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Aquaculture > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

IS VIRAL NERVOUS NECROSIS NOTIFIABLE

A

Yes

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2
Q

What is viral nervous necrosis disease caused by

A

Non-enveloped ssRNA viral nervous necrosis disease, a betanodavirus/ also known as viral encephalopathy and retinopathy

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3
Q

viral nervous necrosis disease: can you breed for resisance

A

No

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4
Q

Where can viral nervous necrosis disease be spread in

A

Marine or fresh water, tropical, moderate and cold areas also in ornamentak

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5
Q

What disease is shown

A

viral nervous necrosis disease

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6
Q

Where is viral nervous necrosis disease acute in

A

Larvae from 10 days old; devestating with up to 100% mortality

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7
Q

What are the clinical sings of viral nervous necrosis disease

A
  • Chromatophores cntact - larvae transparent
  • Cork screw or whirling swimming; hyper-inflated swim bladder
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8
Q

What is seen histologically with viral nervous necrosis disease

A
  • Pathogenic cell vacolisation and necrosis of the central nervous system with lesions occuring in retina and spinal cord
    • Histopathology and nested Polymerase Chain Reaction (PCR) to confirm
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9
Q

Explain the vertical transmission of viral nervous necrosis disease

A

Through the broodstock - virus detected in gonads, fertilised eggs and larvage

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10
Q

Explain the horizontal transmission with viral nervous necrosis disease

A

Through the water with VNN outbreaks in fish farms occuring after introduction of infected juveniles

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11
Q

How to treat viral nervous necrosis disease

A

No specific treatment

  • Ozone treat all incoming eggs and larvae and VNN-free broodstock
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12
Q

What is big belly syndrome

A
  • Intracellular, bi-polar large intracellular coco bacillus bacterium - associated with dsiella ictluri the cause of enteric septicaemia of catfish and bacillary necrsis of cat fish
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13
Q

What are infected individuals with Big Belly Syndrom like

A
  • Darker colour, lethargic, separate from schools and lose equilibrium
  • Poor feeding, emaciation, abdominal distension or ‘pot-belly; and red, swollen anus (vent)
  • Slow systemic infection, onset of mortality is gradual but consistent
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14
Q

How to diagnose BBS

A
  • Impression smears
  • Isolation of bacteria is difficult due to is intracellular nature
  • Once recovered they are knowns as asymptomatic carriers
  • Disease can reoccur is they have been exposed to stress
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15
Q

What is one of the most severe diseases in barra and groupers

A
  • Iridovirus
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16
Q

Iridovirus: who does it affect

A
  • Mainly occurs in fish of 10-50g and causes acute peaks of mortality of up to 80-90%
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17
Q

Iridovirus: how do the fish appear

A
  • Hyper-pigmented with loss of appetite, the gills exhibit pallor and are friable - may bleed when handled
  • Hyphaema is often present giving ‘red eye’ appeararance
  • Pale spleen
    *
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18
Q

Iridovirus: what are related to megalocytoviruses

A
  • Red Sea Iridovirus and Infection Spleen and Kidney Necrosis virus
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19
Q

What is shown here

A

Scale Drop Disease Virus

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20
Q

What can be seen with scale drop disease virus

A

Karyorrhexis and pyknosis

21
Q

What are the signs of scale drop and muscle necrosis

A
  • Scale loss
  • Muslce degredation
  • Death
  • Severe necrosis of muscles
  • Severe haemorrhange
  • Kidney tubules and epithelial cells sloughing
22
Q
A

Scale drop and muscle necrosis diease

23
Q

How to control benedenia spp

A
  • Health monitoring
  • Early diagnosis
24
Q

If left untreated with happens with benedenia spp

A

Skin and tail rot

High mortality rates

25
Q

Where are capsalid monogeneans found

A
  • Skina nd occasionally the eyes of marine fishes
26
Q

What aged fish does Benedenia usually affect

A
  • Younger fish - but if a population has been compromised, it can affect everyone
    *
27
Q

What do Benedenia spp also cause

A

Irritation to the eyes causing opacity and exophthalmia and gradually the caudal and pectoral fins eill become frayed and hemorrhagic when handled

28
Q
A
29
Q

Why is benedenia easy to spot of farms

A
  • Immered in freshwater for some minutesm the parasites will turn opaque
30
Q

What should be done with Benedenia spp

A
  • A specific parasite control prevention program with routine freshwater immersion, skin srapings and gill clips should be considered an integral part of the health management protocols
31
Q
A
32
Q

What does a large number of monogeneans on the skin or gills result in

A

Significant damage and mortality

33
Q

What appears on the skin with Benedenia spp

A
  • Grey patches and open wounds may appear on the skin and the eyes may be swollen and appear cloudy
34
Q

Why do sharks put sand in their gills

A

As an attempt to rub off the parasite

35
Q

What is the treatment of choice for monogenean spp

A

Praziquantal

36
Q

How can monogeneans survive treatment

A

They are protected by mucus

37
Q

How to do environmental control

A
  • Reduce sticking densities
  • Filter them out (Oviparous fluke)
38
Q

Explain potassium permanganate

A
  • Moderately effective against monogeneans and is the treatment of choice if columnaris bacteria or water molds have infected damaged tissue
  • Can be administered as a long bath
  • Fish need to be observed carefully while they are in contact with the cehmical
39
Q

What temp is S.iniae live in

A

Warm waters

40
Q

Is S.iniae zoonotic

A

Yes

41
Q

Explain the sub-acute form of S.iniae

A
  • Exophtalmia
  • Darkened colouration
  • Erratic swimming
42
Q

Explain the acute form of S.iniae

A
  • Heavy losses occuring over night
  • Mild corneal opacity in some cases
43
Q

Transmission of S.iniae

A
  • Pond aquaculture (could be from mud)
  • Faecal-oral and eating carrier fish
44
Q

How to diagnose S.iniae

A
  • G(+) = impression semars
  • Abnormal behaviour
  • Pop-eye
  • Hemorrhages
  • Rapid and severe mortalities
  • G(+) cocci found in the brain, kidney and other organs
45
Q

Treatment of S.iniae

A
  • Erythromycin
  • Oxytetracycline
  • Amoxicillin
  • Flofenicol
46
Q

How to prevent S.iniae

A
  • Autogenous vaccine
47
Q

What causes S.agalactiae

A
  • High stocking densities
  • Poor water condition
  • High temperatures
48
Q
A

Aquaculture (11 decks)

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