2. For long time man was grouping in darkness about
the causation of diseases,
Several theory of diseases were advanced from
time to time to Explain disease causation such as:-
Supernatural theory
Theory of humors by Greek and Indians
Theory of contagion
The miasmatic theory
Theory of spontaneous generation etc
INTRODUCTION
3. The breakthrough came in 1860,when French bacteriologist
Louis Pasteur demonstrated the presence of bacteria in air.
In 1873 he advanced theory of Spontaneous generation ..
Later Robert Koch discovered anthrax caused by bacteria
and GOLDEN ERA of Bacteriology begun with discovery of
microbe after microbe..
Gonnococus in 1879
Typhoid bacillus,Pneumococci in 1880
Tubercle bacillus in 1882
Cholera in 1883
Diptheria in 1884 and so on…
Louis Pasteur
Germ Theory of Disease
4. All attention was focused on microbes and their
role in disease causation, and disease model
accordingly is :-
DISEASE AGENT MAN DISEASE
In 1878 Robert Koch summarized his
experiments on the etiology of wound
infection,By inoculating animals with
material from various sources, he
produced six types of infection, each
caused by a specific microorganism.
He then transferred these infections by
inoculation through several kinds of
animals, reproducing the original six
types.
Robert Koch
5. In that study, he observed differences in
pathogenicity for different species of hosts and
demonstrated that the animal body is an excellent
apparatus for the cultivation of bacteria.
These theories of Pasteur and Koch confirmed the
germ theories of disease.
Later, Robert Koch has given Koch Postulates
6. Koch’s postulates, are:
A specific microorganism is always associated
with a given disease.
The microorganism can be isolated from the
diseased animal and grown in pure culture in the
laboratory.
The cultured microbe will cause disease when
transferred to a healthy animal.
The same type of microorganism can be isolated
from the newly infected animal.
7. The Germ theory has many limitation ,
It was unable to explain
Why only some people suffer from the disease
after exposure to microorganism and not all,as
with exposure to tubercle bacilli.
Why some people do not suffer from the
disease even through they harbor the pathogen
in the body. As in carrier state
This lead to demand of a broader concept of
disease causation that synthesized the basic
factors of Agent, Host and Environment.
8. The limitation of germ theory led to the concept of
“Epidemiological or Ecological Triad”.
According to the theory of Epidemiological triad
everyone 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 contributes to disease.
13. According to this model of Epidemiological triad
disease occurs when the equilibrium between
agent, host and environment is disturbed.
This model explains that some persons do not
suffer from the disease even through they harbor
the pathogens because an equilibrium is
established between the causative agent and the
host.
14. Epidemiological triad theory is not applicable for
non infectious and chronic diseases like Coronary
artery diseaes,Mental illness etc,because these
disease has many causes and multiple factors.
This led us to think for the Multiple Factors
behind a disease causation.
15. The theory of Multifactorial Causation of Disease
was first proposed by Galen in 130-150 AD
In 1819-1901 ,this theory was again put forward
by Peten Kofer of Germany, but this was
overshadowed by germ theory at that time.
Galen said the factors are:-
Predisposing
Exciting and
Environmental
Multifactorial Causation of Disease
16. THESE PREDISPOSING FACTORS ARE:-
SOCIAL
ECONOMICAL
CULTURAL
PSYCHOLOGICAL FACTORS
(Including poverty,illiteracy,Ignorance,
poor living condtion Overcrowding etc)
17. TUBERCULOSIS IS NOT MERELY DUE TO
TUBERCLE BACILLI…
Factors such as -
• Poverty ,
• Overcrowding and
• Malnutrition
Contribute to occurrence of tuberculosis
18. Now it is recognized that a disease is not only
caused by an organism but also predisposed by
many factors contributing to its occurrence .
For example:- “Modern Diseases” of civilization
like –lung cancer,diabetes,coronary heart disease
and mental illness etc has several contributing
factors behind for there occurrence.
19. It is now known that diseases such as Coronary
heart disease and cancer are due to multiple
factors.
For Example-
Excess of fat (saturated) intake, Smoking ,lack
of physical exercise and obesity are involved in
the Pathogenesis of Coronary Heart Disease
Most of these factors are linked to Lifestyle and
human behavior.
21. WEB OF CAUSATION
This model of disease causation was
suggested by Macmahon and Pugh in their book:
Epidemiology :Principles and Methods
This model is ideally suited in the study of
chronic disease, where the disease agent is often
not known ,but is the outcome of interaction of
multiple factors…
22. The “web of causation” considered all the
predisposing factors of any type and their
complex inter relationship with each other
The figure illustrates the complexities of a
casual web of myocardial infarction which is by
no means complete)
23.
24. The basic tenet of epidemiology is to study
the clusters of cause and combinations of
effects and how they relate to each other
casual web provides a model which shows
variety of possible interventions that could
be taken to reduce the occurrence of
disease.
The Multifactorial theory helps us to
understand the various associated causative
factors,prioritize and plan measures to
control the disease
CONCLUSION
25. References:-
1.Book of Community Medicine with Recent
advances by AH Suryakantha
2.Textbook Of Preventive and Social Medicine
by –K.Park
3.Image Sources-Wikipedia and Google
