1. بسم الله الرحمن الرحيم

2. Welcome back

3. Fish Diseases
And
Management

4. Part 2
Fish Diseases

5. FISH DISEASES Ichthyology:
Is the science dealing with the study of all items related to fish.
Fish is unique creature as it live in water, so all organs must adopt living in water.
All fish are poikilothermic hosts , can live in wide range of temperature ( 8 – 37◦c ). On the other hand, human and animals are homothermic hosts their optimum temperciture is 37◦c ( ± 2 )

6. Differences between fish and mammals
Skin of fish is thick rather than human, may be covered with scales sometimes is partially scaled. Some Fish are scaleless.
Skin of fish is covered by slime which is transparent mucous layer
- Slime is rich in immunoglobulin ( IgM )
- Also have bactericidal substance.
- In addition, it contain lysozymes ( non specific immune response
* Slime is the Frist Line of defence, changed continuously (every 28 day) acc. to the immunological state of fish.

7. 3. Fish have no Legs and no fore arms
3. Fish have no Legs and no fore arms. The locomotor system of fish is fins
4. Because water contain low level of dissolved oxygen ( 5mg /L ) in comparison to air, fish must have special and efficient respiratory system to extract the low level of O2. This system is represented in Gills.
5. No bone marrow in the bone of fish. Hemopoiesis occur in other places such as Kidney & Spleen and peyer's patches in intestine ( from which B-lymphocytes originate )

8. Classification of fish diseases
Diseases are classified into 3 main categories
1- Infectious diseases
Bacterial diseases
Viral diseases
Mycotic diseases
2- Invasive diseases
Parasitic diseases
3- Environmental diseases
All diseases
related to environmental parameters such as :-

9. Oxygen level in water (increase or decease)
Water temperature
Water pH
Water hardness
Chemical pollution
Soil characteristics

10. As all parameters in water reflected on the state of water, Any error in the environmental parameters is reflected on the health state of fish.
Forms of infection
1- Peracute form :-
characterized by sudden death without showing any clinical signs of disease. Mortality is 100% - It occur in case of toxicity cas by cyanide ) or electricity or in case of per acute disease ( accompanied with all septicemic viral or bacterial diseases not mycotic )

11. This form of disease is characterized By :-
2- Acute form :-
This form of disease is characterized By :-
- High morbidity may reach 70 – 80 % and mortality reach 50-60%
- Petechial hemorrhage all over the body
- Dropsy - Pop eye (exophthalmia
- General state of depression
- Anorexia ( off food )

12. 3- Chronic form (Carrier state):-
This form is very dangerous as fish is apparently normal and show no clinical signs of disease but disseminate the infection to other fish through excretions which contain the microorganism. It is considered the real problem.

13. (2) Dead fish (3) Invader fish (4) Aquatic birds
Sources of infection of fish
(1) Infected
Fish
Fecal droplets from carrier
(2) Dead fish
(3) Invader fish
(4) Aquatic birds

14. Stress and stress related diseases
is the sum of all physiological responses by which fish can maintain its metabolism.
The collection of the 3 factors result in disease occurrence.

15. The degree of disease vary from one host to another, from fish species to another species which is called species variation. Also the degree of disease vary according to the immune status of the host ( susceptibility of fish )
Water quality also reflect on the state of fish. More than 50% of problems caused by water errors as disturbance in water temperature, oxygen level, pH of water, Hardness and pollution by chemicals or pesticides

16. Types of stressors (1) Physical stressors
Increase temperature than 35◦c →↑stress on fish. Also ↓ temperature than 10◦c →↑ stress and death.
Alteration in the normal O2 level (5-7 mg/L)
↑ O2 level → Gas bubble disease
↓ O2 level → Stress
Transportation of fish inside or outside the farm
Netting during which the water depth decrease then increase again this result in stress on fish which take 14 days to adapt again.
Disturbance in water pH and hardness.

17. Agricultural wastes in water.
2- Chemical stressors
Industrial waste products and heavy metals, It has public health importance be cause heavy metals have cumulative effect.
Agricultural wastes in water.
3- Biological stressors
Represented in all types of causative agents of disease. Its persistence act as continuous stressor.

18. Response of fish Under any type of these stressors, How fish respond?
(1) Alarm stage (Neuroendocrine stage)
Presence of stress stimulate the brain → ACTH increases in the blood stream → inter-renal cells → Secretion of corticosteroids (cortisol)
(2) Adaptive stage
At frist, when the m.o enter the body → lysozymes which are non specific immune response attack the
Then the phagocytic cells attack and try to recognize the antigen.

19. the body then secrete Mast cells and T
the body then secrete Mast cells and T. helper cells which recognize the microbe ( molecular weight ) to secrete the specific antibodies ( after 7 – 10 days ) → Ag. Ab reaction → precipitation
This stage characterized by:
- Hypoproteinemia (↓ immunoglobulins )
- Hypochloremia ( defect in osmosis ) Leucopenia → lowering efficiency of immune system

20. - Hyperlactemia (↑ lactic acid ) → exhaustion of muscles - Hyperglycemia due to ↑ gluconeogensis
- The blood clotting time increased.
(3) Exhaustive stage
This stage characterized by:
- Low growth rate → retarded growth
- Low reproduction ( stop of spawning ) - Off food → ↓ metabolism.
- Increase the liability of fish to infection.