Parasites of Percophis brasiliensis (Percophidae) benefited from fishery regulations: Indicators of success for marine protected areas?

1. Fishing is the greatest source of anthropogenic impact on global marine resources and the ecosystems supporting them. The decline of many fish stocks has led to the need to apply control and protection measures to promote the recovery of these resources.
2. In the Argentine Sea, a multispecies coastal fishery in the El Rincón region has displayed signs of overexploitation since the beginning of the century. Consequently, temporal and spatial protection measures were implemented in 2004.
3. In previous studies, an independent stock of Percophis brasiliensis in El Rincón was identified based on the parasite communities of fish caught in 2005. However, no subsequent studies using parasite communities have been performed since the protective fishery closure measures were applied.
4. To evaluate parasites as indicators of temporal change in the El Rincón stock of P. brasiliensis after the implementation of these protection measures, a sample from 2018 was compared with that from the previous study, as well as with three other samples. Two of the latter (Argentine Common Fishing Zone and San Matías Gulf) corresponded to previously identified independent stocks in the Argentine biogeographical province and the third was a new sample from the Magellanic Province in southern Patagonian waters.
5. The structure and composition of parasite assemblages of the El Rincón stock of P. brasiliensis differed significantly in 2018, after several years of protective measures. The increased loads observed in several parasite species constitute a promising signal of successful ecosystem recovery. A discrete stock in the Magellanic Province was also identified, providing insights into the population structure of P. brasiliensis along its distributional range, with applications for the sustainable management of this resource.

     

Experimental transmission of Enteromyxum leei Diamant, Lom and Dykova, 1994 in sharpsnout sea bream, Diplodus puntazzo C. and the effect on some innate immune parameters

Enteromyxum leei has been implicated in outbreaks in sharpsnout sea bream, causing a serious economic impact on Mediterranean fish farming. Information about transmission and life cycles of marine myxosporea is limited to only a few fish species. In the present study, direct transmission of the infection was achieved by cohabitation of infected and healthy Diplodus puntazzo C. for the first time. The progress of the infection was monitored by the detection of different developmental stages of the parasite in the posterior intestine. Infected fish with E. leei were firstly observed in day 5 (prevalence of 20%). The total prevalence reached 100% in day 19 and was maintained in this high level until the end of the experimental period (day 55). In addition, the initial intensity of the different parasite stages was low, but on day 26 the intensity of trophozoites was suddenly increased, followed by the increased intensity of sporoblasts and mature spores. Also, the experimental transmission of E. leei in recovered D. puntazzo previously treated for parasite elimination proved to be unsuccessful, suggesting of a possible development of protective immunity against the parasite.     

Diseases of north European wrasse (Labridae) and possible interactions with cohabited farmed salmon, Salmo salar L

There have been several reported studies of wrasse health but none of these has shown transmission of wrasse diseases when stocked with farmed Atlantic salmon. Most of the studies have focussed on bacterial and parasite issues, including treatment of bacterial diseases with antibiotics and vaccination of wrasse. Classical and atypical furunculosis have been reported in wrasse following stress, and wrasse have been susceptible to vibrio infection. Further study is required on the vaccination of wrasse for furunculosis with latent carrier status to maximize survival. There are studies on viral diseases such as infectious pancreatic necrosis, infectious salmon anaemia and pancreas disease and although these did not give any undue concern for salmon health, there is also scope for further study in this area. Resident parasite communities of wrasse are largely host-specific and do not appear to be a threat to salmon. Given that wrasse have not, to date, been a vector of disease in salmon, attention should be placed on maintaining best practice in cohabiting wrasse with salmon. Other issues that should be addressed are good welfare of wrasse in pens and identifying measures of this, the identification of losses of wrasse in pens, being alert to potential emerging diseases through health screening of mortalities and assessing the risks associated with carrying forward wrasse from one salmon production cycle to the next. Issues of exploitation by fishing on wild wrasse stocks and improved biosecurity may be addressed by the increased movement by the industry to the stocking of farmed wrasse.     

Molecular diagnosis of Myxobolus spirosulcatus associated with encephalomyelitis of cultured yellowtail, Seriola quinqueradiata Temminck & Schlegel

Mass mortality of cultured yellowtail, Seriola quinqueradiata, has recently been reported from fish farms in western Japan. Previous studies revealed that diseased fish were characterized by encephalomyelitis and presporogonic stages of a myxosporean‐like parasite in the spinal cord. However, the parasite has remained unidentified because of the lack of mature stages being present. Thus, in the present study, analysis of the small subunit ribosomal DNA (18S rDNA) of the parasite as well as in situ hybridization (ISH) studies using histological sections of the infected tissue was conducted. The 18S rDNA of the myxosporean had higher sequence similarities with those of bile‐duct‐infecting myxosporeans rather than those infecting nervous tissues and was identified as Myxobolus spirosulcatus. The ISH using specific probes demonstrated that the DNA amplified was derived from the multinuclear organisms found in histological sections. A highly sensitive and specific PCR‐based assay for M. spirosulcatus was developed, which revealed a high prevalence of infection in cultured yellowtail that exhibited the clinical signs of encephalomyelitis.     

Detection of the intranuclear microsporidian Enterospora nucleophila in gilthead sea bream by in situ hybridization

Enterospora nucleophila is an intranuclear microsporidian responsible for emaciative microsporidiosis of gilthead sea bream (GSB). Its minute size and cryptic nature make it easily misdiagnosed. An in situ hybridization (ISH) technique based on antisense oligonucleotide probes specific for the parasite was developed and used in clinically infected GSB in combination with calcofluor white stain (CW) and other histopathological techniques. The ISH method was found to label very conspicuously the cells containing parasite stages, with the signal concentrating in merogonial and sporogonial plasmodia within the infected cell nuclei. Comparison with CW demonstrated limited ISH signal in cells containing mature spores, which was attributed mostly to the scarcity of probe targets present in these stages. Although spores were detected in other organs of the digestive system as well as in the peripheral blood, proliferative stages or parasite reservoirs were not found in this work outside the intestines. The study demonstrated a frequent disassociation between the presence of abundant spores and the intensity of the infections as determined by the parasite activity. The ISH allows confirmatory diagnosis of GSB microsporidiosis and estimation of infection intensity and will be a valuable tool for a more precise determination of parasite dissemination pathways and pathogeny mechanisms.     

外来寄生虫入侵及其对土著宿主的影响

生物入侵严重威胁着土著物种和生物多样性,外来物种带来的寄生虫入侵问题也应该引起相应的重视。结合外来寄生虫的入侵案例,阐述了寄生虫的引入、种群建立和宿主转移等入侵过程。通常寄生虫入侵后,致病力会变得更大,有些会直接引起土著宿主的死亡,有些间接引起宿主死亡,有的则引起繁殖力下降,从而降低土著宿主的群落多样性,讨论了寄生虫入侵的管理和控制。     

Epizootiology of Parvicapsulaminibicornis in Fraser River sockeye salmon, Oncorhynchusnerka (Walbaum)

Late-spawning Fraser River sockeye salmon, Oncorhynchus nerka , stocks have suffered significant prespawn mortality associated with an unusually early freshwater migration pattern and the myxosporean parasite Parvicapsula minibicornis . Surveys of migrating adult salmon from several spawning populations were conducted in 1999 and 2000 to determine the extent of infection with P. minibicornis , when and where the parasite first becomes detectable during migration, and whether early migrating stocks might be used as sentinels to assess risk of infection in late-spawning stocks. Posterior kidney, preserved in 95% ethanol, was examined for P. minibicornis in stained histological sections and using a polymerase chain reaction (PCR) test. The prevalence of this parasite in all Fraser River sockeye salmon stocks examined was high (range 47–100% infected). In contrast, P. minibicornis was not detected in the fish tested from the two sockeye salmon stocks outside the Fraser River drainage in either 1999 or 2000. The parasite was also not detected histologically or by PCR in the kidney tissue of the fish from the Fraser River that were sampled in salt water or early during their freshwater migration up the river. These findings and the progression in the prevalence and intensity of infection as the fish from three stocks (early Stuart, Weaver Creek and Cultus Lake) were monitored over time, suggest salmon acquired the parasite either in the lower Strait of Georgia or in the lower Fraser River before the confluence of the Harrison River. In both 1999 and 2000 the parasite was present in all Fraser River sockeye salmon stocks sampled, which suggests that early Stuart salmon may be valuable as a sentinel stock for the presence of the parasite in later-spawning stocks.     

鲍苗死亡原因的研究进展及对策

本文从细菌、病毒和寄生虫导致的病害,底栖硅藻膜、鲍苗的种群密度、水环境中的理化条件、赤潮等方面入手,综述了国内外学者近几年对鲍苗死亡原因的研究进展,并提出相应的防治对策。     

Patterns of Tetracapsuloides bryosalmonae infection of three salmonid species in large,deep Norwegian lakes

Proliferative kidney disease (PKD), caused by the myxozoan endoparasite Tetracapsuloides bryosalmonae, is of serious ecological and economical concern to wild and farmed salmonids. Wild salmonid populations have declined due to PKD, primarily in rivers, in Europe and North America. Deep lakes are also important habitats for salmonids, and this work aimed to investigate parasite presence in five deep Norwegian lakes. Kidney samples from three salmonid species from deep lakes were collected and tested using real-time PCR to detect PKD parasite presence. We present the first detection of T. bryosalmonae in European whitefish in Norway for the first time, as well as the first published documentation of the parasite in kidneys of Arctic charr, brown trout and whitefish in four lakes. The observed prevalence of the parasite was higher in populations of brown trout than of Arctic charr and whitefish. The parasite was detected in farmed, but not in wild, charr in one lake. This suggests a possible link with a depth of fish habitat and fewer T. bryosalmonae-infected and PKD-affected fish. Towards a warmer climate, cold hypolimnion in deep lakes may act as a refuge for wild salmonids, while cold deep water may be used to control PKD in farmed salmonids.     

伊维菌素在水产养殖中的应用及其水生态风险

伊维菌素是一种广谱抗寄生虫渔药,在国外被广泛用于鲑鱼、海鲷养殖中的海鲺防治.国内主要用于防治淡水鱼养殖中的各种寄生虫病,其在观赏鱼养殖中的应用也日益普遍.综述了目前国内外伊维茵素在水产养殖中的使用现状,并就其水生态风险进行评估.     

Ichthyophonus‐infected walleye pollock Theragra chalcogramma (Pallas) in the eastern Bering Sea: a potential reservoir of infections in the North Pacific

In 2003, the Alaska walleye pollock industry reported product quality issues attributed to an unspecified parasite in fish muscle. Using molecular and histological methods, we identified the parasite in Bering Sea pollock as Ichthyophonus. Infected pollock were identified throughout the study area, and prevalence was greater in adults than in juveniles. This study not only provides the first documented report of Ichthyophonus in any fish species captured in the Bering Sea, but also reveals that the parasite has been present in this region for nearly 20 years and is not a recent introduction. Sequence analysis of 18S rDNA from Ichthyophonus in pollock revealed that consensus sequences were identical to published parasite sequences from Pacific herring and Yukon River Chinook salmon. Results from this study suggest potential for Ichthyophonus exposures from infected pollock via two trophic pathways; feeding on whole fish as prey and scavenging on industry‐discharged offal. Considering the notable Ichthyophonus levels in pollock, the low host specificity of the parasite and the role of this host as a central prey item in the Bering Sea, pollock likely serve as a key Ichthyophonus reservoir for other susceptible hosts in the North Pacific.     

Combined antiparasitic and anti‐inflammatory effects of the natural polyphenol curcumin on turbot scuticociliatosis

The histiophagous scuticociliate Philasterides dicentrarchi is the aetiological agent of scuticociliatosis, a parasitic disease of farmed turbot. Curcumin, a polyphenol from Curcuma longa (turmeric), is known to have antioxidant and anti‐inflammatory properties. We investigated the in vitro effects of curcumin on the growth of P. dicentrarchi and on the production of pro‐inflammatory cytokines in turbot leucocytes activated by parasite cysteine proteases. At 100 μm , curcumin had a cytotoxic effect and completely inhibited the growth of the parasite. At 50 μm , curcumin inhibited the protease activity of the parasite and expression of genes encoding two virulence‐associated proteases: leishmanolysin‐like peptidase and cathepsin L‐like. At concentrations between 25 and 50 μm , curcumin inhibited the expression of S‐adenosyl‐L‐homocysteine hydrolase, an enzyme involved in the biosynthesis of the amino acids methionine and cysteine. At 100 μm , curcumin inhibited the expression of the cytokines tumour necrosis factor‐alpha (TNF‐α) and interleukin‐1 beta (IL‐1β) produced in turbot leucocytes activated by parasite proteases. Results show that curcumin has a dual effect on scuticociliatosis: an antiparasitic effect on the catabolism and anabolism of ciliate proteins, and an anti‐inflammatory effect that inhibits the production of proinflammatory cytokines in the host. The present findings suggest the potential usefulness of this polyphenol in treating scuticociliatosis.     

The fate of Lernaeocera branchialis (L.) (Crustacea; Copepoda) in Atlantic cod, Gadus morhua L

Lernaeocera branchialis, a copepod crustacean parasite of gadoids, represents a potential threat to both wild and farmed cod, Gadus morhua. The pathological changes associated with the early stages of experimental infection have previously been reported in detail, and this article describes the lesions associated with later chronic stages of experimental infection. Chronic infection is characterised by extravascular granuloma formation and proliferation of fibrovascular tissue around intact and fragmented, degenerate parasites within both the gill arch and cardiac region. The majority of parasite granulomas are located within connective tissues of the gill arch or pericardium; however, low numbers are present within the wall of large vessels. The intraluminal parasites and thrombi of early stage infection are largely absent in these later lesions. We propose that organisation and incorporation of the parasite thrombus into the vessel wall with subsequent granuloma formation and extrusion into the surrounding connective tissue leads to the elimination of the parasite from the vascular system. Thus, rather than being a negative consequence of infection thrombosis is protective, allowing the host to survive the substantial initial vascular insult.     

西藏鱼类寄生虫区系研究现状与影响因素分析

西藏水资源丰富,鱼类进化与青藏高原隆起、自然环境隔离演变息息相关,与鱼类和水环境密切相关的鱼类寄生虫区系也逐渐引起关注和重视。初步的研究显示,尽管西藏鱼类种类单一,但鱼类消化道寄生蠕虫种类较多,显示较高的多样性,而且发现了一些裂腹鱼特有的复殖吸虫和棘头虫种类,以及一些以鸟类为终末宿主的线虫和绦虫种类。西藏特有的放生习俗和候鸟迁徙现象,水电工程兴建和水体污染现状,以及土著鱼类资源量下降和青藏高原气候变化等因素,都有可能影响西藏鱼类寄生虫区系的组成与演变。寄生虫区系调查可为该地区鱼类寄生虫的种类、分布和数量提供详细的数据,进而了解寄生虫的形成与演变过程,弄清环境与寄生虫多样性的关系,为西藏渔业资源的开发与利用提供科学依据。本文对上述问题进行了总结和论述。     

基于文献计量分析的淡水鱼类寄生虫研究现状及热点探析

为了解淡水鱼类寄生虫的研究现状及前沿热点，为该领域研究工作的开展提供科学量化的参考依据，以Web of Science(WOS)核心合集数据库收录的1980—2020年共1 088篇相关文献为数据样本，运用VOSviewer和CiteSpace可视化软件绘制了淡水鱼类寄生虫研究的发文量、发文地区、发文作者、发文机构、关键词频次和突现状况等知识图谱，并对发文趋势和研究热点进行了分析。结果表明，淡水鱼类寄生虫研究领域的发文量总体呈上升趋势，2009年后上升趋势明显；淡水鱼类寄生虫的研究受到广泛关注，巴西、捷克和美国是淡水鱼类寄生虫领域的研究中心；捷克共和国科学院、墨西哥国立自治大学和新西兰奥塔哥大学等3个机构是淡水鱼类寄生虫领域的高产研究机构；Poulin R、Scholz T和Salgado-Maldonado G等3位研究人员是淡水鱼类寄生虫研究的核心力量；发文国家间和机构间形成了良好且稳定的合作关系，但研究者间合作关系较为分散，缺少跨团队合作；International Journal for Parasitology、Parasitology Research、Parasitolo...     

Rainbow trout (Oncorhynchus mykiss) immune response towards a recombinant vaccine targeting the parasitic ciliate Ichthyophthirius multifiliis

The protective effect in rainbow trout (Oncorhynchus mykiss) of an experimental subunit vaccine targeting antigens in the parasite Ichthyophthirius multifiliis has been evaluated and compared to effects elicited by a classical parasite homogenate vaccine. Three recombinant parasite proteins (two produced in E. coli and one in insect cells) were combined and injected i.p., and subsequently, protection and antibody responses were analysed. Both the experimental and the benchmark vaccine induced partial but significant protection against I. multifiliis when compared to control fish. Specific antibody responses of vaccinated trout (subunit vaccine) were raised against one neurohypophysial n‐terminal domain protein #10 of three recombinant proteins, whereas the benchmark vaccine group showed specific antibody production against all three recombinant proteins. The immunogenic parasite protein #10 may be a potential vaccine candidate supplementing the protective I‐antigen in future vaccine trials.     

Immunization of channel catfish, Ictalurus punctatus Rafinesque, against Ichthyophthirius multifiliis (Fouquet): killed versus live vaccines

Abstract. Fish surviving infection with the pathogenic ciliated protozoan, Ichthyophthirius multifiliis (Fouquet, 1876), become resistant to subsequent infection by the parasite. The acquired immunity suggests that development of a vaccine against the parasite may be possible. Because of the advantages of immunoprophylaxis for treatment of the disease, an effort has been made to determine whether fish exposed to killed parasite preparations can resist subsequent lethal challenge. Both the route of administration and the effects of stage specific antigens have been examined. Channel catfish vaccinated by intraperitoneal (i.p.) injection or bath immersion with killed I multifiliis tomites show 100% mortality following a standard challenge protocol. Similarly, 100% mortality was observed in test groups injected with tomite cilia. In both cases, a consistent difference in days to death between control and test group animals was observed. Although complete mortality was seen with fish injected with tomite preparations, fish vaccinated with killed trophonts (the feeding stage of the parasite) had a much greater degree of protection with approximately 50% of fish surviving an otherwise lethal challenge. Finally, animals injected intraperitoneally with live tomites showed nearly complete immunity and were identical in their response to fish which survive natural infection. The response of fish vaccinated with live parasites indicates that animals injected intraperitoneally can develop surface immunity and that i.p. injection is a suitable route of administration for potential I. multifiliis vaccines.     

Parasitism, condition and number of front head breeding tubercles in roach (Rutilus rutilus L.)

Abstract –  In a previous study on the male roach, Rutilus rutilus , we found a positive correlation between sexual ornamentation, breeding tubercles (BTs) on lateral sides and parasite resistance. As a continuation of that study, we examined another measure of sexual ornamentation – number of BTs on front head – of male roach from five populations. BTs on head correlated positively with fish size in two populations and with condition in one population, but not with parasite resistance (proportion of dead parasites) in any of the populations. Moreover, head BTs correlated negatively with the number of two parasite species ( Rhipidocotyle campanula and Myxobolus mülleri ) in two populations, but positively with the number of a third parasite ( Raphidascarus acus ) in one population. In addition, a negative correlation with spleen size was found in one population. The present results suggest that head BTs of male roach – although the patterns vary between populations – may signal condition and parasite load, but not resistance, in contrast to lateral BTs. Therefore, our results are in line with the hypothesis of multiple-message sexual ornaments.     

Infection of the epaulette shark, Hemiscyllium ocellatum (Bonnaterre), by the nematode parasite Proleptus australis Bayliss (Spirurida: Physalopteridae)

Seventy-two epaulette sharks, Hemiscyllium ocellatum (Bonnaterre), were infected with the nematode parasite Proleptus australis Bayliss, 1933. The parasite population was overdispersed. Infection intensity ranged from 3 to 1002 worms per fish stomach, and there was a positive correlation between shark length and number of parasites present. The majority of worms were attached to the stomach wall, and scanning electron microscopy and histological examination showed that worms penetrated the stomach lining. Worms were observed within the lamina propria of the stomach and occasionally penetrated the muscularis mucosa. Little to no inflammatory or cellular immune reaction to the presence of the parasites was observed, except in one case where a worm was being degraded by a host tissue response. There was a large amount of connective tissue proliferation as a result of nematode attachment, but no obvious effects on the overall health of the sharks were seen. Three sharks were also found to be infected by the cestode Callitetrarhynchus sp.