Caligidosis Background

THIS IS A WORKING SYNTHESIS PREPARED BY ACUAIM SPA FOR THE PGSA CONSULTIVE COMMITTEE, IN ORDER TO INFORM ABOUT THE CONTEXT OF THE PROJECT BASED ON THE FOLLOWING ORIGINAL REPORTS: "Establishment of multidisciplinary and integrated research lines and their impact on levels of health intervention against P. salmonis in farmed salmon "by EpiVet EIRL (2017); "SRS: A review of the disease, risk factors and control strategies" by Ausvet (2017); "Scoping Report for Sanitary Management in Aquaculture" by SERNAPESCA (2017); and Estimated Economic Costs for SRS and Caligus Associated with PGSA Impact Indicators "by SERNAPESCA (2017).

INTRODUCTION

Sea lice are parasitic copepods that infect farmed and wild salmonids. They are considered one of the major global challenges for the salmon industry. In the northern hemisphere, Lepeophtheirus salmonis is the most problematic louse, however in Chile, Caligus rogercresseyi is the predominant species of concern. Sea lice feed on the skin causing skin lesions that effect osmosis and make fish vulnerable to secondary infection; as a result, growth, fecundity and survival of fish can be affected.

In Chile, caligid copepods have been reported in wild fish since 1840, when Milne-Edwards first described Caligus ornatus. Wilson later described Caligus teres on wild fish in 1905; however it was not until 1983 that C. teres was first reported on farmed coho salmon. Since then, Caligus serratus, Caligus amplifurcus, Lepeoptheirus and C. rogercresseyi have all been recorded on commercial fish farms, with Atlantic salmon and rainbow trout showing the highest susceptibility. Sea lice have differing impacts on wild salmonoid populations. At low density (less than three lice per fish), lice don’t seem to affect fish. However, lice can cause reduced swimming and cardiac performance in Atlantic salmon. Whether fish suffer more or less predation because of infestation is unknown although it has been suggested that lice can be abundant enough to cause fish mortality in natural conditions.

Although economic data is scant, sea lice have been estimated to cost around US $480 million per year globally, with Chilean producers incurring over one third of these costs. Some researchers have calculated that the cost of treatment alone in Chilean farms to range between US $0.004 – 0.022/kg of fish produced whilst others have estimated the overall cost of sea lice incurred as a result of delousing in the processing plant and poor growth at US $0.30/kg of fish produced. In addition, Chile’s salmon farmers’ monitoring program has recorded an increase in the number of positive cages and intensity of infestations in recent years, suggesting that the economic impact of the problem is likely to grow.

Geographical zones, stocking density, fish weight, fish species, treatment against sea lice performed a month before sampling, and water salinity have all been identified as risk factors for the disease in Chile. In the same study, treatments performed 2–3 months before sampling, use of photoperiod and water temperatures were found to have an insignificant relationship with incidence of disease. In the northern hemisphere a number of additional risk factors have been identified including type of treatment, cage volume, lock flushing time, current speed, population structure at treatment time, presence of infected neighbours, treatment level and fallowing.

Antiparasitic drugs are the most common tool for controlling sea lice, both in Chile and around the world. However, treatment failures have now been reported in most salmon-producing countries. Possible explanations for this failure include low sensitivity of lice to the chemicals been used, suboptimal drug administration methods and re-infestation immediately after treatment. Chemicals originating from five groups of compounds are used to treat sea lice: avermectins, benzoyl ureas, disinfectants, organophosphates and pyrethroids.

In addition to chemical treatment and partly in response to treatment failures, several non-chemical means of control have been attempted. Fallowing, synchronized treatments with neighbouring farms, cleaner fish, delousing laser, and plankton shielding skirts are currently in use whilst snorkel cages and enclosed cages are close to being ready for commercial production.

Overview of sea lice

The pathogen

Basic biology and life cycle.

In Europe and Canada, the most common sea louse is L. salmonis whilst C. rogercresseyi is most important in Chile. A third louse, Caligus elongatus also effects salmonid and non-salmonid species in Europe and Canada but is rarely studied because of its limited impact on fish morbidity. All three species are crustaceans with life cycles ranging from eight to ten stages. The Caligus species have three free-living planktonic stages before attaching to the host for five parasitic instars. They attach to the host by a protein filament and later moult into an adult stage. Gravid females produce egg strings and have high reproductive capacity, although the number of eggs produced and the time taken for eggs to develop into adults is highly temperature depended. Strings extruded from the female carry between 100 to 1000 eggs but the exact number per louse varies with time of year, louse size, louse age, host species and use of parasiticides on farm. In vitro, eggs develop into adults in approximately 400 degree-days for L. salmonis and C. elongatus. Generation times appear to be shorter for C. rogercresseyi and can vary depending on the hosts; they have been estimated at approximately 18 days in summer and 45 days in winter with a minimum development threshold of 4.2°C.

The host and disease

Susceptible hosts

Lice infect both wild and farmed fish and the interaction between the two populations is of great concern. L. salmonis is rarely found on non-salmonids but has a host range covering more than ten species of salmonoids including Atlantic salmon, sea trout and rainbow trout. In contrast, C. elongatus has been found on at least 36 species of fish from 18 different families. C. rogercresseyi can be found on both salmonid and non-salmonid species in Chile and it is proposed that the parasite was first transmitted to farmed fish from populations of the native rock cod, Eleginops maclovinus and Odeonthestes regia. Today, amongst rainbow trout and Atlantic salmon farms, C. rogercresseyi is present in around 99% of marine net pens. Rainbow trout and Atlantic salmon are more susceptible to C. rogercresseyi than Coho salmon.

Modes of transmission

Once advancing past the planktonic stage, sea lice use rasping mouthparts to graze the host, removing skin and tissue. Copepodids are understood to respond visually to hosts, use mechanoreceptors on their antennae to detect vibrations, and use chemoreceptors to determine host suitability. In addition, copepodids and mobile lice may use water-borne chemical cues to find hosts. It is important to note that floating sea cages allow for free movement of parasites between farmed and wild finfish and hence wild populations may get infected through contact with farmed fish.

Clinical signs and mortality

Once infestation occurs, the impact of lice ranges from mild skin damage to stress-induced mortality. The effect of parasitism on host skin includes epithelium loss, bleeding, increased mucus discharge, and tissue necrosis with consequent loss of barrier function. Stress and barrier disruption increase vulnerability to secondary infection. In addition, infested fish can exhibit anorexia, leading to reduction in food conversion efficiency and subsequent growth. Sea lice incursions in the field consist of continual establishment of new infestations, so estimating mortality and morbidity of specific outbreaks is difficult.

Risk factors

Several risk factors for sea lice infestation have been identified in both the northern and southern hemisphere, however this review will focus on risk factors identified in Chile and specifically related to C. rogercresseyi.

Zones

When Yatabe and colleagues analysed data collected in the first stage of a lice surveillance program in Chile, they considered the location of farms whereby cages are nested within farms, farms are located within subzones, and zones are nested within productive-environmental zones. Not surprisingly, productive-environmental zones had a significant effect on lice numbers, consistent with farmers observations of spatially clustered infestations. Zones located within the Los Lagos region were associated with higher infestations, whereas those in Aysen region were associated with lower levels of infestation. This observed difference could be a result of farming density differences between the two regions or the oceanographic factors that have been considered to be important in L. salmonis including water depth, tidal range, patterns of water circulation and flow rate.

Fish species

Taking into account the three most commonly farmed salmonids, it has been proposed that Coho salmon are the most resistant to L. salmonis, followed by rainbow trout and then Atlantic salmon. In the case of C. rogercresseyi, Coho salmon also appear to be the most resistant, with Atlantic salmon and rainbow trout being more susceptible. In relation to L. salmonis, it has been proposed that resistance in Coho salmon results from a heightened response to the parasite, including increased epithelial hyperplasia and inflammation. The same could be true for the resistance of Coho salmon to C. rogercresseyi.

Recent treatment

Emamectin benzoate is considered one of the more effective agents for controlling sea lice because it targets both the juvenile and adult stages: it was the only drug permitted for use against sea lice in Chile between 2000 and 2007. Hydrogen peroxide baths are also used, but the treatment is only active on adult stages, resulting in constant regeneration. Previous work involving L. salmonis suggests that lice numbers are reduced by 7 days post-treatment with emamectin benzoate and that levels remain low for up to 64 days post-treatment. A field trial in Chile involving Caligus species showed that lice numbers can remain low for as long as 96 days post treatment. However it was found that colleagues found that only treatments applied in the last month before sampling were significantly associated with lower lice burdens (both emamectin bezoate and hydrogen peroxide bath); treatments applied two and three months before sampling were not statistically associated with lower burdens. This is easily explained in hydrogen peroxide baths by its selective action against adults only. In emamectin benzoate, this could be associated with resistance arising from a failure to rotate drugs (because no additional drugs were registered for use against lice between 2000–2007 in Chile). Farmers started to report a reduction in effectiveness of the drug in 2005 and this was supported by an in vitro study of C .rogercresseyi’s sensitivity to emamectin benzoate in 2008. Other suggested causes of the loss of sensitivity include the use of generic products and the method of delivery through medicated feeds. Another explanation is that treatment tends to only be applied to cages with high parasitic burdens, whilst those with low loads are not treated.

Stocking density

It was found that stocking density was significantly associated with higher mean parasite counts. This is unsurprising given that high stocking densities have been associated with reduced welfare leading to stress, which is likely to make animals more vulnerable to infestation and disease. It has been suggested that stocking densities over a threshold of 22kg/m3 are associated with a decrease in welfare and hence this might provide some indication of appropriate stocking densities to reduce lice burdens. Interestingly, a study of 40 salmon sites in Scotland over four years found no significant link between stocking density and burdens of L. salmonis.

Fish weight

There is an apparent association between fish weight and parasite burden, with larger fish harbouring greater burdens. This association is likely to be related to the time of exposure, with larger fish more likely to have spent a longer time in the sea. A link between age and burden of L. salmonis has been described in Atlantic salmon. Another possible explanation is that heavier fish have a larger body surface area in which parasites can attach. A laboratory study showed bigger fish acquire higher burdens of L. salmonis but when this is expressed as number of parasites per unit of surface area, smaller fish are more intensely infested.

Water salinity

Larval stages of sea lice are susceptible to low salinity such that they begin to die at a salinity of 20% or less. In addition, sea lice have a preference for saline environments and fish in freshwater lose lice burdens. It has also been suggested that water salinity could affect the settling rate and development rate of some lice. For these reasons, it is not surprising that low salinity has been associated with reduced parasite burdens.

Coinfection

It was found that infection with C. rogercresseyi significantly increased mortality in fish infected with Piscirickettsia salmonis. How P. salmonis impacts susceptibility to sea lice is not described.

Temperature

Many studies have suggested a link between water temperature and sea lice abundance, with particular reference to the faster development of lice at higher temperatures in vivo. However, in many cases analysis of data has failed to demonstrate a statistically significant link between lice burden and water temperature in field conditions. However, this may be linked the narrow range of temperatures recorded in some of these studies.

Infection in neighbouring farms

The role of neighbouring farms as a source of sea lice is becoming a greater concern as the aquaculture industry grows. Multiple studies have identified a link between sea lice burden on farms and the abundance of fish in the surrounding area. Interestingly, have been recently suggested that infection pressure from neighbouring farms was actually greater than the infection pressure from within a farm. In these studies the ‘neighbour effect’ was detected on average up to 30km away. Estimated external infection pressure has been found to be the main predictor of salmon lice populations in newly stocked pens.

Other

Other risk factors identified in the northern hemisphere include cage volume, level of treatment, current speed, loch flushing time, depth of cages and sea lice levels in the proceeding months.

Disease control

Chemical control

The most common method for controlling sea lice globally is the use of anti-parasitic drugs. Organophosphates applied by bath were the first chemicals used to control sea lice in Chile. These were followed by oral treatments. Currently organophosphate azamethiphos, cypermethrin and deltamethrin are the three main bath treatments currently being used in Chile. Emamectin benzoate is the most commonly used oral treatment and in some cases hydrogen peroxide bathing is used.

Synchronised treatments

Sea lice reinfestation from external sources seriously limit the duration of treatment effect when immersion treatments are being used. Numerous studies have found that external sources of lice are associated with higher burdens at farm level and one study found that infection pressure from neighbouring farms was greater than that coming from the farm itself. One strategy to overcome this is synchronised treatments where multiple farms in the same region coordinate their drug administration to interrupt the sea lice cycle at the same time, thus minimising reinfestation from neighbouring farms immediately after the treatment. Recent studies suggest that treatment synchronization is associated with lower adult lice levels five to seven weeks after treatment. Efforts to synchronise treatments may benefit from tools to predict sea lice levels in the upcoming production cycle.

Resistance

Extensive use of chemical treatment has led to resistance and treatment failures have been reported world-wide. In Norway, incidents of non-effective treatments with emamectin benzonate, pyrethroids, azamethiphos and hydrogen peroxide have been reported, but the severity of the problem varies between regions. Evidence of reduced susceptibility to emamectin bezonate has also been found in Scotland and Canada. In Chile, resistance to emamectin bezonate, and deltamethrin have been reported and confirmed by sensitivity bioassays.
Interestingly, the early stage of L.salmonis is highly susceptible to freshwater, prompting suggestions that regular freshwater bathing or creating a freshwater surface layer in cages may provide an alternative traditional chemical treatments.

Physical control

A number of physical measures have been trialled to prevent incursions of sea lice. In Norway, cages protected by cables omitting electronic pulses experienced 50% less new infections than control cages.
In the US, it was demonstrated that L.salmonis egg strings placed on a Petri dish and exposed to air for 4 to 24 hours at 15–19°C failed to hatch: desiccation could therefore be a simple technique for disinfecting some types of fish farm gear, where egg strings can be observed sticking on to the sides.

Hevroy and colleagues experimented with artificial light but found that infestation in groups under artificial light was higher than those under natural light. In the same study, greater lice burdens were seen in groups held at a depth of 0–4m when compared to those at 4–8m and 8–12m. In a more recent studies, keeping fish in closed cages at a depth of 25m appeared to be protective, unless fish were moved between cages with boats or closed cages were stocked with fish from open cages. A recent study describes the use of ‘snorkel’ sea lice barrier technology that restricts salmon from accessing the surface except via a vertical chamber which cannot be penetrated by sea lice larvae. This prevents fish from swimming at depths where free-living stages of sea lice are more prevalent.

Biological control

Two types of successful biological control measures have been documented; polyculture and fallowing. Cleaner fish such as wrasses have been shown to feed on sea lice and consequently reduce the lice burden on salmon when raised in polyculture. Mussels may add to this effect by removing larval forms. A 17-week fallowing period between cycles has been shown to significantly reduce infestation in the first year of grow-out.

Nutritional control

Four nutritional groups have been shown to stimulate disease resistance and consequently reduce lice infestations by up to 25% in Atlantic salmon. These are unmethylated DNA that contains cystosine-phosphate-guanine-oglideoxynucelotides, yeast fermentation extract, ‘AllBrew’/‘NuPro’ and Macrogard®/Optimun®. All four groups have been shown to reduce rates of infestation.

Breeding for resistance

Selective breeding against other diseases is now being successfully applied in aquaculture and has the potential to provide cheap and effective alternatives to the chemical treatment of sea lice. It was found a moderate heritability of .3 when lice per fish were counted and families ranked in a window of 7 to 17 days post infection. Using an epidemiological model of sea lice infestation and control, they stimulated 10 generations of selective breeding and analysed the frequency of treatments needed. These results suggest that “substantially fewer” chemical treatments are needed to control outbreaks in each selected population with the possibility of treatment becoming completely unnecessary in 10 generations.

Vaccines

There are currently no vaccines available for the treatment of sea lice, however there is ongoing research in the area.

Conclusions

Sea lice are a major challenge for the salmon industry, both in Chile and around the world. As the number of fish farms increases in response to market demand, so too does the potential for the spread of density dependent pathogens like sea lice. Expanded salmon farming has altered conditions in favour of the parasite.
The area the farm is located, fish species, time since the last treatment, stocking density, fish weight, water salinity and water temperature have all been identified at risk factors in the southern hemisphere. Additional risk factors from the northern hemisphere include cage volume, level of treatment, current speed, loch flushing time, depth of cages and sea lice levels in proceeding months.
In the past, treatment of farmed fish with antiparasitic preparations has been the most predictable and effective means of controlling lice, leading to widespread use of all the available compounds. As a result, resistance to the common treatments has been reported in every major salmon producing region, suggesting that exclusive chemical control of lice is unlikely to be effective in the future.
Numerous non-chemical means of sea lice control have been investigated (and in some cases implemented) with varying success including fallowing, the use of cleaner fish, breeding for resistance and nutritional supplementation. There are no vaccinations currently available although this is an area currently being explored in research. Future work should focus on identifying interventions that complement and minimize chemical treatment. Further work on risk should concentrate on factors that can be addressed through intervention, rather than those that are realistically difficult to control in field settings e. g water temperature.

 

What factors (risk and protective) regulate the time of the infection, the clinical presentation and the magnitude of a Caligus outbreak? If these exist, how do they act or interact?

Studies evaluating the caligus abundance in farming centers showed that the environmental variabilities related to salinity, temperature and water transparency were associated with abundancy. In addition, the farm density, season, exposure level and water depth in the farming center were also variables that influenced the abundancy of the parasite. No significant differences were found in the abundance between farmed trout and Atlantic salmon. It is important to underline that this study analyzed information from the productive years 2006 and 2007 for 18 farming centers; therefore the results must be interpreted with caution due to the study’s degree of representativeness and contemporaneity of the current industry.

What are the key stages of the C. rogercresseyi life cycle in the infestation process?

The female C. rogercresseyi is an essential stage for the development and maintenance of the parasite populations during an infestation. The genes associated with the sexual determination and differentiation for C. rogercresseyi have recently been defined, which could possibly allow for the development of new methods for the detection and control of mature females rather than other C. rogercresseyi stages or genders. Transcriptomic analyses allowed for the evaluation of the difference in genetic expression during the C. rogercresseyi cycle, which showed that there is a predominance of genes associated with structural and neuronal development during the initial stages, whereas during adult stages there is an increase in genes related with gonadal development, morphogenesis associated with reproduction and molecules linked to the immune response. Similarly, the presence of genes associated with serpin and cathepsin expression during the entire parasitic cycle was confirmed, especially for serpin-10. Serpin-10 is over-expressed during the copepod stage, which allows for its functional association as an immune evasion method during the first stages of infestation. Cathepsin L is expressed during the whole life cycle and is associated with structural development and immune response. An analysis of the genes involved in digestion showed that there was a low presence of genes associated with lipid digestion during the copepod stage, which then increased at the chalimus stage when feeding through the skin and mucus started, and finally a change in the metabolism during sexual maturation.

What are the genetic differences at population level that increase a C. rogercresseyi infestation’s success? What is the population structure like?

Genetic analyses of C. rogercresseyi of different origins showed that there are two predominant haplotypes at a national level, possibly due to the selection pressure following the extensive use of antiparasitic treatments.

What are the salmonid’s immune mechanisms for diminishing the adverse effects of C. rogercresseyi?

A C. rogercresseyi infection is energetically demanding and in severe cases it entails an intense stress response, metabolic alteration and an increase in mucus production. The physiological response of the host to a parasitic infection in Atlantic and Coho salmon showed that the latter responds with nutrient mobilization in a more effective form, and therefore has a more efficient immune response to the infection. In addition, Coho salmon generates a Th2 immune response, contrary to Atlantic salmon which generates a Th1 response.

What is the mechanism involved in the immune response against multiple pathogens? What role do stress and the threshold for immunity play?

A study of the effect of a P. salmonis and C. rogercresseyi co-infection showed that there are significant differences in mortality for P. salmonis infections and for P. salmonis and C. rogercresseyi double infections, demonstrating the importance of the Caligidosis in the SRS dynamic. In addition, it was shown that the resistance mechanisms for P. salmonis infections and for co-infections with both pathogens were genetically different. Another study demonstrated that an increase in ovigerous females could be indirectly related to stress generated by diseases caused by P. salmonis or Neoparamoeba perurans.

What is the most effective antibiotic currently available? What is its sensitivity like?

Regarding antiparasitic treatments against C. rogercresseyi, recent studies have shown that azamethiphos is the most effective treatment and that there is a high resistance and low effectiveness for deltamethrin and emamectin, in addition to a slight resistance to azamethiphos in certain zones. Cypermethrin also proved to be an effective antiparasitic treatment; however more comparative studies are necessary to determine its effectiveness at a general level. Moreover, it was possible to determine a variation in the susceptibility to treatments in different macro-zones, and to establish a higher resistance to antiparasitic treatments in female C. rogercresseyi rather than in males, in addition to demonstrating a difference in efficacy between adult, chalimus, larvae and egg specimens. An analysis of C. rogercresseyi’s susceptibility to antiparasitic treatments before and after its intensive use demonstrated that resistance to deltamethrin has considerably increased over the years. However, a larger scale study of the effects of baths containing cypermethrin and deltamethrin showed that both treatments are effective, having slight differences in effectiveness according to C. rogercresseyi’s gender and cycle stage.

How should alternative treatments (prebiotics, additives, immunostimulants, etc.) be developed and used? How can their optimal functioning be assured?

The addition of immunostimulant and anti-coupling diets diminish the C. rogercresseyi parasitic load as opposed to commercial diets, and increase gene expression associated with the major histocompatibility complex.

What are the areas of the genome (the genetic markers) for the pathogens that codify resistance mechanisms against drugs?

Various genes related to the nervous system and to ABC-family transport proteins were evaluated as possible effectors for resistance to antiparasitic treatments in C. rogercresseyi, , in addition to GluCl ion channels, which are related to resistance to antiparasitic macrolides such as emamectin Genes linked to esterases, cuticle proteins, the cytoskeleton and to metalloproteinases increased their expression during the treatment of C. rogercresseyi specimens with deltamethrin and azamethiphos, which was related to an increased metabolism and resistance to these drugs.

PROPOSED RESEARCH LINES

Research lines proposed to address the Basic Research Questions of the PGSA

Epidemiological studies for Caligus rogercresseyi infestations in farmed salmon

Goal

To identify risk factors and protective factors for Caligus rogercresseyi infestations at cage level and at farming center level.

Objectives

  1. To quantify the probable parasitic loads for caligus at fish level, cage level and farming center level.
  2. To identify risk and protective factors that influence the abundance of Caligus rogercresseyi at different stages (young and adult) at cage level and farming center level.
  3. To establish a risk score system at cage and farming center level based on identified factors.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

C. rogercresseyi transmission mechanisms between cages, farming centers and CMF (Cluster of Marine Facilities)

Goal

To identify the transmission mechanisms for Caligus rogercresseyi, within and between farming centers, including CMF.

Objectives

  1. To identify direct and indirect transmission mechanisms involved in the dissemination of Caligus between cages, between farming centers and CMF.
  2. To establish the existing relationship between intra and inter-farming center transmission and its impact on CMF.
  3. To design a spatial dispersion model for caligus that captures the identified dispersion mechanisms.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Epidemiological modelling for Caligus rogercresseyi for the evaluation of control strategies

Goal

To implement an epidemiological model for estimating the abundance of Caligus rogercresseyi and for evaluating control strategies

Objectives

  1. To design, program and implement an epidemiological model for Caligus rogercresseyi.
  2. To incorporate the epidemiological component based on risk and protective factors at farming center level and CMF level.
  3. To incorporate the spatial component in Caligus rogercresseyi dispersion at farming center level and ACS level.
  4. To evaluate control strategies that minimize the parasitic load at farming center level and ACS level.
  5. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Spatial characterization of zones with high and low potential for Caligus rogercresseyi abundance

Goal

To identify the influence of oceanographic characteristics on the Caligus rogercresseyi population

Objectives

  1. To identify the influence of climatic, oceanographic, bathymetric and other variables on parasitic abundance and its various stages.
  2. To characterize spatial areas with a high or low parasitic potential (high and low sanitary risk areas).
  3. To define a spatial zoning model for caligus sanitary management.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

The ecosystem’s role in the abundance of Caligus rogercresseyi

Goal

To establish the influence of the ecosystem on the abundance of Caligus, as well as the impact of Caligus on the ecosystem.

Objectives

  1. To quantify the surrounding ichthyofauna’s role in the abundance and reservoir capacity of Caligus rogercresseyi.
  2. To identify biological interaction at a phytoplanktonic level (predation, competition) and its influence on the abundance of Caligus rogercresseyi.
  3. To quantify the consequences of the superabundance of nutrients in the parasite’s population dynamics.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Establishing a research-based regulatory framework

Goal

To define a set of regulations and legal procedures derived from research results with proven impacts on public, animal and environmental health.

Objectives

  1. To integrate and coordinate the results of the WP into consolidated research-based regulations.
  2. To define a control program based on Caligidosis prevention procedures.
  3. To integrate the public Q&A feedback into technical feedback.
  4. To define a research-based Caligidosis control program.

The economy of Caligus rogercresseyi control and animal health

Goal

To define integrated strategies for Caligus control within a bio-economic framework

Objectives

  1. To quantify the costs associated with caligus prevention and control in farmed salmon (farming center and ACS).
  2. To define productive performance indicators and Caligus’ impact on these indicators.
  3. To define the best and most economically favorable control strategies for caligus.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Population structure and transmission stages for Caligus rogercresseyi in the ecosystem

Goal

To characterize the Caligus rogercresseyi population structure and the role of planktonic stages in its transmission

Objectives

  1. To identify the stages of development involved in parasitic infestation.
  2. To establish transmission mechanisms at planktonic, young and adult level as well as the infestation risk in farming centers.
  3. To characterize the genetic population structure for Caligus rogercresseyi.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Antiparasitic resistance mechanisms in the field

Goal

To identify the best sanitary strategies that minimize antiparasitic resistance.

Objectives

  1. To quantify the frequency of resistant specimens in wild and farmed fish.
  2. To establish the mechanisms related with the generation of antiparasitic resistance.
  3. To define drugs, treatment models and strategies that minimize resistance to antiparasitic treatments.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Evaluation of genetic resistance mechanisms for Caligus rogercresseyi in the field

Goal

To identify genetic resistance mechanisms for Caligus rogercresseyi in field conditions.

Objectives

  1. To identify genetic markers in Caligus rogercresseyi that play a part in antiparasitic resistance mechanisms in field conditions.
  2. To describe the genetic mechanisms in different stages of parasitic development.
  3. To correlate the genetic resistance mechanisms of Caligus rogercresseyi to antiparasitic treatments, and to describe them experimentally in field conditions.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Evaluation of the salmon’s genetic resistance mechanisms in the field

Goal

To identify genetic resistance mechanisms for farmed salmon in field conditions.

Objectives

  1. To identify genetic markers in fish that codify resistance to Caligus rogercresseyi in field conditions.
  2. To correlate genetic resistance mechanisms and describe them experimentally in field conditions.
  3. To identify the aspects of genetic selection that interfere with sanitary-productive aspects in the field.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Evaluation of the immune response for salmon and caligidosis

Goal

To evaluate the farmed salmon’s immune response to Caligus rogercresseyi parasitism

Objectives

  1. To identify the mechanisms related to the fish’s immune response against a parasitic infestation in field conditions.
  2. To identify the immune response mechanisms in conditions involving stress and coinfections.
  3. To establish criteria for smolt quality and salmon well-being and their association with the sanitary response against Caligus rogercresseyi.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

Studies on therapeutic effectiveness in the field

Goal

To determine the effectiveness of antiparasitic products in the field

Objectives

  1. To evaluate the prescribed dosage versus the administered dosage in farmed salmon.
  2. To evaluate the effectiveness of the use of antiparasitic treatments administered to farmed salmon in the field.
  3. To determine the effectiveness and costs associated with a coordinated treatment strategy for caligus control.
  4. To propose recommendations that aim towards a caligus control program taking into consideration the results of this research line.

RESEARCH