Participating organizations (WP leader in bold): P1. HCMR, P2.
FCPCT, P5. UNIABDN, P8. IEO and P15.
ULL.
Task 25.1. Study of Epitheliocystis during larval rearing. This is an infectious disease recorded in greater amberjack larvae. It is caused by Chlamydia-related organisms and is considered mostly as benign, since it is associated with low if any mortality when it is detected in juvenile or adult fish. Epitheliocystis, however is a fatal disease when it occurs at early stages with mortalities reaching 100% overnight (Katharios, 2008); in these incidences epitheliocystis may be misdiagnosed due to the rapid deterioration of the delicate fish larvae.
Previous experience with greater amberjack larval has shown that epitheliocystis is the major pathological problem at the early stages, especially when mesocosm technology is used. Therefore development of early diagnosis methodology is essential. This methodology will include, firstly, sampling of rearing water, live feeds and fish during mesocosm rearing of greater amberjack, in order to screen for Chlamydia.
Early diagnosis tools will be developed using new molecular probes that allow early detection of the pathogenic strains, based on the sequences that will be obtained from the Chlamydia screening. These probes will be applied during the mesocosm larval rearing under WP4.2 Larval husbandry – greater amberjack as an early diagnostic tool. The efficacy of the new tool will be assessed by screening water samples and monitoring fish for Chlamydia infection in mesocosm rearing greater amberjack.
Task 25.2. Promoting resistance to parasitic incidence on greater amberjack. A number of parasitic diseases occur during on-growing of amberjack juveniles, inducing growth retardation, low feed efficiency, immune-suppression and increased mortality. Parasitic infection is difficult to control in sea cages in an effective way. One potential effective way to improve resistance to parasitic infection is through the increase of mucus efficacy and immune potential using dietary mucus stimulation products.
In addition, an increase of knowledge on the physiological and physical barriers for parasites will help increase the efficacy of the treatments. Different levels of mucus stimulation products, such as some prebiotics or certain phytobiotics, will be studied during the early on-growing of juvenile amberjack under controlled conditions. Fish health will be monitored and samples will be provided for Task 25.3. Growth, survival and immune markers (those determined in Task 25.3) will be monitored. Resistance to opportunistic pathogens and to monogenean infection will be also conducted with infection experiments by cohabitation with monogenean parasites infected animals. Morphometric and ultrastructure of target tissues (i.e. gills, intestine, etc), including several morphometric variables, will be studied and evaluated by image analysis.
Task 25.3. Identification of immune markers. A number of important immune molecules that are essential for initiating and effecting mucosal defences, including IL-17 and IL-22, antimicrobial peptides, iNOS and IgT will be cloned. The impact of the different dietary treatments on expression of these molecules will be examined at mucosal sites and during development. Ways to induce these molecules will also be studied using gill leucocyte primary cultures and/or gill explants, as a key mucosal tissue affected by these diseases. Lastly, the cutaneous mucus layer itself will be analysed and its immune potential characterized in terms of antimicrobial activity, protease activity, presence of lectins and immunoglobulins.
Task 25.4. Effectiveness of stocking density and anti-oncomiracidia attaching substances in the control of monogenean parasites. The monogenean parasites (Benedenia seriolae and Zeuxaptaseriolae) cause high mortalities in cultures of Seriola sp. The implementation of measures, including biosecurity practices, inhibition of oncomiracidia attaching capacity, as well as reinforcement of the fish immune system against stressful rearing conditions must be developed to obtain uninfected fish. PIT-tagged juveniles of greater amberjack reared in two different stocking densities will be subjected (or not) to baths of lectin type anti-oncomiracidia attaching substances. Fish growth and hematological and biochemical indicators of health and welfare will be studied. Tank collector devices will be placed, and regularly checked, for evaluation of presence and density of parasites.
Task 25.5. Description, diagnosis and treatment of other bacterial/viral infectious diseases occurring in amberjack. Increase in fish production, particularly in fast growing species such as greater amberjack, may lead to the emergence of bacterial diseases such as vibriosis or photobacteriosis, lactococcosis, streptococcosis and some viral diseases such as, nodavirus, limphocystis, iridovirus and aquabinnavirus disease. In this task, greater amberjack will be monitored throughout the year to establish the seasonality of the potential diseases. External morphology, necropsies and samples of liver, spleen, kidney, gut and nervous system will be studied to determine the presence of pathogenic organisms and histopathological damage to the different organs. These samples will be processed for determination of bacterial diseases by classical microbiological techniques, and by PCR.
For viral diseases cell cultures suited to each disease (eg SS-1, SAF-1)will be used for virus propagation, following by RT-PCR or PCR verification depending on the specific virus.
Susceptibility of greater amberjack will be set against field and reference strains of the following pathogens: Vibrio anguillarum, Photobacterium damselae subsp. piscicida, and betanodavirus. These studies will be conducted in the biosecurity station.
Task 25.6 Diagnostic-recommendation manual for greater amberjack health. This will be a practical diagnostic manual and recommendation guide for greater amberjack health issues targeted to fish health specialists and aquaculture scientists and producers. The manual will be the synopsis of major findings of WP24. It will be published in electronic format (pdf file) and uploaded in the project website, and will be freely available for the public. The manual will be organized in chapters describing the major diseases of the species with original photographic material, epidemiological and pathological data.
Task 25.1. Study of Epitheliocystis during larval rearing. This is an infectious disease recorded in greater amberjack larvae. It is caused by Chlamydia-related organisms and is considered mostly as benign, since it is associated with low if any mortality when it is detected in juvenile or adult fish. Epitheliocystis, however is a fatal disease when it occurs at early stages with mortalities reaching 100% overnight (Katharios, 2008); in these incidences epitheliocystis may be misdiagnosed due to the rapid deterioration of the delicate fish larvae.
Previous experience with greater amberjack larval has shown that epitheliocystis is the major pathological problem at the early stages, especially when mesocosm technology is used. Therefore development of early diagnosis methodology is essential. This methodology will include, firstly, sampling of rearing water, live feeds and fish during mesocosm rearing of greater amberjack, in order to screen for Chlamydia.
Early diagnosis tools will be developed using new molecular probes that allow early detection of the pathogenic strains, based on the sequences that will be obtained from the Chlamydia screening. These probes will be applied during the mesocosm larval rearing under WP4.2 Larval husbandry – greater amberjack as an early diagnostic tool. The efficacy of the new tool will be assessed by screening water samples and monitoring fish for Chlamydia infection in mesocosm rearing greater amberjack.
Task 25.2. Promoting resistance to parasitic incidence on greater amberjack. A number of parasitic diseases occur during on-growing of amberjack juveniles, inducing growth retardation, low feed efficiency, immune-suppression and increased mortality. Parasitic infection is difficult to control in sea cages in an effective way. One potential effective way to improve resistance to parasitic infection is through the increase of mucus efficacy and immune potential using dietary mucus stimulation products.
In addition, an increase of knowledge on the physiological and physical barriers for parasites will help increase the efficacy of the treatments. Different levels of mucus stimulation products, such as some prebiotics or certain phytobiotics, will be studied during the early on-growing of juvenile amberjack under controlled conditions. Fish health will be monitored and samples will be provided for Task 25.3. Growth, survival and immune markers (those determined in Task 25.3) will be monitored. Resistance to opportunistic pathogens and to monogenean infection will be also conducted with infection experiments by cohabitation with monogenean parasites infected animals. Morphometric and ultrastructure of target tissues (i.e. gills, intestine, etc), including several morphometric variables, will be studied and evaluated by image analysis.
Task 25.3. Identification of immune markers. A number of important immune molecules that are essential for initiating and effecting mucosal defences, including IL-17 and IL-22, antimicrobial peptides, iNOS and IgT will be cloned. The impact of the different dietary treatments on expression of these molecules will be examined at mucosal sites and during development. Ways to induce these molecules will also be studied using gill leucocyte primary cultures and/or gill explants, as a key mucosal tissue affected by these diseases. Lastly, the cutaneous mucus layer itself will be analysed and its immune potential characterized in terms of antimicrobial activity, protease activity, presence of lectins and immunoglobulins.
Task 25.4. Effectiveness of stocking density and anti-oncomiracidia attaching substances in the control of monogenean parasites. The monogenean parasites (Benedenia seriolae and Zeuxaptaseriolae) cause high mortalities in cultures of Seriola sp. The implementation of measures, including biosecurity practices, inhibition of oncomiracidia attaching capacity, as well as reinforcement of the fish immune system against stressful rearing conditions must be developed to obtain uninfected fish. PIT-tagged juveniles of greater amberjack reared in two different stocking densities will be subjected (or not) to baths of lectin type anti-oncomiracidia attaching substances. Fish growth and hematological and biochemical indicators of health and welfare will be studied. Tank collector devices will be placed, and regularly checked, for evaluation of presence and density of parasites.
Task 25.5. Description, diagnosis and treatment of other bacterial/viral infectious diseases occurring in amberjack. Increase in fish production, particularly in fast growing species such as greater amberjack, may lead to the emergence of bacterial diseases such as vibriosis or photobacteriosis, lactococcosis, streptococcosis and some viral diseases such as, nodavirus, limphocystis, iridovirus and aquabinnavirus disease. In this task, greater amberjack will be monitored throughout the year to establish the seasonality of the potential diseases. External morphology, necropsies and samples of liver, spleen, kidney, gut and nervous system will be studied to determine the presence of pathogenic organisms and histopathological damage to the different organs. These samples will be processed for determination of bacterial diseases by classical microbiological techniques, and by PCR.
For viral diseases cell cultures suited to each disease (eg SS-1, SAF-1)will be used for virus propagation, following by RT-PCR or PCR verification depending on the specific virus.
Susceptibility of greater amberjack will be set against field and reference strains of the following pathogens: Vibrio anguillarum, Photobacterium damselae subsp. piscicida, and betanodavirus. These studies will be conducted in the biosecurity station.
Task 25.6 Diagnostic-recommendation manual for greater amberjack health. This will be a practical diagnostic manual and recommendation guide for greater amberjack health issues targeted to fish health specialists and aquaculture scientists and producers. The manual will be the synopsis of major findings of WP24. It will be published in electronic format (pdf file) and uploaded in the project website, and will be freely available for the public. The manual will be organized in chapters describing the major diseases of the species with original photographic material, epidemiological and pathological data.