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AVBS3005 > Fish Health and Diseases > Flashcards

Fish Health and Diseases Flashcards

1
Q

Why do farmed fish get sick?

A

Increased stocking densities
infected carriers
infected facilities
poor nutrition
substandard water quality

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2
Q

Immune response in fish compared to mammals

A

Highly specific response
Reponse to the foreign agent similar to mammals
immune system “scans” body to identify any foreign substance
differentiates between “self” and “non-self”
works with several types of WBC –> located throughout body –> work together in highly intergrated way

All together pretty similar

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3
Q

Fish innate immunity

A
  1. humeral response (extracellular pathogens and toxins)
  2. Acquired immunity, immunologic memory and protection (survival)
  3. Cell-mediated immune response (Intracellular pathogens and viruses)
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4
Q

All fish pathogens contain______

A

Antigens

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5
Q

Fish are________________

A

the most primative vertebrates

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6
Q

What are the 2 lines of defence?

A

1st (external) - skin, scales, mucous membranes and secretions
2nd (internal) - chemical signals, antimicrobial proteins, phagocytic cells and inflammatory response

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7
Q

What role does mucus play in defending fish from pathogens?

A

Skin, gills and gut covered in mucus
trap microorganisms continuously (stops opportunistic paths)

Mucus a glycoprotein layer containing (antibodies, lysomoes (kil bacteria) and mediates inflam response)

mucus secreting cells in epidermis

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8
Q

What is the role of lymph in fish?

A

4x volume of blood
movement of immune cells, chems and enzymes around body
No secondary lymph nodes

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9
Q

What is the role of the kidney?

A

– most important for immunity and hematopoiesis
– early immune response handled by entire kidney
– head kidney (anterior) is important for making white and red
blood cells
– head kidney also serves as a secondary lymphoid organ
– blood flows through the kidney and antigens are trapped or
exposed to macrophages and endothelial cells and can capture
~70% of blood borne bacteria
– head kidney is a major producer of antibody (memory)

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10
Q

What is the role of the spleen

A

– secondary to kidney
– made of red and white pulp
– red pulp contains macrophages and lymphocytes
– white pulp is important in plasma filtration and capturing blood borne substances

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11
Q

What is the role of the liver

A

– involved in production of complement cascade components, not really clear

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12
Q

What is the role of the Thymus

A

– production of T cells
– not always seen across the different fish species

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13
Q

what are the Nonspecific humoral factors

A
  • soluble substances secreted in mucous, lymph and blood
  • protective function by inhibiting growth of microorganisms
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14
Q

How does the complement system work in fish?

A

A lytic compound
* a cascade of >20 serum proteins and glycoproteins that act as enzymes
* activated by antibodies or bacterial antigens
– lysis of pathogen cell walls
* can work at low temperatures 0-40C in fish
– leads to direct killing or opsonisation and
phagocytosis
– works on Gram negative bacteria
* key participant in the inflammatory process

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15
Q

How do lysozymes work in fish?

A

Lytic compound

  • More active in fish than that of higher vertebrates
  • Targets bacterial cell wall peptidoglycans resulting in lysis
    – Works best against Gram +ve bacteria
    – Also works against Gram –ve bacteria in fish
  • Can activate the complement pathway and phagocytosis

Why does it work so well on Gram +ve bacteria?

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16
Q

How do cytokines work?

A
  • Interferon – antimicrobial protein in serum
    – anti viral activity
    – inhibits viral replication
    – not virus specific
  • Tumour necrosis factor
    – stimulated by bacterial lipopolysaccharide
    – results in an increase of phagocytosis
    – antibacterial
  • Interleukins
    – activates other cytokines leading to inflammation
    – IL-6 is also antibacterial
17
Q

How do transferrins work?

A

Growth inhibitor

– binds iron
– iron is essential for bacterial survival
– pathogenic bacteria may produce chelating agents to overcome this defence

18
Q

How do lectins work?

A
  • proteins able to bind certain sugars
  • activates the lectin pathway of complement
  • increased opsonisation and phagocytosis
19
Q

What are C reactive proteins

A
  • pattern recognition proteins that are important components of the acute phase of infection/injury
  • higher levels in fish
  • binds to phosporyl choline on the surface of the bacterial cell walls
  • activates the complement pathway
20
Q

What are natural antibodies?

A
  • produced with out any apparent specific antigen stimulation
    – high production in fish
  • low specificity- binds to bacterial, parasitic and viral proteins
    – low affinity but high avidity
    – activates phagocytosis and the complement pathway
  • present in the: mucus, lymphoid tissue, plasma and other body fluids
21
Q

What are non-specific immune cells

A

– Monocytes and tissue macrophages:
* most important cells in immune response
* produce cytokines
* primary cells involved in phagocytosis and first killing of pathogens

– Neutrophils:
* primary cells in early stages of inflammation
* produce cytokines to recruit immune cells to damaged or infected
area
* phagocytic

– Natural killer cells:
* use receptor binding to target cells and lyse
* important in parasitic and viral immunity

22
Q

What is inflammation and what causes it

A

basic protective response to tissue damage regardless of cause

  • key feature is vasodilation and influx of leucocytes from blood to the site of inflammation
  • arrival of the neutrophils and macrophages cells is the start inflammation of infected tissue
  • the cells are attracted to the infection site by tissue damage and chemokines
23
Q

What are the 3 specific immune responses

A

humoral immunity (immunglobulin)

Cell mediated immunity (lymphocytes and macrophages)

Immunological memory (adaptive change in lymphoid cell pops/ secondary response if challenged again with same path)

24
Q

What are lymphs in fish?

A

T and B cells

25
Q

How are antibodies produced?

A

By B1 and B2 cells
B1 = natural antibodies of innate immune system

B2 = produce antigen specific

26
Q

What types of antibodies do fish produce?

A

IgM
IgT - active in parasitic infections in gut
IgD

27
Q

Are fish endo or ectothermic

A

ectothermic

*low temps slow aquired immune response

28
Q

Factors that affect the immune response of fish

A

– Drug treatments
– Photo period/ season
– Life transitions – larval-juvenile-adult
– stress
– fish produce cortisol which can alter the immune
system
– in fish, cortisol results in decreased leucocyte
migration, and antibody production

29
Q

Fish require ____ antigen than mammals

A

Antigen

AVBS3005 (8 decks)

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