Lecture 9 Flashcards
Where does nephrocalcinosis occur
- Intensively farmed salmon
What is nephrocalcinosis associated with
- High ambient free CO2 levels and/or nutritional aspects involving magnesium deficiency or selenium toxicity
Signs of fish with nephrocalcinosis
- Abdominal swelling
- Exophalmia
- Ventral haemorrhage
What is diagnosis of nephrocalcinosis based on
- Gross lesions
- Histopathological changes showing edposits in the collecting ducts which typically stain dark blue in HandE sections and black with von Kossa stain
What is furunculosis
- Infection with the bacterium Aeromonas salmonicidia subsp. salmonicida
- Intracellular so can avoid host immune defences
When do outbreaks of furunculosis occur
- Temperatures above 10 degrees
- In young fish: 2-4 degrees
- Endogenous stressor and exogenous stressors
How does horizintal transmission occur with furunculosis
Via water column
Where have furunculosis been detected
Surface of fertilised eggs
How is vertical transmission with furunculosis prevented
Iodine
Why are fish that survive furunculosis a problem
They are carriers
What is the gross pathology of furunculosis
- Mortalities withouy any clinical signs other than darkening of skin can occur in peracute infections, particularly in juvenile salmon
- Depends on water temperature, fish age and virulence of the agent
- During the chronic stages the fish show lethargy, inappetence and darkening of the skin, which is similar to most bacterial septicaemias
- Ventral haemorrhage is common
- Liquefactive, haemorrhagic furuncles involving skin and or musc;e, progressing to crater lesions are seen in subacute or chronic pt salmon
- Furuncles not alwyas present and are not a diagnostic deature
Histopathology if furunculosis
- Dense aggregates of bacteria in organs such as heart, kidney, spleen, muscle and gills almost pathogenic
- Mural thrombi
- There is remarkably little tissue reaction around agregates of bacteria in early stages of the disease, but tissue necrosis and liquefaction may become extensive in late chronic stages
Aeromonas salmonicida atypical is a biovar for what
Acheron is a new typical strains recently described in Tasmaia causing MAS in Atlantic Salmon
What is enteric redmouth disease caused by
Yersinia ruckeri - hagerman strain
Virulent form is endemic in australia
What does enteric redmouth disease produce in salmon
Produces septicaemic conditions known as yersiniosis
What does enteric redmouth disease cause
- Hyperaemia of the oral cavity and jaw as a result f congestion of the submucosa, is not alwyas evident
Transmission of enteric redmouth disease
Horizontally and many species of asymptomatic carriers as wellas birds being reservoirs of infection
Common signs of Yersiniosis in salmon
- Development of a marked unilateral or bilateral exophtalmos often with frank patces of harmorrhagic congestion o the iris of the eye, a characteristic that gave rise to the epithet salmoinid blood disease
- Vaccination is used
- Subcutaneous haemorrhage in the mouth and throat
Waht do fish in Australa with Y.ruckeri cause
- Petechiation on the pyloric caecae
- Hypertrophy of the spleen
- Peritonitis
- GIT must be empty
- Agressive form
- Erythema around the meninges may also be seen
- Bacteria are readily detected free in the blood and in circulating and sequestered macrophages
- Ascites, exophthalmia, cutaneous petehiae and localisation of haemorrhage
What is seen with Yersiniosis at necropsy
- Gneral congestion
- Intestinal haemorrhage
- Petechiae on serosa membranes
- Swollen kidney
- Splenomegaly
What is the proper name for sea lice
Lepeophtheirus salmonis
What is the most NB ectoparasite in salmon farming
sea lice
How to treat sea lice
- Bay
- Tidal done
- Water catchment
No. development stages in sea lice
10
What in the infective free living stage of sea lice called
- Copepodid - found on ventral surface
- N when doing counts
- Adults located in scaleless areas
Gross pathology with sea lice
- Damage as lic graze on host tissue
- Skin ulcerations
- Petechiae
- Hyperpigmentation
- Resultant ulcers break the osmotic barrier and are consequently sites for secondary infection
treatment of sea lice
- Organophosphates
- Evamectin benzoate in feed
- Hydrogen peroxide
What are the Caligus spp
- Non-host specific
- Smaller and ligether than salmon
- 8 stage lifecycle
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What is whirling disease
- Myxobolus cerebralisis the causal agent of a persistent and economical important condition termed ‘whirling disease’
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CS of whirling disease
- Spiralling
- Darkening of the caudal region and severe skeletal deformities of the cranial area, jaw and opercula
- Errosion of cartilage surrounding auditory organ causes it - pressure on the caudal nerve
What are multifunctional gills
Responsible for a number of critical function in addition to respiration, including osmoregulation, excretion of nitrogenous waste, pH regulation and hormone production
Proliferative gill inflammatin
Describes recurrent gill disease outbreaks that occur in autumn in salmon farms in Norway
Proliferative gill disease
Occurs in the same season as norway
Called this due to the proliferative histological features and uncertain aetiology and with probably less infection
Complex gill disease
Used to refer to this varied syndrome of probable multifactorial aetiology and variable histopathology anf the term encompasses the syndromes referred to as PGI or PGD
