The document provides an overview of immunization programs and tropical diseases, detailing the expanded program for immunization (EPI) in Pakistan, types of immunity, and the various vaccines available for preventable diseases. It also highlights the importance of the cold chain in vaccine storage and administration, as well as the roles of healthcare staff in immunization efforts. Additionally, the document covers various tropical diseases, their causes, and classifications, emphasizing the global impact of communicable diseases.

1. Immunization & Tropical
Diseases
Mumtaz Ali Khan
Lecturer-MCN Matta Swat

2. Objectives
1. Overview of expanded Expended programme for
Immunization(EPI) in Pakistan.
2. Review different types of immunity.
3. Enlist vaccines preventable diseases.
4. Explain the types of vaccines.
5. Identify contraindications of vaccines.
6. Tabulate vaccination schedule.
7. Discuss the importance of cold chain cold chain.
8. Discuss the responsibilities of a nurse to maintain
cold chain.

3. Immunization
Immunization is the process whereby a person
is made immune or resistant to an infectious
disease, typically by the administration of a
vaccine. Vaccines stimulate the body’s own
immune system to protect the person against
subsequent infection or disease.(WHO)

4. Expanded Programme on Immunization (EPI)
•Expanded program on immunization is mainly
designed for delivering vaccines to children all over
the world to control potential health disorders.
•Established by world health organization in 1974.
•It is a disease prevention activity aiming at reducing
illness, disability and mortality from childhood
diseases preventable by immunization.

5. Immunity
•Immunity is the body's ability to fight off harmful
microorganisms (Pathogens) that invade it.
•The immune system produces antibodies or cells
that can deactivate pathogens.
•Fungi, protozoans, bacteria, and viruses are all
potential pathogens.

6. Types of immunity

7. Types of immunity

8. Innate immunity
•It is inborn or natural immunity. One may inherit
some form of immunity like resistance of skin to
the invasion by bacteria, destruction of germs in the
stomach by its acidic secretion & enzymes and
phagocytosis of bacteria and other invaders by
WBCs.

9. Active Immunity
Active Immunity occurs when one makes his/her own
antibodies. This type of immunity is long term. It has
two subtypes
• Naturally-Acquired Active Immunity: If you get an
infectious disease (like VARICELLA), often times, that
stimulates the production of MEMORY cells which
are then stored to prevent the infection in the future.
• Artificially-Acquired Active Immunity: Injecting or
taking antigens by mouth. Takes time for T and B cells
to be activated but gives long lasting immunity.

10. Passive Immunity
Passive Immunity occurs when the antibodies come
from some other source. This type of immunity is short
term.
• It has further divided in to two types.
• Natural passive: Mother to child through placenta or
milk.
• Artificial passive: Used during potentially fatal
diseases. Provides an instant response but only
temporary as antibodies are not the body's own so
memory cells are not created. E.g. tetanus - injection
of antitoxins given.

11. Vaccine Preventable Diseases
Vaccine preventable diseases includes:
• Poliomyelitis
• Neonatal Tetanus
• Measles
• Diphtheria
• Pertussis (Whooping Cough)
• Hepatitis-B
• Childhood Tuberculosis
• These diseases are preventable and can be eradicated like
Smallpox, as very safe & effective vaccines are available.

12. Vaccine
•A vaccine is a biological preparation that improves
immunity to a particular disease.
•A vaccine typically contains an agent that resembles
a disease-causing microorganism, and is often made
from weakened or killed forms of the microbe, its
toxins or one of its surface proteins.

13. Types of vaccines
•Live vaccines
•Inactivated (killed vaccines)
•Toxoids
•Cellular fraction
• Combinations

14. Types of vaccines
Live attenuated vaccines are produced by modifying
a disease-producing virus or bacteria in a laboratory.
The resulting vaccine organism retains the ability to
replicate (grow) and produce immunity, but usually
does not cause illness. Live attenuated vaccines
include BCG, Oral polio, Measles, Mumps and Rubella
etc.

15. Types of vaccines
Inactivated vaccines can be composed of either whole
viruses or bacteria, or fractions of either:
• Fractional vaccines are either protein-based or
polysaccharide-based.
• Protein-based vaccines include toxoids (inactivated
bacterial toxin), and subunit or subvirion products.
• Most polysaccharide-based vaccines are composed
of pure cell-wall polysaccharide from bacteria.

16. Types of vaccines
₋ Conjugate polysaccharide vaccines are those in
which the polysaccharide is chemically linked to a
protein. This linkage makes the polysaccharide a
more potent vaccine.
• Inactivated vaccines includes pertussis, influenza,
hepatitis B etc.

17. Types of vaccines
Toxoids
Certain organism produce exotoxins e.g. diphtheria
and tetanus bacilli. The toxins produce in these
organisms are detoxicated and used in the
preparation of vaccines. The antibody produced
neutralize the toxic moiety produced during infection
rather then act upon the organism. These vaccine are
safe and effective.

18. Types of vaccines
Cellular Fraction
Some vaccine are prepared from extracted cellular
fraction, e.g. meningococcal, vaccine from the
polysaccharide part of the cell wall, the
pneumococcal vaccine from the polysaccharide
contained in the capsule of the organism. These
vaccine are safe and effective.

19. Age of vaccination Type of vaccination Dose Mode of administration
At birth BCG 0.05 ml right deltoid; intradermal
OPV0 2 drops Oral
6 weeks
OPV-I
Pneumococcal-I
Rotavirus-I
Pentavalent-I
0.5 ml Oral
Front outer side of the thigh
muscle (intramuscular)
OPV1 2 drops Oral
10 weeks
Pneumococcal-II
Rotavirus-II
Pentavalent-Il
0.5 ml Front outer side of the thigh
muscle (intramuscular)
OPV-II 2 drops Oral
14 weeks Pneumococcal-III
IPV I
Pentavalent-III
0.5 ml Front outer side of the thigh
muscle (intramuscular)
OPV-III 2 drops Oral
9 months MR-I Typhoid
IPV – II
0.5 ml Upper right arm; subcutaneous
15 months MR-II 0.5ml Upper right arm; subcutaneous
EPI Schedule

20. EPI Schedule
At Birth
Vaccine Disease Type of vaccine Dose Rout of
administration
BCG TB Live attenuated
variant
0.01ml intradermal
OPV (0) Polio Live
Attenuated
2drops Oral

21. EPI Schedule
06- weeks
vaccine Disease Type of Vaccine Dose Rout of vaccine
OPV (1) polio Live attenuated 2 drops Oral
HiB Hib disease Polysaccharide
conjugate
0.5ml IM thigh
HBV Hepatitis B Recombinant,
yeast
Derived HBs
antigen
0.5ml IM thigh
DPT Diphtheria
Pertussis
Tetanus
Toxoid
Toxoid
Killed Pertussis
0.5 IM thigh

22. EPI Schedule
10 weeks
Vaccine Disease Type of vaccine Dose Rout of
administration
OPV(2) Polio Live attenuated 2 drops Oral
HiB Hib disease Polysaccharide
conjugate
0.5mal IM thigh
DPT Diphtheria
pertussis
Tetanus
Toxoid
Toxoid
Killed pertussis
0.5ml IM thigh

23. EPI SCHEDULE
14 weeks
Vaccine Disease Type of vaccine Dose Rout of
administration
OPV (3) Polio Live attenuated 2 drops Oral
HiB Hib disease Polysaccharide
conjugate
0.5ml IM thigh
HBV Hepatitis B Recombinant,
yeast
Derived HBs
antigen
0.5ml IM thigh
DPT Diphtheria
pertussis
Tetanus
Toxoid
Toxoid
Killed pertussis
0.5ml IM thigh

24. 09 month
Vaccine The
Disease
Type of
the
Vaccine
Dose Mode of
administration
Measles Measles All
Live
attenuated
0.5ml Subcutaneous

25. 15 month
Vaccine The
Disease
Type of the
Vaccine
Dose Mode of
administration
MMR Measles
Mumps
German
Measles
All
Live
attenuated
0.5ml Subcutaneous

27. Contraindications
In very few conditions, vaccination is contraindicated
• All vaccines are contraindicated in those who have had:
• An anaphylactic reaction to a previous dose
• Inactivated or killed vaccines are contraindicated in people
with known allergy to vaccines.
• Live vaccines are contraindicated in pregnancy and in
those who are on systemic steroid therapy or
immunosuppressed for any reason.
• Avoid during acute febrile illnesses.

28. Action for reactions after Immunization
•Explain to mother that the reaction after BCG
vaccination should be small lump or papule which
will appear in the third or fourth week, will form
puss in sixth week this is normal.it should not be
touch or scratched. Small scar will appear at the end
of 10 t0 12 weeks.
•Explain some of the more common reactions such
as fever, mild swelling and pain at the vaccination
spot.

29. Cold chain
•“Cold chain” refers to the process used to maintain
optimal conditions during the transport, storage,
and handling of vaccines, starting at the
manufacturer and ending with the administration of
the vaccine to the client.
•The optimum temperature for refrigerated vaccines
is between +2°C and +8°C. For frozen vaccines the
optimum temperature is -15°C or lower.

30. Manufacturer
Air port
Central
vaccine store
Regional store
District
store
Health Center
Immunization
staff
The level of cold chain

31. The administrative levels of cold chain according to the duration
of the storage and temperature required to keep the vaccine
potent
The
administrative
level
Storage
period
temperature The vaccine
Central and
regional store
Maximum
three month
-20 to 30 C OPV, Measles,
MMR, BCG
+2 to +8 C DPT, DT, TT, HB,
HiB
Districts stores
and local
immunization
center
Maximum
three month
0 C to 8 C OPV, Measles,
MMR, BCG
+2 to + 8 C DPT, DT, TT, HB,
HiB

32. 32
Components of the cold chain
The equipment
and tool
Procedure
Staff

33. Equipment and tools
• Refrigerator
• Cold boxes
• Vaccine carriers
• Ice Packs
• Cards
• Register

34. Tools for monitoring the cold
chain
•Cold chain monitor card
•Freeze watch indicator
•Cold chain refrigerator graph
•Vaccine vial monitors
•Shak test

35. Care of refrigerator
• Placed in the coolest place of the health centers away from
sunlight
• Well ventilated and adequate air circulation around it
• Kept locked and open only when necessary
• Defrosted regularly
• Ice packs are kept in the freezer
• Record temperature two time daily
• Do not place food in the freezer
• The temperature chart should stuck on the door out side the
refrigerator
• Diluent should be kept on the lowest shelf

38. Vaccine Vial Monitor

39. Nurses Role During Immunization
• An estimation of beneficiaries
• Identifying non participants and dropouts
• Meet with the community
• Identification of influence
• Identify communication site
• Schedule for immunization session
• Organize immunization session

40. WHAT IS Health?
• “A state of complete physical,
mental, and social well-being
and not merely the absence of
disease or infirmity”
WHO. (1948).
40

41. DISEASE
• The term “disease” literally means “without ease” (without
easiness).
• The simplest definition of disease is; “any deviation from
normal functioning or state of complete physical or mental
well being”.
• The Oxford English Dictionary defines disease as “a
condition of the body or some part or organ of the body in
which its functions are disrupted or deranged”.
41

42. Tropical Diseases
Tropical disease, any disease that is indigenous to tropical or
subtropical areas of the world or that occurs principally in those areas.
Examples of tropical diseases include malaria, cholera, Chagas
disease, schistosomiasis, yellow fever, African trypanosomiasis
and dengue.
The term tropical diseases encompasses all diseases that
occur principally in the tropics & it covers all CDs NCDs,
genetic disorders, and disease caused by nutritional
deficiencies or environmental conditions (such as heat,
humidity, and altitude) that are encountered in areas that lie
between, and alongside, the Tropic of Cancer and Tropic
of Capricorn belts.

43. Tropical Diseases
Tropical Diseases
It encompasses all diseases that occur in the tropics and the
term refers to infectious diseases that thrive in hot and
humid conditions.
The main reasons that infectious diseases spread in such
regions are due to both environmental and biological factors
that support high levels of biodiversity of pathogens and
vectors, and hosts.
Social factors also play a role as to why the infections spread
because efforts to control these diseases are undermined.

44. Most common tropical diseases ?
The following are the most common types of tropical diseases:
Tuberculosis – this infection represents the leading cause of death
associated with infectious diseases globally, especially in developing
countries and in immigrants from these countries. It is a chronic
bacterial disease caused by Mycobacterium tuberculosis. The disease
develops slowly and the illness is prolonged. Symptoms of TB include
coughing for three weeks or more, coughing up blood and chest pain.
Malaria – this is an infectious, hematologic disease caused by a
Plasmodium parasite. It is a life-threatening mosquito-borne disease
transmitted to humans through the bite of the Anopheles mosquito.
Symptoms include shaking chills, high fever, sweating, headache, nausea
and vomiting.
Peru.

45. Most common tropical diseases ?
Diarrhoea
• Rotavirus is one of the most common diseases that can affect young
children.
• Rotavirus is found in countries such as Bangladesh, Somalia, Rwanda and
Nepal.
• More serious epidemics can cause dysentery due to the bacteria Shigella
dysenteriae.
• Symptoms include watery diarrhoea, fever, vomiting and abdominal pain.

46. Most common tropical diseases ?
Leishmaniasis
This disease is caused by parasites of the Leishmania type and is spread through
the bite of certain types of sandflies.
It can be present in three main forms.
1. The first, visceral leishmaniasis is the most deadly if left untreated in over
95% of cases. Most cases occur in Brazil, East Africa and South-East Asia.
Symptoms include fever, weight loss, anemia and enlargement of the spleen
and liver.
2. The most common type is cutaneous leishmaniasis, which causes skin lesions,
mainly ulcers on exposed parts of the body. These can leave lifelong scars and
a person with a serious disability.
3. The third strain of leishmaniasis is Mucocutaneous leishmaniasis, which leads
to partial or total destruction of mucous membranes of the nose, mouth and
throat. This is usually contracted in Bolivia, Brazil, Ethiopia and Peru.

47. TYPES OF DISEASES
TYPES OF DISEASES
COMMUNICABLE
DISEASES
NON-COMMUNICABLE
DISEASES

48. Non-Communicable Diseases (NCDs)
• Non-communicable diseases
(NCDs), also known as chronic
diseases, are not passed from
person to person.
• They are of long duration and
generally slow progression.
• The four main types of non-
communicable diseases are:
48

49. Communicable Disease
• A communicable disease is one that is transmitted to a
person from an infected person, animal, or non-living source.
• Disease transmissible (as from person to person) by direct
contact with an affected individual or the individual's
discharges or by indirect means (as by a vector)
49

50. Classification of Diseases by Duration
• Acute Diseases
 Communicable:
• Examples: Common cold,
pneumonia, mumps,
measles, pertussis, typhoid
fever, flu
 Non-communicable:
• Examples: Appendicitis,
poisoning, trauma
• Chronic Diseases
Communicable:
• Examples: tuberculosis, AIDS,
Hepatitis B
Non-communicable
• Examples: Diabetes,
Coronary heart disease,
Rheumatoid Arthritis
50

51. Communicable Disease
51

52. Communicable Disease
• Communicable diseases make a huge contribution to
the burden of disease, disability and death globally
and particularly in low- and middle-income
countries.
• The six leading groups of infectious diseases (acute
respiratory infections, HIV/AIDS, diarrheal diseases,
tuberculosis, malaria and measles) together cause
over 11 million deaths worldwide every year.
52

53. Communicable Disease
•By contrast, at least 1 billion people are affected
by the so-called ‘neglected tropical diseases’,
including leprosy and schistosomiasis, and/or by
intestinal parasites such as tapeworm and
hookworm.
53

54. 54

55. Epidemiological Classification
• Based on the mode of transmission of the infectious
agent, communicable diseases can be classified as:
1. Food & Water borne diseases: transmitted by the
ingestion of contaminated food & water.
• For Example: acute gastro-enteritis, bacillary dysentery,
giardiasis, amoebiasis, cholera, enteric fevers,
poliomyelitis, viral hepatitis.
55

56. Epidemiological Classification
2. Airborne diseases: transmitted through the air.
• For Example: Acute respiratory infections,
Meningitis (bacterial and fungal), Tuberculosis
3. Vector-borne diseases: transmitted by vectors,
such as mosquitoes and flies.
• For Example: Dengue fever, Malaria,
Schistosomiasis, Leishmaniasis.
56

57. Epidemiological Classification
4.Sexually transmitted diseases: Transmitted through
sexual contact.
• For example: HIV/AIDS, Syphilis, Gonorrhea
5.Zoonosis: Infectious disease that is transmissible
under natural conditions from vertebrate animals to
humans.
• For Example: brucellosis, rabies, tetanus.
57

58. Epidemiological Classification
•Contact Diseases: Infectious diseases resulting
from direct or indirect contact.
•For Example: scabies, bedbugs, fungal skin
infections, acute bacterial conjunctivitis.
58

59. Patterns of Communicable Diseases
59

60. • The word sporadic means “scattered about”.
• A sporadic disease is one that occurs only
occasionally in a population (i.e., prevalence is zero).
• The cases are few and separated widely in time and
place that they show no or little connection with each
other, nor a recognizable common source of infection
e.g. meningococcal meningitis, tetanus….
60
Sporadic Disease

61. • An endemic disease is one that is always present in
a population at a predictable rate (i.e., never zero
prevalence).
• For example, malaria in Pakistan.
61
Endemic Disease

62. Epidemic
• ( Epi= upon; Demos= people)
• This is the occurrence of disease cases at a
frequency that is higher than the normal for the
population in a give period of time.
• Epidemics can occur upon endemic states too.

64. Pandemic and Exotic
• Pandemic Disease:
An epidemic usually affecting a large proportion of
the population, occurring over a wide geographic area
such as a section of a nation, the entire nation, a
continent or the world, e.g. Influenza pandemics.
• Exotic diseases
These are those which are imported into a country in
which they do not otherwise occur.

65. Dynamics of Disease Transmission
(Chain of Infection)
65

66. Chain of Infection
• Transmission is a process in which several events happen
one after the other in the form of a chain.
• Hence, this process is known as a Chain of
Infection/Transmission.
66

67. Chain of Infection
• Six factors involved in the
chain of infection include;
1. Infectious agent,
2. Reservoir,
3. Route of exit,
4. Mode of transmission,
5. Route of entry, and
6. Susceptible host
67

68. Infective Agent
• An infective agent is an organism that will
cause an infection/ disease.
i. Virus
ii. Bacteria
iii. Fungus
iv. Parasites
68

69. Reservoir
•Reservoir/ Source: The place where the infectious
agent is normally present before infecting a new
human.
•This could be infected person, animal, or non-living
objects (air, water, food, soil).
•Humans and animals which serve as reservoirs for
infectious agents are known as infected hosts.
69

70. Types of Reservoirs
Reservoir
Human
reservoir
Animal
reservoir
Non-living
reservoir

71. Host
Host refer to the susceptible population
• Some people are more prone to infections . This
may be due to various factors such as;
i. Age group e.g. children, older age group
ii. Lack of previous contact with the disease
iii. Immuno-suppressive illnesses such as AIDS
iv. Malnutrition
v. Drugs that a person may be consuming.
71

72. Mode of Transmission
• Mode of transmission of disease as mechanisms by which
an infectious agent is transported from reservoir to
susceptible human host.
• The main modes of transmission include:
1. Direct Transmission
2. Indirect Transmission
72

73. Mode of Transmission
• Direct Transmission
It involves the spread of microbes from person-to-person
via body contact
OR
• Immediate transfer of the disease agent by direct contact
between the infected and the susceptible individuals
73

74. Mode of Transmission
• Occurs through such acts as
touching, biting, kissing, sexual
contact or by direct projection
(droplet spread) by coughing or
sneezing within a distance of
one meter
• Examples of diseases for which
transmission is usually direct
are AIDS, syphilis, gonorrhea,
and the common cold
74

75. Mode of Transmission
• Droplet transmission occurs
when microbes trapped in mucus
and saliva are released from the
mouth or nose as a result of
speaking, coughing or sneezing,
and travel less than 1 meter to
contact the next host.
• E.g; Acute bronchiolitis,
Pneumonia, seasonal influenza
75

76. Indirect Transmission
•May be one of three types:
1. Air-borne,
2. Vehicle-borne
3. Vector-borne

77. Indirect Transmission
• Air-borne transmission -- transmission of microbial
aerosols to a suitable port of entry, usually the
respiratory tract.
o Microbial aerosols are suspensions of dust or droplet
nuclei made up wholly or in part by microorganisms -- may
be suspended and infective for long periods of time.
o Examples of air-borne diseases include Tuberculosis,
Influenza, Histoplasmosis

78. Indirect Transmission
•Vehicle - Borne Transmission - contaminated
materials or objects (fomites) serve as vehicles,
nonliving objects by which communicable agents are
transferred to a susceptible host.
o The agent may or may not have multiplied or developed
on the vehicle
o Examples of vehicles include toys, handkerchiefs, soiled
clothes, bedding, food service utensils, and surgical
instruments

79. Indirect Transmission
Also considered vehicles
are;
water, milk, food (Food-
borne / water-borne
transmission )
For Example: Bacillary
dysentery, Cholera,
Hepatitis A & Hepatitis E
79

80. Indirect Transmission
Biological products such as
blood, serum, plasma,
organs and tissues
For Example: Hepatitis B &
C, HIV/AIDS
80

81. Indirect Transmission
•Vector-borne transmission -- disease transfer by
a living organism, such as a mosquito, fly, or tick.
Transmission may be;
•Mechanical - via the contaminated mouth parts
or feet of the vector,
•Biological - involving multiplication or
developmental changes of the agent in the
vector before transmission occurs

82. Indirect Transmission
• In Mechanical transmission, multiplication and
development of the disease agent does not usually
occur in vector
• For example; organisms that cause dysentery, polio,
cholera, and typhoid fever have been isolated from
such insects as cockroaches and house flies and could
presumably be deposited on food prepared for human
consumption

83. Indirect Transmission
• In Biological Transmission , multiplication and/or
developmental changes of the disease agent occur in
the vector before transmission occurs
• Biological transmission is much more important than
mechanical transmission in terms of its impact on
public/community health
• Examples of biological vectors include mosquitoes,
fleas, ticks, lice, flies and other insects

84. Vector-Borne Transmission
Biological vectors Mechanical vectors

85. Indirect Transmission
• Mosquitoes are extremely important vectors of
human diseases
• For example they transmit the viruses that cause
yellow fever and dengue fever as well as 200 other
viruses -- they also transmit malaria, which infects 100
million people in the world each year (most in tropical
areas), killing at least 1 million of them each year
• Ticks are another important biological vector,
transmitting Rocky Mountain spotted fever, relapsing
fever, and Lyme disease

86. Mode of Transmission
• Vertical Transmission:
• From the pregnant mother to
the foetus
• For Example: Congenital rubella
Syndrome, Congenital syphilis
86

87. Factors that Caused Increased CD`s Prevalence
1. Explosive population growth
2. Spreading Poverty
3. Global Warming
4. Urban Migration
5. New Pathogens
6. Increased international trade & travel
7. Loss of national border laws
8. Rise of antibiotic resistant pathogens
87

89. Prevention and Control of CDs
•Prevention refers to measures that are applied to
prevent the occurrence of a disease.
•Control refers to measures that are applied to
prevent transmission after the disease has
occurred.
89

90. Prevention and Control of CDs
1. The principles of control and prevention should
be directed towards:
2. Attacking the source (reservoir) of the disease
causing organism
3. Interrupting the transmission cycle
4. Protecting the susceptible host.

91. Break the Chain of Infection

92. Prevention and Control of CDs
1. Measures targeting the reservoir of infection:
•The prevention and control measures undertaken
depend on the type of reservoir.
i. Human
ii. Animal
iii. Non-living
92

93. Measures Targeting the Reservoir of
Infection
•Identifying and treating cases as early as possible.
•There are two ways to identify an infected individual:
1. Screening
2. Diagnosis and treatment of patient presenting with
clinical sign and symptoms of diseases.
93

94. Isolation
Isolation = Separation, for the period of communicability,
of infected persons or animals from others so as to prevent
the direct or indirect transmission of the communicable
agent to a susceptible person/host
• It is not indicated for every infection, but it is important to isolate
people with severe and easily transmitted diseases.
• The isolation period lasts until the risk of transmission from the
infected person has reduced or stopped.
94

95. Quarantine
•Quarantine is limitation of freedom of
movements of healthy persons/animals exposed
to communicable disease for at least the longest
incubation period of a disease

96. Notification/Reporting
•Cases of communicable diseases should be
reported to a nearby health centre or Health
Office periodically, using the national surveillance
guidelines.
96

97. Measures Targeting the Reservoir of Infection
• Animal Reservoirs:
• When infected animals are the reservoir involved in the
transmission of communicable diseases, different
measures can be undertaken against them.
• The type of action depends on the animal reservoir, and
ranges from treatment to destroying the infected animal,
depending on the usefulness of the animal and the
availability of treatment.
97

98. Measures Targeting the Mode of
Transmission
2. Measures targeting the mode of transmission;
• The measures that can be applied to interrupt transmission of
infectious agents in water, food, other vehicles and by vectors
include;
• Vector control
• Safe water supply
• Food Hygiene
• Screening of blood before transfusion
98

99. Safe Water Supply
• Measures to prevent transmission of infection due to
contaminated water include;
i. Boiling the water,
ii. Adding chemicals like chlorine
iii. Use of physical agents - filtering water through a
box of sand, or pouring it through several layers of
fine cloth.
iv. Prevent fecal contamination of water by protecting
water sources & through proper use of latrines.
99

100. Food Hygiene
• Measures to prevent transmission in contaminated food
include:
i. Washing raw vegetables and fruits,
ii. Washing household utensils for cooking, eating and
drinking
iii. Boiling milk, and cooking meat and other food items
thoroughly before eating.
iv. Prevent fecal contamination by hand washing and
proper use of latrines.
100

101. Vector Control
•Measures against vectors include preventing
breeding of vectors through:
i. Proper disposal of faeces and other wastes,
ii. Eradication of breeding sites
iii. Dis-infestation
iv. Disinfection
101

102. Vector Control
• Disinfestation is the procedure of destroying or
removing small animal pests, particularly arthropods
and rodents, present upon the person, the clothing, or
in the environment of an individual, or on domestic
animals.
• Disinfestation is usually achieved by using chemical or
physical agents, e.g. spraying insecticides to destroy
mosquitoes, and removing lice from the body and
clothing.
102

103. Disinfection
• Disinfection is the procedure of killing most, but not all,
infectious agents outside the body of host.
103

104. Types of Disinfection
1. Concurrent: Microorganism are destroyed as soon as
they are released from the body.
• It is technique applied at the bed side of the patient
during the course of illness. Consists of disinfection of
urine, feces, vomit, clothes, sputum etc
2. Terminal:
• It is done at termination of illness after the patient has
been removed by death or recovery.
• For example: sterilization of bed and room of the
patient.

105. Types of Disinfection
3. Prophylactic disinfection:
• It is done before start of the disease.
• For example; pasteurization of milk, chlorination of
water

106. Disinfection
•Disinfectants are the Chemicals used for
destruction of microorganism.
Agents used of disinfection:
1. Natural agent: Sunlight and air
106

107. Disinfection
2. Artificial agents:
i. Physical agents e.g.
burning, hot air, boiling,
autoclaving, radiation etc.
107
ii. Chemical agents
e.g. Phenol, alcohol,
formaldehyde,
insecticide,
deodorants etc.

108. Sterilization
• Sterilization involves destruction of all forms of micro-organisms
by physical heat, irradiation, gas or chemical treatment.
• The difference between disinfection and sterilization is that
disinfection kills most, but not all, micro-organisms.
• Disinfection can be done using alcohol, chlorine, iodine or heating
at the domestic level;
• whereas sterilization has to use extreme heating, irradiation or
strong chemicals like a high concentration of chlorine.
108

109. Measures Targeting the Susceptible Host
• The susceptible host may be protected by one of
the following methods:
1. Specific measures:
• Immunization/Vaccination
• Chemoprophylaxis
109

110. Vaccination
• Vaccination refers to
administration of vaccines to
increase the resistance of the
susceptible host against specific
vaccine-preventable infections.
• For example, measles
vaccination helps to protect the
child from measles infection,
and BCG vaccination gives some
protection from tuberculosis
110

111. 111

112. Chemoprophylaxis
• Chemoprophylaxis refers to the drugs given to
exposed and susceptible hosts to prevent them from
developing an infection.
• For example, individuals from non-malarial areas
who are going to a malaria endemic area can take a
prophylactic drug to prevent them from developing
the disease if they become infected with malaria
parasites from a mosquito bite.
112

113. Susceptible Host
2. Non specific measures:
• Maintaining a healthy lifestyle (Proper nutrition
and physical activity)
• Limiting exposure to reservoirs of infection
• Health education
• Surveillance and control

114. Non Specific Measures
•Limiting exposure to reservoirs of infection:
i. use of insecticide treated nets (ITNs) at night,
insect repellants and wearing protective clothing
to prevent diseases transmitted by insect
vectors.
ii. Condom use to prevent transmission of HIV and
other sexually transmitted infections (STIs).
iii. Keeping personal hygiene
114

115. Models/Theories of Disease Causation
1. Germ theory
2. Epidemiologic Triad
3. Wheel of Causation
4. Web of Causation
115

116. 116

117. 117
Web of Causation

118. Web of Causation
• McMahon and Pugh forwarded the theory of
“epidemiological web of causation”, wherein the
various factors (e.g.
hypercholesterolemia,smoking,hypertension) are
like an interacting web of a spider.
• Each factor has its own relative importance in
causing the final departure from the state of health,
as well as interacts with others, modifying the effect
of each other.
118

119. The Wheel of Causation
• Wheel theory:
• As medical knowledge advanced, an additional aspect
of interest that came into play is the comparative role
of “genetic” and the “environmental” (i.e. extrinsic
factors outside the host) factors in causation of
disease.
• The “triad” as well as the “web” theory does not adequately cover
up this differential.
• To explain such relative contribution of genetic and
environmental factors, the “wheel” theory has been
postulated (Mausner & Kramer, 1985) .
119

120. The Wheel of Causation
• The theory de-emphasizes the
agent as the sole cause of
disease.
• The theory visualizes human
disease in the form of a wheel,
which has a central hub
representing the “genetic
components” and the peripheral
portion representing the
“environmental component”.
120

121. The Wheel of Causation
• Like any wheel, the outer part
(environmental component) has
spokes (3 in this model) and the
environmental component is
thus divided into 3 sub
components;
1. Physical
2. Biological
3. Social
121

122. Epidemiological Triad
• The best known, but most
dated model of disease
(communicable) is the
“Epidemiologic Triad”.
• According to this model
disease results from an
interaction among;
i. Agent
ii. Host
iii. Environment
122

123. Epidemiological Triad
1. Agent — cause of the disease
2. Host — Living things, usually humans or animals,
which are exposed to and harbor a disease.
3. Environment —external factors that cause or allow
disease transmission.
123

124. Epidemiological Triad
• The mere presence of agent,
host and environmental
factors is not sufficient to
start the disease in man.
• It is the interaction of these
factors; that is required to
initiate the disease process in
man.
124

125. Epidemiological Triad: Examples
125

126. Epidemiological Triad
126

127. Epidemiological Triad
127

128. Disease Agents
• Biologic (Infectious agents,
insect and animal allergens)
• Chemical (Air pollutants, toxic
wastes, pesticides)
• Physical (Noise, radiation, heat,
cold, electricity)
128

129. Agents
• Mechanical Agents (Exposure to
chronic friction & other
mechanical forces may result in
crushing, tearing, sprains,
dislocation& even death)
• Social (poverty, access to health
care, social isolation,
deprivation)
129

130. Host Factors
•Host factors refers to the factors that make an
individual vulnerable to the specified illness. The
host factors include;
i. Biological characteristics
ii. Demographic characteristics
iii. Socioeconomic characteristics
iv. Lifestyle factors
130

131. Environmental Factors
• The environment of man is divided into three components;
1. Physical
2. Biological
3. Psychosocial
131

132. Epidemiological Triad
• In the case of many communicable
diseases, the agent can only reach
the host via a third party, called the
vector
• Vector is a vehicle that some of
disease causing organism require
to be move from one point to the
other, some require it to complete
their developmental cycle
132

133. Epidemiological Triad
• For example: mosquito in
transmission of malaria.
• Not all communicable
diseases require a vector
for transmission.
133

134. 134

135. Epidemiological Triad
• The “epidemiological triad theory” was very
effectively used by Leavel and Clark in explaining
the natural history of disease and levels of prevention
for obviating such departures from the state of health.
• But it could not explain the causation of non
communicable diseases like IHD or road accidents.
135

136. References
• Basavanthappa, B. T. (2008). communnity health nursing (2nd ed.).
india newdehli: jaypee brothers medical publisher (p) Ltd
• Cochi S, Bilous J, Cutts F. “Vaccination Programs in Developing
Countries.” Chapter 55
• Communicable Diseases HEAT Module
• Centre for disease control and prevention (CDC).
• Immunization Against Infectious Disease - "The Green Book".
Chapter 6 Contraindications and special considerations (January
2013)
• Introduction to Communicable Diseases (include epidemiology)
• Website: http://clinicalgroupbncm.blogspot.com/
• Website; http://www.cdc.gov/ophss/csels/dsepd/SS1978/Lesson1/Section10.html
136

137. Thank you