Modes of transmission

This ppt contains all the information about Modes of disease transmission. It is useful for students of the medical field learning Preventive and social medicine, Swasthavritta (Ayurved), and everyone who is interested in knowing about it

1. Dr. Shubhangi S. Kshirsagar
Assistant professor
Department of Swasthavritta & Yoga
Modes of Transmission

2. •Communicablediseasesaretransmittedfrom
sourceofinfectiontosusceptibleindividualin
manydifferentways,dependingoninfectious
agent,portalofentryandlocalecological
conditions.
•Themodeoftransmissionofdiseasemaybe
classifiedasbelow-
A.Directtransmission
B.Indirecttransmission
Dr. ShubhangiKshirsagar

3. Modes of Transmission
1. Direct transmission
1.Direct contact
2.Droplet infection
3.Contact with Soil
4.Inoculation into Skin
or Mucosa
5.Trans-placental
(vertical)
2. Indirect transmission
1.Vehicle Borne
2.Vector Borne
a. Mechanical
b. Biological
3. Air-borne
a. Droplet nuclei
b. Dust
4. FomiteBorne
5. Unclean Hands And
Fingers
Dr. ShubhangiKshirsagar

4. Direct transmission
Dr. ShubhangiKshirsagar

5. 1. Direct transmission
1.Direct contact
2.Droplet infection
3.Contact with Soil
4.Inoculation into Skin or Mucosa
5.Trans-placental (vertical)
Dr. Shubhangi Kshirsagar
A. Direct transmission

6. A. Direct transmission
1.Direct contact
Infection may be transmitted by direct
contact from skin to skin , mucosa to
mucosa, mucosa to skin with same
or another person.
Direct and immediate transfer of
infectious agent.
By touching, kissing, sexual intercourse
or continued close contact.
Larger dose of infection.
Ex. STD, AIDS, leprosy, leptospirosis,
skin & eye infection
Dr. ShubhangiKshirsagar

7. 2.Dropletinfection
Thisisadirectprojectionofasprayof
dropletsofsalivaandnasopharyngeal
secretionduringcoughing,sneezing,speaking,
spittingintosurroundingatmosphere.
Expelleddropletmayimpingedirectlyuponthe
conjunctiva,oro-respiratorymucosaoraskinof
closecontact.
Dr. ShubhangiKshirsagar

8. Diameterof10mmmorgreaterparticlesare
filteredbynose.
Diameterof5mmmorlessparticlescanpenetrate
deeplyandreachthealveoli.
Dropletspreadupto30-60cmbetweensource
andhost.
Ex.Respiratoryinfections,eruptivefevers,common
cold,diphtheria,TB,whoopingcough.
Potentialofdropletspreadincreasedinconditionsof
closeproximity,overcrowdingandlackofventilation.
Dr. ShubhangiKshirsagar

9. 3.Contactwithsoil
Directexposureofsusceptibletissuetothe
diseaseagentinthesoil,compostordecaying
matterinwhichitnormallyleadsasaprophytic
existance.
Ex.Hookwormlarvae,
tetanus
Dr. ShubhangiKshirsagar

10. 4. Inoculation into skin or mucosa
The disease agent may be inoculated directly
into the skin or mucosa.
Examples –
Rabies virus by dog bite
Hepatitis B virus through contaminated
needles and syringes.
Dr. ShubhangiKshirsagar

11. 5.Transplacentalorvertical
Diseaseagentcanbetransmittedtransplacentally.
Ex.TORCH (Toxoplasmagondii,Rubellavirus,
Cytomegalovirus,Herpesvirus),HepatitisB,
CoxsackieB,AIDS,Syphilis,Varicellavirus.
Inthesecases,thediseaseagentproduces
malformationsoftheembryobydisturbingits
growth.
Dr. ShubhangiKshirsagar

12. Indirect transmission
Dr. Shubhangi Kshirsagar

13. •Thisembracesvarietyofmechanismsincluding
thetraditional5F’s–Flies,Fingers,Fomites,
FoodandFluid.
•Essentialrequirementforindirecttransmissionis
thattheinfectiousagentmustbecapableof
survivingoutsidethehumanhostintheexternal
environmentandretainitsbasicpropertiesof
pathogenesisandvirulencetillitfindsanewhost.
Dr. ShubhangiKshirsagar
B. Indirect transmission

14. 2. Indirect transmission
1.Vehicle Borne
2.Vector Borne
a. Mechanical
b. Biological
3. Air-borne
a. Droplet nuclei
b. Dust
4. FomiteBorne
5. Unclean Hands And Fingers
Dr. ShubhangiKshirsagar

15. B. Indirect transmission
1.Vehicleborn
Transmissionofinfectiousagentthroughthe
agencyofwater,food(includingraw
vegetables,fruits,milk,&milkproducts),ice,
blood,plasma,andotherbiological
productssuchastissue,organ.
Waterandfood–mostfrequent.
Dr. ShubhangiKshirsagar

16. Infectious agent may -
Multiplied or developed in a vehicle before
being transmitted (ex. S. aureusin food) OR
Only passively transmitted in the vehicle (ex.
Hepatitis A virus in water).
Dr. ShubhangiKshirsagar

17. Diseases transmitted by vehicle are –
Water & food –alimentary tract infection e.g.
diarrhoea, typhoid fever, Cholera, polio,
hepatitis A, food poisoning
Blood –Hepatitis B, maleria, syphilis
Organ transplantation –Cytomegalovirus in
association with kidney transplant
Dr. ShubhangiKshirsagar

18. 2.Vectorborn
Definitionofvector–Vectorisanarthropodor
anylivingcarrier(ex.Snail)thattransportan
infectiousagenttoasusceptibleindividual.
Dr. ShubhangiKshirsagar

19. Epidemiological classification of
vector born disease
1.By vector
2.By transmission chain
3. By method in which vector transmit agent
4. By method in which vector are involved in
the transmission and propagation of parasites
Dr. ShubhangiKshirsagar

20. Epidemiological classification of
vector born disease
Vector born
diseases
1. By vector
By transmission
chain
By method in
which vector
transmit agent
By method
Dr. Shubhangi Kshirsagar

21. 4. By method in which vectors are involved in
the transmission and propagation of parasites
a.Mechanicaltransmission
Infectiousagentismechanicallytransportedby–
Crawlingorflyingarthropodthroughthesoiling
ofitsfeetorproboscisor
Bythepassageoforganismthroughits
gastrointestinaltractandpassivelyexcreted.
Thereisnodevelopmentormultiplicationof
theinfectiousagentonORwithinthevector.
Dr. ShubhangiKshirsagar

22. B.Biologicaltransmission
Theinfectiousagentundergoesreplicationor
developmentorbothinthevectorand
requiresanincubationperiodbeforevector
cantransmit.
Dr. Shubhangi Kshirsagar

23. b. Biological transmission types
1.Propagative-The agent merely multiplies in
vector, but no change in form.
Ex. Plague bacilli in rat fleas
2. Cyclo-propagative–The agent changes in
form and number.
Ex. Malaria parasites in mosquito
3. Cyclo-developmental –The agent undergoes
only development but no multiplication.
Ex. Microfilaria in mosquito
Dr. ShubhangiKshirsagar

24. Transovarialtransmission–infectious
agentistransmittedverticallyfromthe
infectedfemaletoherprogenyinthe
vector.
Transstadialtransmission–Transmissionof
diseaseagentfromonestageoflifecycle
toanother.
•Ex.Nymphtoadult
Dr. ShubhangiKshirsagar

25. 3. Air borne Drpletnuclei
Dust
a. Droplet nuclei
Type of particles (tiny) 1-10micron range that
represents the dried residue of droplets.
They are formed by –
a.Evaporation of droplets coughed or sneezed
into the air
b.Generated purposefully by a variety of
atomizing devices (aerosols)
c.Also formed accidently in microbiological
laboratories, rendering plants, autopsy rooms.
Dr. ShubhangiKshirsagar

26. Thedropletnucleimayremainair-bornforlong
periodoftime.
Someretaining&otherlosingtheirinfectivity.
Floatsintheairandalsodisseminatedbyair
currentsfromthepointoftheirorigin.
Particles in the size 1-5micron –easily drawn into
the alveoli of the lungs and may be retained
there.
Ex. TB, influenza, chicken pox, measles, Q fever
Toxic air pollutant (smog)-air pollution epidemic
Dr. ShubhangiKshirsagar

27. Dr. Shubhangi Kshirsagar

28. 3. Air borne
b. Dust
Larger droplets which are expelled during talking,
coughing or sneezing
settle down by their weight on the floor,
carpets, furniture, cloths, bedding and other
objects in the immediate environment
and become part of dust.
Dr. ShubhangiKshirsagar

29. Avarietyofinfectiousagentsfoundinthedust
ofhospitalwardsandlivingrooms.
Duringtheactofsweeping,dustingandbed-
making;thedustisreleasedintotheairand
becomesonceagainairborn.
Dustparticles–blownfromthesoilbywindex.
Fungalspores–coccidiodomycosis
Otherex.Streptococcalandstaphylococcal
infection,TB,pneumonia.
Dr. ShubhangiKshirsagar

30. 4. Fomiteborn
Fomitesare --
inanimate articles or substances other than
water or food
contaminated by the infectious discharges
from a patient
capable of harbouringand transferring the
infectious agentto a healthy person.
Dr. ShubhangiKshirsagar

31. Fomitesincludesoiledcloths,towels,linen,
handkerchiefs,cups,spoon,books,toys,drinking
glasses,doorhandles,syringes,instrumentsand
surgicaldressings.
Ex.Diphtheria,typhoidfever,bacillarydysentery,
hepatitisA,eyeandskininfection.
Dr. ShubhangiKshirsagar

32. 5. Unclean hands
& fingers
Hands–mostcommonmediumbywhich
pathogenicagentsaretransferredtofoodfromthe
skin,nose,bowelandfromotherfoods.
Thetransmissiontakesplace–
Directly–handtomouth
Indirectly
Ex.Staphylococcal&streptococcalinfections,
typhoidfever,hepatitisA,intestinalparasites
Dr. ShubhangiKshirsagar

33. Thank You !