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CONCEPTS OF DISEASE CAUSATION PowerPoint PPT Presentation


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

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CONCEPTS OF DISEASE CAUSATION

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Concepts of disease causation l.jpg

CONCEPTS OF DISEASE CAUSATION

DR MIRZA INAMUL HAQ

AP COMMUNITY MEDICINE


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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 ?


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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?


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WHAT IS A DISEASE?

DISEASE CAN BE SIMPLY EXPLAINED

AS DISAT EASEOR ILL HEALTH

SOME DESCRIBE IT AS DISTURBANCE IN EQUILIBRIUM BETWEEN MAN AND HIS TOTAL ENVIRONMENT.


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HOW THE DISEASE IS CAUSED?

  • SUPERNATURAL THEORY OF DISEASE

  • ECOLOGICAL THEORY

  • GERM THEORY

  • MULTIFACTORIAL CAUSATION THEORY


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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


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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.


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ECOLOGICAL THEORY

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


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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.


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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


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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


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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.

ROBERT KOCH


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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.


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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.

PETTENKOFFER


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WHEN THE DISEASE OCCURS?

Agent (SEED) factors

DISEASE OCCURS ONLY WHEN THE HOST FACTORS AND ENVIRONMENTAL FACTORS MAKE THE AGENT SUFFICIENT ENOUGH TO CAUSE THE DISEASE

D

Environmental factors

(SHOWER)

Host factors (SOIL)


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CAUSAL CONSTELLATIONS

disease

A F G H J K

A R S T X

A B C D E

A L M N P Q

Causal constellations 1 2 3 4

A = NECESSARY CAUSE

B TO X = CAUSAL PARTNERS


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EXAMPLES

LUNG CANCER IS CAUSED BY A CONSTELLATION OF CAUSES LIKE

  • SMOKING

  • UNFILTERED CIGARETTES

  • 10 YEARS DURATION

  • AND HOST SUSCEPTIBILITY


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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


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DISEASE INITIATION

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


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HOW IT PROGRESSES?

  • Natural history of disease

Pre-pathogenic

period

Incubation

Period/Generation time

Disease initiation at

Cellular level

Carrier

State

Pathogenic

period

Death

Convalescent

period


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HOW THE DISEASE IS TRANSMITTED?

Susceptible

Host/Non –

Immune/

Poor herd immunity

MODE OF TRANSMISSION THROUGH SOME VEHICLE OR VECTOR

RESERVOIR/

SOURCE OF

AGENT


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DISEASE DISTRIBUTION

TIME DISTRIBUTION OF THE DISEASE

  • SHORT TERM FLUCTUATIONS,

  • LONG TERM FLUCTUATIONS,

  • PERIODIC FLUCTUATIONS,

  • CYCLICAL, SEASONAL, SECULAR TRENDS


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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


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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


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