Difference between revisions of "Sea Lice"

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{{OpenPagesTop}}
 
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{{Podcasts
 
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|link = https://bloomsbury.mediacore.tv/media/sea-lice}}
 
 
{{Taxobox
 
{{Taxobox
 
|name              = Caligidae
 
|name              = Caligidae
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|sub-kingdom        =
 
|sub-kingdom        =
 
|phylum            = Arthropoda
 
|phylum            = Arthropoda
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|super-class        = [[:Category:Crustacea|Crustacea]]
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|super-class        = Crustacea
 
|class              = Copepoda
 
|class              = Copepoda
 
|sub-class          =
 
|sub-class          =
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|sub-family        =
 
|sub-family        =
 
|genus              =
 
|genus              =
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|species            = ''Caligus'' spp. and ''Lepeotheirus'' spp.
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|species            = Caligus spp. and Lepeotheirus spp.
 
}}
 
}}
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Also Known As: '''''Caligidae infection'''''
 
  
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Caused By: ''Lepeotheirus salmonis — L. Pectoralis — L. Thompsomni — L. Europaensis — Caligus elongatus — C. orientalis — C. teres — C. rogercresseyi — C. punctatus — C. epidemicus''
 
  
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==Introduction==
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[[File:Male female sea lice.jpg|thumb|200px|right|Male and female sea lice. Wikimedia Commons]]
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[[File:Male female sea lice.jpg|thumb|200px|right|Male and female sea lice. (Wikimedia Commons)]]
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[[File:Sea lice on salmon.jpg|thumb|200px|right|Sea lice on a salmon. Wikimedia Commons]]
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[[File:Sea lice on salmon.jpg|thumb|200px|right|Sea lice on a salmon. (Wikimedia Commons)]]
 
  
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Sea lice are '''parasites of the Caligidae family of arthropods''' and are among the most '''notorious pests''' affecting cultured marine fish. They have a particularly large impact upon salmonid fish production. The parasites '''feed on body mucus, epidermal tissues and blood''' from their hosts, causing significant superficial damage and consequent impact upon circulatory volume.
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*Economic importance to the fish farming industries
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**Especially in North American and in Northern Europe
  
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The lice are brown-red in colour, have 5 pairs of legs and the female is considerably larger than the male (10mm and 6mm respectively) with a long egg sac. Three leg pairs are for swimming and the other two adapted for eating.
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*''Lepeophtheirus'' is found only in the Northern hemisphere
  
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==Lifecycle==
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*''Caligus'' is found worldwide
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Eggs are released into the aquatic environment from long egg sacs. There are '''two non-parasitic larval stages''' that include copepod, chalimus and pre-adult. Larval migration may exceed 1km and they may be carriers of bacteria and viruses as they migrate from fish to fish.
 
  
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'''Seven parasitic larval stages follow including copepod, chalimus and pre-adult'''. The larvae damage the fish’ skin by penetrating the epidermis an dermis with first their antennae followed by their cephalothoracic shield which causes separation from the basement membrane. They then secrete a substance which hardens to form their frontal filament and moult into the '''first chalimus''' stage.<ref>Bron, J. E., Sommerville, C., Jones, M., Rae, G. H (1991) '''The settlement and attachment of early stages of the salmon louse, Lepeophtheirus salmonis (Copepoda: Caligidae) on the salmon host, Salmo salar.''' ''J Zoology'', 224:201-212</ref>
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'''Recognition'''
  
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The chalimus then typically attaches to the '''dorsal or pectoral fin and anus'''. They are <4mm long and require microscopy for identification.
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*Males measure 6mm in length
  
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'''Pre-adult and adult''' stages move freely over their hosts and can also move between hosts. They attach by '''suction''' generated by their cephalothorax.
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*Females measure 1cm long
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**Have a long egg sac
  
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Dependent on temperature, the life cycle can take '''3 weeks to 4 months''' to complete. Adults then live for up to three weeks.
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*5 pairs of legs
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**3 pairs for swimming
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**2 pairs modified for eating
  
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==Distribution==
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*Brown to red in colour
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Most sea lice infections occur in '''tropical and temperate waters'''. Infection is thought to occur as the parasites rise to the shallows during the day and sink at night, thus crossing the path of the salmon migrating in the opposite direction.
 
  
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''L. salmonis'' is the exception, affecting '''Atlantic salmon in the colder waters''' of the Northern hemisphere. It also infects salmonids is Japan.
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*Similar in appearance to the horse shoe crab
  
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''C. orientalis'' is also found on rainbow trout in '''Japan'''. ''C. elongatus'' is the most common species in '''British waters''', ''C. teres'' and ''C. rogercresseyi'' in '''Chile''', ''C. epidemicus, C. punctatus'' and ''C. orientalis'' in '''Asia''' and ''L. pectoralis'' occurs in the north-east '''Atlantic Ocean, Balic Sea and White Sea'''.
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'''Life Cycle'''
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*Eggs released from long egg sacs into environment
  
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No significant problems appear to occur in the Southern hemisphere except for ''C. elongatus'' in '''Australia''' which originated from wild fish and is thought to have been introduced by ballast water translocated from northern Asia.
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*2 non-parasitic larval stages
  
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==Signalment==
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*7 parasitic larval stages (nauplius)
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''L. salmonis'' is the most host specific of the sea lice while ''C. elongates'' is cosmopolitan and has been found in over 80 species of fish.
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**Copepod, chalimus and pre-adult
  
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''L. pectoralis'' affects pleuronectids (flatfish) such as plaice and flounder.
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*Life cycle takes 3 weeks to 4 months depending on temperature
  
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Many factors including breed, location and immune status will affect susceptibility to sea lice.
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'''Epidemiology'''
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*Largely found in salt water
  
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==Clinical Signs==
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*Most wild salmonids migrate to the sea for part of their life cycle
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Infected fish have '''skin erosions, often near the head'''. These often begin as '''whitish spots''', becoming open wounds in advanced disease. Erosion may be deep enough to '''expose the underlying bones'''. Secondary infection is common, which may be '''fungal if the fish is returned to freshwater'''.<ref> Hastein, T., Bergsjo, T (1976) '''The salmon lice Lepeophtheirus salmonis as the cause of disease in farmed salmonids'''. ''Revista Italiana Piscicoltura e Ittiopatologia'', II:3-5</ref> Erosion of the eyes can lead to '''corneal ulceration''' and secondary infection causing blindness and cataract formation. The '''fins may also be damaged''' by the parasites and the body is often covered in mucus. Malaise and interference with feeding behaviour lead to '''loss of condition and anorexia.'''
 
  
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Even when not feeding, the presence of the parasites is '''stressful''' to the fish and therefore reduces condition and productivity/breeding performance.
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*Sealice numbers are low on wild salmonids (adults only)
  
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'''Mortalities''' can be significant in heavily infected fish. The principal cause is thought to be '''osmoregulatory failure due to extensive skin damage'''. Osmotic balance is also affected when '''anaemia results from a large parasite burden.'''
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*Sealice numbers are high on farmed salmonids (larvae and adults)
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**90% prevalence
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**Average of 5-10 sealice upon a single fish
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**Most sealice found on dorsal fin, head and back and underside of tail and fins
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**Adults survive for over 3 weeks
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**Migration of larval stages can be up to 1km
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**Larvae locate host by responding to changes in light and vibration
  
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==Diagnosis==
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'''Pathogenesis'''
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The '''large female caligoids''', although well camouflaged, are usually '''visible to the naked eye''' and are usually on the '''gills, fins or in the buccal or opercular cavities''' on the fish. They can then be identified microscopically.
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*Adults and larval stages are epidermal browsers
  
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==Treatment==
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*Mouth tube of toothed ridges abrades fish epidermis
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'''[[Ectoparasiticides]] (e.g. organophosphates, pyrethroids, hydrogen peroxide) ''' are available in a variety of formulations but '''not all are approved for food fish''' so care should be taken when selecting. Resistance is also an issue.
 
  
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In-feed treatments include coating the feed with drugs (e.g. avermectins) or with growth inhibitors (e.g. Teflubenzuron).
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*Heavy infections leads to:
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**Epidermal abrasion
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**Haemorrhage
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**Immunosuppression
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**Decreased productivity
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**Death
  
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==Control==
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'''Control'''
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'''[[Ectoparasiticides]]''' can also be used prophylactically.
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*Ectoparasiticides
  
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'''Biological control''' has also been investigated, in a search for feeder species such as '''wrasse''' (natural predator) which may decrease louse numbers.
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*Hidden antigen vaccine
  
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Management improvements are imperative, and an '''all-in-all-out system''' is ideal.
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*Wrasse which feed on sealice
  
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'''Selective breeding''' from resistant breeds is also advised but difficult.
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*Management improvements
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**E.g. ''All in, all out'' and 6 week fallowing
  
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'''Good animal husbandry''' including fallowing, removal of dead and sick fish, and preventing net fouling help in preventing serious outbreaks.
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*Stock selection
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**e.g. Selective breeding for resistance
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==Test Yourself with the Mites Flashcards==
  
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{{Learning
 
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|flashcards = [[Sea Lice Flashcards]]
 
 
[[Crustacea_Flashcards_-_WikiBugs|Crustacea Flashcards]]
 
[[Crustacea_Flashcards_-_WikiBugs|Crustacea Flashcards]]
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}}
 
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==References==
 
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<references/>
 
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Burka, J.F., Fast, M.D. Revie, C.W. (2011). '''''Lepeophtheirus salmonis'' and ''Caligus rogercresseyi'''''. In: '''Fish Parasites: Pathobiology and Protection''' (eds. P.T.K. Woo and K. Buchmann), ''CABI'', Wallingford, U.K. pages 350-370
 
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{{CABI source
 
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|datasheet = [http://www.cabi.org/ahpc/?compid=3&dsid=64879&loadmodule=datasheet&page=2144&site=160 Sea lice (Caligidae) infection of fish] and [http://www.cabi.org/ahpc/Default.aspx?site=160&page=2144&LoadModule=datasheet&CompID=3&dsID=106444 Caligidae]
 
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|date =11 July 2011
 
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}}
 
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<br><br>
 
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{{Patrick Woo
 
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|date=20 September 2011
 
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}}
 
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{{OpenPages}}
 
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[[Category:Fish Diseases]]
 
 
[[Category:Crustacea]]
 
[[Category:Crustacea]]
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[[Category:CABI Expert Review Completed]][[Category:CABI AHPC Pages]]
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[[Category:To_Do_-_CABI]]

Revision as of 19:32, 11 July 2011

Caligidae
Kingdom Metazoa
Phylum Arthropoda
Super-class Crustacea
Class Copepoda
Order Siphonostomatoida
Family Caligidae
Species Caligus spp. and Lepeotheirus spp.


Male and female sea lice. Wikimedia Commons
Sea lice on a salmon. Wikimedia Commons
  • Economic importance to the fish farming industries
    • Especially in North American and in Northern Europe
  • Lepeophtheirus is found only in the Northern hemisphere
  • Caligus is found worldwide

Recognition

  • Males measure 6mm in length
  • Females measure 1cm long
    • Have a long egg sac
  • 5 pairs of legs
    • 3 pairs for swimming
    • 2 pairs modified for eating
  • Brown to red in colour
  • Similar in appearance to the horse shoe crab

Life Cycle

  • Eggs released from long egg sacs into environment
  • 2 non-parasitic larval stages
  • 7 parasitic larval stages (nauplius)
    • Copepod, chalimus and pre-adult
  • Life cycle takes 3 weeks to 4 months depending on temperature

Epidemiology

  • Largely found in salt water
  • Most wild salmonids migrate to the sea for part of their life cycle
  • Sealice numbers are low on wild salmonids (adults only)
  • Sealice numbers are high on farmed salmonids (larvae and adults)
    • 90% prevalence
    • Average of 5-10 sealice upon a single fish
    • Most sealice found on dorsal fin, head and back and underside of tail and fins
    • Adults survive for over 3 weeks
    • Migration of larval stages can be up to 1km
    • Larvae locate host by responding to changes in light and vibration

Pathogenesis

  • Adults and larval stages are epidermal browsers
  • Mouth tube of toothed ridges abrades fish epidermis
  • Heavy infections leads to:
    • Epidermal abrasion
    • Haemorrhage
    • Immunosuppression
    • Decreased productivity
    • Death

Control

  • Ectoparasiticides
  • Hidden antigen vaccine
  • Wrasse which feed on sealice
  • Management improvements
    • E.g. All in, all out and 6 week fallowing
  • Stock selection
    • e.g. Selective breeding for resistance

Test Yourself with the Mites Flashcards

Crustacea Flashcards

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