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Pathogens (Agent factors)

Pathogens (Agent factors). OBJECTIVES. By the end of this lecture students should know: 1-Definition of pathogen or agent factor. 2-The different types of disease agents. A major goal of epidemiology is to assist in the prevention and control of disease by

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Pathogens (Agent factors)

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  1. Pathogens (Agent factors)

  2. OBJECTIVES By the end of this lecture students should know: 1-Definition of pathogen or agent factor. 2-The different types of disease agents.

  3. A major goal of epidemiology is to assist in the prevention and control of disease by discovering the cause of disease( the disease agent or pathogen).

  4. Epidemiological triad Environment HostAgent

  5. Pathogens are what we know as agent factors of disease. Definition :-Disease agent is defined as a living or non-living substance or a force the presence or lack of which may initiate the disease process.

  6. Classification of disease agents :- 1-Biological agents 2-Nutritional agents. 3-Physical agents. 4-Chemical agents 5-Social agents. 6- mechanical agents. 7-Absence or insufficiency or excess of a factor necessary for life, .(( as insulin and oestrogen

  7. 1-Biological agents :- These are living agents of disease as viruses, bacteria ,fungi, protozoa,metazoa , …….etc. The disease may be inapparent , apparent , severe or fatal.

  8. 2-Nutritional agents :- These are proteins ,carbohydrates ,fat , vitamins, minerals and water. Any excess or deficiency of intake of any one may lead to nutritional disorders. The common nutritional problems are PEM(protein energy malnutrition), anaemia ,goiter, obesity and vitamins deficiencies.

  9. 3-Physical agents :- Exposure to excessive heat ,cold, pressure ,radiation ,electricity ,sound ,light……etc.

  10. 4-Chemical agents :- 1-Endogenous chemicals :-these are chemicals produced by the body in certain conditions as urea (ureamia), serum bilirubin (jaundice), ketones(ketosis) ,uric acid(gout) ,calcium carbonate(kidney stones)…….. etc. 2-Exogenous chemicals :-These are agents from outside the human host. Examples allergens, metals, fumes, dust, gases, insecticides……..etc.These can be acquired by inhalation, ingestion or inoculation and may lead to certain Diseases.

  11. 5-Social agents :- Examples of social factors of disease as poverty, smoking, abuse of drug and alcohol, unhealthy lifestyles, social isolation, maternal deprivation……….etc.

  12. 6-Mechanical agents :- Exposure to chronic friction or other mechanical forces may result in crushing, tearing, sprains , dislocation ,fractures or even death.

  13. 7-Absence or insufficiency or excess of a factor necessary for health :- a-chemical factors :-as hormones (insulin or oestrogen) , enzymes. b-nutrients-as mentioned above. c-lack of structure e.g. thymus. d-lack of part of structure as cardiac defects.

  14. THANK YOU

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