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1.
PLoS One ; 15(6): e0234116, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32544162

RESUMO

Changes in parasite communities might result in new host-parasite dynamics and may threaten local fish populations. This phenomenon has been suggested for acanthocephalan parasites in the river Rhine and Danube where the species Pomphorhynchus tereticollis is becoming replaced by the Ponto-Caspian P. laevis. Developing knowledge on morphologic, genetic and behavioural differences between such species is important to follow such changes. However, disagreements on the current phylogeny of these two acanthocephalan species are producing conflicts that is affecting their correct identification. This study is offering a clearer morphological and genetic distinction between these two species. As P. tereticollis is found in rhithral tributaries of the Rhine, it was questioned whether the local salmonid populations were hosts for this species and whether P. laevis was expanding into the Rhine watershed as well. In order to test for this, brown trout, Salmo trutta, and grayling, Thymallus thymallus from South-Western Germany watersheds have been samples and screened for the occurrence of acanthocephalan parasites. For the first time, both species were confirmed to be hosts for P. tereticollis in continental Europe. P. tereticollis was found to be common, whereas P. leavis was found only at a single location in the Danube. This pattern suggest either that the expansion of P. laevis through salmonid hosts into rhithral rivers has not yet occurred, or that not yet ascertained biotic or abiotic features of rhithral rivers hinder P. laevis to spread into these areas.


Assuntos
Acantocéfalos/genética , Doenças dos Peixes/parasitologia , Salmonidae/parasitologia , Acantocéfalos/anatomia & histologia , Acantocéfalos/classificação , Animais , DNA de Helmintos/genética , DNA de Helmintos/metabolismo , Doenças dos Peixes/epidemiologia , Doenças dos Peixes/patologia , Alemanha/epidemiologia , Microscopia Eletrônica de Varredura , Filogenia , Prevalência , Truta/parasitologia
2.
Proc Biol Sci ; 287(1925): 20200388, 2020 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-32315591

RESUMO

Genetic variation in defence against parasite infections is fundamental for host-parasite evolution. The overall level of defence of a host individual or population includes mechanisms that reduce parasite exposure (avoidance), establishment (resistance) or pathogenicity (tolerance). However, how these traits operate and evolve in concert is not well understood. Here, we investigated genetic variation in and associations between avoidance, resistance and tolerance in a natural host-parasite system. Replicated populations of Atlantic salmon (Salmo salar) and sea trout (an anadromous form of brown trout, Salmo trutta) were raised under common garden conditions and infected with the eye fluke Diplostomum pseudospathaceum. We demonstrate significant genetic variation in the defence traits across host populations and negative associations between the traits, with the most resistant populations showing the weakest avoidance and the lowest infection tolerance. These results are suggestive of trade-offs between different components of defence and possibly underlie the genetic variation in defence traits observed in the wild. Because the three defence mechanisms affect host-parasite evolution in profoundly different ways, we emphasize the importance of studying these traits in concert.


Assuntos
Doenças dos Peixes/parasitologia , Interações Hospedeiro-Parasita , Animais , Parasitos , Salmo salar/parasitologia , Salmo salar/fisiologia , Trematódeos , Truta/parasitologia , Truta/fisiologia
3.
J Parasitol ; 106(1): 198-200, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32097104

RESUMO

Salmincola californiensis (Dana, 1853) (Subclass Copepoda: Family Lernaeopodidae) is known to parasitize salmonids of the genus Oncorhynchus including Oncorhynchus mykiss (rainbow trout), Oncorhynchus tshawytscha (chinook salmon), and Oncorhynchus kisutch (coho salmon). These 3 salmonids have been introduced to the Great Lakes intermittently since the mid-1800s. As we demonstrate here, the introduction of these salmonids to the Great Lakes was followed, at some point, by the introduction of their parasitic gill copepod, S. californiensis. Given anecdotal accounts of S. californiensis in introduced salmonids in Lake Ontario since 2012, we chose to conduct a survey to formally document the occurrence of this introduced species. Our survey took place during spring, summer, and fall of 2018 and during spring of 2019 at the south-eastern side of Lake Ontario. Prevalence of S. californiensis was 69, with a mean intensity of 2.7 in 61 rainbow trout examined in 2018. In 2019, prevalence of S. californiensis was 71, with a mean intensity of 3.6 in 59 rainbow trout examined. The prevalence of S. californiensis was 39, with a mean intensity of 1.6 in 223 chinook salmon examined in 2018. No specimens of S. californiensis were found in the 100 coho salmon examined in 2018. The prevalence of S. californiensis in rainbow trout is of great concern considering that it is double that found in rainbow trout in the native range (69 [in 2018] and 71 [in 2019] vs. 35). This is the first formal documentation of the invasion of S. californiensis in Lake Ontario. Future fisheries management decisions in Lake Ontario and its tributaries should take into account these data.


Assuntos
Copépodes/crescimento & desenvolvimento , Ectoparasitoses/veterinária , Doenças dos Peixes/parasitologia , Truta/parasitologia , Animais , Ectoparasitoses/epidemiologia , Ectoparasitoses/parasitologia , Doenças dos Peixes/epidemiologia , Pesqueiros , Brânquias/parasitologia , Lagos , New York/epidemiologia , Prevalência
4.
Parasit Vectors ; 12(1): 569, 2019 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-31783772

RESUMO

BACKGROUND: Tetracapsuloides bryosalmonae is a myxozoan parasite which causes economically important and emerging proliferative kidney disease (PKD) in salmonids. Brown trout, Salmo trutta is a native fish species of Europe, which acts as asymptomatic carriers for T. bryosalmonae. There is only limited information on the molecular mechanism involved in the kidney of brown trout during T. bryosalmonae development. We employed RNA sequencing (RNA-seq) to investigate the global transcriptome changes in the posterior kidney of brown trout during T. bryosalmonae development. METHODS: Brown trout were exposed to the spores of T. bryosalmonae and posterior kidneys were collected from both exposed and unexposed control fish. cDNA libraries were prepared from the posterior kidney and sequenced. Bioinformatics analysis was performed using standard pipeline of quality control, reference mapping, differential expression analysis, gene ontology, and pathway analysis. Quantitative real time PCR was performed to validate the transcriptional regulation of differentially expressed genes, and their correlation with RNA-seq data was statistically analyzed. RESULTS: Transcriptome analysis identified 1169 differentially expressed genes in the posterior kidney of brown trout, out of which 864 genes (74%) were upregulated and 305 genes (26%) were downregulated. The upregulated genes were associated with the regulation of immune system process, vesicle-mediated transport, leucocyte activation, and transport, whereas the downregulated genes were associated with endopeptidase regulatory activity, phosphatidylcholine biosynthetic process, connective tissue development, and collagen catabolic process. CONCLUSION: To our knowledge, this is the first RNA-seq based transcriptome study performed in the posterior kidney of brown trout during active T. bryosalmonae development. Most of the upregulated genes were associated with the immune system process, whereas the downregulated genes were associated with other metabolic functions. The findings of this study provide insights on the immune responses mounted by the brown trout on the developing parasite, and the host molecular machineries modulated by the parasite for its successful multiplication and release.


Assuntos
Doenças dos Peixes/imunologia , Nefropatias/veterinária , Myxozoa/patogenicidade , Doenças Parasitárias em Animais/imunologia , Truta/parasitologia , Animais , Infecções Assintomáticas , Biologia Computacional , Doenças dos Peixes/parasitologia , Expressão Gênica , Perfilação da Expressão Gênica , Interações Hospedeiro-Parasita/genética , Interações Hospedeiro-Parasita/imunologia , Rim/parasitologia , Nefropatias/imunologia , Nefropatias/parasitologia , Análise de Sequência de RNA , Organismos Livres de Patógenos Específicos , Truta/imunologia
5.
Parasitol Res ; 118(12): 3241-3252, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31728722

RESUMO

Myxobolus neurofontinalis n. sp. infects the brain and medulla oblongata of brook trout (Salvelinus fontinalis [Mitchill, 1814]) in the New River, western NC. It is the first species of Myxobolus described from the brook trout and resembles another congener (Myxobolus arcticus Pugachev and Khokhlov, 1979) that infects nerve tissue of chars (Salvelinus spp.). The new species differs from M. arcticus and all congeners by myxospore dimensions and by having a mucous envelope and distinctive sutural markings. A phylogenetic analysis of the small subunit rDNA (18S) suggests that the new species shares a recent common ancestor with some isolates identified as M. arcticus and that the new species and its close relatives (except Myxobolus insidiosus Wyatt and Pratt, 1973) comprise a clade of salmonid nerve-infecting myxobolids. The phylogenetic analysis indicates that several isolates of "M. arcticus" (sensu lato) in GenBank are misidentified and distantly related to other isolates taken from the type host (Oncorhynchus nerka [Walbaum, 1792]) and from nearby the type locality (Kamchatka Peninsula, Russia). Serial histological sections of infected brook trout confirmed that myxospores of the new species are intercellular and infect nerve cord and medulla oblongata only. A single infected brook trout showed an inflammatory response characterized by focal lymphocytic infiltrates and eosinophilic granulocytes; however, the remaining 4 brook trout lacked evidence of a histopathological change or demonstrable host response. These results do not support the notion that this infection is pathogenic among brook trout.


Assuntos
Doenças dos Peixes/parasitologia , Bulbo/parasitologia , Myxobolus/classificação , Tecido Nervoso/parasitologia , Truta/parasitologia , Animais , Região dos Apalaches , Doenças dos Peixes/patologia , Myxobolus/genética , Filogenia , RNA Ribossômico 18S/genética , Especificidade da Espécie
6.
J Fish Dis ; 42(12): 1745-1760, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31637741

RESUMO

To identify the pathogens causing saprolegniosis among farmed fish in Nova Scotia, 172 infected tissues and 23 water samples were collected from six species of teleosts: Atlantic salmon (Salmo salar), brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), brook trout (Salvelinus fontinalis), striped bass (Morone saxatilis) and rainbow trout (Oncorhynchus mykiss) at nine facilities over a 600 km range. Following laboratory culture, 132 isolates were recovered. Six species of oomycetes were identified from analysis of the internal transcribed spacer (ITS) sequence of the nrDNA: Saprolegnia parasitica, Saprolegnia ferax, Saprolegnia diclina, Saprolegnia aenigmatica, Saprolegnia torulosa, Saprolegnia sp. and Pythiopsis cymosa. Further phylogenetic analyses of the ITS and cytochrome c oxidase subunit 1 (Cox1) regions revealed four strains of Saprolegnia parasitica (named here as S1, S2, S3 and S4), of which S1 and S2 were common (37% and 42% of the isolates), and two strains of S. ferax. Among S. parasitica, S2 and S3 are more closely related to each other than to S1 based on the phylogenetic analyses and predicted RNA secondary structure of the ITS region. Sexual structures with a similar morphology were formed by S1 and S3 in vitro, but were not formed by S2.


Assuntos
Doenças dos Peixes/parasitologia , Filogenia , Saprolegnia/classificação , Animais , Bass/parasitologia , DNA Espaçador Ribossômico/genética , Complexo IV da Cadeia de Transporte de Elétrons/genética , Pesqueiros , Nova Escócia , Conformação de Ácido Nucleico , Oncorhynchus mykiss/parasitologia , RNA Ribossômico 18S/genética , Salmo salar/parasitologia , Truta/parasitologia
7.
J Parasitol ; 105(5): 769-782, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31625813

RESUMO

Truttaedacnitis truttae is a cucullanid nematode of primarily salmonine fishes. Brown trout (Salmo trutta) in Europe reportedly become parasitized by ingesting lampreys (Lampetra planeri) carrying infective larvae. However, our field and laboratory observations suggested that North American specimens of T. truttae have an alternative life cycle. High abundances and potential impact of T. truttae in rainbow trout, Oncorhynchus mykiss, in the Colorado River drainage in Grand Canyon, where there are no lampreys, prompted a study on the transmission dynamics of this nematode. Eggs of T. truttae, collected from live gravid females, were incubated in the laboratory. Snails, Physa gyrina and Lymnaea sp., were exposed to T. truttae larvae 3-4 wk later. Active larvae of T. truttae were observed penetrating the intestinal wall of exposed snails, and worm larvae were found in the visceral tissues when examined 1 wk after exposure. Larvae in snails showed little growth and development 2 wk later and corresponded to L3 larvae. Infected snails were fed to hatchery-reared juvenile rainbow trout. Developing stages were subsequently found in the mucosal lining and lumen of trout intestines. Adult male and female (gravid) worms were found in the ceca of trout examined 5-6 mo after consuming infected snails. Larvae found in pepsin/trypsin digests and mucosal scrapings from wild, naturally infected, trout corroborate laboratory findings. Screening of Physa sp. and gammarids collected from Colorado River, Grand Canyon, for natural infections with T. truttae using the ITS1 rDNA marker gave positive results. Truttaedacnitis truttae is the second species, after Truttaedacnitis clitellarius of lake sturgeon, capable of using a snail first intermediate/paratenic host and is similar to several other cucullanids in having a histotropic phase of development in the definitive fish host.


Assuntos
Doenças dos Peixes/parasitologia , Estágios do Ciclo de Vida , Caramujos/parasitologia , Infecções por Spirurida/veterinária , Spirurina/crescimento & desenvolvimento , Truta/parasitologia , Animais , Ceco/parasitologia , DNA de Helmintos/isolamento & purificação , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/isolamento & purificação , Feminino , Larva/crescimento & desenvolvimento , Masculino , Oncorhynchus mykiss/parasitologia , Projetos Piloto , Reação em Cadeia da Polimerase/veterinária , Rios , Infecções por Spirurida/parasitologia , Spirurina/anatomia & histologia
8.
Transbound Emerg Dis ; 66(5): 2107-2119, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31155828

RESUMO

This study documents the development of a non-lethal sampling method to recover gyrodactylid parasites from large numbers of fish that will underpin an improved surveillance strategy for Gyrodactylus salaris. A review of published literature identified over 80 compounds that have previously been tested against gyrodactylids or closely related parasite species. Five safe and relatively fast-acting compounds were selected for testing to determine their efficiency in removing gyrodactylids from host fish in small-scale aquaria trials using three-spined stickleback infected with Gyrodactylus gasterostei as a model host-parasite system. The most effective compound was hydrogen peroxide; short-duration exposure (3 min) achieved a parasite detection sensitivity of 80%-89%. The practicality of exposing farmed salmonids to hydrogen peroxide for G. salaris surveillance was tested in the field by conducting a parasite recovery trial using a brown trout stock endemically infected with G. truttae and G. derjavinoides and comparing this to the whole-body examination procedure currently conducted by UK authorities. Significantly more parasites were recovered after exposing fish to hydrogen peroxide and filtering the treatment solution than by direct whole-body examination of killed fish (mean: 225 vs. 138 parasites per fish). The gyrodactylid recovery rate of the two methods was 84.6% and 51.9%, respectively. A comparison of timings for the two methods indicated scope for significant time savings in adopting the chemical screening method. The study demonstrated that hydrogen peroxide bath treatment may be successfully applied to the surveillance of gyrodactylid parasites and established as a non-lethal method for sampling farmed and wild fish. This approach has the potential to reduce resources required to collect and isolate parasites for diagnostic testing and improve the sensitivity and confidence of surveillance programmes designed to demonstrate freedom from disease, thus underpinning a robust and defensible surveillance strategy for G. salaris for the UK aquatic animal disease contingency plan.


Assuntos
Doenças dos Peixes/parasitologia , Peróxido de Hidrogênio/administração & dosagem , Platelmintos/efeitos dos fármacos , Salmão/parasitologia , Trematódeos/efeitos dos fármacos , Infecções por Trematódeos/tratamento farmacológico , Truta/parasitologia , Animais , Aquicultura
9.
Parasitol Res ; 118(7): 2121-2127, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31073829

RESUMO

The genus Eimeria comprises obligate intracellular protozoan parasites belonging to the phylum Apicomplexa. Members of this genus cause enteric disease in a wide range of vertebrate hosts, including fish, reptiles, birds, and mammals. A total of 157 species of Eimeria that parasitize fish have been described; however, molecular information regarding these piscine parasites is scarce. In the present study, Eimeria oocysts were detected in 189 of 613 (30.8%) gastrointestinal tracts of brown trout (Salmo trutta) captured in several rivers in Galicia (NW Spain). Measurements of the sporulated oocysts, sporocysts, and other morphological characteristics enabled identification of the oocysts as Eimeria truttae. By molecular analysis of the small subunit ribosomal RNA (SSU-rRNA) gene, a single sequence of ~ 420 bp was obtained in 100 fish samples. After amplification of a ~ 1300-bp fragment of the same locus, two representative sequences that exhibited five nucleotide differences were obtained. Phylogenetic analysis grouped the samples within the piscine clade closest to Eimeria nemethi as they exhibited 96.7% similarity with this species. This study is the first to characterize E. truttae at the molecular level, thus helping to clarify the phylogenetic relationships between this and other Eimeria species isolated from fish and contributing further to the knowledge about this protozoan parasite.


Assuntos
Coccidiose/veterinária , Eimeria/isolamento & purificação , Doenças dos Peixes/parasitologia , Truta/parasitologia , Animais , Coccidiose/parasitologia , Eimeria/classificação , Eimeria/genética , Trato Gastrointestinal/parasitologia , Oocistos , Filogenia , Espanha
10.
Parasitol Res ; 118(5): 1519-1532, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30937615

RESUMO

The freshwater pearl mussel (Margaritifera margaritifera) is an endangered bivalve with an obligate parasitic stage on salmonids. Host suitability studies have shown that glochidial growth and load vary significantly between host strains as well as among individuals of a suitable strain. Variation in host suitability has been linked to environmental conditions, host age and/or size, genetic composition of the host and parasite, or a combination of these factors. In our study, we wanted to investigate if brown trout (Salmo trutta) displayed an age-dependent response to glochidial infestation. We hypothesised that 1+ naive brown trout hosts tolerate glochidial infestation better than 0+ hosts. In order to test our hypothesis, we infested 0+ and 1+ hatchery reared brown trout with glochidia from closely related mothers and kept them under common garden conditions. This allowed us to observe a pure age dependent host response to infestation, as we eliminated the confounding effect of genotype-specific host interactions. We analysed the interaction between glochidial load and host condition, weight and length, and observed a significant age-dependent relationship. Glochidial load was negatively correlated to host condition in 0+ fish hosts and positively correlated in 1+ hosts. These contradictory findings can be explained by a change in host response strategy, from resistance in young to a higher tolerance in older fish. In addition, we also examined the relationship between glochidial load and haematocrit values in the 1+ hosts and observed that haematocrit values were significantly higher in heavily infested hosts. Our results have important conservation implications for the management of wild pearl mussel populations, as well as for captive breeding programmes.


Assuntos
Bivalves/crescimento & desenvolvimento , Bivalves/fisiologia , Interações Hospedeiro-Parasita/fisiologia , Larva/crescimento & desenvolvimento , Truta/parasitologia , Fatores Etários , Animais , Água Doce
11.
J Parasitol ; 105(1): 170-179, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30807710

RESUMO

This study reports for the first time the molecular characterization of Cryptosporidium spp. in Salmo trutta. A total number of 613 brown trout was captured by local anglers in 44 Galician rivers within 10 river basins (NW Spain) during the 2015 fishing season (March-August) and classified into groups according to their size. The gastrointestinal tracts were dissected and differentiated in pyloric ceca and intestine, which were homogenized and concentrated in phosphate-buffered saline 0.04 M pH 7.2/diethyl ether (2:1). Cryptosporidium oocysts were observed by immunofluorescence microscopy in 103 of 613 specimens (16.8%), with a mean intensity of 326.7 oocysts/trout. The highest prevalence rate was detected in specimens <2 yr (23.1%). Considering the anatomical location, Cryptosporidium oocysts were observed in pyloric ceca (72 trout, 69.9%), intestine (15 trout, 14.6%), or in both locations (16 trout, 15.5%), showing statistically significant differences between the 2 locations ( P < 0.01). The prevalence rate in the pyloric ceca increased with the age/size of the fish (62.2% vs. 70.8% vs. 83.3% for trout <2, 2-3, and >3 yr, respectively). By contrast, the prevalence rate in the intestinal location decreased with the age/size of specimens (21.6% vs. 12.5% vs. 7.7% for trout <2, 2-3, and >3 yr, respectively), but statistically significant differences were not determined. The microscopic observation of clusters of 4-20 oocysts in the pyloric ceca from 5 specimens of 20-28-cm body length is remarkable. By polymerase chain reaction amplification and sequencing of fragments of small-subunit ribosomal DNA ( SSU-rDNA), GP60, hsp70, and actin loci, Cryptosporidium molnari-like genotype was identified in 1 trout and Cryptosporidium parvum (subtypes IIaA15G2R1 and IIaA18G3R1) in 47 fish, including those specimens in which oocyst clusters were observed. This finding may indicate a true infection by C. parvum, as the homogenization process would break the epithelial cells, releasing oocysts, free or in clusters. Cryptosporidium oocysts were detected in wild trout captured from 27 of 44 rivers sampled in Galicia (61.4%), belonging to 9 of the 10 river basins considered, confirming the presence of this protozoan parasite in Galician rivers and proving their wide dispersion in aquatic freshwater environments. The identification of the zoonotic species C. parvum in brown trout may indicate a risk to public health as trout may be a potential source of infection to humans. Thus, edible wild fish extend the range of foodstuffs involved in the transmission of cryptosporidiosis.


Assuntos
Criptosporidiose/parasitologia , Cryptosporidium/classificação , Doenças dos Peixes/parasitologia , Truta/parasitologia , Animais , Sequência de Bases , Ceco/parasitologia , Criptosporidiose/epidemiologia , Criptosporidiose/transmissão , Cryptosporidium/genética , Cryptosporidium parvum/classificação , Cryptosporidium parvum/genética , DNA Ribossômico/genética , Genótipo , Intestinos/parasitologia , Microscopia de Fluorescência , Oocistos/isolamento & purificação , Filogenia , Prevalência , Piloro/parasitologia , Rios , Estações do Ano , Espanha/epidemiologia , Zoonoses
12.
J Helminthol ; 93(5): 559-566, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29911512

RESUMO

Parasite distribution patterns in lotic catchments are driven by the combined influences of unidirectional water flow and the mobility of the most mobile host. However, the importance of such drivers in catchments dominated by lentic habitats are poorly understood. We examined parasite populations of Arctic charr Salvelinus alpinus from a series of linear-connected lakes in northern Norway to assess the generality of lotic-derived catchment-scale parasite assemblage patterns. Our results demonstrated that the abundance of most parasite taxa increased from the upper to lower catchment. Allogenic taxa (piscivorous birds as final host) were present throughout the entire catchment, whereas their autogenic counterparts (charr as final hosts) demonstrated restricted distributions, thus supporting the theory that the mobility of the most mobile host determines taxa-specific parasite distribution patterns. Overall, catchment-wide parasite abundance and distribution patterns in this lentic-dominated system were in accordance with those reported for lotic systems. Additionally, our study highlighted that upper catchment regions may be inadequate reservoirs to facilitate recolonization of parasite communities in the event of downstream environmental perturbations.


Assuntos
Distribuição Animal , Lagos/parasitologia , Parasitos/fisiologia , Truta/parasitologia , Animais , Ecossistema , Noruega
13.
Parasit Vectors ; 11(1): 609, 2018 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-30497499

RESUMO

BACKGROUND: The causal relation between parasitic sea lice on fish farms and sea lice on wild fish is a controversial subject. A specific scientific debate has been whether the statistical association between infestation pressure (IP) from fish farms and the number of parasites observed on wild sea trout emerges purely because of a confounding and direct effect of temperature (T). METHODS: We studied the associations between louse infestation on wild sea trout, fish farm activity and temperature in an area that practices coordinated fallowing in Nordhordland, Norway. The data were sampled between 2009 and 2016. We used negative binomial models and mediation analysis to determine to what degree the effect of T is mediated through the IP from fish farms. RESULTS: The number of attached lice on sea trout increased with the T when the IP from fish farms was high but not when the IP was low. In addition, nearly all of the effect of rising T was indirect and mediated through the IP. Attached lice remained low when neighbouring farms were in the first year of the production cycle but rose substantially during the second year. In contrast to attached lice, mobile lice were generally seen in higher numbers at lower water temperatures. Temperature had an indirect positive effect on mobile louse counts by increasing the IP which, in turn, raised the sea trout louse counts. Mobile louse counts rose steadily during the year when neighbouring farms were in the first year of the production cycle and stayed high throughout the second year. CONCLUSIONS: The estimates of the IP effect on louse counts along with the clear biennial pattern emerging due to the production cycle of fish farms clearly indicate that fish farms play an important role in the epidemiology of sea lice on wild sea trout. Furthermore, the mediation analysis demonstrates that a large proportion of the effect of T on louse counts is mediated through IP.


Assuntos
Arguloida/fisiologia , Doenças dos Peixes/parasitologia , Infestações por Piolhos/veterinária , Truta/parasitologia , Animais , Animais Selvagens/parasitologia , Aquicultura , Arguloida/genética , Infestações por Piolhos/parasitologia , Modelos Estatísticos , Noruega , Água do Mar/química , Água do Mar/parasitologia , Temperatura
14.
J Aquat Anim Health ; 30(4): 264-279, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30133011

RESUMO

Placer Creek, a tributary of Sangre de Cristo Creek in Colorado's San Luis Valley, supported an allopatric core conservation population of native Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis during much of the 20th century. After the failure of gabion barriers in the late 1990s, Brook Trout Salvelinus fontinalis infected with Myxobolus cerebralis invaded from Sangre de Cristo Creek. By 2005, whirling disease (WD) and competition from Brook Trout reduced Rio Grande Cutthroat Trout numbers to less than 10% of the total trout population. New barriers were constructed in 2006 and the stream was treated with rotenone in 2007 and 2009 to eliminate all fish prior to the reintroduction of Rio Grande Cutthroat Trout. Results of WD research studies in Montana, California, and Colorado indicated it might be possible to break the life cycle of the parasite in some situations. Our management interventions included (1) reducing the fish population in the stream to zero for approximately 14 months, (2) introducing lineage V and VI Tubifex tubifex worms, which are not susceptible to M. cerebralis, and (3) eliminating a small off-channel pond that provided optimal habitat that sustained a localized high-density population of lineage III T. tubifex, the oligochaete host susceptible to M. cerebralis. Electrofishing during the fall of 2009 and spring of 2010 indicated the drainage was devoid of fish. Fry, juvenile, and adult Rio Grande Cutthroat Trout were stocked in September and October of 2010 and 2011. Approximately 975,000 lineage V and VI T. tubifex were introduced into Placer Creek between 2010 and 2012 as possible oligochaete competitors for the lineage III worms. The off-channel pond was filled in, and the surface was reseeded in April 2012. No evidence of M. cerebralis infection was detected among more than 280 Rio Grande Cutthroat Trout tested between July 2012 and July 2016, indicating the parasite had been eradicated from the Placer Creek basin upstream of the barriers.


Assuntos
Doenças dos Peixes/parasitologia , Myxobolus , Oncorhynchus/parasitologia , Animais , Colorado , Reservatórios de Doenças/parasitologia , Doenças dos Peixes/prevenção & controle , Oligoquetos/genética , Oligoquetos/parasitologia , Doenças Parasitárias em Animais/parasitologia , Doenças Parasitárias em Animais/prevenção & controle , Rios , Rotenona , Truta/parasitologia
15.
J Parasitol ; 104(6): 628-638, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30138083

RESUMO

Since the late 19th century, the ectoparasitic copepod Salmincola cf. edwardsii has been observed infecting brook trout ( Salvelinus fontinalis) in Wisconsin streams. A perceived increase in the incidence of S. cf. edwardsii infection across the state and the observation of an S. edwardsii epizootic leading to declines in brook trout recruitment in Ash Creek, Wisconsin, have raised concerns about the extent to which S. edwardsii threaten other populations of brook trout in Wisconsin streams. In 2013-2017, brook trout were inspected in 282 streams across the state to determine the distribution, prevalence, and maximum intensity of infection of adult female copepods whose morphology was consistent with S. edwardsii. Salmincola cf. edwardsii were present in 79% of streams and absent from 21%. Prevalence of infection ranged from 0.4 to 100% where the parasite was present. Maximum intensity of infection was low (1-5 S. cf. edwardsii) in 31% of streams, moderate (6-14) in 35% of the streams, and high (≥15) in 34% of the streams. Maximum intensity was high and prevalence exceeded 90% of brook trout in 9 streams, suggesting epizootics as observed in Ash Creek are uncommon. Our statewide distributional data are critical to understanding the scope of S. cf. edwardsii infection of brook trout in Wisconsin's recreational fisheries and will provide a baseline for ongoing and future investigations of S. cf. edwardsii-brook trout dynamics.


Assuntos
Copépodes/crescimento & desenvolvimento , Ectoparasitoses/veterinária , Doenças dos Peixes/parasitologia , Truta/parasitologia , Animais , Ectoparasitoses/epidemiologia , Ectoparasitoses/parasitologia , Feminino , Doenças dos Peixes/epidemiologia , Brânquias/parasitologia , Prevalência , Rios , Wisconsin/epidemiologia
16.
J Parasitol ; 104(6): 645-650, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30142293

RESUMO

The distribution of the freshwater myxozoan parasite Ceratonova shasta in the Pacific Northwest of North America is limited to overlap in the ranges of its 2 hosts: the polychaete Manyunkia sp., and Pacific salmonids. Studies in the Klamath River (Oregon/California) and Deschutes River (Oregon), showed that the parasite population is comprised of multiple sympatric genotypes, some of which correlate with particular salmonid host species and with differences in clinical disease in those hosts. The 3 primary genotypes O, I, and II are defined by the number of a specific tri-nucleotide repeat in the internal transcribed spacer-1 region. To understand the spatial extent of host-parasite genotype patterns, we sequenced the parasite from 448 salmonid fishes from river basins in California, Oregon, Washington, Idaho, and British Columbia, Canada. We sampled intestinal tissues from 6 species of salmon and trout, both those that exist naturally with the parasite (sympatric) and those that do not naturally co-occur with the parasite and were exposed artificially in cages (allopatric). In most river basins we detected the same primary C. shasta genotypes that were described from the Klamath and Deschutes rivers, and we did not detect any novel primary genotypes. Host-parasite genotype patterns were consistent with previous data: genotype O was found in sympatric trout only; genotype I predominantly in Chinook salmon, and genotype II in all 6 fish species but dominant in coho salmon. Our findings of widespread, consistent host-parasite genotype patterns support the hypothesis that C. shasta has a long evolutionary history with salmonid fishes in the Pacific Northwest, and impels additional studies to determine if these parasite genotypes should be considered different species.


Assuntos
Doenças dos Peixes/parasitologia , Myxozoa/fisiologia , Doenças Parasitárias em Animais/parasitologia , Salmão/parasitologia , Truta/parasitologia , Adaptação Biológica , Animais , Evolução Biológica , Colúmbia Britânica , California , DNA/isolamento & purificação , Água Doce/parasitologia , Genótipo , Interações Hospedeiro-Parasita/genética , Enteropatias Parasitárias/parasitologia , Enteropatias Parasitárias/veterinária , Intestinos/parasitologia , Myxozoa/classificação , Myxozoa/genética , Oregon , Rios/parasitologia , Washington
17.
J Evol Biol ; 31(10): 1498-1512, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29961959

RESUMO

Resource polymorphisms exhibit remarkable intraspecific diversity and in many cases are expected to be maintained by diversifying selection. Phenotypic trade-offs can constrain morphologically intermediate individuals from effectively exploiting both alternate resources, resulting in ecological barriers to gene flow. Determining if and how phenotypic trade-offs cause fitness variation in the wild is challenging because of phenotypic and environmental correlations associated with alternative resource strategies. We investigated multiple pathways through which morphology could affect organismal performance, as measured by growth rate, and whether these effects generate diversifying selection in polymorphic Icelandic Arctic charr (Salvelinus alpinus) populations. We considered direct effects of morphology on growth and indirect effects via trophic resource use, estimated by stable isotopic signatures, and via parasitism associated with trophic resources. We sampled over 3 years in (lakes) Thingvallavatn and Vatnshlíðarvatn using the extended selection gradient path analytical approach and estimating size-dependent mortality. We found evidence for diversifying selection only in Thingvallavatn: more streamlined and terminally mouthed planktivore charr experienced greater growth, with the opposite pattern in small benthic charr. However, this effect was mediated by parasitism and nontrophic pathways, rather than trophic performance as often expected. Detection of between-morph differences in the presence (Vatnshlíðarvatn) and direction (Thingvallavatn) of size-dependent mortality, together with nontrophic effects of shape, suggests that a morphological trophic performance explanation for polymorphism is insufficient. This rare insight into selection during early diversification suggests that a complex of interacting local factors must be considered to understand how phenotype influences fitness, despite morphological variation reflecting intuitive trade-off explanations.


Assuntos
Seleção Genética , Truta/anatomia & histologia , Truta/fisiologia , Adaptação Fisiológica , Animais , Tamanho Corporal , Diphyllobothrium/isolamento & purificação , Cadeia Alimentar , Islândia , Lagos , Mortalidade , Truta/parasitologia
18.
J Fish Biol ; 93(4): 664-673, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29992561

RESUMO

The effects of introgression on parasitism in brook charr Salvelinus fontinalis were investigated in 28 lakes with various levels of stocking in Québec, Canada. No effect of genetic background on parasitism was found at the individual level. Body length seemed to explain most of the variation observed at this level, with largest fish being more infected. However, lakes with the greater average domestic genetic background were found to display significantly lower parasite prevalence and diversity. Since our results indicate no effect of domestic genes at the individual level, the negative association with introgression found at the population level may be mainly attributed to differences in intrinsic environmental quality of lakes (e.g. fishing pressure, availability of food resources, abiotic characteristics).


Assuntos
Interações Hospedeiro-Parasita/genética , Truta/genética , Animais , Tamanho Corporal , Hibridização Genética , Lagos , Carga Parasitária/veterinária , Quebeque , Truta/anatomia & histologia , Truta/parasitologia
19.
Sci Total Environ ; 642: 656-664, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29909333

RESUMO

In the present study novel histopathological approach, using fish intestine as a sensitive bioindicator organ of pollution impact in the freshwater ecosystem, was proposed. Histopathological alterations were compared between native brown trout (Salmo trutta Linnaeus, 1758) from the reference (Krka River spring) and pollution impacted location (influence of technological/municipal wastewaters and agricultural runoff near the Town of Knin) of the karst Krka River in Croatia. In brown trout from both locations, severe parasitic infestation with acanthocephalan species Dentitruncus trutae was found, enabling evaluation of acanthocephalan infestation histopathology, which indicated parasite tissue reaction in a form of inflammatory, necrotic and hyperplastic response that extended throughout lamina epithelialis mucosae, lamina propria, and lamina muscularis mucosae. New semi-quantitative histological approach was proposed in order to foresee alterations classified in three reaction patterns: control tissue appearance, moderate (progressive) tissue impairment and severe (regressive and inflammatory) tissue damage. The most frequent progressive alteration was hyperplasia of epithelium on the reference site, whereas the most frequent regressive alterations were atrophy and necrosis seen on the polluted site. Furthermore, histopathological approach was combined with micromorphological and macromorphological assessment as an additional indicator of pollution impact. Among 15 observed intestinal measures, two biomarkers of intestinal tissue damage were indicated as significant, height of supranuclear space (hSN) and number of mucous cells over 100 µm fold distance of intestinal mucosa (nM), which measures were significantly lower in fish from polluted area compared to the reference site. Obtained results indicated that combined histological and morphological approach on fish intestinal tissue might be used as a valuable biological tool for assessing pollution impact on aquatic organisms. Therefore, semi quantitative scoring and multiparametric morphological assessment of intestinal tissue lesion magnitude should become a common approach to handle environmental pollution impact.


Assuntos
Estresse Fisiológico , Truta/fisiologia , Poluição da Água/estatística & dados numéricos , Acantocéfalos/crescimento & desenvolvimento , Animais , Biomarcadores , Croácia , Monitoramento Ambiental , Intestinos/parasitologia , Truta/parasitologia
20.
J Antibiot (Tokyo) ; 71(8): 741-744, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29686353

RESUMO

Saprolegnia parasitica, belonging to oomycetes, is one of virulent pathogen of fishes such as salmon and trout, and causes tremendous damage and losses in commercial aquacultures by saprolegniasis. Previously, malachite green, an effective medicine, had been used to control saprolegniasis. However, this drug has been banned around the world due to its mutagenicity. Therefore, novel anti-saprolegniasis compounds are urgently needed. As a new frontier to discover bioactive compounds, we focused on the deep-sea fungi for the isolation of anti-saprolegniasis compounds. In this paper, on the course of anti-saprolegniasis agents from 546 cultured broths of 91 deep-sea fungal strains, we report a new compound, named quellenin (1) together with three known compounds, diorcinol (2), violaceol-I (3) and violaceol-II (4), from deep-sea fungus Aspergillus sp. YK-76. This strain was isolated from an Osedax sp. annelid, commonly called bone-eating worm, collected at the São Paulo Ridge in off Brazil. Compounds 2, 3 and 4 showed anti-S. parasitica activity. Our results suggest that diorcinol and violaceol analogs and could be good lead candidates for the development of novel agents to prevent saprolegniasis.


Assuntos
Antiparasitários/farmacologia , Aspergillus/metabolismo , Doenças dos Peixes/tratamento farmacológico , Doenças dos Peixes/parasitologia , Salmão/parasitologia , Saprolegnia/efeitos dos fármacos , Truta/parasitologia , Animais , Testes de Sensibilidade Parasitária , Fenóis/farmacologia , Éteres Fenílicos/farmacologia
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