FISH DISEASES

CHAPTER NINE

FISH DISEASES

Disease is any condition of an aquatic animal that impairs normal physiological functions.

Also, disease is a disordered or incorrectly functioning organ, part, structure or system of the body resulting from  the effect of genetic or developmental errors, infection, poisons, nutritional deficiency or imbalances, toxicity or unfavourable environmental factor, illness, sickness and ailment.

Fish disease outbreak increase production cost because of the investment loss in dead fish, the cost of treatment and decrease growth during convalescence.

Ability to recognize a disease condition in a fish population is essential to early detection and effective control. Some visible sign of disease are change in body colour, presence of swelling or nodules on body, erectic or sluggish swimming, emaciation, mortalities, skeletal deformities.

There are two main types of fish diseases:

1.         INFECTION DISEASES :- These are caused by pathogenic organism present in the environment or carried by other fish e.g parasitic diseases, bacterial diseases ,viral disease, fungal diseases

2.         NON-INFECTION DISEASES:- Are caused by environmental problem, nutritional deficiencies or genetic defects,

9.1   SOME OF THE MAIN CAUSES OF DISEASE IN FARMED FISH ARE:

1.         Poor feed and feeding

2.         Poor quality or contaminated feed.

3.         Exposure to extreme condition or toxic environment.

4.         Extremes in pH where the water is either too acidic or alkaline.

5.         Presence of dissolved oxygen.

6.         Over crowding or behavioral stressed for example in storage of transport,

7.         Presence of toxic gasses such as ammonia.

8.         Improper or excessive handling.

9.         Toxin in food such as fungal toxins in store feeds.

10.     Water pollution by agricultural or industrial effluents, sewage effluent heavy silt loads.

9.2               COMMON DISEASE SYMPTOMS IN FISHS

BEHAVIORAL SIGNS:

1.         Weak lazy or erratic swimming.

2.         Decreased feeding.

3.         Roughing against hard surfaces.

4.         Floating on water belly up and crowding / gathering at the inlet.

PHYSICAL SIGNS

1.         Gapping mouth

2.         Loss of scales, open sores, bloated belly,

3.         Cloudy or distended eyes

4.         Abnormally folded or eroded fins

5.         Presence of disease organism on skins, gill, fins.

SELECTED DISEASES OF FISH 

 

 

SYMPTOMS

 

PREVENTION/TREATMENT

PARASTIC

1. Tapeworm e.g corallobi thrum  fimbriatum

 

There may be no outward indication but fish may lose weight or become sterile.

 

1. Avoid maintaining or purchasing infected fry.

2. Drain dry and disinfected pond after each harvesting.

 

2. Ich or white spot disease

 

1. Small raised spot over the entire body surface and fins.

2. Heavily infected fish often congregate at the intake or outtake of pond.

 

1. Avoid contaminated water, nets and other equipment.

2. Provide good water and balance feed.

3. Formalin, table salt, copper sulphate and potassium per maganate  therapeutic agent.

3. Fish lice

1. Infected fish will flash or rub against tanks.

2. Show red spots.

1. Stocking of parasite for fish.

2. Masoten (dylox) can be used as therapeutic agents.

FUNGUS

1. Saproleyenia and achyla

 

1. Fish have general cotton-like appearance associated area or lesion.

2. Fungus assume the colour of material suspended in the water.

 

1. Maintain good water quality and nutritionally adequate feeds.

2. CuSO4 kMnO4 or formation can be used.

 BACTERIAL

1. Bacterinia (Haemorrhagic septicemia)

 

1. Shallow, irregular-margined, reddish sores on sides.

2.pop eye.

3. enlarged fluid, filled belly.

4. A reddened area around the anus.

 

1. Avoid over crowding and rough handling.

2. provide good water quality and feed well fortified with vitamin C.

3. Oxytetracycline addition to diet is there is therapeutic.

COLUMNARIS

1. Discoloured patches and scale loss.

2. Mouth and barbell erosion , tail erosion.

3. 30-70% mortality

1. Treatment of water with potassium permanganate.

2. Medication of feed with oxytetracycline.

NUTRITIONAL

1. broken back disease

2. broken head disease

3. no blood disease

 

1. Deformation of spinal cord on the head

2. Fish became anaemic and dic

 

1. fortify feed with vitamin C.

2. vitamin C and bone meal added to feed.

3. folic acid which is added to new feed after the old ones as discarded.

 

Vitamin  deficiencies

Scoliosis (curved  spine), reduce growth, Axorexia( loss or lack of appetite) and low fish weight. 

1. Weekly feed your fish a minimum of 3 different types of food.

2. 20% water changes accompanied with gravel washing.

3. feed with right diet.

Protein deficiency

Poor growth, caudal fin erosion, loss of appetite

Feed protein rich food e.g soya beans fish meal.

Fat deficiency

Poor growth

Feed with energy. Rich food

 9.3                                          DISEASE INDENTIFICATION

There are two method of indentifying a fish disease. These are:-

1.         VISUAL METHOD:- This is a method by naked eye observation. Areas that can be examined are as follow;

a)         BODY:-Put the diseased fish on a plate and examine the head, eyes, gill, cover, scale and fins for visible pathogens such as nematodes. Argulus, Glochidium and saprolegnia. It is also possible to see the pathogens of bacterial erythrodermatitis, albinoderm, stigmatosis and furunculosis with the naked eye.

b)         GILLS:- Inspect the gill, with an emphasis on the gill filaments. Observe the colour of the gill lamella, the quantity of mucus, and the congestion and putridity of filament tips after and opercular incision is performed.

c)         INTERNAL ORGANS:- Mainly check the intestines. Begin to observe abdominal hydrops and visible parasites{e.g lchthyoxenus, Nematodes, Ligulos, then observe other internal organs, extract the internal organ with a knife and scissors and separate the liver, Gall bladder, air bladder, etc finally open the intestine to search for any signs of  pathological changes.

2.         MICROSCOPIC EXAMINATION:- Without a microscope it is simply impossible to tell the difference between a water quality and a parasite problems. Normally only the skin, gills, intestines, eyes, and brain need be observed microscopically.

a)         SKIN:- Scrape a tissue and mucus from the skin, put them on a shade with a drop of distilled water and observed the combination under a microscope after pressing with a coverslip. One should always start with the low power objective. Samples from at least three different points on the skin should be inspected. Common parasites on the skin are trichodina, Ichthyophthirius, chilodonella, costia, glochidium etc.

b)         GILL:- Place some gill filaments and mucus onto a slide. The following parasites may be identified through microscopic observation Dactylogyrus, Gyrodactylus, Cryptobia, and Myxosporidia.

c)         INTESTINES:- Transfer a little mucus from the anterior intestinal wall to the slide. Nematodes, Eimeria and Myxosporidia may be seen.

d)        EYES:- Press the entire ocular bulb crystalline body on the slide. cysts of Diplosfomulus are an indicator of diplostumulumsis.

e)         BRAIN:- Open the central cavity of a fish with whirling diseases.White cysts of myxosporidia in the lymphatic fluid beside the brain should be observed. Remove the cysts and placed them on a slides, after crushing with a coverslip, the spores can be seen.

9.4                              DISEASE PREVENTIONS                                               

          

The concept that prevention is better than treatment is fundamental to the maintenance of a healthy stock of fish. Fish are hard to observe individually, making the diagnosis and treatment of diseases difficult following preventive measures will be considered:

    CULTURAL METHODS:- The cultural practice on prevention of diseases of fish is by:

     i.               AVOID OVER FEEDING:- To avoid problems with overfeeding the following precaution should be taken, feed on a schedule, feed the proper amount of feed by feeding the proper food, removal of uneaten food.

   ii.               CHANGE OF WATER METHOD:- To assist in maintaining water quality at an acceptable rate, regular monitoring of water is required.

 iii.               QUARANTINE:- This is a method of preventing of the infected fish from other fishes to avoid and outbreak of diseases.

PROPHYLAXES METHOD: - This is a therapeutic treatment that can monitor health status of an animal. The following prophylaxes method can be used in aquaculture:

1.         OXYGENATION CHEMICAL:- These chemicals are  used in emergency treatment of oxygen deplection in a pond in order to avoid loss of fish. The chemical that can be used for this purpose are potassium permanganate, triplesuperphosphate and hydrated lime.

2.         ANTIFOAMING CHEMICALS:- Antifoam is an effective way to reduce foam formation on the water surface. It is effective at every low concentration. One to two ppm concentration are normally sufficient to control foaming in most aquacultures systems. The active ingredient in antifoaming agents is polydimethyl siloxane.The advantages of antifoam chemical is their use does keep the water more clear so that the fish can be observed better.

3.         SALT WATER DEEPS: (5%sodium chloride) for suspected fishes carrying disease or infection.

9.5                                                   CURE OF FISH DISEASES

 

CHEMICAL TREATMENT

a.          POTASSIUM PER MANGANATE:- Add six to eight pounds of potassium permanganate per acre-foot.This oxidizer organic material in the water and reduces the demand for oxygen. The water will become a purple colour. If the colour disappears within one hour, repeat treatment at one-half the rate. This material can be toxic to fish so avoid overtreatment.

b.         COPPER (ii) SULPHATE:- This is used to treat a variety of external parasites of fish. It is also an effective  algicide  and piscicide, it can kill aquatic plants and fish and is approved for use as an algicide. In water with and alkalinity less that 50mg/l, copper sulphate can be toxic to fish and it should not be used unless a bioassay has been run in the water first with a limited number of the fish to be treated. Since copper sulphate is and algicide consideration must be given to dissolved oxygen in a pond to be treated if a pond already has low dissolved oxygen an alternate treatment should be used. Copper sulphate will only aggravates low dissolved oxygen problems by killing the primary source of oxygen (the algae) and by adding a large biological oxygen demand in the form of dead and decomposing algae.

c.          BIOLOGICAL METHOD: - This is methods by which animals and plants are introduced that eat or compete with water weeds represents another control method. Herbivores animals (those that eat plants) include a wide variety of insects snails crayfish, tadpoles, turtles, grass carp, ducks, geese and swans which can be stocked in pond to consume aquatic plants.

d.         MECHANICAL MEHTOD:- This involves physically removing the large clumps of filamentous algae using a rake or net.

STRUCTURE QUESTIONS

 1.           Which of the following is not a parasite in fishery? (a) fish louse (b) fish rot (c) worms (d) leeches (e)      Nematodes

2.          Which of the following is a fish disease? (a) coccidiosis (b) fowl pox (c) pullorum (d) Newcastle (e) saprolegina

3.          .Fin-rot disease in fish is caused by (a) Bacteria (b) fungus (c) parasite (d) nematode (e) virus

  4.          Which of these is not a common ailment of fish? (a) constipation (b) dropsy (c) fungus (d) influenza

5.          Which of these disease is diagnosed by small white spots on the body and fins? (a) Fish louse (b) septicemia (c) hole in the head (d) fresh water ich

6.          Fungus is diagnosed when you see which of the symptoms? (a) fluffy white growth on the body  or fins (b) small black spots on the body (c) torn, choppy  or disintegrated fins (d) eyes inflamed and protruding from their socket.

7.          Marine velvet is caused by which of the following? (a) fish lice (b) amylodinium ocellatum (c) saprolegnia (d) Aeromonas

8.          Why is your fish doing the doggie paddle upside down? (a) Swim bladder disease (b) carbondioxide poisoning (c) dropsy (e) gill parasites

9.          Which of the following is a common disease in fish behavioral sign (a) erratic swimming (b) Roughing against hard surfaces (c) decreased feeding (d) all of the above

10.         Disease in farmed fish can be caused by (a)poor feed (b) overcrowding (c) excessive handling (d) all of the above

11.        Which chemical is use to treat hole in the head? (a) gentian violet (b) malachite green (c) flagyl (d) Anthelmintic.

12.        Which of the fish disease has no cure? (a) tuberculosis (b) ich (c) dropsy (d) hole in the head

13.          The following are the major area observed by visual method of fish diseases identification except              (a) body (b) internal organ (c) gills (d) brain.

14.          The two method of indentifying fish diseases are (a) visual and skipping (b) microscopic and visual         (c) visual and manual (d) none of the above

15.          The following are the culture methods of disease prevention in fish except (a) Quarantine (b) avoid overfeeding (c) feeding regularly (d) change of water

16.     The active ingredient in antifoaming agent is (a) polysacharrides (b) polymethylsiloxane (c) sodium  chloride (d) potassium per manganate.

17.     Which of these are disease causing agents (a) virus(b) bacteria (c) parasite (d) all of the above.

18.     A diseased fish can be identified by the following symptoms except (a) bleeding (b) fast growth (c) gill damage (d) white patches in the mouth.

19.     The following are source of pathogens in fish farm except (a) contaminated culturing facilities (b) contaminated water (c) pure water (d) unprocessed organic manure.

20.     The following are bacterial diseases of fish except (a) columnaris (b) dropsy (c) fin rot (d) furuuculosis.

                                                      THEORY

1.      Mention five symptoms of parasitic diseases in fish.

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2.      State five sources of pathogens in fish farms.

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3.      State five fish diseases and one symptom each.

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4.      State two diseases of tilapia and one way of controlling each.

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5.      Name two bacteria diseases of fish.

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6.            Explain the visual method of disease identification

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7.            Explain the fish diseases prevention under the following heading :

 (a) Prophylaxes method

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 (b) Cultural method

 

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8.            Briefly explain potassium per manganate and copper sulphate as a way of curing fish disease.

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