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Pathology literally means study of disease or discourse of disease
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Pathology is that branch of medicine treating of the essential nature of disease especially of the changes in body tissues and organs which cause or caused by disease (Dorland).
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Pathology is study of the molecular, biochemical, functional and morphological aspects of diseases in the fluids, cells, tissues and organs of the body. Summary: Pathology is study of the functional and morphological alterations in tissues and fluids of the body during the disease (Thomson, 1984)
Health
Disease (Dis – Negative ease)
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Any deviation from or interruption of normal structure or function of any body part, organ, or system that is manifested by a characteristic set of symptoms and signs whose aetiology, pathology, and prognosis may be known or unknown.
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Disease is any departure from healthy state.
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The following are the essential components in the study of diseases :
Aetiology
Incubation period
Pathogenesis
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Pathogenesis is development of morbid conditions or of disease or mechanism by which the causes produce diseases. e.g. In traumatic reticuloperitonitis in cattle sharp objects like nails ingested are usually trapped in the reticulum.
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Movement of reticulum and pressure from pregnant uterus in cows favours the piercing of foreign body through the wall of the reticulum, setting up reticulitis and then into peritoneal cavity causing injury causing peritonitis.
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If the foreign body is carrying pyogenic organisms purulent inflammation is found.
Clinical signs
Lesions
Pathognomonic lesion(s)
Course of the disease
Termination of disease
Diagnosis
Morphological diagnosis
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Where diagnosis is based on the alterations observed in a tissue or organ. i.e. naming the lesion e.g. Pneumonia (Inflammation of lungs), enteritis (Inflammation of intestine). This provides information to clinician on the extent, duration, distribution and type of lesion.
Aetiological diagnosis
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Where specific cause of the disease can be identified i.e. naming the cause. e.g. Cause of pneumonia-Bacteria, virus, fungus, foreign body
Specific or definitive diagnosis
Differential diagnosis
Prognosis
Sequelae
Morbidity
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Morbidity is the percentage of affected animals that get exposed
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Number of animals exposed is 100
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Number of animals affected is 50
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Morbidity 50%
Mortality rate
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Mortality rate of a disease is the percentage of deaths among animals affected by that disease.
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Number of animals exposed is 100
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Number of animals affected is 60
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Morbidity 60%
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Number of deaths among affected animals 30
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Mortality rate 50%
Autopsy
Necropsy
Biopsy
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Biopsy is examination of biological samples like fluid, tissue, etc., collected from living animals.
Scope of Pathology
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Pathology is aiding in the diagnosis of diseases.
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Helps in understanding the disease process.
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Hence, prognosis, control and rationale treatment and prevention are possible.
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