CM 1.3 Agent Host and environmemtal factors ,epidemiological triad ,multi factorial causation od disease.pptx

This lecture is for the First Year Students -Agent Host and environmental factors(CM3.1) -Causation of disease has given various concepts- ranging from older theories to modern theories
Older theories started from 10,000 years ago back till the early 19th century which was based on supernatural theory, bad air, living things generation form non-living things
These theories were followed by the germ theory of disease given in 1960 by Louis Pasteur when he demonstrated the presence of bacteria in the air and disapproved of the spontaneous generation of disease
1873 advanced germ theory was established
1877 Robert Koch showed that anthrax is caused by bacteria
After that gonococcus, typhoid cholera, TB, and diphtheria bacterium were discovered and finally, medicine shed the dogma of magic and superstition and wore the robe of scientific knowledge

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2. A gent, Host, and Environmental factors, Epidemiological triad and Multifactorial causation Dr Anjali Mall 6/17/2022

3. Specific Learning objectives Introduction and a brief history of the concept of health (10 mts ) To enumerate various concepts of causation of disease. (10 mts ) To describe and interpret the epidemiological triangle and agent, host, and environmental factors. (15 mts ) To explain the multifactorial and web of causation of disease with examples. (10mts) Conclusion and MCQs (15mts) 6/17/2022

4. 1. Introduction and Brief History Health is one of the most precious commodity. Responsible for socioeconomic development of the country. Democritus in 5 th century BC-without health ,nothing is of use ,not money or anything else. Concept of health is multidimensional. 6/17/2022

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6. Concept of Health and a Brief History 1/2 Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity Recently added – “ability to lead a socially and economically productive life” Dynamic, not a static concept ; a relative concept “Optimal functioning of the organism given the genetic and environmental conditions” Positive health – perfect functioning of the body and mind 6/17/2022

7. The Agricultural revolution1/2 6/17/2022

8. Hippocratic corpus1/3 6/17/2022

9. The Bubonic Plague1/4 6/17/2022

10. 2. Various concepts of causation of disease Old theories Modern theories germ theory epidemiological triad (tetrad) multifactorial causation – socioeconomic, cultural, genetic, psychological web of causation wheel of causation 6/17/2022

11. Discovery of microbiology - turningpoint ▶ GERM THEORY OF DISEASE ▶ Microbes as sole cause of disease CONCEPT OF CAUSATION 17 Older theories Supernatural theory Theory of Humors Concept of contagion Miasmatic theory Theory of spontaneous generation Contagion theory Miasmatic theory 6/17/2022

12. Limitations of Germ Theory Why only some people suffer from the disease even after exposure Why do certain people carry pathogens but do not show manifestations of the disease Why a disease would be epidemic sometimes It does not take into account the multi-factorial causation even in the diseases in which micro-organism is the “necessary cause”. 6/17/2022

13. 3. Epidemiological triad or triangle Epidemiological triad : Arose out of limitations of the Germ Theory of Disease Focuses on outcome of interaction of agent, host and environment More applicable to infectious diseases 6/17/2022 TIME

14. Triad of epidemiology 1/3 6/17/2022

15. Epidemiological triad – 2/ 3 Agents - Substance living or non-living , or a force, tangible or intangible, the excessive presence or relative lack of which may initiate or perpetuate a disease process Biological Physical Chemical Mechanical Insufficiency or excess of factors, hormones, nutrients, parts, structural defects, chromosomal factors, immunological factors Social 6/17/2022

16. Epidemiological triad – 3/ 3 Host Demographic Biological – genetic, biochemical, immunological, physio functions Social and economic condition Lifestyle Level of exposure State of health and overall fitness 6/17/2022 Human host – SOIL , Disease agent – SEED

17. Epidemiological triad – 4/ 3 Environment Physical, Biological, Ps y chosocial 6/17/2022

18. Risk factors and risk groups 5/3 Risk factors Modifiable, non-modifiable Examples for CVD Risk groups 6/17/2022 Where the disease agent is not firmly established, the etiology is generally discussed in terms of risk factors. The term risk factor is used by different authors with at least two meanings- An attribute or exposure which is significantly associated with the development of the disease A determinant that can be modified by intervention, thereby reducing the possibility of occurrence of disease or other specified outcomes

19. Interpretation of the triad 6/3 : Disease Characteristics: Toxicity, virulence, infectivity Susceptibility to antibiotics Ability to survive outside body Interventions: Eradicate Genetically modify Interventions: remove breeding grounds Improve sanitations Interventions: Educate Change activity patterns Quarantine Host Characteristics: Age Prior exposure Susceptibility Co-infection Immune response Interventions: Treat, isolate Immunize Nutrition Environment Characteristics: Climate Physical Structures Population Density Social Structure Interventions: Housing Quality Sanitation, Water Preventive Measures Interventions: Protect Educate After exposures Agent Pathogen

20. An epidemiological triad of Malaria 5/3 : Malaria Characteristics: Plasmodium Interventions: Eradicate Genetically modify Interventions: remove breeding grounds Improve sanitations Interventions: Educate Change activity patterns Host Characteristics: Age Susceptibility Immune response Interventions: Treat, mosquito protective measures Diet and nutrition Environment Characteristics: Climate Physical Structures Population Density Social Structure Interventions: Breeding places Chemical control Preventive Measur es Interventions: Protect Educate Agent Pathogen

21. 4 . Multifactorial causation : Pettenkoffer of Munich(1890-1901) proposed it in the 19 th century Aimed to overcome shortcomings of Germ Theory of disease in causation of “modern” epidemic diseases Equal importance to – – Social – Economic – Cultural – Genetic – Psychological factors An advanced model of the Triangle of Epidemiology Replaces “agent” with “causative factors ” Purpose to know, quantify and prioritize for modification 6/17/2022

22. Poor nutrition Low immunity Concurrent disease Poverty Ove r c r owding malnutrition Mycobacterium tuberculi Multifactorial causation : E xample - TB

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24.  O n e su f f i c i en t triad m i g ht i n c l u de: con t a c t w ith a carrier, low immunity, and crowding.  A n other triad m i g ht i n c l u de co n t ac t w ith a c a r r i e r , having AIDS, poor hygiene.   B oth triads a r e su f f i c i en t to p r o d u c e d i s e ase , b u t factors differ. Thus for TB, both triad must have the TB organism, as a necessary factor for TB to occur. C ON TD …… … . 6/17/2022

25. Web of Causation 1/4 Suggested by McMahon and Pugh. Ideally suited for chronic diseases where the agent is not known. Emphasizes breaking the weak link in the chain or web of causation to prevent and/or control disease. “Web of causation” considers all the predisposing factors of any type and their complex interrelationship with each other. Removal or elimination of just one link or chain may be sufficient to control the disease, provided that link is sufficiently important in the pathogenetic process. 6/17/2022

26. Web of Causation 2/4 26

27. Conclusion There are various concepts for the causation of diseases- Germ theory of disease- agent and host Epidemiological triad- interaction and interdependence with Agent, host, and environment and time Multifactorial causation- multiple factors eg -non communicable disease –prioritize and work Web of causation-chronic disease- every factor has equal weightage 6/17/2022

28. Self assessment tool(MCQ) All of the following are components of the epidemiological triad Except Environment Agent Host Manpower 6/17/2022

29. (MCQ) 2. Web of causation is most appropriate – Mostly applicable to common disease Better for all the related factors associated with causation of disease Epidemiological ratio Helps to interrupt the risk of transmission 6/17/2022