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14 pages, 3957 KiB

Open AccessArticle

Reduced Antioxidant Response of the Fan Mussel Pinna nobilis Related to the Presence of Haplosporidium pinnae

by Antonio Box, Xavier Capó, Silvia Tejada, Gaetano Catanese, Amalia Grau, Salud Deudero, Antoni Sureda and José María Valencia

Pathogens 2020, 9(11), 932; https://doi.org/10.3390/pathogens9110932 - 11 Nov 2020

Cited by 25 | Viewed by 2627

Abstract

The endemic fan mussel (Pinna nobilis) in the Mediterranean Sea is at high risk of disappearance due to massive mortality events. The aim of the study was to evaluate the antioxidant response of P. nobilis collected in the Balearic Islands (Western [...] Read more.

The endemic fan mussel (Pinna nobilis) in the Mediterranean Sea is at high risk of disappearance due to massive mortality events. The aim of the study was to evaluate the antioxidant response of P. nobilis collected in the Balearic Islands (Western Mediterranean) before and after the mass mortality event. Individuals collected before (between 2011 and 2012) and after (between 2016 and 2017) the event were analyzed by histological, molecular, and biochemical methods to compare pathogenic loads and biochemical responses. All the individuals collected during 2016–2017 presented symptoms of the disease and were positive for Haplosporidium pinnae, while acid-fast bacteria or/and Gram-negative bacteria were detected in some individuals of both sampling periods. The activities of the antioxidant enzymes catalase and superoxide dismutase in the gills were significantly lower in P. nobilis affected with the parasite compared to those in the asymptomatic ones, while levels of malondialdehyde, as an indicator of lipid peroxidation, were higher in infected individuals. When analyzing the differential effects of H. pinnae and Mycobacterium sp. on P. nobilis, it was observed that significant effects on biomarkers were only observed in the presence of H. pinnae. Co-infection of P. nobilis by H. pinnae with other pathogens such as Mycobacterium sp. constitutes a serious problem due to its high mortality rate in the Balearic Island waters. This concerning situation for P. nobilis is favored by a reduction in antioxidant defenses related to H. pinnae infection that induces oxidative stress and cell damage. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

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15 pages, 2668 KiB

Open AccessArticle

Probiotics Modulate Tilapia Resistance and Immune Response against Tilapia Lake Virus Infection

by Pitchaporn Waiyamitra, Mehmet Arif Zoral, Aksorn Saengtienchai, Amorn Luengnaruemitchai, Olivier Decamp, Bartolomeo Gorgoglione and Win Surachetpong

Pathogens 2020, 9(11), 919; https://doi.org/10.3390/pathogens9110919 - 6 Nov 2020

Cited by 26 | Viewed by 5521

Abstract

Tilapia lake virus (TiLV) causes an emerging viral disease associated with high mortality and economic damage in tilapia farming around the world. The use of probiotics in aquaculture has been suggested as an alternative to antibiotics and drugs to reduce the negative impact [...] Read more.

Tilapia lake virus (TiLV) causes an emerging viral disease associated with high mortality and economic damage in tilapia farming around the world. The use of probiotics in aquaculture has been suggested as an alternative to antibiotics and drugs to reduce the negative impact of bacterial and viral infections. In this study, we investigate the effect of probiotic Bacillus spp. supplementation on mortality, viral load, and expression of immune-related genes in red hybrid tilapia (Oreochromis spp.) upon TiLV infection. Fish were divided into three groups, and fed with: control diet, 0.5% probiotics-supplemented diet, and 1% probiotics-supplemented diet. After 21 days of experimental feeding, the three groups were infected with TiLV and monitored for mortality and growth performances, while organs were sampled at different time points to measure viral load and the transcription modulation of immune response markers. No significant difference was found among the groups in terms of weight gain (WG), average daily gain (ADG), feed efficiency (FE), or feed conversion ratio (FCR). A lower cumulative mortality was retrieved from fish fed 0.5% and 1% probiotics (25% and 24%, respectively), compared to the control group (32%). Moreover, fish fed with 1% probiotic diet had a significantly lower viral load, than those fed with 0.5% probiotic and control diet at 5, 6, 9, and 12 days post infection-challenge (dpc). The expression patterns of immune-related genes, including il-8 (also known as CXCL8), ifn-γ, irf-3, mx, rsad-2 (also known as VIPERIN) showed significant upregulation upon probiotic treatment during the peak of TiLV pathogenesis (between 9 and 12 dpc) and during most of the study period in fish fed with 1% probiotics-supplemented diet. Taken together, these findings indicate that dietary supplementation using Bacillus spp. probiotics may have beneficial effects to strengthen tilapia immunity and resistance against TiLV infections. Therefore, probiotic treatments may be preventively administered to reduce losses caused by this emerging viral infection in tilapia aquaculture. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

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7 pages, 204 KiB

Open AccessCommunication

Feed Supplementation with a Commercially Available Probiotic Solution Does Not Alter the Composition of the Microbiome in the Biofilters of Recirculating Aquaculture Systems

by Simon Menanteau-Ledouble, Rui A. Gonçalves and Mansour El-Matbouli

Pathogens 2020, 9(10), 830; https://doi.org/10.3390/pathogens9100830 - 10 Oct 2020

Cited by 4 | Viewed by 2085

Abstract

Recirculating aquaculture relies on the treatment of ammonia compounds from the water by a bacterial flora growing inside biofilters. Another increasingly common practice in aquaculture is the supplementation of feed with live probiotic bacteria to boost the immune system of the farmed animals [...] Read more.

Recirculating aquaculture relies on the treatment of ammonia compounds from the water by a bacterial flora growing inside biofilters. Another increasingly common practice in aquaculture is the supplementation of feed with live probiotic bacteria to boost the immune system of the farmed animals and hinder the implantation of pathogenic bacteria. In the present study, we investigated the bacterial flora within the biofilters of recirculating farming units in which African catfish (Clarias gariepinus) were being farmed. Our results suggested that these two farming systems could be compatible as feeding of the probiotic feed had no detectable effect on the composition of the microbiome within the biofilters and none of the bacteria from the feed could be detected in the biofilters. These findings suggest that supplementation of the fish feed with probiotic supplements did not interfere with the microbiome residing inside the biofilter and that it is a safe practice in recirculating aquaculture systems. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

20 pages, 3309 KiB

Open AccessEditor’s ChoiceArticle

Transcriptome Response of Atlantic Salmon (Salmo salar) to a New Piscine Orthomyxovirus

by Francisca Samsing, Pamela Alexandre, Megan Rigby, Richard S. Taylor, Roger Chong and James W. Wynne

Pathogens 2020, 9(10), 807; https://doi.org/10.3390/pathogens9100807 - 30 Sep 2020

Cited by 11 | Viewed by 3247

Abstract

Pilchard orthomyxovirus (POMV) is an emerging pathogen of concern to the salmon industry in Australia. To explore the molecular events that underpin POMV infection, we challenged Atlantic salmon (Salmo salar) post-smolts in seawater via cohabitation. Tissue samples of the head kidney [...] Read more.

Pilchard orthomyxovirus (POMV) is an emerging pathogen of concern to the salmon industry in Australia. To explore the molecular events that underpin POMV infection, we challenged Atlantic salmon (Salmo salar) post-smolts in seawater via cohabitation. Tissue samples of the head kidney and liver were collected from moribund and surviving individuals and analyzed using transcriptome sequencing. Viral loads were higher in the head kidney compared to the liver, yet the liver presented more upregulated genes. Fish infected with POMV showed a strong innate immune response that included the upregulation of pathogen recognition receptors such as RIG-I and Toll-like receptors as well as the induction of interferon-stimulated genes (MX, ISG15). Moribund fish also presented a dramatic induction of pro-inflammatory cytokines, contributing to severe tissue damage and morbidity. An induction of major histocompatibility complex (MHC) class I genes (B2M) and markers of T cell-mediated immunity (CD8-alpha, CD8-beta, Perforin-1, Granzyme-A) was observed in both moribund fish and survivors. In addition, differential connectivity analysis showed that three key regulators (RELA/p65, PRDM1, and HLF) related to cell-mediated immunity had significant differences in connectivity in “clinically healthy” versus “clinically affected” or moribund fish. Collectively, our results show that T cell-mediated immunity plays a central role in the response of Atlantic salmon to the infection with POMV. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

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14 pages, 1967 KiB

Open AccessEditor’s ChoiceArticle

Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease

by Tina Oldham, Tim Dempster, Philip Crosbie, Mark Adams and Barbara Nowak

Pathogens 2020, 9(8), 597; https://doi.org/10.3390/pathogens9080597 - 22 Jul 2020

Cited by 14 | Viewed by 2585

Abstract

Amoebic gill disease (AGD), caused by the amoeba Neoparamoeba perurans, has led to considerable economic losses in every major Atlantic salmon producing country, and is increasing in frequency. The most serious infections occur during summer and autumn, when temperatures are high and [...] Read more.

Amoebic gill disease (AGD), caused by the amoeba Neoparamoeba perurans, has led to considerable economic losses in every major Atlantic salmon producing country, and is increasing in frequency. The most serious infections occur during summer and autumn, when temperatures are high and poor dissolved oxygen (DO) conditions are most common. Here, we tested if exposure to cyclic hypoxia at DO saturations of 40–60% altered the course of infection with N. perurans compared to normoxic controls maintained at ≥90% DO saturation. Although hypoxia exposure did not increase initial susceptibility to N. perurans, it accelerated progression of the disease. By 7 days post-inoculation, amoeba counts estimated from qPCR analysis were 1.7 times higher in the hypoxic treatment than in normoxic controls, and cumulative mortalities were twice as high (16 ± 4% and 8 ± 2%), respectively. At 10 days post-inoculation, however, there were no differences between amoeba counts in the hypoxic and normoxic treatments, nor in the percentage of filaments with AGD lesions (control = 74 ± 2.8%, hypoxic = 69 ± 3.3%), or number of lamellae per lesion (control = 30 ± 0.9%, hypoxic = 27.9 ± 0.9%) as determined by histological examination. Cumulative mortalities at the termination of the experiment were similarly high in both treatments (hypoxic = 60 ± 2%, normoxic = 53 ± 11%). These results reveal that exposure to cyclic hypoxia in a diel pattern, equivalent to what salmon are exposed to in marine aquaculture cages, accelerated the progression of AGD in post-smolts. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

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10 pages, 701 KiB

Open AccessCommunication

Efficacy of Erymicin 200 Injections for Reducing Renibacterium salmoninarum and Controlling Vertical Transmission in an Inland Rainbow Trout Brood Stock

by Eric R. Fetherman, Brad Neuschwanger, Tracy Davis, Colby L. Wells and April Kraft

Pathogens 2020, 9(7), 547; https://doi.org/10.3390/pathogens9070547 - 7 Jul 2020

Cited by 8 | Viewed by 2743

Abstract

Bacterial Kidney Disease, caused by Renibacterium salmoninarum (Rs), is widespread and can cause significant mortality at most life stages in infected salmonids. Rs is commonly found in inland trout, which can be carriers of the bacterium. Lethal spawns can be used [...] Read more.

Bacterial Kidney Disease, caused by Renibacterium salmoninarum (Rs), is widespread and can cause significant mortality at most life stages in infected salmonids. Rs is commonly found in inland trout, which can be carriers of the bacterium. Lethal spawns can be used to control vertical transmission to progeny through the culling of eggs from infected parents, but can be costly, time-consuming, and can negatively impact important and rare brood stocks. Erymicin 200 is an Investigational New Animal Drug (INAD) intended to reduce Rs levels in hatchery brood stocks and control vertical transmission to progeny. We tested the efficacy of Erymicin 200 injections in a positive, hatchery-resident rainbow trout (Oncorhynchus mykiss) brood stock in Colorado, USA. Brood fish age two and three were injected with 25 mg per kg of body weight Erymicin 200 three times prior to spawning. Erymicin 200 was effective in reducing Rs to below detectable levels in treated fish. However, both negative treated and control brood fish produced positive progeny, suggesting that Erymicin 200 did not prevent the vertical transmission of Rs. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

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Review

Jump to: Research

19 pages, 1660 KiB

Open AccessEditor’s ChoiceReview

Renibacterium salmoninarum—The Causative Agent of Bacterial Kidney Disease in Salmonid Fish

by Mohammad Reza Delghandi, Mansour El-Matbouli and Simon Menanteau-Ledouble

Pathogens 2020, 9(10), 845; https://doi.org/10.3390/pathogens9100845 - 15 Oct 2020

Cited by 22 | Viewed by 6933

Abstract

Renibacterium salmoninarum is one of the oldest known bacterial pathogens of fish. This Gram-positive bacterium is the causative agent of bacterial kidney disease, a chronic infection that is mostly known to infect salmonid fish at low temperatures. Externally, infected fish can display exophthalmia [...] Read more.

Renibacterium salmoninarum is one of the oldest known bacterial pathogens of fish. This Gram-positive bacterium is the causative agent of bacterial kidney disease, a chronic infection that is mostly known to infect salmonid fish at low temperatures. Externally, infected fish can display exophthalmia as well as blebs on the skin and ulcerations alongside haemorrhages at the base of the fins and alongside the lateral line. Internally, the kidney, heart, spleen and liver can show signs of swelling. Granulomas can be seen on various internal organs, as can haemorrhages, and the organs can be covered with a false membrane. Ascites can also accumulate in the abdominal cavity. The bacterium is generally cultivated on specialized media such as kidney disease medium-1 (KDM-1), KDM-2 and selective kidney disease medium (SKDM), and a diagnostic is performed using molecular tools such as PCRs or real-time quantitative PCRs (RT-qPCRs). Several virulence mechanisms have been identified in R. salmoninarum, in particular the protein p57 that is known to play a role in both agglutination and immunosuppression of the host’s defense mechanisms. Control of the disease is difficult; the presence of asymptomatic carriers complicates the eradication of the disease, as does the ability of the bacterium to gain entrance inside the eggs. Bacterin-killed vaccines have proven to be of doubtful efficacy in controlling the disease, and even more recent application of a virulent environmental relative of R. salmoninarum is of limited efficacy. Treatment by antibiotics such as erythromycin, azithromycin and enrofloxacin can be effective but it is slow and requires prolonged treatment. Moreover, antibiotic-resistant strains have been reported. Despite being known for a long time, there is still much to be discovered about R. salmoninarum, notably regarding its virulence mechanisms and its vaccine potential. Consequently, these gaps in knowledge continue to hinder control of this bacterial disease in aquaculture settings. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

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9 pages, 1795 KiB

Open AccessReview

Abalone Viral Ganglioneuritis

by Serge Corbeil

Pathogens 2020, 9(9), 720; https://doi.org/10.3390/pathogens9090720 - 1 Sep 2020

Cited by 11 | Viewed by 3867

Abstract

Abalone viral ganglioneuritis (AVG), caused by Haliotid herpesvirus-1 (HaHV-1; previously called abalone herpesvirus), is a disease that has been responsible for extensive mortalities in wild and farmed abalone and has caused significant economic losses in Asia and Australia since outbreaks occurred in the [...] Read more.

Abalone viral ganglioneuritis (AVG), caused by Haliotid herpesvirus-1 (HaHV-1; previously called abalone herpesvirus), is a disease that has been responsible for extensive mortalities in wild and farmed abalone and has caused significant economic losses in Asia and Australia since outbreaks occurred in the early 2000s. Researchers from Taiwan, China, and Australia have conducted numerous studies encompassing HaHV-1 genome sequencing, development of molecular diagnostic tests, and evaluation of the susceptibility of various abalone species to AVG as well as studies of gene expression in abalone upon virus infection. This review presents a timeline of the most significant research findings on AVG and HaHV-1 as well as potential future research avenues to further understand this disease in order to develop better management strategies. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

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11 pages, 630 KiB

Open AccessReview

Immune Control of Herpesvirus Infection in Molluscs

by Jacinta R Agius, Serge Corbeil and Karla J Helbig

Pathogens 2020, 9(8), 618; https://doi.org/10.3390/pathogens9080618 - 29 Jul 2020

Cited by 6 | Viewed by 3533

Abstract

Molluscan herpesviruses that are capable of infecting economically important species of abalone and oysters have caused significant losses in production due to the high mortality rate of infected animals. Current methods in preventing and controlling herpesviruses in the aquacultural industry are based around [...] Read more.

Molluscan herpesviruses that are capable of infecting economically important species of abalone and oysters have caused significant losses in production due to the high mortality rate of infected animals. Current methods in preventing and controlling herpesviruses in the aquacultural industry are based around biosecurity measures which are impractical and do not contain the virus as farms source their water from oceans. Due to the lack of an adaptive immune system in molluscs, vaccine related therapies are not a viable option; therefore, a novel preventative strategy known as immune priming was recently explored. Immune priming has been shown to provide direct protection in oysters from Ostreid herpesvirus-1, as well as to their progeny through trans-generational immune priming. The mechanisms of these processes are not completely understood, however advancements in the characterisation of the oyster immune response has assisted in formulating potential hypotheses. Limited literature has explored the immune response of abalone infected with Haliotid herpesvirus as well as the potential for immune priming in these species, therefore, more research is required in this area to determine whether this is a practical solution for control of molluscan herpesviruses in an aquaculture setting. Full article

(This article belongs to the Special Issue Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture)

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