Control of the sea louse Caligus rogercresseyi in the Chilean salmonid industry is reliant on chemical treatments. Azamethiphos was. PDF | On Jan 1, , J F Burka and others published 22 Lepeophtheirus salmonis and Caligus rogercresseyi. One of the pathogens causing the highest economic impacts on the Chilean salmon industry is the ectoparasite copepod Caligus rogercresseyi.
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A sea louse plural sea licenot to be confused with sea fleasis a member of a family of copepods small crustaceans within the order Siphonostomatoidafamily Caligidae. There are roughly species in 37 genera include around Lepeophtheirus and Caligus species. Sea lice are marine ectoparasites external parasites that feed on the mucus, epidermal tissue, and blood of host marine fish.
The genera Lepeophtheirus and Caligus parasitize marine fish, in particular those species that have been recorded on farmed salmon. Lepeophtheirus salmonis and various Caligus species are adapted to salt water and are major ectoparasites of farmed and wild Atlantic salmon. Several antiparasitic drugs have been developed for control purposes. Caligus rogercresseyi has become rogrrcresseyi major parasite of concern on salmon farms in Chile,  and studies are under way to gain a better understanding of the parasite and the host-parasite interactions.
Recent evidence is also emerging that L. The family Caligidae is estimated to contain around species in 37 genera. Most understanding of the biology of sea lice, other than the early morphological studies, is based on laboratory studies designed to understand issues associated with sea lice infecting fish caligsu salmon farms.
Information on sea lice biology and interactions with wild fish is sparse in most areas with a long-term history of open net-cage development, since understanding background levels of sea lice and transfer mechanisms have rarely been a condition of tenure caligks for farm operators. Many sea louse species are specific with regard rogercresssyi host genera, for example L. Lepeophtheirus salmonis can parasitize other salmonids to varying degrees, including brown trout sea trout: Salmo truttaArctic char Salvelinus alpinusand all califus of Pacific salmon.
In the case of Pacific salmon, cohochumand pink salmon Oncorhynchus kisutchO.
How planktonic stages of sea lice disperse and find new hosts is still not completely known. The source of L. Sea lice die and fall off anadromous fish such as salmonids when they return to fresh water. Atlantic salmon return and travel upstream in the fall to reproduce, while the smolts do not return to salt water until the next spring.
Pacific salmon return rogercrezseyi the marine nearshore starting in June, and finish as late as December, dependent upon species and run timing, whereas the smolts typically outmigrate starting in April, and ending in late August, dependent upon species and run timing. Sea lice possibly survive on fish that remain in the estuaries or they transfer to an as yet unknown alternate host to spend the winter.
Smolt get infected with rogercrezseyi lice larvae, or even possibly adults, when they enter the estuaries in the spring. How sea lice distribute between fish in the wild also is not known. Adult stages of Lepeophtheirus spp. The body consists of four regions: It acts rpgercresseyi a suction cup in holding the louse on the fish. All species have mouth parts shaped as a siphon or oral cone characteristic of the Siphonostomatoida.
The second antennae and oral appendages are modified to assist in holding the parasite on the fish. The second pair of antennae is also used by males to grasp the female during copulation.
Two egg strings of to eggs L. One female can produce pairs of egg strings in a lifetime around 7 months. Sea lice have both free-swimming planktonic and parasitic life stages, all separated by moults.
Caligus – Wikipedia
The lifecycle of L. Eggs hatch into nauplii I, which moult to a second naupliar stage; both naupliar stages are nonfeeding, depending on yolk reserves for energy, and adapted for swimming.
The copepodid stage is the infectious stage and it searches for an appropriate host, likely by chemo- and mechanosensory clues.
Currents, salinity, light, and other factors also assist copepodids in finding a host. Sea lice continue their development through three additional chalimus stages each separated by a moult.
A characteristic feature of all four chalimus stages is that they are physically attached to the host by a structure referred to as the frontal filament. Differences in the timing, method of production, and the physical structure of the frontal filament are seen between different species of sea lice. With exception of a short period during the moult, the preadult and adult stages are mobile on the fish, and in some cases, can move between host fish.
Adult females, being larger, occupy relatively flat body surfaces on the posterior ventral and dorsal midlines and may actually outcompete preadults and males at these sites. The naupliar and copepodid stages until they locate a host are nonfeeding and live on endogenous food stores.
Once attached to the host, the copepodid stage begins feeding and begins to develop into the first chalimus stage. Copepods and chalimus stages have a developed gastrointestinal tract and feed on host mucus and tissues within range of their rgoercresseyi. Preadult and adult sea lice, especially gravid females, are aggressive feeders, in some cases feeding on blood in addition to tissue and mucus.
Blood is often seen in the digestive tract, especially of adult females. Sea lice cause physical and enzymatic damage at their sites of attachment and feeding, which results in abrasion-like lesions that vary in their nature and severity depending upon a number of factors, including host species, age, and general health of the fish. Whether stressed fish are particularly prone to infestation is unclear.
Sea-lice infection causes a generalized chronic stress response in fish since feeding and attachment cause changes in the mucus consistency rogercrezseyi damage the epithelium resulting in loss of blood and fluids, electrolyte changes, and cortisol release.
This can decrease salmon immune responses and make them susceptible to other diseases and reduce growth and performance. The degree of damage is also dependent on the species of sea lice, the developmental stages that rogwrcresseyi present, and the number of sea lice on a fish.
Little evidence exists of host tissue responses in Atlantic salmon at the sites of feeding and attachment, regardless of the development stage.
In contrast, coho and pink salmon show strong tissue responses to L. This results in rejection of the parasite within the first week of infection in these species of salmonids. Some evidence indicates that sea lice flourishing on salmon farms can spread to nearby wild juvenile salmon and devastate these populations.
When exposed in river estuaries containing large numbers of open-net farms, mathematical models have suggested that many young wild salmon may be infected   Adult salmon may survive otherwise critical numbers of sea lice, but small, thin-skinned juvenile salmon migrating to sea are highly vulnerable. Sea trout populations in recent years may have seriously declined due to infestation by sea lice,  and Krkosek et al. Several scientific studies have suggested that caged, farmed salmon harbour lice to a degree that can destroy surrounding cakigus salmon populations.
Control on salmon farms. Cleaner fishincluding five species of wrasse Labridaeare used on fish farms in Norway and cakigus a lesser extent in Scotland, Shetland and Ireland.
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Good husbandry techniques include fallowing, removal of dead and sick fish, prevention of net fouling, etc. Bay management cligus are in place in most fish farming regions to keep sea lice below a level that could lead to health concerns on the farm or affect wild fish in surrounding waters.
rogercreszeyi These include separation of year classes, counting and recording of sea lice on a prescribed basis, use of parasiticides when sea lice counts increase, and monitoring for resistance to parasiticides. Early findings suggested genetic variation in the susceptibility of Atlantic salmon to Caligus elongatus. In October,The grocery chain Sobeys pulled whole Atlantic salmon from 84 store locations rogercrssseyi the Canadian Maritimes after concerns were raised over sea lice.
The range of therapeutants for farmed fish was limited, often due to regulatory processing limitations. All drugs used have been assessed for environmental impact and risks. There are both advantages and disadvantages to using bath treatments. Bath treatments are more difficult and need more manpower to administer, requiring skirts or tarpaulins to be placed around the cages to contain the drug.
Prevention of reinfection is a challenge since it is practically impossible to treat an entire bay in a short time period. Since the volume of water is imprecise, the required concentration is not guaranteed. Crowding of fish to reduce the volume of drug can also stress the fish. Recent use of well-boats containing ca,igus drugs has reduced both the concentration and environmental concerns, although transferring fish calugus the well boat and back to the cage can be stressful.
The major advantage to bath treatments is that all the fish will be treated equally, in contrast to in-feed treatments where amount of drug ingested can vary due to a number rlgercresseyi reasons. Organophosphates are acetylcholinesterase inhibitors and cause excitatory paralysis leading to death of sea lice when given as a bath treatment.
Dichlorvos was used for many years in Europe and later replaced by azamethiphosthe active ingredient in Salmosan, which is safer for operators to handle.
Resistance to organophosphates began to develop in Norway in the mid s, apparently due to acetylcholinesterases being altered due rogercressyi mutation.
Pyrethroids are direct stimulators of sodium channels in neuronal cells, inducing rapid depolarization and spastic paralysis leading to death. The effect is specific to the parasite since the drugs used are only slowly absorbed by the host and rapidly metabolized once calligus.
Cypermethrin Excis, Betamax and deltamethrin Alphamax are the two pyrethroids commonly used to control sea lice. Resistance to pyrethroids has been reported in Norway and appears to be due to a mutation leading to a structural change in the sodium channel which prevents pyrethroids rogercredseyi activating the channel.
It is environmentally friendly since H 2 O 2 dissociates to water and oxygen, but can be toxic to fish, depending on water temperature, as well as to operators. In-feed treatments are easier to administer and pose less environmental risk than bath treatments. Feed is usually rogercreeseyi with the drug and drug distribution to the parasite is dependent on the pharmacokinetics of the drug getting in sufficient quantity to the parasite.
The drugs have high selective toxicity for the parasite, are quite lipid-soluble so that there is sufficient drug to act for approximately 2 months, rkgercresseyi any unmetabolized drug is excreted so slowly that there are little to no environmental concerns.
Avermectins belong to the family of macrocyclic lactones and are the major drugs used as in-feed treatments to kill sea lice. The first avermectin used was ivermectin at doses close to the therapeutic level and was not submitted for legal approval for use on fish by its manufacturer. Emamectin benzoate, which is the active agent in the formulation SLICE,  has been used since and has a greater safety margin on fish. Withdrawal times vary with jurisdiction from 68 days in Canada  to degree days in Norway.
Avermectins act by opening glutamate-gated chloride channels in arthropod neuromuscular tissues, causing hyperpolarization and flaccid paralysis leading to death. Resistance has been noted in Chalimus rogercresseyi in Chile and L. The resistance is likely due to prolonged use of togercresseyi drug leading to up-regulation of P-glycoprotein,  similar to what has been seen in nematode resistance to macrocyclic lactones.
Teflubenzuron, the active agent in the formulation Calicide,  is a chitin synthesis inhibitor and prevents moulting. It thus prevents further development of larval stages of sea lice, calgus has no effect on adults. It has been used only sparingly in sea lice control, largely due to concerns that it may affect the moult cycle of non-target crustaceansalthough this has not been shown at the concentrations recommended. A number of studies are underway to examine various antigens, particularly from the gastrointestinal tract and reproductive endocrine pathways, as vaccine targets, but no vaccine against sea lice has been reported to date.
Two published studies have tested vaccine candidate antigens against salmon lice, which resulted in a reduced infection rate Grayson et al. Branchiuransfamily Argulidae, order Arguloida are known as fish lice and parasitize fish in freshwater. From Wikipedia, the free encyclopedia.