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Pathology Minne > Quaglio lecture 1 > Flashcards

Quaglio lecture 1 Flashcards

1
Q

Definition etiology

A

Scientific study of the cause of diseases.

These causes can be physical, chemical and biological (virus, bacteria, parasite and fungi).

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2
Q

Sequence of events in diagnostic fish pathology

A
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3
Q

Definition anamnesis

A

History or narration of the facts or situations that may have a direct or indirect relationship with the present fish pathology

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4
Q

Environmental anamnesis

A
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5
Q

What are most fish diseases mediated by?

A
  • Stress
  • A physiological state caused by environmental condition or other factor which interferes with the fish’s ability to maintain a “normal” health state
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6
Q

Environmental anamnesis

A
  • Study of environmental characteristics
  • E.g.:
    Water depth
    Flow
    Daily water exchange
    Color
    Presence of algae
    Type of culture system (intensive or extensive farmin)
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7
Q

What type of fish farming do we see here?

A

Intensive fish farming

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8
Q

What type of fish farming do we see here?

A

Semi intensive fish farming

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9
Q

Different ways of water supply in fresh water fish farming

A
  • River or surface water (rich in dissolved O2, varying seasonal temperatures, can contain pathogens transmitted by wild fish and carry (in)organic suspended material)
  • Ground water source: Spring or well (constant temperature of 15C, no dissolved O2, supersaturated with N2, CO2, methane, argon and freon)
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10
Q

Gas bubble disease (GBD) or gas supersaturation or Poppeye disease

A
  • associated with supersaturation, with nitrogen or oxygen.
  • Most gas emboli produced by excess of nitrogen
  • Occurs when total pressure of gasses dissolved in water is higher than atmospheric pressure
  • Severity of disease depends on nr of gas bubbles formed and tissues affected
  • presence of protruding eyes, exophthalmos or popeye is a sign commonly
    associated with gas bubble disease
  • Can lead to: brain damage, abnormal swimming and death
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11
Q

Why are most gas emboli produced by excess of N2 and not O2?

A

Because oxygen is assimilated metabolically and thus less likely to form persistent bubbles.

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12
Q

Acute gas bubble disease

A

Manifests as acute mortality and may occur in minutes.

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13
Q

Chronic gas bubble disease

A
  • a few mortalities
  • embolism in cutis, cornea, opercula, mouth, gastrointestinal tract and secondary infections which can lead to higher mortality rates.
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14
Q

What do we see here?

A

Hyperinflation of the swim bladder with erratic
swimming and flotation caused by gas bubble disease

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15
Q
A

Fry (juvenile) showing embolism or gas bubbles in yolk sac

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16
Q
A
  • Gill embolism
  • Presence of gas emboli in gill and other organs is pathognomonic for gas bubble disease.
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17
Q
A

Loss of an eye because of gas bubble disease

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18
Q

Fish are poikilothermic, what does that mean?

A
  • Variable body temperature that tends to fluctuate with and is similar to or slightly higher than the temperature of its environment
  • growth and metabolic rates, inflammatory and immunological responses are greatly influenced by the water temperature.
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19
Q

Vulnerable species in regards to warm water/ low oxygen levels

A

Trout and salmon

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20
Q

Better resistant species against warm water/ low oxygen levels

A

Carp and eels

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21
Q

What does a decrease in water temperature cause?

A

It suppresses the immune response

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22
Q

What does the tolerable temperature range in fish depend on?

A
  • Species
  • Age
  • Times of thermal excursion
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23
Q

Does the temperature have an effect on the defense mechanism of the fish?

A
  • Yes
  • It acts on the speed of the hosts defense mechanism and on the production of antibodies
  • Higher temperatures facilitate their behaviour
  • higher temperatures are preferred for vaccination
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24
Q

Temperature for fish can be divided into…

A
  • Optimal
  • Suboptimal (lower and upper)
  • Incipient (lower and upper) lethal temperature
  • Critical thermal (minima and maxima)
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25
Q
A

Tolerance limits and optimum temperature ranges for some commonly cultured
fish species (Nile tilapia, African catfish, common carp and rainbow trout)

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26
Q

In high temperature and low oxygen conditions…

A
  • Carp refuse food
  • Trout feed but have enteritis (inflammation of small intestine)
  • convulsive movements (spasmic), dark coloring, open opercula (bony flap covering the gill slits) are observed
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27
Q
A
  • Fish saprolegniosis (mycotic/ fungal infection) happens in winter
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28
Q
A
  • Epidermal and dermal lesions are seen in sunburn, in very clear water by effect to high levels of ultraviolet radiation
  • The most exposed areas of the skin are :
    head, back, dorsal fins.
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29
Q
A

Sunburn-induced acute epidermal necrosis,
particularly in depigmented fish

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30
Q

Nets at fish farms can protect the fish from..

A
  • UV radiation
  • Predators
31
Q

Why is it important to control birds at aquculture farms?

A
  • Epidermal lesions of mechanical origin caused by aggression from the birds
  • Act directly by causing injuries
  • Act indirectly by causing access of bacteria and parasites through these injuries
  • Birds frequently stress the fish. They stop feeding
32
Q

Turbidity

A
  • measurement of the clarity of the water
  • Suspended solids, sediment, silt and particles like dirt, mud, sand, algae, induce the turbidity
  • particles and sediments in highly turbid water will absorb sunlight causing the water to warm, this leads to decreased oxygen levels
33
Q

How is turbidity measured?

A
  • With Grey Jackson Turbidity Meter With Glass Tube & Candle, measured in Jackson Turbidity Units JTU’s
  • Less than 20 JTU’s are optimal
  • Or with Secchis disc
34
Q

Oxygen (as water quality factor)

A
  • Most important water-quality factor for fish health, but poorly soluble in water.
  • Dissolved oxygen in water comes from atmospheric oxygen and photosynthesis.
  • The dissolved oxygen in water is expressed as a concentration ppm or mg/L
35
Q

What is the major source of dissolved oxygen in ponds?

A

Photosynthesis (dependent on light availability, so:

  • O2 production decreases during cloudy days
  • Stops at night
  • Decrease in increasing water depth and with water turbidity
36
Q

What is winter kill?

A
  • completely snow covered pond can cause the death of fish
  • One winter management strategy is to use a diffuser type aerator to add oxygen
    and keep a small area free of ice.
37
Q

Oxygen demand in fish is dependent on

A
  • Cold or warm water species
  • Body weight
  • Water temperature
  • Diet.
  • Fish activity
  • Stocking density
  • Transport
  • Health (gill status)
38
Q

DO content of fish farming can be
increased in several ways

A
  • Mechanical aeration systems
  • Liquid oxygen
39
Q

Examples of mechanical aeration systems

A
40
Q

What are important strctures for oxygenation in aquaculture?

A
  • water exchange and flow through design and management
  • structures that cause water to splash for example by use of cascades along the inlet canal and raised inlet pipes before the water gets into the tanks.
41
Q

Clinical signs of anoxia

A
  • Swimming on the surface.
  • Fish are not feeding well or stop feeding.
  • Fish are coming to the water surface to breathe from the better oxygenated surface water (this is called piping).
  • Fish bite air.
  • Reduction of motor activity.
  • Lethargy.

In emergency in ponds: use potassium permanganate (3-6 ppm)

42
Q

Killed fish (through lack of oxygen)

A
  • Opercural chambers and mouth open.
  • Gastric repletion.
  • No macroscopic and microscopic pathological lesion is detectable in tissues
43
Q

H+ ions are responsible for…
OH- ions are responsible for..

A

H+ = acidity
OH- = alcalinity

44
Q

Why are they daily fluctuations of pH in the water?

A
  • Plants and animals remove oxygen and produce CO2 with acidifying effect
  • During the day plants absorb CO2 to produce energy and the water becomes more basic.
45
Q

How to measure pH?

A
  • pH chemical kit
  • PH paper test strips
46
Q

What is preferred pH for most fish species?

A

pH of 6.5-8

47
Q

Symptoms of low/high pH shock

A
  • Struggle breathing –> causes them to naturally gravitate towards top or bottom of pond
  • fish become paler –> high basicity
  • 6 > pH > 8.5 can be lethal or cause lesions to skin, gills and eyes
  • pH of the water may cause haematic acidosis or alkalosis
48
Q
A

Sublethal stress levels, increased mucus, epithelial gill hyperplasia (increased cell production) with often fatal consequences

49
Q

Changes in pH can increase toxicity of…

A
  • Ammonia: more toxic in basic pH
  • Aluminium: more toxic in acidic pH
50
Q

Effects of low pH on metal ions

A
  • They become soluble –> concentration in water increases –> become more toxic for fish
51
Q

Ammonia

A
  • product of the decomposition of proteins
  • main nitrogenous waste product of fish
    catabolism
  • Ammonia poisoning is one of the most common water quality problems in aquaculture.
52
Q

How does ammonia end up in water?

A
  • fish metabolism
  • organic fertilizers
  • Presence organic waste
53
Q

Nitrogen cycle (picture)

A
54
Q

2 forms of ammonia

A
  • NH3 –> unionized (toxic) and ionized (less toxic)
  • NH4+ –> ammonium
  • unionized ammonia concentrations in pond water should be kept bellow 0,2 mg/L
55
Q

When does the concentration of ammonia increase?

A
  • During fall and winter, possible because of a decrease in algal and bacterial metabolism at low temperature.
  • May also rise after an algae crash or massive die-off.
  • High fish densities
56
Q

Signs ammonia poisoning in fish

A
57
Q

Biosecurity

A
  • implementation of methods to prevent the transmission of infectious diseases in a culture operation.
  • also important in preventing the escape of pathogens from a farm, so that they don’t affect wild fish populations or adjacent farms
  • For hygiene, water quality, and controlling disease problems the parallel design
    (raceways) is better, as any contamination flows and pathogens through only a small part
    of the system.
58
Q

Two types of disinfection in tanks

A
  • Physical methods –> drying, sunlight, heat, uv
  • Chemical methods –> Ca(OH)2, ammonia, iodine, formalin, iodophor
59
Q

How is feeding regulated in intensive breeding facilities?

A

It is based on the administration of artificial feed distributed mechanically,
automatically or manually

60
Q
A
  • Demand feeders are controlled by the fish themselves according to their appetite.
  • These feeders are easy to install and operate.
  • The level of the feed in the container is a good indication of the health condition of
    the fish.
61
Q

Chronically ill fish are often emaciated, which means..

A
  • Loss of dorsal muscle
  • Concave abdomen
  • Enophthalmos (sunken eyes)
62
Q

Main types of abnormal swimming related to infectious diseases

A
  • Fish lethargic, on the surface, with “air gulping”.
  • Candletstick attitude with head out from the water
  • Fish with sudden jerks, flashing (can indicate surface irritation) and exposure of the abdomen.
  • Circular and spiral swimming as cork-screwing.
63
Q

Betanodavirus or nervous necrosis virus (NNV)

A
  • More than 40 species (mostly marine) susceptible
  • Clinical signs: lethargy (lack of energy), anorexia, nervous symptoms, uncoordinated and spiral swimming with loss of balance; and change in pigmentation of the skin.
64
Q

Whirling disease is caused by?

A
  • Myxobolus (Myxosoma) cerebralis
  • Is a parasite of salmonids (salmon and trout)
  • Infects the cartilage and possibly the nervous tissue, causing a potentially lethal infection in which the host develops a black tail, spinal deformities, and more deformities in the anterior part of the fish.
65
Q

Oxygen deprivation leads to…

A
  • Gulping
  • lethargy
  • Belly up motion
  • Rolling motion
66
Q

Nodular gill disease (NGD)

A

Amoebae are able to proliferate on the gill surface of teleosts and cause severe
hyperplasia and inflammatory reactions.

67
Q

Clinical exam present state (behaviour and particular signs)

A
  • Increased feed consumption followed by cessation of feed
  • Skin lesions
  • Ulcers
  • Dark color of the skin
  • Exophthalmos
68
Q

Why is sampling important?

A
  • for a simple diagnostic check
  • suspected pathology
  • for clinical or pathological observations
  • for inspection and sanitation investigation in the market
  • for serious mortality phenomena
69
Q

Characteristics of fresh dead fish

A
  • Clear eyes
  • Good coloration
  • Red or pink gills
  • No bad odor
70
Q

When do autolytic phenomena start?

A
  • 15-30 min after death of fish
  • tissues of fish with intense physical activity autolyse more quickly than those with slow activity
71
Q

Preferred order of methods of sending samples to the laboratory

A
  1. Live fish transported into triple plastic bags (1/3 water remaining oxygen) within a refrigerator or box containing some ice
  2. dead fish, quickly transported in separate plastic bags without water
  3. Organs and fish fixed in formalin are valid only for histopathological examinations.
72
Q

WHy should samples for histological examination not be frozen?

A
  • Formation of ice crystals damages the tissue
72
Q

Most widely used anaesthetics for fish?

A
  • Tricaine methanesulfonate MS-222
  • In absence: use sodium bicarbonate

Pathology Minne (6 decks)

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