg Cd/l). The effects were clearly time dependent, and thus it is conceivable that more severe biological effects would be elicited by these low concentrations of Cd at longer exposure periods. Therefore, biomarkers and histopathology in combination provide early-warning indications of altered health status after waterborne Cd exposure in sole juveniles, a prospective sentinel for biological effects assessment of metal contamination in pollution monitoring programs in estuaries and coastal areas.

Amoeba species colonizing the gills of rainbow trout (Oncorhynchus mykiss) in Swiss aquaculture.

Nodular gill disease (NGD) is an infectious condition characterized by proliferative gill lesions leading to respiratory problems, oxygen deficiency and mortality in fish. Globally, NGD primarily impacts freshwater salmonids in intensive aquaculture systems. In recent years, numerous outbreaks of severe gill disease have affected more than half of the larger rainbow trout (Oncorhynchus mykiss) farms in Switzerland, mainly during spring and early summer. Mortality has reached up to 50% in cases where no treatment was administered. Freshwater amoeba are the presumed aetiologic agent of NGD. The gross gill score (GS) categorising severity of gill pathology is a valuable first-line diagnostic tool aiding fish farmers in identifying and quantifying amoebic gill disease (AGD) in farmed marine salmonids. In this study, the GS was adapted to the NGD outbreak in farmed trout in Switzerland. In addition to scoring disease severity, gill swabs from NGD-affected rainbow trout were sampled and amoeba were cultured from these swabs. Morphologic and molecular methods identified six amoeba strains: Cochliopodium sp., Naegleria sp., Vannella sp., Ripella sp., Saccamoeba sp. and Mycamoeba sp. However, the importance of the different amoeba species for the onset and progression of NGD still has to be evaluated. This paper presents the first description of NGD with associated amoeba infection in farmed rainbow trout in Switzerland.

Reciprocal hybrids of Atlantic salmon (Salmo salar) x brown trout (S. trutta) confirm a heterotic response to experimentally induced amoebic gill disease (AGD)

Amoebic gill disease (AGD) affects global marine aquaculture production of Atlantic salmon, requiring costly reiterative treatment and negatively impacting fish performance and welfare. Although there has been gradual and ongoing progress in genetic selection to improve host resistance to the causative agent (Neoparamoeba perurans) there has been little focus on the response of interspecific hybrids to AGD challenge. Previous research has demonstrated that Atlantic salmon x brown trout hybrids had reduced requirement for freshwater bathing (based on gross gill signs) during chronic natural AGD exposure, yet there has been no histological or molecular evidence confirming differential host response or parasite abundance. In this study we exposed Atlantic salmon (SS), brown trout (TT) and their reciprocal interspecific hybrids (TS and ST) to a single laboratory challenge (∼700 amoebae.l−1 for 18 days) and compared the resultant infection and disease signs characteristic of AGD. Gill score was significantly higher in SS than in TT and hybrids. Copy number quantification of amoebae on gills was higher in salmon than in hybrids or trout but did not differ between hybrids and trout. Gill histopathology confirmed both an increased amoebae abundance and higher expression of host tissue reaction in SS with significantly higher percentages of lesions harboring hyperplastic lesions. Mid-parent and best-parent heterosis of resistance to N. perurans and host response (gill lesions) was confirmed but did not differ between hybrid crosses. Although limited to a single laboratory infection event, our results support previously reported observations (from natural infection/reinfection) of reduced AGD signs in trout and interspecies hybrids. We conclude that interspecies hybrids have potential to improve our understanding of salmonid resistance to amoebic branchitis and support future gene-based research toward fish disease management.

Ectoparasitic diversity, gill alterations in Hoplerythrinus unitaeniatus (Characiformes: Erythrinidae) and Cichlasoma bimaculatum (Perciformes: Cichlidae) and quality of fishing water in the Quilombola zone in Maranhão State, Brazil

The current study aimed to investigate the ectoparasitic diversity and gill alterations in Hoplerythrinus unitaeniatus (Characiformes: Erythrinidae) and Cichlasoma bimaculatum (Perciformes: Cichlidae) and evaluate the microbiological and physicochemical quality of water samples deriving from a Quilombola zone in Maranhão State, Brazil. Water samples and 42 fish specimens, 21 H. unitaeniatus and 21 C. bimaculatum, were collected from a floodable environment. Water samples were subjected to physicochemical and microbiological analyses in the laboratory environment. Fish specimens were euthanized to collect and identify ectoparasites in animals' mucus, body surface, and gills, as well as to enable the histological analysis of the second right gill arch. The herein-identified ectoparasites have shown 30.95% prevalence and comprised three phyla: Platyhelminthes, Trematoda and Arthropoda. The herein-identified main histological changes comprised incomplete and complete fusion of several lamellae, lifting of respiratory epithelium, lamellar disorganization, lamellar epithelial hyperplasia, and blood sinus dilation. The herein calculated histological alteration index has shown that 23.80% of specimens presented mild-to-moderate tissue damage, 4.77% presented moderate-to-severe tissue changes, and 9.52% presented irreparable tissue damage. It was possible concluding that histological gill lesions identified in fish specimens analyzed may be adaptive responses to the affected environment and the incidence of ectoparasites.

Potential Symbiotic Effects of β-1,3 Glucan, and Fructooligosaccharides on the Growth Performance, Immune Response, Redox Status, and Resistance of Pacific White Shrimp, Litopenaeus vannamei to Fusarium solani Infection

The potential effects of dietary supplementation with β-1,3 glucan and fructooligosaccharides (β-1,3 GF) on antioxidant activities, immunological response, and growth performance of Pacific white shrimp (Litopenaeus vannamei) was investigated. Four diets (iso-energetic and iso-nitrogenous) with different levels of β-1,3 GF (0, 0.5, 1.0, and 1.5 g kg−1) were fed to healthy shrimp juveniles weighing 3 ± 0.5 g for 75 days. Shrimps were randomly distributed into 12 net enclosures at a density of 30 shrimp/net, and the experiment was performed in triplicate. The results revealed that long-term supplementation with 1.5 g kg−1 β-1,3 GF significantly improved shrimp weight gain, feed conversion ratio, and digestive enzyme profiles compared to the control diet group. However, there were no substantial variations in the contents of moisture, crude protein, total lipids, and ash in the muscles of shrimp fed on different diets. Surprisingly, all antioxidants (superoxide dismutase, catalase, glutathione peroxidase) and immune biomarkers (lysozyme, total hemocyte count, phenol oxidase, and respiratory burst) activities were significantly elevated with increasing levels of β-1,3 GF in the shrimp diet, and the highest values were recorded in the 1.5 g kg−1 diet groups. Challenge test results revealed that F. solani could cause a high mortality rate (86.7%) in a group fed a normal basal diet within 14 days at a dose of 5 × 104 conidia mL−1. Surprisingly, all dietary treated groups with different doses of β-1,3 GF showed high resistance against F. solani, represented by lower cumulative mortality rates (20–43.3%) compared to the control group. Moreover, most of the infected shrimp showed a typical black to brown gill lesion similar to that observed in the natural infection, where an identical fungus was successfully re-isolated from infected gills and muscles. Overall, this study recommends an appropriate incorporation level of β-1,3 GF that could enhance growth performance and improve the antioxidant activities, non-specific immunity, and disease resistance of L. vannamei, with an optimal level of 1.5 g kg−1.

Microplastic and oil pollutant agglomerates synergistically intensify toxicity in the marine fish, Asian seabass, Lates calcalifer

Asian seabass, Lates calcarifer frys were exposed to polystyrene (MP: 0.5 mg/l), oil (0.83 ml/l) and agglomerates (MP + oil + Corexit) as eight treatments in three replicates, and fresh synthetic marine water (control) for 15 days. The synergistic effect was confirmed (P ˂ 0.05) by bio-indicators including RBC count, total plasma protein, aspartate aminotransferase (AST), catalase (CAT), glutathione S-transferase (GST), basophils, thrombocyte and eosinophils percentages. Most of the significant and synergistic effects were observed in the highest doses (5 mg/l MP and 5 mg/l MP-oil-dispersant). Exposure to MP and a combination of MP+ oil caused tissue lesions in gill, liver and intestine. Our results suggest there are no critical health issues for Asian seabass in natural environments. However, the bioaccumulation of MPs, oil, and their agglomerates in consumers' bodies may remain a concern.

Pseudomurraytrema fergusoni n. sp. (Monogenea: Dactylogyridae) from gills of Pealip Redhorse, Moxostoma pisolabrum (Catostomidae) from Arkansas, USA, with a description of gill pathology.

Pseudomurraytrema fergusoni n. sp. is described from the Pealip Redhorse, Moxostoma pisolabrum from the Black River (White River drainage), Lawrence County, Arkansas, USA. This represents the second monogenean described from M. pisolabrum as well as the second species of Pseudomurraytrema reported from an Arkansas catostomid. The description includes partial 18S rRNA and 28S rRNA gene sequences (732 bp and 851 bp, respectively), helping fill a void in sequence data from North American monogeneans, particularly those in the genus Pseudomurraytrema. In addition, histopathologic changes associated with the infection resulted in severe localized pathologic lesions in gills of the host, suggesting compromise of respiratory surfaces within affected areas adjacent to the worms.

Prospective Longitudinal Study of Putative Agents Involved in Complex Gill Disorder in Atlantic salmon (Salmo salar).

Complex gill disorder (CGD) is an important condition in Atlantic salmon aquaculture, but the roles of the putative aetiological agents in the pathogenesis are uncertain. A longitudinal study was undertaken on two salmon farms in Scotland to determine the variations in loads of CGD-associated pathogens (Desmozoon lepeophtherii, Candidatus Branchiomonas cysticola, salmon gill pox virus (SGPV) and Neoparamoeba perurans) estimated by quantitative PCR. In freshwater, Ca. B. cysticola and SGPV were detected in both populations, but all four pathogens were detected on both farms during the marine stage. Candidatus B. cysticola and D. lepeophtherii were detected frequently, with SGPV detected sporadically. In the marine phase, increased N. perurans loads associated significantly (p < 0.05) with increases in semi-quantitative histological gill-score (HGS). Increased Ca. B. cysticola load associated significantly (p < 0.05) with increased HGS when only Farm B was analysed. Higher loads of D. lepeophtherii were associated significantly (p < 0.05) with increased HGS on Farm B despite the absence of D. lepeophtherii-type microvesicles. Variations in SGPV were not associated significantly (p > 0.05) with changes in HSG. This study also showed that water temperature (season) and certain management factors were associated with higher HGS. This increase in histological gill lesions will have a deleterious impact on fish health and welfare, and production performance.

Genotoxic and histopathological effects of the Ili River (Kazakhstan) water pollution on the grass carp Ctenopharyngodon idella

ABSTRACT In the present study, genotoxic, histological and hematological effects of water pollution were evaluated in Ctenopharyngodon idella from the Ili river. Water and fish were sampled at three sites. The concentrations of the following heavy metals were measured in the water: Pb, Co, Mg, Cd, Cu, Zn, Fe. Water pollution with metals gradually increased from P1 to P3: in P1, Cu and Fe levels exceeded the maximum permissible concentrations for fish culture, in P2 – Pb, Cu, Zn, Fe, and in P3 – Pb, Cd, Cu, Zn, Fe. In fish from the Ili river, the highest frequency and severity of DNA damage and liver damage were noted in P3, the lowest in P1. Gill lesions were more pronounced and frequent in fish from P3 compared to grass carp from P2 and P1. Fish from P1 showed a higher frequency of neutrophils and a lower percentage of lymphocytes compared to the control. The results also revealed: genotoxicity measured by comet analysis and liver histology were the most sensitive and showed the magnitude of lesions directly related to the level of water contamination. Gill histology also clearly showed pathological changes caused by pollution, while differential leukocyte count was the least useful indicator, as it showed only minor differences between fish from unpolluted and polluted water.

Temporal Trends in Macroscopic Indicators of Fish Health in the South Branch Potomac River

AbstractOver recent decades, the South Branch Potomac River, West Virginia, has experienced fish kills and episodes of suppressed health in adult fish that have spanned small stretches to nearly 120 km of contiguous habitat. Although factors such as endocrine disruption, chemical contaminants, and infectious agents have been detected, no single causal mechanism has been identified. To gain information about the temporal nature of abnormalities, differences in life stage impacts, and potential risk factors, investigations of rank scores of macroscopic fish health indicators were conducted utilizing seasonal and annual boat electrofishing surveys for Smallmouth Bass Micropterus dolomieu (SMB) and Golden Redhorse Moxostoma erythrurum (GDR). Gill and body abnormalities were assigned rank scores for each fish based on visual severity and were tested for correlation with seasonal climatic (flow and stream temperature) and environmental (stream pH, dissolved oxygen, and turbidity) factors. Comparisons between juveniles and adults for these species indicated that body lesions were more common for adult GDR and gill lesions were more common for adult SMB. Significantly higher rank sums of adult gill abnormalities corresponded with heavy annual mortality of SMB between ages 2 and 3 (86%), the period during which this species transitions from juvenile to adult length. Higher ranks were frequently assigned to fish of both species for gill and body/fin lesions in summer and fall samples. Low stream discharge and lower pH correlated with elevations of body raised lesions (GDR) and body erosions (GDR and SMB) as well as erosions of the gill lamellae (SMB). This study connects the disciplines of fisheries management, fish health, and environmental monitoring, providing information gained through tracking the macroscopic conditions of these two indicator species to focus future studies and better understand risks to fish health.

Histopathologic Lesions in Bivalve Mollusks Found in Portugal: Etiology and Risk Factors

Bivalve mollusks are an important resource due to their socioeconomic value and to the historical and genetic value of some species. Two nationally important oyster species-Portuguese oyster (Crassostrea angulata) and Japanese oyster (Crassostrea gigas) from distinctive areas in Portugal were studied to evaluate their sanitary status. Oysters were sampled from four different sites in Portugal. Oysters collected from Japanese oyster populations were cultivated in a strong ocean-influenced environment and Portuguese oyster populations were cultivated in wild-beds. The histopathological examination of both oyster species revealed the presence of parasites in gills, mantle epithelium, digestive gland tubules and connective tissue, with a moderate prevalence. In both populations was observed hemocytosis in the connective tissue, edema and metaplasia in the digestive gland and tissues necrosis. In wild populations from Sado and Mira estuaries the prevalence of mud blisters and gill lesions were higher than from populations produced on 0.50 m tables from mudflats. Biosecurity measures and diagnostic techniques are fundamental to control pathogenic agents, including the identification of pathogens at an early stage in their life cycles. This will prevent diseases and improve pathogen reduction on transport of animals from different countries and regions to new production areas to avoid the transmission of diseases.