Fish Health and Diseases Flashcards
Why do farmed fish get sick?
Increased stocking densities
infected carriers
infected facilities
poor nutrition
substandard water quality
Immune response in fish compared to mammals
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
Fish innate immunity
- humeral response (extracellular pathogens and toxins)
- Acquired immunity, immunologic memory and protection (survival)
- Cell-mediated immune response (Intracellular pathogens and viruses)
All fish pathogens contain______
Antigens
Fish are________________
the most primative vertebrates
What are the 2 lines of defence?
1st (external) - skin, scales, mucous membranes and secretions
2nd (internal) - chemical signals, antimicrobial proteins, phagocytic cells and inflammatory response
What role does mucus play in defending fish from pathogens?
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
What is the role of lymph in fish?
4x volume of blood
movement of immune cells, chems and enzymes around body
No secondary lymph nodes
What is the role of the kidney?
– 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)
What is the role of the spleen
– 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
What is the role of the liver
– involved in production of complement cascade components, not really clear
What is the role of the Thymus
– production of T cells
– not always seen across the different fish species
what are the Nonspecific humoral factors
- soluble substances secreted in mucous, lymph and blood
- protective function by inhibiting growth of microorganisms
How does the complement system work in fish?
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
How do lysozymes work in fish?
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?
How do cytokines work?
- 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
How do transferrins work?
Growth inhibitor
– binds iron
– iron is essential for bacterial survival
– pathogenic bacteria may produce chelating agents to overcome this defence
How do lectins work?
- proteins able to bind certain sugars
- activates the lectin pathway of complement
- increased opsonisation and phagocytosis
What are C reactive proteins
- 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
What are natural antibodies?
- 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
What are non-specific immune cells
– 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
What is inflammation and what causes it
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
What are the 3 specific immune responses
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)
What are lymphs in fish?
T and B cells
