Theories of disease causation..ppt

Theories of disease causation

Presented by:
Monika sharma
M.Sc. Nursing 1st year

INTRODUCTION

Disease is a dynamic process and it is just opposite to
the health. Health denotes perfect harmony and normal
functioning of all the body system or state of complete
wellness whereas disease denotes disharmony and
deviation from normal functioning of various body
functioning system.

DEFINITION OF DISEASE:

 According to webster ,

“disease is a condition in which
body health is impaired, a departure from state of
health, an alteration of human body function and
interrupting the performance of vital function".

CONT…

 According to oxford English dictionary ,”disease is a
condition of body or some part of body or organ of
body in which its function are disrupted”.
OR
 According to ecological point of view, “ disease is a
maladjustment of the human organism to the
environment”

THEORIES OF DISEASE
CAUSATION
INTRODUCTION

CONT…

 Before the discovery of micro-organism (bacteria
by loies pasture in 1822-1895)several theories
explaning the cause of disease were put forward
time to time

 germ theory
 epidemiological triad
 multifactorial causation theory
 web of causation
 devers epidemiological model

THE GERM THEORY:

 According to this theory, there is one single specific
cause of every disease. This refers to one to one
relationship between the causative agent and
disease.

CAUSATIVE AGENT MAN DISEASE

CAUSE EFFECT
(FOR EX..DIPTHERIA DUE TO CORNEBACYERIUM
DIPTHERIA)

THEORY OF EPIDEMIOLOGICAL TRIAD :

 According to this theory, every one exposed to
disease agent did not contract the disease. This
means it is not only the causative agent that is
responsible for disease but there are another factors
also ,related to man and environment which
contribute to disease.

Bacteria

Viruses
AGENT

Fungi

Ameoba

Genetic
makeup
Age

Sex
HOST

Health
immunity behaviour

sanitation
water

air

ENVIRONMENT

Noise

customs

AGENT

HOST ENVIRONMENT

MULTIFACTORIAL CAUSATIONTHEORY:

 Epidemiological theory is not applicable for non
infectious and chronic diseases like coronary artery
diseases etc. because it has many causes or multiple
factors.
 This theory helps to understand the various
associated causative factors, prioitise and plan
preventive and plan measures to control the disease.

CAUSE

CAUSE EFFECT

CAUSE

WEB OF CAUSATION

 Given by macmohan and pugh.
according to him
disease never depends upon single isolated cause
rather it develops from a chain of causation in
which each link itself is a result of complex
interaction of preceding events these chain of
causation which may be the fraction of the whole
complex is known as web of causation.

DEVERS EPIDEMIOLOGICAL MODEL

 This model is composed of four major categories of
factors
 human biology
lifestyle,
environment and
health system.

CONT….

 all these factors influence health status
positively or negatively.
 Human biological --- epidemiological triad and
include genetic inheritance, complex physiological
systems, factors related to maturation and ageing
 Life style factors include daily living
activities, customs, traditions, health habits etc

CONT…

 . Environmental factors include
physical, biological, social and spiritual
components
 Health care system factors include
availability, accessibility, adequacy and use of
health care services at all levels.

SPECTRUM OF DISEASE:

 “Spectrum of disease” is the graphical
representation of variation in the manifestations
of disease.

CONT…

 At one end of disease spectrum are subclinical
infections which are not ordinarily identified and
at the other end are fatal illness.. In the middle of
the spectrum lie illness ranging in severity from
mild to severe.

ICEBERG OF DISEASE:

 To this the disease can be closely related with an
iceberg. The floating tip of the iceberg represents
what the physician sees in the community i.e.
clinical cases.

CONT…

 The vast submerge portion of the iceberg
represents the hidden mass of disease i.e.
latent, unapparent, presymptomatic and
undiagnosed cases and carrier in the community.
he waterline represents the demarcation between
apparent and unapparent diseases

ROLE OF NURSE IN PREVENTION OF DISEASE:

 participate in early diagnosis and treatment.
 notification of certain specific diseases.
 identify source of infection and method of spread.
 health education of people in general.
 control of communicable diseases .

SUMMARIZATION:
 Introduction
 Definition of disease
 Various theories of disease causation
- germ theory
-epidemiological triad
- multifactorial causation theory
-web of causation

CONT…

- deversepidimiological model
 Role of nurse in disease prevention
 Spectrum of disease
 Iceberg of disease

BIBLIOGRAPHY

 Gulani k.k.community health nursing.2009(new
delhi):kumar publishing house.21-23
 Park k .preventive and socialmedicine. 2007(New
Delhi):banarsidas bhanot.24-28

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