EPI
DEMI
OLOGI
CALTRI
AD
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U
LTI
FACTORI
ALCAU
SATI
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V
EDVRA
TPALIW
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MBBS2021
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O
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Forlongtimemanwasgroupingindarknessaboutthe
causationofdiseases,
Severaltheoryofdiseaseswereadvancedfromtimeto
tim
etoExplaindiseasecausationsuchas:-
Supernatural theory
Theoryofhum
ors byGreekandI
ndians
Theoryofcontagion
Them
iasm
atic theory
Theoryofspontaneousgenerationetc
K. Park’s textbook of preventive and social
medicine 25th edition
G
ermTheoryofD
isease
The breakthrough came in 1860,when French bacteriologist Louis
Pasteur dem
onstrated the presence of bacteria in air. I
n 1
87
3 he
advancedtheoryofSpontaneousgeneration..
Later Robert Koch discovered anthrax caused by bacteria and
G
OLDEN ERA of Bacteriology begun w
ith discovery of m
icrobe
aftermicrobe..
G
onnococus in1
879
Typhoidbacillus,Pneumococciin1
8
8
0
T
uberclebacillusin1
882
Cholerain1
883
D
iptheriain1
884andsoon
…
Louis Pasteur
K. Park’s textbook of preventive and social
medicine 25th edition
All attentionw
as focusedonm
icrobes andtheir rolein
diseasecausation,anddiseasemodelaccordinglyis:-
• D
I
SEASEAGENT MAN D
I
SEASE
•
• I
n1
878RobertKochsum
m
arizedhis
experim
ents ontheetiologyofw
ound
infection,Byinoculatinganim
alsw
ith
m
aterial fromvarioussources,he
producedsixtypesofinfection,each
causedbyaspecific m
icroorganism
.
• H
ethentransferredtheseinfections by
• inoculationthroughseveral kindsof
animals,reproducingtheoriginalsix
types.
Robert Koch
K. Park’s textbook of preventive and social
medicine 25th edition
Inthatstudy,heobserveddifferencesin pathogenicityfor
differentspeciesofhostsanddemonstratedthatthe
animalbodyisanexcellentapparatusforthecultivationof
bacteria.
K. Park’s textbook of preventive and social
medicine 25th edition
Thesetheories ofPasteur andKochconfirm
edthegerm
theoriesofdisease.
Later,RobertKochhasgivenKochPostulates
Aspecificmicroorganismisalwaysassociatedwith
agivendisease.
Themicroorganismcanbeisolatedfromthediseased
anim
al andgrow
ninpurecultureinthelaboratory.
Theculturedmicrobewillcausediseasewhen
transferredtoahealthyanim
al.
Thesametypeofmicroorganismcanbeisolatedfrom
thenew
lyinfectedanim
al.
K. Park’s textbook of preventive and social
medicine 25th edition
Koch’spostulates,are:
TheGermtheoryhasmanylimitation,Itwas
unabletoexplain
Whyonlysomepeoplesuffer fromthediseaseafter
exposure to microorganism and not all,as with
exposuretotuberclebacilli.
Whysomepeopledonotsufferfromthedisease
eventhroughtheyharborthepathogeninthebody.As
incarrier state
This lead to demand of a broader concept of
disease causation that synthesized the basic
factorsofAgent,HostandEnvironment.
K. Park’s textbook of preventive and social
medicine 25th edition
Thelimitationofgermtheoryledtotheconceptof
“Epidem
iological orEcological T
riad”.
AccordingtothetheoryofEpidem
iological triad everyone
exposedtodiseaseagentdidnotcontractthedisease,
Thismeansitisnotonlythecausativeagentthatis
responsiblefor disease.
ButthereareanotherFactorsalsorelatedtoManand
Environmentwhichcontributestodisease.
K. Park’s textbook of preventive and social
medicine 25th edition
AGENT
K. Park’s textbook of preventive and social
medicine 25th edition
HOST
ENVIORNMENT
AGENT
K. Park’s textbook of preventive and social
medicine 25th edition
BIOLOGICAL
MECHANICHAL
NUTRITIONAL
PHYSICAL/CHEMICAL
HOST
K. Park’s textbook of preventive and social
medicine 25th edition
GENETIC
MAKEUP
AGE/SEX
LITERACY
INCOME
LIFE
STYLE
IMMUNITY
ENVIRONMENT
K. Park’s textbook of preventive and social
medicine 25th edition
PHYSICAL
BIOLOGICAL
PSYCHOLOGICAL
CUSTOMS
AccordingtothismodelofEpidemiologicaltriad
diseaseoccurswhentheequilibriumbetweenagent,
hostandenvironm
entisdisturbed.
K. Park’s textbook of preventive and social
medicine 25th edition
Thismodelexplainsthatsomepersonsdonotsuffer
fromthediseaseeventhroughtheyharbor the
pathogens becauseanequilibriumis established
betw
eenthecausativeagentandthehost.
Epidem
iological triadtheoryis notapplicablefor non
infectious andchronicdiseases likeCoronaryartery
diseaes,M
ental illness etc,becausethese diseasehas
m
anycauses andm
ultiplefactors.
Thisledustothinkfor theM
ultipleFactorsbehind
adiseasecausation.
K. Park’s textbook of preventive and social
medicine 25th edition
MULT
IFACT
ORIALCAUSAT
ION
K. Park’s textbook of preventive and social
medicine 25th edition
ThetheoryofMultifactorialCausationofDiseasewas
firstproposedbyG
alenin1
30-1
50AD
In1
8
1
9
-
1
9
0
1,thistheorywasagainputforwardby
PetenKofer ofG
erm
any,butthis w
as overshadow
edby
germtheoryatthattim
e.
G
alensaidthefactors are:-
 Predisposing
 Exciting and
 Environmental
K. Park’s textbook of preventive and social
medicine 25th edition
MultifactorialCausationofDisease
T
H
ESEPREDI
SPOSI
N
GFACT
O
RSARE:-
SOCIAL
ECONOMICAL
CULTURAL
PSY
CH
OLOGI
CALFACT
O
R
S
(I
ncludingpoverty,illiteracy,I
gnorance, poor
livingcondtionO
vercrow
dingetc)
K. Park’s textbook of preventive and social
medicine 25th edition
TUBERCU
LOSI
S I
SN
O
TM
ERELYD
U
ET
OT
U
BERCLE
BACILLI…
Factors suchas -
• Poverty,
• O
vercrow
dingand
• Malnutrition
Contributetooccurrenceoftuberculosis
K. Park’s textbook of preventive and social
medicine 25th edition
Now it is recognized that a disease is not only
causedbyanorganismbutalsopredisposedby m
any
factors contributingtoits occurrence.
For exam
ple:- “M
odernD
iseases”ofcivilization like–
lungcancer,diabetes,coronaryheartdiseaseandm
ental
illnessetchasseveralcontributingfactorsbehindfor
thereoccurrence.
K. Park’s textbook of preventive and social
medicine 25th edition
I
tis nowknow
nthatdiseases suchas Coronaryheart
diseaseandcancerareduetomultiplefactors.
For Exam
ple-
Excess of fat (saturated) intake, Smoking ,lack of
physical exercise and obesity are involved in the
Pathogenesis ofCoronaryH
eartD
isease
MostofthesefactorsarelinkedtoLifestyleandhuman
behavior.
K. Park’s textbook of preventive and social
medicine 25th edition
Groupor
Popullations
andtheir
Charcteristics
Enviornment,Behaviour,
Culture,
Physiological Factors,
Ecological Elem
ents
CausativeFactors
T
I
M
E
K. Park’s textbook of preventive and social
medicine 25th edition
This m
odel of disease causationw
as suggestedby
MacmahonandPughintheirbook:Epidemiology
:Principles andM
ethods
Thismodelis ideallysuitedinthestudyofchronic
disease,wherethediseaseagentisoftennotknown,but
istheoutcomeofinteractionofmultiplefactors…
K. Park’s textbook of preventive and social
medicine 25th edition
W
EBOFCAU
SAT
I
O
N
 The “w
eb
K. Park’s textbook of preventive and social
medicine 25th edition
of causation” considered all the
predisposing factors of any type and their
com
plexinter relationshipw
itheachother
 Thefigureillustratesthecomplexitiesofa casualweb
ofm
yocardial infarctionw
hichis bynom
eans
complete)
K. Park’s textbook of preventive and social
medicine 25th edition
 Thebasic tenetofepidem
iologyis tostudythe
clusters ofcauseandcom
binations of effects
andhowtheyrelatetoeachother casual w
eb
providesamodelwhichshowsvarietyof
possibleinterventionsthatcouldbetakento
reducetheoccurrenceof disease.
 TheMultifactorialtheoryhelpsustounderstand
thevarious associatedcausativefactors,prioritize
andplanmeasuresto controlthedisease
K. Park’s textbook of preventive and social
medicine 25th edition
CONCLUSION
TH
ANKY
O
U

EPIDEMIOLOGICAL TRIAD VED.pptx