CONCEPTS OF DISEASE CAUSATION

1. CONCEPTS OF DISEASE CAUSATION DR MIRZA INAMUL HAQ AP COMMUNITY MEDICINE

2. LEARNING OBJECTIVES The student should learn disease process What are the theories of causation of disease? How is it transmitted? How it spreads? How it is distributed? And why? How it can be prevented and its importance in public health ?

3. WHAT EXACTLY IS A DISEASE IS STILL A ? IS IT A SEQUENCE OF PATHOLOGICAL CHANGES AND THEIR EFFECTS OCCURRING IN THE INDIVIDUAL? IS IT A COMPOSITE OF EFFECTS DUE TO DISTURBANCE IN MAN�S RELATIONSHIP WITH HIS ENVIRONMENT BY AN AGENT/FACTOR?

4. WHAT IS A DISEASE? DISEASE CAN BE SIMPLY EXPLAINED AS DIS AT EASE OR ILL HEALTH SOME DESCRIBE IT AS DISTURBANCE IN EQUILIBRIUM BETWEEN MAN AND HIS TOTAL ENVIRONMENT.

5. HOW THE DISEASE IS CAUSED? SUPERNATURAL THEORY OF DISEASE ECOLOGICAL THEORY GERM THEORY MULTIFACTORIAL CAUSATION THEORY

6. NO UNANIMOUS OPINION AT LEAST 10% OF THE PEOPLE IN DEVELOPED COUNTRIES AND 30% IN DEVELOPING COUNTRIES STILL BELIEVE IN SUPERNATURAL ORIGIN EVEN TODAY SUPERSTITIONS ARE BECOMING MAJOR OBSTACLES IN DISEASE CONTROL MOST OF THE LITERATES VIEW THAT DISEASE IS THE RESULT OF MICROBES MOST OF THE UNEDUCATED PEOPLE (90%) BELIEVE THAT DISEASE IS DUE TO BAD PHYSICAL ENVIRONMENT VERY FEW PEOPLE KNOW AND ACCEPT THAT IT IS DUE TO THEIR OWN NEGATIVE LIFE STYLES (FAULTS) SCIENTIFIC PEOPLE BELIEVE IN ALL , INCLUDING SUPERNATURAL ORIGIN AS THEY CANNOT EXCLUDE IT AS A CAUSE OF THE DISEASE. ARE THE CONCEPTS OF ORIGIN OF THE DISEASE REALLY CHANGING OR MIXING ? VERY FEW PEOPLE KNOW AND ACCEPT THAT IT IS DUE TO THEIR OWN NEGATIVE LIFE STYLES (FAULTS) SCIENTIFIC PEOPLE BELIEVE IN ALL , INCLUDING SUPERNATURAL ORIGIN AS THEY CANNOT EXCLUDE IT AS A CAUSE OF THE DISEASE. ARE THE CONCEPTS OF ORIGIN OF THE DISEASE REALLY CHANGING OR MIXING ?

7. SUPERNATURAL THEORY OF DISEASE: IN THE EARLY PAST, THE DISEASE WAS THOUGHT MAINLY DUE TO EITHER THE CURSE OF GOD OR DUE TO THE EVIL FORCE OF THE DEMONS. ACCORDINGLY, PEOPLE USED TO PLEASE THE GODS BY PRAYERS AND OFFERINGS OR USED TO RESORT TO WITCHCRAFT TO TAME THE DEVILS.

8. ECOLOGICAL THEORY AROUND 463 BC, HIPPOCRATES IS THE FIRST EPIDEMIOLOGIST WHO ADVISED TO SEARCH THE ENVIRONMENT FOR THE CAUSE OF THE DISEASE.

9. ENVIRONMENTAL INFLUENCE INTERACTIONS AMONG HUMANS, OTHER LIVING CREATURES, PLANTS, ANIMALS, MICRO ORGANISMS, ECOSYSTEMS, AND CLIMATE, GEOGRAPHY, AND TOPOGRAPHY ARE SO COMPLEX THAT DESPITE MUCH STUDY WE ARE OFTEN UNCERTAIN WHAT IS REALLY HAPPENING.

10. ECOLOGICAL DETERMINANTS OF DISEASE  MCKEOWN HAS POINTED OUT, IMPROVED HEALTH OWES LESS TO ADVANCES IN MEDICAL SCIENCE THAN TO THE OPERATION OF NATURAL ECOLOGICAL LAWS

11. PLANETS AND DISEASE IT IS WELL KNOWN THAT PLANETS (EARTH,SUN, MOON ) AND THEIR MOVEMENTS, THEIR INTER DISTANCES AND RELATIONSHIPS WILL CAUSE SEASONS OF THE YEAR PLANETS� INFLUENCE ON ORIGIN OF SEASONAL DISEASES AND THEIR CONTROL IS STILL A PANDORA BOX

12. GERM THEORY Germ theory: Microbes (germs) were found to be the cause for many known diseases. Pasteur, Henle, Koch were the strong proponents of microbial theory after they discovered the micro-organisms in the patients� secretions or excretions.

13. HENLE-KOCH POSTULATES Henle and Koch have postulated that Each disease will be caused by a germ Without that germ that disease will not be caused By introducing that germ , that disease can be caused in animals experimentally, And that germ can again be isolated from that sick animal experimented with.

14. MULTIFACTORIAL CAUSATION THEORY PETTENKOFFER STATED THAT AGENT, HOST AND ENVIRONMENTAL FACTORS WILL ACT AND INTERACT SYNERGISTICALLY AND ACT AS JOINT INDEPENDENT PARTNERS IN CAUSING THE DISEASE.

15. WHEN THE DISEASE OCCURS? FOR A PLANT TO GROW, SEED MUST BE PLANTED IN A FERTILE SOIL AND SHOULD BE NOURISHED WITH WATER. SIMILARLY, THE DISEASE OCCURS ONLY WHEN THE AGENT (SEED) FINDS A SUSCEPTIBLE HOST (FERTILE SOIL) AND FAVORABLE ENVIRONMENT (SHOWER) FOR INTERACTION. FOR A PLANT TO GROW, SEED MUST BE PLANTED IN A FERTILE SOIL AND SHOULD BE NOURISHED WITH WATER. SIMILARLY, THE DISEASE OCCURS ONLY WHEN THE AGENT (SEED) FINDS A SUSCEPTIBLE HOST (FERTILE SOIL) AND FAVORABLE ENVIRONMENT (SHOWER) FOR INTERACTION.

16. CAUSAL CONSTELLATIONS Actually, several causes form into groups or constellations to cause the disease. A necessary or principal cause will be helped and complemented by other causes (predisposing, enabling, precipitating, reinforcing causes) making it sufficient to initiate the disease. Unless a necessary cause has enough support by other causes by means of their complementing and synergistic action, that cause can never become sufficient enough for disease initiation. These causal partners will not loose their identity and individuality while complementing necessary cause but just help the necessary cause. While doing so, these causal partners form a web of cumulative and synergistic action with the necessary cause to initiate the disease. That means when a necessary cause is fully complemented with its causal partners, it becomes sufficient enough to cause the disease. Presence of a sufficient cause means that disease is initiated. This explanation is true serves for both the infectious and non-infectious disease. Actually, several causes form into groups or constellations to cause the disease. A necessary or principal cause will be helped and complemented by other causes (predisposing, enabling, precipitating, reinforcing causes) making it sufficient to initiate the disease. Unless a necessary cause has enough support by other causes by means of their complementing and synergistic action, that cause can never become sufficient enough for disease initiation. These causal partners will not loose their identity and individuality while complementing necessary cause but just help the necessary cause. While doing so, these causal partners form a web of cumulative and synergistic action with the necessary cause to initiate the disease. That means when a necessary cause is fully complemented with its causal partners, it becomes sufficient enough to cause the disease. Presence of a sufficient cause means that disease is initiated. This explanation is true serves for both the infectious and non-infectious disease.

17. EXAMPLES LUNG CANCER IS CAUSED BY A CONSTELLATION OF CAUSES LIKE SMOKING UNFILTERED CIGARETTES 10 YEARS DURATION AND HOST SUSCEPTIBILITY

19. INCUBATION THE AGENT INCUBATES TO ACQUIRE THE CRITICAL DENSITY TO INITIATE THE DISEASE IT MULTIPLIES OR INCREASES IN INTENSITY FOR A SPECIFIC PERIOD BEFORE BECOMING OVERT AND CLINICAL

20. DISEASE INITIATION THE DISEASE IS INITIATED AT THE CELLULAR LEVEL WHEN THE NECESSARY CAUSE (AGENT) BECOMES SUFFICIENT I.E. COMPLIMENTED BY ITS CAUSAL PARTNERS

21. HOW IT PROGRESSES? Natural history of disease Natural history of the disease is that course, the disease takes, if it is left on its own , without any interference or intervention either of preventive, promotive , curative, medical or surgical nature. A disease when it is left like that (very rare) either ends in recovery or death. It follows usually this course as shown in the slideNatural history of the disease is that course, the disease takes, if it is left on its own , without any interference or intervention either of preventive, promotive , curative, medical or surgical nature. A disease when it is left like that (very rare) either ends in recovery or death. It follows usually this course as shown in the slide

22. HOW THE DISEASE IS TRANSMITTED?

23. DISEASE DISTRIBUTION TIME DISTRIBUTION OF THE DISEASE SHORT TERM FLUCTUATIONS, LONG TERM FLUCTUATIONS, PERIODIC FLUCTUATIONS, CYCLICAL, SEASONAL, SECULAR TRENDS

24. DISEASE PREVENTION PRIMORDIAL PREVENTION-- INTERVENTIONS TAKEN BEFORE THE DEVELOPMENT OF RISK FACTOR PRIMARY PREVENTION -- INTERVENTIONS TAKEN BEFORE THE DISEASE IS ESTABLISHED SECONDARY PREVENTION-- INTERVENTIONS TAKEN AFTER THE DISEASE IS ESTABLISHED- TERTIARY PREVENTION -- INTERVENTIONS TAKEN TO PREVENT COMPLICATIONS

25. PUBLIC HEALTH PROBLEM DISEASE WILL BE A PUBLIC HEALTH PROBLEM WHEN IT CAUSES HIGH MORBIDITY AND MORTASLITY DEMANDS URGENT HEALTH ACTION EITHER IN THE FORM OF CONTROL ELIMINATION ERADICATION