Chap-5 Diagnostic and treatment principle.pptx

Brief & short explanation of Dx & Rx Principle of fish

1. FISHERY AND FISH DISEASES By Dr. Megersa Akasa For 4 th Year Veterinary Science Students Ambo University Guder Mamo Mezemir Campus 1

2. Ethiopian Fish F auna Nile Tilapia Labeo hori Cat fish Barbus Nile Perch 2

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4. Diagnostic and Treatment Principles in Aquatic Medicine Aquatic medicine encompasses the diagnosis and treatment of diseases and health issues in aquatic animals, including fish, reptiles, amphibians, and invertebrates. The principles of diagnosis and treatment in aquatic medicine are similar to those in other branches of veterinary medicine, but there are specific considerations for aquatic environments. 4

5. Diagnostic Principles Clinical Examination: assess overall health of the aquatic animal . V isual inspection, physical palpation, and evaluation of behavior, appetite, respiration, and other relevant parameters. Water Quality Assessment: taking parameters such as; Temperature , pH, salinity, dissolved oxygen levels, and ammonia/nitrite/nitrate concentrations. Laboratory Testing: perform v arious diagnostic tests; Blood work, tissue sampling, microbiological cultures, and parasitological examinations. Imaging Techniques: Radiography (X-rays), ultrasonography, and endoscopy can be utilized to visualize internal structures and diagnose conditions such as fractures, tumors, or gastrointestinal issues. 5

6. Treatment Principles Water Quality Management R egular monitoring and adjustment of parameters. Medications and Treatments Antibiotics , antiparasitics, antifungals, and other therapeutic agents may be used to treat specific diseases or infections. Supportive Care Providing appropriate nutrition, addressing stressors, managing environmental conditions, and implementing measures to support the animal's immune system and overall health . Quarantine and Biosecurity : Isolation and quarantine protocols; B iosecurity measures; disinfection protocols and proper handling and disposal of infected materials, helps minimize disease transmission . Environmental Enrichment and Behavioral Management Providing suitable habitat, hiding places, and appropriate social interactions. 6

7. Principles of Disease Diagnosis Diagnosis of the aetiological agent is the most important aspect of the health management of any animal against any of the infectious diseases. Identification of causative agent of infection as well to identify subclinical infections if any. 7

8. Investigation of the Possible Disease Problems Level I - Changes in feeding or swimming behaviour followed by appropriate sampling and analysis . Level II - Traditional diagnostic techniques like histopathology , bacteriology, virology and water analysis . Level III - Advanced techniques like PCR using molecular biological methods for fast and confirmatory diagnosis of infections. 8

9. How To Inspect the Health of Your Fish Stock Regular monitoring of fish health is an effective way to identify disease causes and appropriate treatments. One major cause of serious fish kill is: T he contagiousness of fish diseases and D elaying treatment . As such, adequate care and treatment should be given to infected fish promptly. 9

10. Sick Versus Healthy Fish Sick Fish Healthy Fish Activity Swimming slowly; sluggish response Swimming actively; sharp and responsive Body colour Dull, dark or discoloured Bright and glossy Body surface White layered patches Intact Body shape Thin Normal size Feed intake Poor appetite Good appetite Organs Different fish diseases cause damage to different organs Internal organs are healthy and normal 10

11. Behavioural changes in fish Reduced or stop feeding Viral, bacterial, parasitic and environmental Lethargic swimming Viral, bacterial, parasitic, fungal and water quality Spinning, erratic swimming Viral, parasitic or toxicants. Case history would give a presumptive idea about the nature of problem that caused the infection. Look for clinical signs indicative of diseased condition. Clinical signs not giving direct indication of aetiology go for confirmatory diagnosis using various diagnostic tests. Case History and Clinical S ign in Diagnosis 11

12. Case History Questions flow in the following three pathways: Basic fact questions (e.g., genus, sex, species, age, etc), Open ended questions ( e.g. give the owner chance to answer), Specific questions (e.g. feed husbandry, water quality, previous disease, etc). 12

13. Cont … A. Fish Species : Some diseases are restricted to certain spp than others. SVC : affect cyprinids only , so when you ask a question restrict it to cyprinids and not other spp like cichlids. Carp pox: affect carp only , so don’t ask questions related to other spp. Furunculosis : affect salmonids , so be restricted in your questions to diseases of salmonids and not other spp. 13

14. Cont … Sex : Some diseases are only affecting females and others affect males. Also, incidences of some diseases are much higher in females than males ( visa versa). Age : Some diseases are only affecting the young fishes and others affecting adults, S o when you ask a question focus on those restricted to each age. E.g., W hirling disease only affects young salmonids (fingerlings) and early mortality syndrome only affect yolk sac and fry stages. Weight (Size): large fishes do need more dietary requirements than small ones , S o when diet is deficient in one of these ingredients or in amount, then a disease problem will develop. Thus , knowing the standard requirement for each stage of fish (weight) will be clue for solving such disease problem. 14

15. Cont … Source of Fish: Knowing the source of fish ( marine, brackish , freshwater , sewage, underground water, earthen pond, agricultural drainage water, etc) will help in directing the question to follow up the disease problem. Streptoccocosis is a disease arising from sewage problem so when considered you have to ask about the source of fish. Date of introduction of new fish species: will help in determining if the disease is endemic or brought up with fishes coming from another fish farm. 15

16. Cont … B. Husbandry and Management Type of aquaculture facility i. Glass aquarium ii. Earthen pond iii. Green house iv. Fiberglass tank i ii iii iv 16

17. Cont … Feed i. Type : Some disease are related to feeding the faulty type of pellets to the fish. E .g . tilapia fish is a surface feeder fish that fed floating pellets so when sinking pellets rendered to them , they will not feed and pellets will accumulate in the pond, purified leading to high organic matter and gill problems. ii. Amount: If fish feed 1 kg three times daily, but if 3 kg feed were thrown in pond will be accumulated, purified, high organic matter, gill problem develops. Also , if small amounts of food than required, after certain period fish will suffer from dietary deficiency problem . iii. Method: Manual or automatic feeders . iv. Storage: Mycotoxin problems due to high temperature and high humidity. 17

18. Cont … Water i. Source ii. Depth iii. Rate of water change iv. Analysis: (Temp., O2, pH, Salinity, Ammonia) 18

19. Cont … C. Disease Itself Course of the disease (acute, sub-acute, chronic). Morbidity , Mortality, Case fatality. Control measures (vaccination, disinfection, etc .). Previous occurrence of the disease. 19

20. Remote Examination (Visual Examination) Farm Visit 1. Inspect normal (Fish reflexes) Types of Fish Reflexes A. Inside Water i. Escape reflex: Fish are responsive to different physical stimuli ; fish escape and hide away in a hiding place while sick fish cannot hide or response to stimuli. ii. Feeding reflex: Fish normally adapted to come through the water (jumps, make bubbling in water) once they smell food. But sick fish are not responsive to such reflex and they are off food (anorexic). 20

21. Cont … B. Outside Water i. Eye reflex: the eye moves freely towards the side you turn to. When fish are sick they lose the ability to move their eyes to each of these directions. 21

22. Cont … ii. Tail reflex: the tail moves freely towards the right and left in healthy fish when hold in vertical position . Sick fish are not able to move their tail. 22

23. Cont … iii . Defense reflex: Fish erect their fins ( dorsal fin and pectoral fin ) as a mean of defense against aggressors and flap up on board . Unhealthy fish appears lethargic and unable to defend . 23

24. 2. Compare the case history with the actual finding on the farm visit . 3. Observe the abnormal behavioral changes in the fish population within water. Cont … A . Surfacing, gasping, piping, rapid opercular movement and aggregation at water inlet (Gill problem, Low dissolved oxygen). B. Darkening (generalized as in severe stress due to cannibalism or at posterior part only as incase of whirling disease (black tail)). C. Loss of buoyancy or balance: Swim bladder diseases. D. Flashing movement: external and internal parasites. E. Whirling (circling): e.g. whirling disease, streptococcosis, enteric septicemia of catfish and viral nervous necrosis. F . Resting at the bottom of pond with erected pectoral fin: water pollution. G . Rubbing body against fixed object and walls of pond: External parasitic infestation. 24

25. Cont … 4. Mortality Patterns Different fish mortality patterns and their possible causes. Mortality pattern Possible causes Extended course of mortality Internal and external parasites Mortality in the form of bell-shaped curve Bacterial, viral and fungal infections Mortality rises in ascending manner reaching a peak then remains high. Nutritional deficiency, including deficiency in quantity and quality or complete food deprivation Mortality occurs in early morning with physical changes in water Low dissolved oxygen Mortality occurs abruptly in the fish pond involving all fish Poisoning 25

26. Normally F ound External S igns in Fish and Causes Gills necrotic – Bacterial, parasitic, fungal Gills with excess mucus – Bacterial, parasitic, environmental or nutritional Gills pale – Viral, bacterial, nutritional Skin with excess mucus – Parasitic, environmental Red pigmented areas in skin – Bacterial or parasitic Dark skin pigmentation – Viral, bacterial, nutritional, eye parasite Haemorrhage, erythema – Viral, bacterial, parasitic, toxicants 26

27. Cont . .. Frayed, eroded, erythema in fins – Bacterial, Parasite, mechanical/Physiological disorder . Exophthalmia, haemorrhaged opaque eyes – Viral, Bacterial, parasitic, gas super saturation. Ulceration, necrotisation – Bacterial, parasitic . Hydropsy – Bacterial, viral, metazoan parasite. Enlarged abdomen (fluid accumulation) – Viral, bacterial, parasitic . Growth, nodules, raised spot on skin – Viral, parasitic neoplasmic , fungal. 27

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30. S ampling for Diagnostic P urposes I. Fish Sample Sample characteristics Sample should be representative. Moribund fish: at different stages of the disease (early, peak, late stage ). 30

31. Cont... Includes healthy fish: for comparison with those showing clinical signs of the disease. Freshly dead fish: (< 1 hours after death as maximum) Size of sample varies according to : Age Size Suspect disease 1. Acute toxicity (1-5 fish) 2. Infectious diseases ( small fish: 10-15 fish & large fish : 5-10 fish) 31

32. Cont... Sample should not include dead fish due to the following Fish tissues rapidly decomposed ( PM autolysis ). Once fish started decomposition protozoa and viruses leaves fish body , so you will not be able to diagnose those diseases . Signs of freshness Item Fresh Decomposed Purified Eye Slightly bulged Transparent Slightly sunken Slightly opaque Deeply sunken Complete opacity Scales Firmly attached Loosely attached Detached Vent Closed Open Open and prolapsed Colour of gills Rosy red Pale red Whitish or greyish Dorsal Muscles Firm (elastic) Soft (non elastic) Very soft (doughy) 32

33. Cont... II. Water Sample Sample characteristics Sample should be representative collected from three points ( inlet, outlet and the middle of the pond ). Sample should be taken in a separate container. Sample should be taken under complete aseptic condition using sterile glass bottle (500 ml ). Bottle should be only opened under water surface at depth not less than 0.5 meter. 33

34. Cont... Parameters to be examined in the water sample 1. pH: measured on spot using pH meter . 2. Temperature: measured on spot using the water thermometer . 3. Dissolved O2: measured on spot using oxygen meter. 4. Turbidity : measured using Sicchi disc. 5. Ammonia: measured on spot to avoid the rapid conversion to nitrite and nitrates using the nitrosomonas and nitrosobacter bacteria . 6. Salinity: measured using refractometer . 34

35. pH Meter 35

36. Water Thermometer 36

37. Oxygen Meter 37

38. Sicchi Disc 38

39. Colorimeter Benchtop Meter Portable Meter Instrument used to measure ammonia 39

40. Refractometer 40

41. Histological Techniques Histology:- Microscopic examination of thin, stained tissue sections in order to study their structure and function. Determine changes that occur in the tissues due to pathogens and disease. Histopathology can be used as diagnostic tool for identifying a variety of pathological conditions associated with many of the disease conditions. Immuno-histochemical methods are also used to detect specific pathogens in tissue sections. 41

42. Direct M icroscopical O bservation of the Pathogen in the Tissue S ample Fresh preparations are made from different fish tissues and observed microscopically. Many of the parasites are detected primarily by their movement. The preparations of skin scrapings and gill are examined under the microscope and examined for the presence of for parasites. 42

43. Direct Culture of the Infectious A gents and Identification Aseptically collected samples of tissues are used for the isolation and culture of aetiological agents such as bacteria, fungi or viruses using appropriate culture techniques. Using standard techniques to identify a pathogens: B iophysical characteristics, B iochemical tests, I mmunological or nucleic acid based diagnostic. 43

44. Immunodiagnostic Techniques Make use of the basic principle of the specificity of antigen and antibody. Simplest form – agglutination test – for particulate antigens- bacterial identification. Improved techniques like ELISA are now available. 44

45. General Cautions to be C onsidered D uring F ish D isease T reatment Always follow the dosing instructions on the bottle. Do not use more than one disease treatment at a time. Keep all medicines away from children. If in doubt seek advice from your aquatic retailer. 45

46. C hemicals U sed in Treatment of Some F ish D iseases Wide range of chemicals and drugs can be used for treating diseased fishes. If a particular chemical or drug has never been used to treat fish, it is always a good idea: T o test it first on a small number of fish before an entire pond or holding unit is treated. 46

47. Chemical Concentration and Time of Exposure Calomel ( mercury (I) chloride) 0.2% in food daily for 3 days Malachite green (oxalate) 2ppm for 30 minutes Malachite green (zinc-free) 5ppm for 30 minutes Formalin (37-40%) 25 - 250ppm as bath method for 30 -60 minutes Malachite green (14 gm ), Formalin (one gallon) mixture 25ppm for up to 6 hours daily. Carbersone 0.2% in food daily for 3 days 47

48. Chemical Concentration and Time of Exposure Potassium permanganate 3-5ppm as bath method for 15- 30 minutes 5-10 ppm for 1-2 hours Acriflavin 10ppm for 60 minutes Sodium chloride 1-2% as dip for 10-20 minutes 3-5% as bath for 1-2 minutes Copper sulfate 1-2 ppm as bath for 15 minutes Organophosphorous compounds ( masoten , diptrex , diazinon , etc ) 16 ppm as bath for 10-20 minutes 48

49. Chemical Concentration and Time of Exposure Florfenicol (FL) 55-70 mg/kg of fish in food for 10 days Oxytetracycline (OTC) 55 mg/kg of fish in food for 10 days Erythromycin phosphate or Erythromycin thiocyanate 55-70 mg/kg of fish in food for 10 days Sulphonamide e.g. Sulfamethaxzole -Trimethoprim (SXT) 256 mg/kg of fish in food for 3 days followed by 156 mg/kg of fish in food for 11 days 49

50. Formalin Aqueous solution of 37 – 40% by weight of formaldehyde gas. It kills protozoan, fungal and helminth parasites. Formalin is highly toxic to phytoplankton and oxygen depletion may occur in pond due to algal death BKC ( Benzalkonium Chloride) It is a compound of mixture of alkyl dimethyl benzyl ammonium chlorides. It has anti-bacterial and anti-fungal property. This compound is available as 50% and 20% solution commercially. Dosage for treatment of pond water is 0.5 – 1.0 ppm for 50% solution and 1.0-2.0 ppm for 20% solution. 50

51. Potassium Permanganate It is a strong oxidising agent with good antimicrobial activity. It releases nascent oxygen while desolving in water. The nascent oxygen destroys micro organisms as well as organic substances , through its oxidising action. Do not use Potassium permanganate frequently since the manganese metal and manganese dioxide may settle on the gill surface of fish/prawn and interfere with their respiration Malachite Green It is greenish crystal with metalic lusture . It is very soluble in water. The water solution appears as blue-green. It is very effective against fungal disease. 51

52. Zeolite It occurs naturally in sedimentary and volcanic rocks. Commercially it is found in the form of grayish-powder form. The cations in zeolite are mobile and capable of undergoing ion exchange. Therefore zeolite act as a cation exchanger. It can selectively absorb NH 4 + in water Acriflavine It is also known as 3,6-Diamino-10-methylacridinium chloride It is an antiseptic, protozoacide . 52

53. Oxytetracycline (OTC) It is a broad-spectrum antibiotic against gram-positive and gram- negative bacteria. It is also effective against some protozoan infections It inhibits the synthesis of bacterial proteins. Thus the growth of bacteria is controlled. It is readily absorbed from the intestinal tract and can get into bacterial cell quickly. Hence it is more effective when given orally. 53

54. Strategies For Health Management 54

55. INTRODUCTION Diseases are difficult to be completely removed from aquaculture , can be controlled and frequency of occurrence can be minimised . As the disease in aquaculture is a result of interaction between H ost, pathogen and environment , controlling all the three factors become important. Controlling the entry of obligate pathogen to the culture systems and reducing build up of opportunistic pathogens are also equally important. 55

56. Strategies for Controlling the Disease Use of closed or semi-closed recycle system with increased water reuse. Construct reservoirs for storing water without directly taking from the sea. Minimise water exchange . Treat reservoir water ( chlorine at the rate of 30 ppm calcium hypochlorite - 60% active ingredient) before use in the ponds. Prevent entry of wild shrimps, crabs and fish in to the ponds. 56

57. Cont … In case of a disease outbreak , disinfect contaminated water before discharge. Maintain good pond preparation by drying pond bottom and removing top layer of the sediment. Avoid over stocking . Maintain good water quality . Feed nutritionally balanced diet at the required quantity avoiding excess feed. 57

58. Cont … Selection of a species is one of the potential methods of disease control . Selection of healthy larvae and avoiding contamination during culture. Disease avoidance by using specific pathogen free ( SPF ) stock. Specifically, quarantining the stocks that are imported or transferred over a wide geographic area has to be practised. 58

59. Molecular Biotechnological Techniques Play an important role in controlling the disease incidences ; By improving the effectiveness of screening and detection of pathogens, Elucidation of pathogenicity , Development of effective control and preventive measures , Treatment of diseases. 59

60. Vaccination The ideal prophylactic measure that can be undertaken for: Protecting the fish from any infectious disease . A number of formulations of fish vaccination are available and many of them are also commercially marketed. Formulations of different vaccines can be given: By injection Through bathing Per Os 60

61. Prophylaxis: Fish Vaccines in Use Aeromonas salmonicida Vibrio salmonicida V. anguillarum Yersinia ruckeri Renibacterium salmoninarum Flavobacterium psychrophilum F. columnare Piscirickettsia salmonis Lactococcus garvieae Streptococcus iniae Photobacterium damselae subsp. piscicida Edwardsiella ictaluri among others... I njection B ath Per os 61

62. VACCINATION 62

63. Immunostimulants Immunostimulant is a chemical, drug, stressor or action that elevates the non-specific defence mechanisms by: I ncreasing phagocytosis, L eucocytic activity and macrophage and neutrophil migration or specific immune response. Play a significant role in the management of fish health and disease control in aquaculture farms. Reduce the immune suppressive effects of stress . 63

64. Immunostimulants Used In Aquaculture Glucans, Lipopolysaccharides , Chitin, Chitosan , Peptidoglycans , Muramyldipeptides , Polypeptides, Levamisole , Vitamin C, Vitamin E etc. 64

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66. Probiotics It is a live microbial feed supplements , which beneficially affects the host animal by improving its intestinal microbial balance. The probiotic microbes when administered through feed could pre-emptively colonise the gut and eliminate or minimize the pathogenic microbes through competitive exclusion process . Lactic acid bacteria (LAB) and bifidobacteria are the most common types of microbes used as probiotics; but also certain yeasts and bacilli are available. Lactobacillus has been effectively used as probiotic in improving the general health and growth characteristics of fishes. 66

67. Co n t … In general probiotics have a beneficial effect on the digestive processes of aquatic animals , because: Probiotic strains synthesize extracellular enzymes as well as provide growth factors such as vitamins, fatty acids , and aminoacids . 67

68. Bio- remediators Bioremediation is the use of living organisms ( Bio- remediators ), such as microbes, bacteria, microalgae, fungi and plants to remove contaminants, pollutants, and toxins from soil and water. Improve water quality by nitrification , removal of toxic substances such as ammonia, hydrogen sulphide and nitrite from the culture systems. Efficiently recycle the waste material by decomposing the complex organic substances and generating nutrients in the form of simple inorganic compounds. Gram-positive Bacillus spp . are generally more efficient in converting organic matter back to CO 2 than are gram-negative bacteria. Other bacterial species of importance towards bioremediation are: Nitrobacter , Pseudomonas, Enterobacter , Cellulomonas , and Rhodopseudomonas spp. 68