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:

Cause of Disease Etiological agent –specific cause 1.Inanimate 1.Without life (endogenous/exogenous) Animate 1. 2.

Cause of Disease Non-etiological agent –Contributing cause 1.Extrinsic (originate from outside body) Intrinsic (within body)

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

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

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

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

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

Pathological change Inflammation: (acute or chronic) Helps to minimize effect of irritant or pathogen on tissue. –Classic signs (mammals): 1.Redness (hyperemia) Pain 5.

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:

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

Disease recognition and diagnosis Clinical signs (what can be determined) –Behavioral signs

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

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

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

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

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

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.

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

Disease Management Feed management: – Water flow management: Aeration management: Waste management: Disease treatment/vaccination practices