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Also Known As – '''''Caligidae infection'''''
Caused By – ''Lepeotheirus salmonis – L. Pectoralis – L. Thompsomni – L. Europaensis - Caligus elongatus – C. orientalis – C. teres – C. rogercresseyi – C. punctatus – C. epidemicus''
==Introduction==
[[File:Male female sea lice.jpg|thumb|200px|right|Male and female sea lice. Wikimedia Commons]]
[[File:Male female sea lice.jpg|thumb|200px|right|Male and female sea lice. Wikimedia Commons]]
[[File:Sea lice on salmon.jpg|thumb|200px|right|Sea lice on a salmon. Wikimedia Commons]]
[[File:Sea lice on salmon.jpg|thumb|200px|right|Sea lice on a salmon. Wikimedia Commons]]
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 blood''' from their hosts, causing significant superficial damage and consequent impact upon circulatory volume.
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. 3 leg pairs are for swimming and the other two adapted for eating.
==Lifecycle==
Eggs are released into the environment from long egg sacs. There are then '''two non-parasitic larval stages'''. Larval migration may exceed 1km.
'''Recognition'''
'''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>
The chalimus then typically attaches to the '''dorsal or pectoral fin and anus'''. They are <4mm long and require microscopy for identification.
'''Pre-adult and adult''' stages move freely over their hosts and can also move between hosts. They attach by '''suction''' generated by their cephalothorax.
Dependent on temperature, the life cycle can take '''3 weeks to 4 months''' to complete. Adults then live for up to three weeks.
==Distribution==
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.
''L. salmonis'' is the exception, affecting '''Atlantic salmon in the colder waters''' of the Northern hemisphere.It also infects salmonids is Japan.
'''Life Cycle'''
''C. orientalis'' is also found in '''Japan''' in rainbow trout
''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'''
'''Epidemiology'''
''L. pectoralis'' occurs in the north-east '''Atlantic Ocean, Balic Sea and White Sea'''
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.
==Signalment==
''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.
''L. pectoralis'' affects pleuronectids (flatfish) such as plaice and flounder.
Many factors including breed, location and immune status will affect susceptibility to sea lice.
==Clinical Signs==
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.'''
Even when not feeding, the presence of the parasites is '''stressful''' to the fish and therefore reduces condition and productivity/breeding performance.
'''Control'''
'''Mortalities''' can be significant in heavily infected fish. The prinicipal 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.'''
==Diagnosis==
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.
==Treatment==
'''[[Ectoparasiticides]]''' 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.
==Control==
'''[[Ectoparasiticides]]''' can also be used prophylactically.
'''Biological control''' has also been investigated, in a search for feeder species such as '''wrasse''' which may decrease louse numbers.
Management improvements are also imperative, and an '''all-in-all-out system''' is ideal.
'''Selective breeding''' from resistant breeds is also advised but difficult.
{{Learning
|flashcards = [[Sea Lice Flashcards]]
[[Crustacea_Flashcards_-_WikiBugs|Crustacea Flashcards]]
[[Crustacea_Flashcards_-_WikiBugs|Crustacea Flashcards]]
}}
==References==
<references/>
Animal Health & Production Compendium, '''Sea Lice datasheet''', accessed 11/07/2011 @ http://www.cabi.org/ahpc/
Animal Health & Production Compendium, '''Caligoidae datasheet''', accessed 11/07/2011 @ http://www.cabi.org/ahpc/
[[Category:Crustacea]]
[[Category:Crustacea]]
[[Category:To_Do_-_CABI]]
[[Category:To Do - CABI review]]