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Dr.N.Ankamma, M.Sc,Ph.D Govt

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Dr.N.Ankamma, M.Sc,Ph.D Govt PATHOLOGY AND PARASITOLOGY IN AQUACULTURE AQUACULTURE Dr.N.Ankamma, M.Sc,Ph.D Govt. College for Women (A) Guntur Email. Id : [email protected] LEARNING OBJECTIVES Understand the concept of Fish diseases Understand the Categories of fish diseases Relation between Disease and environment Changes in cell structure of diseased fish Management of fish health INTRODUCTION • Aquaculture is one of the fastest growing food producing sector • Provides food security and lively hood in developing countries • Pathogens poise alarming threat to Aquaculture production • Higher densities increases opportunity for spreading diseases • Water quality management,nutrient and metabolic accumulation • Environmental factors Host Disease pathogen Environment PATHOGENS Pathogens are the causative agent. Pathogens are of two types i) Obligate pathogen Organism which will cause disease because of the mere presence in the culture system Eg. Aeromonas salmonella ii) Opportunistic pathogen Organism which will not cause disease even if it is present in the culture system. Eg. Vibrio sp in shrimps, Aeromonas hydrophila DISEASE: ANY DEVIATION FROM NORMAL PHYSIOLOGICAL BEHAVIOUR OF FISH. pathogen , is anything that can cause disease. (Gk: pathos "suffering"genes "producer of") • The term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan,& fungus • certain kinds of worms and insects can also produce disease .These animals are called as parasites rather than pathogens. • study of disease that may include these pathogens is called pathology. • Parasitology is the study of parasites and the organisms that host them. CATEGORIES OF FISH DISEASES Infectious and communicable PARASITIC FISH DISEASES Viral Bacterial Fungal Protozoan Helminths Crustacean COMMON DISEASES 1.Viral diseases: Viral hemorrhagic septicemia(VHS), https://upload.wikimedia.org/wikipedia/co infectious hematopoietic necrosis, swim bladder inflammation. mmons/a/a9/Hemorrhagic_Septicemia.jpg 2.Bacterial diseases: Fin rot and tail rot, Dropsy, Eye disease, columnaris, Edwardsiellosis and ulcer disease 3.Fungal diseases: Saprolegnaiasis,Gill rot, xenoma (Microsporidians),epizootic ulcerative syndrome. https://upload.wikimedia.org/wikipedia/commons/3/ 3e/Glugea_stephani.jpg 4.protozoan diseases: Ichthyophthiriasis , costiasis , Mixosporiadiasis etc 5.Helminth diseases: Gyrodactylosis , Dactylogyrosis , Black spot disease etc. 6. crustacean diseases: Argulosis , Lernaeasis and Ergasilosis etc. DISEASE AND ENVIRONMENT cold-blooded animals, the impact of environment in fish is more than worm-blooded animals. • change in normal condition i.e. change in chemical, physical, biological, physiological factors or parameters cause stress. • stressful environment is suitable for disease episodes • Aquaculture is the intensive, high density production of fish in a controlled environment. • Stocking rates are typically thousandfold greater than wild environment which creates stress in fish leads to manifestation of many diseases. Guiding principle in Aquaculture is the water quality . production is directly related to good water chemistry. Poor water quality of the pond environment leads to 1.Hypoxia 2.Gas bubble disease 3.PH Acidosis , alkalosis and 4.Algal toxicosis etc. METHODS TO DIAGNOSE DISEASE The diseases can be identified by following characteristics 1.Diseased fish settles in the bottom and die and dead fish floats on the water surface 2.Abnormal swimming behavior 3.Body color changes to pale 4.Production of excessive mucous from skin, gills and fins 5. Exophthalmos 6. Hemorrhage’s can be seen on the body surface and at the base of the fins 7. Change in the color, size and shape of digestive system, swim bladder, liver, kidney etc. 8. Fluid accumulation and hemorrhage’s in abdominal cavity 9. Presence of helminth parasites in the internal organs DISTURBANCE IN CELL STRUCTURE • The healthy cell is unit in which the various organelles and enzymes carry out the metabolic activities to maintain the cell viability and support its normal functions. Normal function of the cell depends on ❖ The immediate environment of the cell; ❖ A continuous supply of nutrients like glucose, amino acids; and oxygen ❖ Constant removal of the products of metabolism including CO2. • Injuries to the tissues of fish cause cell death called necrosis DEGENERATION Nonlethal injury to a cell may produce cell degeneration, which is manifested as abnormality of biochemical function, structural change, or a combined biochemical and structural abnormality. Degeneration is reversible but may progress to necrosis if injury persists. When it is associated with abnormal cell function, cell degeneration may also cause clinical disease. NECROSIS It is a premature cell death Always pathological It occurs due to bacterial and fungal toxins Causes severe inflammation in surrounding tissue Necrosis is followed by structural and biochemical changes which are irreversible. INFILTRATION • The diffusion or accumulation of foreign substances in to cells and tissues in excess to normal range is called infiltration • The substances collected in excess are called infiltrates. • Atrophy : Atrophy is the partial or complete wasting away of a part of the body. • Hypertrophy ( "excess" "nourishment") is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number. • Neoplasms or tumours are tissue growths of abnormal cells that proliferate uncontrollably • Several kinds of tumours occurs in fish without any indication of disease causing agent STRATIGIES FOR MANAGEMENT OF HEALTH: 1.Minimizing the stress in culture fish 2.selection of disease-free fish seed 3.maintaing good water quality parameters 4. proper density and rational culture 5.proper handling. SUMMARY • Infectious diseases take the lion share causing huge loss in Aquaculture. • Planning of prevention and control strategy should be based on globally accepted and locally applicable principles • There is a need to strengthening disease control measures by ensuring • optimal biosecurity measures • good husbandry practices & • effective vaccination to protect fish infectious diseases..
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