Pathology

1. Pathology • Study of functional and morphological alterations that develop in an organism as a result of injurious agents, nutritional deficiencies, or inherited characteristics. • Basic Terms: • Etiology: • Etiological agent: • Pathogenesis: • Pathogenicity: • Virulence: • Lesion: • Clinical Signs: • Histology: • Histopathology:

2. Cause of Disease • Etiological agent • specific cause • Inanimate • Without life (endogenous/exogenous) • Animate

3. Cause of Disease • Non-etiological agent • Contributing cause • Extrinsic (originate from outside body) • Intrinsic (within body)

4. Pathological change • Used to aid in recognition and identification of disease • Circulatory disturbances: (lesions that reflect injury to the vascular system) • Anemia: • Hemorrhage: • Edema: • Ascites: • Exopthalmia: fluid behind or in the eye

5. Pathological change • Circulatory disturbances (cont.) • Hyperemia: • Telangiectasis: bulging of a blood vessel in the gills (similar to an aneurysm in higher vertebrates) • Embolism:

6. Pathological change • Cellular degeneration: process in which cells or tissues deteriorate • Results from: • Mechanical, thermal, electrical injury

7. Pathological change • Cellular degeneration: (types) • Cloudy swelling: • Fatty degeneration: results from accumulation of lipids • Necrosis:

8. Pathological change • Developmental and growth disturbances: • Atrophy: • Hypertrophy: Increase in size of body part or organ due to increase in size of cells • Hyperplasia: increase in size of body part or organ due to increase in number of cells

9. Pathological change • Inflammation: (acute or chronic) Helps to minimize effect of irritant or pathogen on tissue. • Classic signs (mammals): • Redness (hyperemia) • Pain

10. Pathological change • Inflammation: (cont.) • Serous: exudates of clear fluid from the vascular system (ex: blister) • Fibrinous: escape of large amounts of fibrin from blood vessels and form a clear clot when exposed to air • Purulent:

11. Pathological change • Inflammation: (cont.) • Catarrhal: excessive production of mucus on the epithelial surfaces of the skin, gills, and digestive tract • Hemorrhagic: • Granulomatous:

12. Disease recognition and diagnosis • Clinical signs (what can be determined) • Behavioral signs

13. Disease recognition and diagnosis • Clinical signs • External signs • Generally not distinctive to particular disease • Some characterized by specific lesions • Common signs include: • Deformities

14. Disease recognition and diagnosis • Gross internal lesions • Necropsy (general characteristics: important to determine if bacterial, parasitic, or viral) • Clear, straw-colored fluid in abdominal cavity • Small uniform cysts in internal organs

15. Disease recognition and diagnosis • Disease diagnosis • Examine small number of animals • Perform complete laboratory examination • External/internal exam (parasites)

16. Disease recognition and diagnosis • General procedures: • Parasitic diseases: • Perform external/internal exam before disinfectant applied • Anesthetic may affect external parasites • Internal parasites identified by observing various organs • Histopathology may be valuable to identify tissue dwelling parasites

17. Disease recognition and diagnosis • General procedures: • Viral diseases • Require special techniques • Electron microscopy • Serological and molecular procedures

18. Disease recognition and diagnosis • General procedures: • Bacterial diseases: • Isolation of pathogen on/in media • Characterize/identify biochemically, serologically, or by molecular methods • Most grow on general media (BHI, TSA, TYE, etc.) • FAT, ELISA, etc.

19. Disease Management (specific considerations) • Fish handling/stocking: • “Fish are not potatoes” • Transporting, sorting, spawning and stocking • Treating during transport • Acclimating to temperature changes • Crowding/density

20. Disease Management • Feed management: • Water flow management: • Aeration management: • Waste management: • Disease treatment/vaccination practices