History and importance of epidemiological triad and triangle

1. EPIDEMIOLOGICAL TRIAD
&
MULTIFACTORIAL CAUSATION
VEDVRAT PALIWAL (95)
MBBS 2021-22
ASMC,ETAH

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
K. Park’s textbook of preventive and social
medicine 25th edition

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…
Germ Theory of Disease
Louis Pasteur
K. Park’s textbook of preventive and social
medicine 25th edition

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
K. Park’s textbook of preventive and social
medicine 25th edition

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
K. Park’s textbook of preventive and social
medicine 25th edition

6. ➢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.
Koch’s postulates, are:
K. Park’s textbook of preventive and social
medicine 25th edition

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.
K. Park’s textbook of preventive and social
medicine 25th edition

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.
K. Park’s textbook of preventive and social
medicine 25th edition

9. AGENT HOST
ENVIORNMENT
K. Park’s textbook of preventive and social
medicine 25th edition

10. AGENT
BIOLOGICAL
MECHANICHAL
NUTRITIONAL
PHYSICAL/CHEMICAL
K. Park’s textbook of preventive and social
medicine 25th edition

11. HOST
GENETIC
MAKEUP
AGE/SEX
LITERACY
INCOME
LIFE
STYLE
IMMUNITY
K. Park’s textbook of preventive and social
medicine 25th edition

12. ENVIRONMENT
PHYSICAL
BIOLOGICAL
PSYCHOLOGICAL
CUSTOMS
K. Park’s textbook of preventive and social
medicine 25th edition

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.
K. Park’s textbook of preventive and social
medicine 25th edition

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.
K. Park’s textbook of preventive and social
medicine 25th edition

15. MULTIFACTORIAL CAUSATION
K. Park’s textbook of preventive and social
medicine 25th edition

16. ▪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
K. Park’s textbook of preventive and social
medicine 25th edition

17. THESE PREDISPOSING FACTORS ARE:-
➢SOCIAL
➢ECONOMICAL
➢CULTURAL
➢PSYCHOLOGICAL FACTORS
(Including poverty,illiteracy,Ignorance, poor
living condtion Overcrowding etc)
K. Park’s textbook of preventive and social
medicine 25th edition

18. TUBERCULOSIS IS NOT MERELY DUE TO TUBERCLE
BACILLI…
Factors such as -
• Poverty ,
• Overcrowding and
• Malnutrition
Contribute to occurrence of tuberculosis
K. Park’s textbook of preventive and social
medicine 25th edition

19. ▪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.
K. Park’s textbook of preventive and social
medicine 25th edition

20. 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.
K. Park’s textbook of preventive and social
medicine 25th edition

21. Group or
Popullations
and their
Charcteristics
Enviornment,Behaviour,
Culture,
Physiological Factors,
Ecological Elements
Causative Factors
TIME
K. Park’s textbook of preventive and social
medicine 25th edition

22. ➢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…
WEB OF CAUSATION
K. Park’s textbook of preventive and social
medicine 25th edition

23. ➢ 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)
K. Park’s textbook of preventive and social
medicine 25th edition

24. K. Park’s textbook of preventive and social
medicine 25th edition

25. ❖ 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
K. Park’s textbook of preventive and social
medicine 25th edition

26. THANK YOU