Tropical Diseases and Immunization & TD.pptx

Immunization Lecture By : Mumtaz Ali Khan

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

2. Objectives Overview of expanded Expended programme for Immunization(EPI) in Pakistan. Review different types of immunity. Enlist vaccines preventable diseases. Explain the types of vaccines. Identify contraindications of vaccines. Tabulate vaccination schedule. Discuss the importance of cold chain cold chain. 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 P reventable D iseases 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. V accine 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

26. 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.

27. 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.

28. 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.

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

30. 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

31. 32 Components of the cold chai n The equipment and tool Procedure Staff

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

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

34. 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

35. Vaccine Vial Monitor

36. 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

37. 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

38. 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

39. Tropical Diseases T ropical 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.

40. 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.  

41. 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 .

42. 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.  

43. Most common tropical diseases ? Leishmaniasis   T his 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. 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. 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. 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.

44. TYPES OF DISEASES TYPES OF DISEASES COMMUNICABLE DISEASES NON-COMMUNICABLE DISEASES

45. 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

46. 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

47. 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

48. Communicable Disease 51

49. 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

50. 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

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52. Epidemiological Classification Based on the mode of transmission of the infectious agent, communicable diseases can be classified as: 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

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

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

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

56. Patterns of Communicable Diseases 59

57. 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 S poradic D isease

58. 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 D isease

59. 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.

60. 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.

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

62. C hain 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

63. Chain of Infection Six factors involved in the chain of infection include; Infectious agent, Reservoir, Route of exit, Mode of transmission, Route of entry, and Susceptible host 67

64. I nfective A gent An infective agent is an organism that will cause an infection/ disease. Virus Bacteria Fungus Parasites 68

65. 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

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

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

68. 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: Direct Transmission Indirect Transmission 72

69. 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

70. 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

71. 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

72. Indirect Transmission May be one of three types: Air-borne, Vehicle-borne Vector-borne

73. Indirect Transmission Air-borne transmission -- transmission of microbial aerosols to a suitable port of entry, usually the respiratory tract. 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. Examples of air-borne diseases include Tuberculosis, Influenza, Histoplasmosis

74. 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. The agent may or may not have multiplied or developed on the vehicle Examples of vehicles include toys, handkerchiefs, soiled clothes, bedding, food service utensils, and surgical instruments

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

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

77. 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

78. 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

79. 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

80. V ector-Borne T ransmission Biological vectors Mechanical vector s

81. 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

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

83. Factors that Caused Increased CD`s Prevalence Explosive population growth Spreading Poverty Global Warming Urban Migration New Pathogens Increased international trade & travel Loss of national border laws Rise of antibiotic resistant pathogens 87

84. 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

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

86. B reak the Chain of Infection

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

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

89. 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

90. 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

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

92. 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

93. Measures Targeting the Mode of Transmission 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

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

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

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

97. 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

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

99. Types of Disinfection 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 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.

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

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

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

103. 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

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

105. 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

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107. 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

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

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

110. Models/Theories of Disease Causation Germ theory Epidemiologic Triad Wheel of Causation Web of Causation 115

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112. 117 Web of Causation

113. 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

114. 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

115. 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

116. 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; Physical Biological Social 121

117. 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; Agent Host Environment 122

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

119. 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

120. Epidemiological Triad: Examples 125

121. Epidemiological Triad 126

122. Epidemiological Triad 127

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

124. 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

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

126. Environmental Factors The environment of man is divided into three components; Physical Biological Psychosocial 131

127. 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

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

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130. 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

131. 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

132. Thank you