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At least 109 records · Page 6Linked to original sources
USGS1997

Evidence for retrovirus infections in green turtles Chelonia mydas from the Hawaiian islands

Apparently normal Hawaiian green turtles Chelonia mydas and those displaying fibropapillomas were analyzed for infection by retroviruses. Strikingly, all samples were positive for polymerase enhanced reverse transcriptase (PERT) with levels high enough to quantitate by the conventional reverse transcriptase (RT) assay. However, samples of skin, even from asymptomatic turtles, were RT positive, although the levels of enzyme activity in healthy turtles hatched and raised in captivity were much lower than those observed in asymptomatic free-ranging turtles. Turtles with fibropapillomas displayed a broad range of reverse transcriptase activity. Skin and eye fibropapillomas and a heart tumor were further analyzed and shown to have reverse transcriptase activity that banded in a sucrose gradient at 1.17 g ml-1. The reverse transcriptase activity purified from the heart tumor displayed a temperature optimum of 37??C and showed a preference for Mn2+ over Mg2+. Sucrose gradient fractions of this sample displaying elevated reverse transcriptase activity contained primarily retrovitalsized particles with prominent envelope spikes, when negatively stained and examined by electron microscopy. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of gradient-purified virions revealed a conserved profile among 4 independent tumors and showed 7 prominent proteins having molecular weights of 116, 83, 51, 43, 40, 20 and 14 kDa. The data suggest that retroviral infections are widespread in Hawaiian green turtles and a comprehensive investigation is warranted to address the possibility that these agents cause green turtle fibropapillomatosis (GTFP).

Hawai'i↗
USGS1997

Sequence analysis and expression of the M1 and M2 matrix protein genes of hirame rhabdovirus (HIRRV)

We have cloned and sequenced a 2318 nucleotide region of the genomic RNA of hirame rhabdovirus (HIRRV), an important viral pathogen of Japanese flounder Paralichthys olivaceus. This region comprises approximately two-thirds of the 3' end of the nucleocapsid protein (N) gene and the complete matrix protein (M1 and M2) genes with the associated intergenic regions. The partial N gene sequence was 812 nucleotides in length with an open reading frame (ORF) that encoded the carboxyl-terminal 250 amino acids of the N protein. The M1 and M2 genes were 771 and 700 nucleotides in length, respectively, with ORFs encoding proteins of 227 and 193 amino acids. The M1 gene sequence contained an additional small ORF that could encode a highly basic, arginine-rich protein of 25 amino acids. Comparisons of the N, M1, and M2 gene sequences of HIRRV with the corresponding sequences of the fish rhabdoviruses, infectious hematopoietic necrosis virus (IHNV) or viral hemorrhagic septicemia virus (VHSV) indicated that HIRRV was more closely related to IHNV than to VHSV, but was clearly distinct from either. The putative consensus gene termination sequence for IHNV and VHSV, AGAYAG(A)(7), was present in the N-M1, M1-M2, and M2-G intergenic regions of HIRRV as were the putative transcription initiation sequences YGGCAC and AACA. An Escherichia coli expression system was used to produce recombinant proteins from the M1 and M2 genes of HIRRV. These were the same size as the authentic M1 and M2 proteins and reacted with anti-HIRRV rabbit serum in western blots. These reagents can be used for further study of the fish immune response and to test novel control methods.

Diseases of Aquatic Organisms↗
USGS2017

Complete sequences of 4 viral hemorrhagic septicemia virus IVb isolates and their virulence in northern pike fry

Four viral hemorrhagic septicemia virus (VHSV) genotype IVb isolates were sequenced, their genetic variation explored, and comparative virulence assayed with experimental infections of northern pike Esox lucius fry. In addition to the type strain MI03, the complete 11183 bp genome of the first round goby Neogobius melanostomus isolate from the St. Lawrence River, and the 2013 and 2014 isolates from gizzard shad Dorosoma cepedianum die-offs in Irondequoit Bay, Lake Ontario and Dunkirk Harbor, Lake Erie were all deep sequenced on an Illumina platform. Mutations documented in the 11 yr since the MI03 index case from Lake St. Clair muskellunge Esox masquinongy showed 87 polymorphisms among the 4 isolates. Twenty-six mutations were non-synonymous and located at 18 different positions within the matrix protein, glycoprotein, non-virion protein, and RNA polymerase genes. The same 4 isolates were used to infect northern pike fry by a single 1 h bath exposure. Cumulative percent mortality varied from 42.5 to 62.5%. VHSV was detected in 57% (41/72) of the survivors at the end of the 21-d trial, suggesting that the virus was not rapidly cleared. Lesions were observed in many of the moribund and dead northern pike, such as hemorrhaging in the skin and fins, as well as hydrocephalus. Mean viral load measured from the trunk and visceral tissues of MI03-infected pike was significantly higher than the quantities detected in fish infected with the most recent isolates of genotype IVb, but there were no differences in cumulative mortality observed.

Diseases of Aquatic Organisms↗
USGS2017

Investigating seagrass in Toxoplasma gondii transmission in Florida (Trichechus manatus latirostris) and Antillean (T. m. manatus) manatees

Toxoplasma gondii is a feline protozoan reported to cause morbidity and mortality in manatees and other marine mammals. Given the herbivorous nature of manatees, ingestion of oocysts from contaminated water or seagrass is presumed to be their primary mode of infection. The objectives of this study were to investigate oocyst contamination of seagrass beds in Puerto Rico and determine the seroprevalence of T. gondii in Antillean ( Trichechus manatus manatus ) and Florida ( T. m. latirostris ) manatees. Sera or plasma from Antillean (n = 5) and Florida (n = 351) manatees were tested for T. gondii antibodies using the modified agglutination test. No T. gondii DNA was detected via PCR in seagrass samples (n = 33) collected from Puerto Rico. Seroprevalence was 0%, suggesting a lower prevalence of T. gondii in these manatee populations than previously reported. This was the first study to investigate the potential oocyst contamination of the manatee diet, and similar studies are important for understanding the epidemiology of T. gondii in herbivorous marine mammals.

Diseases of Aquatic Organisms↗
USGS2018

Occurrence of Batrachochytrium dendrobatidis in anurans of the Mediterranean region of Baja California, México

Chytridiomycosis is caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd ) and is regarded as one of the most significant threats to global amphibian populations. In México, Bd was first reported in 2003 and has now been documented in 13 states. We visited 33 localities and swabbed 199 wild-caught anurans from 7 species (5 native, 2 exotic) across the Mediterranean region of the state of Baja California. Using quantitative PCR, Bd was detected in 94 individuals (47.2% of samples) at 25 of the 33 survey localities for 5 native and 1 exotic frog species. The exotic Xenopus laevis was the only species that tested completely negative for Bd . We found that remoteness, distance to agricultural land, and elevation were the best predictors of Bd presence. These are the first Bd -positive results for the state of Baja California and its presence should be regarded as an additional conservation threat to the region’s native frog species.

Baja California↗
USGS2018

Ichthyophonus in sport-caught groundfishes from southcentral Alaska

This report of Ichthyophonus in common sport-caught fishes throughout the marine waters of southcentral Alaska represents the first documentation of natural Ichthyophonus infections in lingcod Ophiodon elongates and yelloweye rockfish Sebastes ruberrimus . In addition, the known geographic range of Ichthyophonus in black rockfish S. melanops has been expanded northward to include southcentral Alaska. Among all species surveyed, the infection prevalence was highest (35%, n = 334) in Pacific halibut Hippoglossus stenolepis . There were no gross indications of high-level infections or clinically diseased individuals. These results support the hypothesis that under typical conditions Ichthyophonus can occur at high infection prevalence accompanied with low-level infection among a variety of fishes throughout the eastern North Pacific Ocean, including southcentral Alaska.

Alaska↗
USGS2019

Isolation, characterization and molecular identification of a novel aquareovirus that infects the endangered fountain darter, Etheostoma fonticola

The fountain darter Etheostoma fonticola (FOD) is a federally endangered fish listed under the US Endangered Species Act. Here, we identified and characterized a novel aquareovirus isolated from wild fountain darters inhabiting the San Marcos River. This virus was propagated in Chinook salmon embryo (CHSE)-214, rainbow trout gonad-2 and fathead minnow cells at 15°C. The epithelioma papulosum cyprini cell line was refractory at all temperatures evaluated. High throughput sequencing technologies facilitated the complete genome sequencing of this virus utilizing ribosomal RNA-depleted RNA extracted from infected CHSE-214 cells. Conventional PCR primer sets were developed for the detection and confirmation of this virus to assist diagnostic screening methods. Phylogenetic analysis suggests this virus belongs to the Aquareovirus A genus. This research provides requisite initial data critical to support hatchery and refugia biosecurity measures for this endangered species.

Diseases of Aquatic Organisms↗
USGS2018

Internal parasites of the two subspecies of the West Indian manatee Trichechus manatus

The West Indian manatee Trichechus manatus is divided into 2 subspecies: the Antillean ( T. m. manatus ) and Florida ( T. m. latirostris ) manatees. This study reports sample prevalence of manatee parasites from populations of these 2 subspecies in different geographical locations. Although necropsy is a valuable diagnostic tool for parasite infections, the need for antemortem diagnostic techniques is important. Fecal samples collected during necropsies of Antillean manatees (n = 3) in Puerto Rico and Florida manatees (n = 10) in Crystal River, Florida, as well as from live-captured Florida manatees (n = 11) were evaluated using centrifugal flotation with sucrose and ethyl acetate sedimentation to compare parasites from each of the populations. Although both fecal examination methods provided similar results, the centrifugal flotation method required less time for diagnosis. The most common parasite eggs found in both populations included the trematodes Pulmonicola cochleotrema and Nudacotyle undicola , oocysts of the coccidian Eimeria spp., and eggs of the ascarid Heterocheilus tunicatus . Eggs of the trematode Chiorchis groschafti were found in both populations of manatees; however, eggs of a related species, Chiorchis fabaceus, were abundant in the Florida samples, but not found in Puerto Rico populations. Trematode eggs of Moniligerum blairi were found in both populations, but were more common in the Florida manatee (42%) than the Antillean manatee (33%). To our knowledge, this is the first report of both Eimeria manatus and Eimeria nodulosa oocysts in Antillean manatees from Puerto Rico.

Diseases of Aquatic Organisms↗
USGS2019

Modelling sea lice control by lumpfish on Atlantic salmon farms: interactions with mate limitation, temperature, and treatment rules

Atlantic salmon farming is one of the largest aquaculture sectors in the world. A major impact on farm economics, fish welfare, and potentially nearby wild salmonid populations, is the sea louse ectoparasite Lepeophtheirus salmonis . Sea louse infestations are most often controlled through application of chemicals, but in most farming regions sea lice have evolved resistance to the small set of available chemicals. Therefore, alternative treatment methodologies are becoming more widely used. One increasingly common alternative treatment involves the co-culture of farmed salmon with cleaner fish, which prey on sea lice. However, despite their wide use, little is understood about the situations in which cleaner fish are most effective. For example, previous work suggests that a low parasite density results in sea lice finding it difficult to acquire mates, reducing fecundity and population growth. Other work suggests that environmental conditions such as temperature and external sea louse pressure have substantial impact on this mate limitation threshold and may even remove the effect entirely. We use an Agent-Based Model (ABM) to simulate cleaner fish on a salmon farm to explore interactions between sea louse mating behaviour, cleaner fish feeding rate, temperature, and external sea lice pressure. We found that sea louse mating has a substantial effect on sea louse infestations under a variety of environmental conditions. Our results suggest that cleaner fish can control sea louse infestations most effectively by maintaining the population below critical density thresholds.

Diseases of Aquatic Organisms↗
USGS2019

Seasonal development of the coccidian parasite Goussia bayae and hepatobiliary histopathology in white perch Morone americana from Chesapeake Bay

The coccidium Goussia bayae infects the gallbladder and bile ducts of white perch Morone americana from Chesapeake Bay, USA. Seasonal changes in coccidian infections were analyzed from bile specimens of 1588 fish from the Choptank River during 2016-2018 using wet mount preparations with a Sedgwick-Rafter counting chamber. Histopathology of the gallbladder and liver was analyzed from a subset (n = 480) of these fish. Maximum parasite prevalence (100%) and intensities in the gallbladder occurred during the fish spawning season in March and April. Asynchronous coccidian development and prevalence of infections in fish increased gradually during autumn and winter, but coccidian intensity increased sharply 2-4 wk prior to the onset of fish spawning activity and decreased after spawning activity concluded. Sporulation was internal, and the gallbladder was the primary reservoir for oocysts. Two previously undescribed species of coccidia were observed in the intestine. Lesions in the gallbladder were rare and included cholecystitis and epithelial necrosis. Intrahepatic bile duct lesions were more common and included distension, cholangitis, epithelial erosion and necrosis, cholestasis, hyperplasia, and neoplasia. Cholangitis and necrosis of intrahepatic bile ducts were significantly associated with coccidial infections, while plasmodia of a myxosporean (spore morphology consistent with the genera Myxidium and Zschokella ) were significantly associated with bile duct hyperplasia. Biliary neoplasia included cholangiomas (5% prevalence) and cholangiocarcinomas (1% prevalence). No association was detected between G. bayae and biliary neoplasms, but an association may exist between these lesions and the myxosporean plasmodia.

Maryland, Virginia↗
USGS2019

A geographic hot spot of Ichthyophonus infection in the southern Salish Sea, USA

The prevalence of Ichthyophonus infection in Pacific herring Clupea pallasii was spatially heterogeneous in the southern Salish Sea, Washington State, USA. Over the course of 13 mo, 2232 Pacific herring were sampled from 38 midwater trawls throughout the region. Fork length was positively correlated with Ichthyophonus infection at all sites. After controlling for the positive relationship between host size and Ichthyophonus infection, the probability of infection was approximately 6-fold higher in North Hood Canal than in Puget Sound and the northern Straits (12 vs. 2% predicted probability for a 100 mm fish and 30 vs. 7% predicted probability for a 180 mm fish). Temporal changes in Ichthyophonus infection probability were explained by seasonal differences in fish length, owing to Pacific herring life history and movement patterns. Reasons for the spatial heterogeneity remain uncertain but may be associated with density-dependent factors inherent to the boom-bust cycles that commonly occur in clupeid populations.

Washington↗
USGS1998

Performance of serum-free broth media for growth of Renibacterium salmoninarum

Growth of Renibacterium salmoninarum was compared in 14 different broth media; 13 serum-free, and 1 that contained newborn calf serum, KDM2+M. Supplementation with 1% v/v R. salmoninarum MCO4M metabolite was evaluated for 6 of the media that do not utilize it as part of their ingredients. Viable cells were enumerated on Days 10, 20, and 30 post inoculation to evaluate performance. The experiment was repeated 3 times using high, low, and medium (trials 1 to 3, respectively) cell concentrations as inoculum. In general there was no optimal medium and all performed well. The choice of which to employ depends on the ease of preparation and presence of certain ingredients that might affect subsequent assays. In trials 2 and 3, the pH was estimated using test papers at the same time as cells were counted. Maximum pH increase occurred with KDM2+M and those media containing charcoal. For most media, a simple pH determination could be used as a means to check that growth has occurred in a culture, particularly if charcoal was added directly to the media and a visual inspection could not be made to detect growth.

Diseases of Aquatic Organisms↗
USGS1998

Soft shell clams Mya arenaria with disseminated neoplasia demonstrate reverse transcriptase activity

Disseminated neoplasia (DN), a proliferative cell disorder of the circulatory system of bivalves, was first reported in oysters in 1969. Since that time, the disease has been determined to be transmissible through water-borne exposure, but the etiological agent has not been unequivocally identified. In order to determine if a viral agent, possibly a retrovirus, could be the causative agent of DN, transmission experiments were performed, using both a cell-free filtrate and a sucrose gradient-purified preparation of a cell-free filtrate of DN positive materials. Additionally, a PCR-enhanced reverse transcriptase assay was used to determine if reverse transcriptase was present in tissues or hemolymph from DN positive soft shell clams Mya arenaria. DN was transmitted to healthy clams by injection with whole DN cells, but not with cell-free flitrates prepared from either tissues from DN positive clams, or DN cells. The cell-free preparations from DN-positive tissues and hemolymph having high levels of DN cells in circulation exhibited positive reactions in the PCR-enhanced reverse transcriptase assay. Cell-free preparations of hemolymph from clams having low levels of DN (<0.1% of cells abnormal), hemocytes from normal soft shell clams, and normal soft shell clam tissues did not produce a positive reaction in the PCR enhanced reverse transcriptase assay.

Diseases of Aquatic Organisms↗
USGS1998

Occurrence of Loma cf salmonae brook, brown and rainbow trout from Buford Trout Hatchery, Georgia, USA

During a 6 mo study of moribund trout from Buford hatchery, Buford, Georgia, USA, a Loma cf. salmonae microsporidian parasite was studied in the gills of brook trout Salvelinus fontinalis , brown trout Salmo trutta , and rainbow trout Oncorhynchus mykiss . This parasite was morphologically similar to L. salmonae and L. fontinalis but differed in spore size. Scanning and transmission electron microscopy demonstrated that xenomas were embedded in gill filaments. Transmission electron micrographs prepared from fresh tissue showed mature spores with 12 to 15 turns of their polar tube. Spore diameters for the Georgia strain from formalin-fixed gill tissues measured 3.5 (SD ±0.1) by 1.8 (SD ±0.1) µm. Electron micrographs of formalin-fixed, deparaffinized tissues of rainbow trout from Pennsylvania and West Virginia show spores with a diameter of 3.5 (±0.2) by 1.7 (±0.1) µm and 3.4 (±0.2) by 1.8 (±0.1) µm, respectively. Transmission electron micrographs of spores from Pennsylvania and West Virginia show that mature spores from both states had 13 to 15 turns of their polar tubes. Measurements from transmission electron micrographs prepared from alcohol-fixed tissues from Virginia fish contained spores with a diameter of 3.0 (±0.3) by 1.1 (±0.3) µm and 12 to 15 turns of their polar tubes. These measurements are consistent with L. salmonae and therefore suggest that the parasite is present on the east coast of the United States. During the height of the Georgia epizootic, the percentage of fish with observed xenomas reached 62.2% (N = 87), and the highest number of xenomas counted per 10 gill filaments was 133 (N = 87). The microsporidian epizootic occurred either during the autumn months or when intake river water quality reached combined iron-manganese concentrations as high as 1.01 (mean 0.44, SD ±0.42) mg -1 .

Diseases of Aquatic Organisms↗
USGS1998

Development of a nested polymerase chain reaction for amplification of a sequence of the p57 gene of Renibacterium salmoninarum that provides a highly sensitive method for detection of the bacterium in salmonid kidney

Nucleic acid-based assays have shown promise for diagnosing Renibacterium salmoninarum in tissues and body fluids of salmonids. DeVelopment of a nested polymerase chain reaction (PCR) method to detect a 320 bp DNA segment of the gene encoding the p57 protein of R. salmoninarum is described. Whereas a conventional PCR for a 383 bp segment of the p57 gene reliably detected 1000 R. salmoninarum cells per reaction in kidney tissue, the nested PCR detected as few as 10 R. salmoninarum per reaction in kidney tissue. Two DNA extraction methods for the nested PCR were compared and the correlation between replicate samples was generally higher in samples extracted by the QIAamp system compared with those extracted by the phenol/chloroform method. The specificity of the nested PCR was confirmed by testing DNA extracts of common bacterial fish pathogens and a panel of bacterial species reported to cause false-positive reactions in the enzyme-linked immunosorbent assay (ELISA) and the fluorescent antibody test (FAT) for R. salmoninarum. Kidney samples from 74 naturally infected chinook Salmon were examined by the nested PCR, the ELISA, and the FAT, and the detected prevalences of R. salmoninarum were 61, 47, and 43%, respectively.

Diseases of Aquatic Organisms↗
USGS2020

Amphibian chytrid prevalence on boreal toads in SE Alaska and NW British Columbia: Tests of habitat, life stages, and temporal trends

Tracking and understanding variation in pathogens such as Batrachochytrium dendrobatidis ([Bd]), which causes amphibian chytridiomycosis and has caused population declines globally, is a priority for many land managers. However, there has been relatively little sampling of amphibian communities at high latitudes. We used skin swabs collected during 2005–2017 from boreal toads (Anaxyrus boreas; N = 248), in southeast Alaska (USA; primarily in Klondike Gold Rush National Historical Park [KLGO]) and northwest British Columbia (Canada) to determine how Bd prevalence varied across life stages, habitat characteristics, local species richness, and time. Across all years, Bd prevalence peaked in June and was >3 times greater for adult toads (37.5%) vs. juveniles and metamorphs (11.2%). Bd prevalence for toads in the KLGO area, where other amphibian species are rare or absent, was highest from river habitats (55.0%), followed by human-modified upland wetlands (32.3%) and natural upland wetlands (12.7%) — the same rank-order these habitats are used for toad breeding. No Columbia spotted frogs (N = 12) or wood frogs (N = 2) from the study area tested Bd-positive, although all were from an area of low host density where Bd has not been detected. Prevalence of Bd on toads in the KLGO area decreased during 2005–2015. This trend from a largely single-species system may be encouraging or concerning, depending on how Bd is affecting vital rates, and emphasizes the need to understand effects of pathogens before translating disease prevalence into management actions.

Southeastern Alaska, Northwestern British Columbia↗
USGS2020

Hyperpigmented melanistic skin lesions of smallmouth bass Micropterus dolomieu from the Chesapeake Bay watershed

Hyperpigmented melanistic skin lesions (HPMLs) of smallmouth bass Micropterus dolomieu are observed in the Potomac and Susquehanna rivers, Chesapeake Bay watershed, USA. Routine, nonlethal population surveys were conducted at 8 sites on the mainstem Susquehanna River and 9 on the Juniata River, a tributary of the Susquehanna River, between 2012 and 2018, and the prevalence of HPMLs was documented. A total of 4078 smallmouth bass were collected from the mainstem Susquehanna River and 6478 from the Juniata River. Lesions were primarily seen in bass greater than 200 mm, and prevalence in the Susquehanna River (8%) was higher (p < 0.001) than in the Juniata River (2%). As part of ongoing fish health monitoring projects, smallmouth bass were collected at additional sites, primarily tributaries of the Susquehanna (n = 758) and Potomac (n = 545) rivers between 2013 and 2018. Prevalence in the Susquehanna River (13%) was higher (p < 0.001) than the Potomac (3%). Microscopically, HPMLs were characterized by an increased number of melanocytes in the epidermis or within the dermis and epidermis. RNAseq analyses of normal and melanistic skin identified 3 unique sequences in HPMLs. Two were unidentified and the third was a viral helicase (E1). Transcript abundance in 16 normal skin samples and 16 HPMLs showed upregulation of genes associated with melanogenesis and cell proliferation in HPMLs. The E1 transcript was detected in 12 of the 16 melanistic areas but in no samples from normal skin. Further research will be necessary to identify the putative new virus and determine its role in melanocyte proliferation.

Delaware, Maryland, Pennsylvania, Virginia, West V↗
USGS2020

High prevalence of biliary neoplasia in white perch Morone americana: Potential roles of bile duct parasites and environmental contaminants

Recent surveys of white perch Morone americana from Chesapeake Bay, USA, revealed a high prevalence of hepatic and biliary lesions, including neoplasia, and bile duct parasites. Here, we describe lesions in the liver and gallbladder and evaluate for statistical associations among lesions, parasites, and biomarkers of chemical exposure in fish from 2 tributaries of Chesapeake Bay. Fish were collected from an estuarine site in the Choptank River (n = 122, ages 3-11), a tributary with extensive agriculture within the watershed, and the Severn River (n = 131, ages 2-16), a tributary with extensive urban development. Passive integrative samplers were deployed at the fish collection site and an upstream, non-tidal site in each river for 30 d. Intrahepatic biliary lesions observed in fish from both rivers included neoplasia (23.3%), dysplasia (16.2%), hyperplasia (46.6%), cholangitis (24.9%), and dilated ducts containing plasmodia of Myxidium sp. (24.9%). Hepatocellular lesions included foci of hepatocellular alteration (FHA, 15.8%) and neoplasia in 4 Severn River fish (2.3%). Age of fish and Myxidium sp. infections were significant risk factors for proliferative and neoplastic biliary lesions, age alone was a risk factor for FHA, and Goussia bayae infections were associated with cholangitis and cholecystitis. Lesion prevalence was higher in fish from the Severn River, which contained higher concentrations of PAHs, organochlorine pesticides, and brominated diphenyl ethers. Metabolite biomarkers indicated higher PAH exposures in Severn River fish. This study suggests Myxidium sp. as a promoter of bile duct tumors, but more data are needed to evaluate the biological effects of environmental contaminants in this species.

Chesapeake Bay↗