Chapter 14 Lecture Outline-1 PDF

Chapter 14 Principles of Disease and Epidemiology 1 Pathology, Infection and Disease Pathology - the study of disease studying the relationship between the pathogen and host the origin Etiology - the study of the cause of a disease due to a causative agent (pathogen) mechanism Pathogenesis - the dev...

Chapter 14 Principles of Disease and Epidemiology 1 Pathology, Infection and Disease Pathology - the study of disease studying the relationship between the pathogen and host the origin Etiology - the study of the cause of a disease due to a causative agent (pathogen) mechanism Pathogenesis - the development of disease attachment bypathogen sometimes Infection invasion or colonization of the body by pathogens can l ead to a disease, immune system can prevent the disease Disease - an abnormal state in which body is not performing normal functions 1. Infectious disease involve a pathogen transmitted from host to host (could be human to human, animalto human) 2. Non-infectious disease ex: autoimmune disease, cancer, diabetes etc Casil l as 2 Normal Microbiota Normal microbiota resident microbes not cause harm to host Microbes that are always present in/on the human host does ifN.M remain in certain area. temporary Transient microbiota Microbes that take-up temporary residence Remain in the body for only hours to months Where in/on the human body would you expect to find transient microbiota? SKIN, because skin sheds, you wash your hands, take shower 3 Microbe and Host Relationships Symbiosis - relationship between microbe and the host normalmicrobiota Host doesnt benefit, host is not harm Figure 14.2 E.Col i -doesnt harm host, makes Vitamin K not normalmicrobiota ALW AYS invol ves pathogen obl igate intercel l ul ar parasites -Virus 4 Rul es/Conditions Koch’s Postulates Establ ished Germ Theory-specific pathogen causes specific disease, with specific signs and symptoms. Four criteria designed to establish a causative relationship causes between a microbe and a disease 1. The same pathogen must be present in every case of the disease. 2. The pathogen must be isolated from the diseased host and grown in pure culture. 3. The pathogen from the pure culture must cause the disease when it's inoculated into a healthy host (laboratory animal). 4. The pathogen must be isolated from the inoculated animal and must be shown to be the original organism. 5 Koch’s Postulates - Understanding Disease observed and ID Figure 14.3 6 Koch’s Postulates Koch's postulates are used to determine the cause of an infectious disease: specific pathogen  specific disease Based on this work, what “theory” did Koch support?  the Germ Theory of disease Exceptions to Koch's postulates: S.Pyoj enes can cause BOTH Scarl et Fever & Strepthroat 1. Some pathogens can cause several disease conditions 2. Some pathogens cause disease only in humans You cant use lab animals to investigate ou cant do some l ab workon some 3. Some microbes cannot grow on artificial media ypathogens 7 Classifying Infectious Diseases Symptoms Changes in body function that are felt by a patient Signs not observed, not measured. Ex: Pain, fatigue. Changes in a body that can be measured or observed Syndrome fever, weight, bl ood pressure, gl ucose l evel s. severalsets ofsigns and symptoms A specific group of signs & symptoms that accompany a disease Ex: Down syndrome, AIDS 8 Classifying Infectious Diseases INVOLVING PATHOGEN Communicable disease bypathogen A disease that is spread from one host to another Contagious disease = disease that is easily & rapidly spread Ex - Chickenpox (Airborne transmission)--you dont controlwhat air you breath, like you can controlwhat you eat. Noncommunicable disease bypathogen A disease that is not spread from one host to another Ex - Tetanus 9 Frequency Occurrence of A Disease Incidence (inside the prevalence) Number of people who develop a disease during a specific time period Prevalence is a l ong timel ine. Number of people who develop a disease at a certain time, regardless of when it first appeared; takes into account both old and new cases (Allcases, old and new) Indicates how widespread the disease is Which one of these terms refers to a larger time period? PREVALENCE 10 Incidence vs Prevalence 6 month 60 month 11 Occurrence of A Disease Sporadic disease Ex-Madcow disease Endemic disease diseases that are al ways there;Ex-Mal aria Disease that occurs only occasionally There is no pattern to the disease;happens randomly Disease constantly present in a population Epidemic disease (“outbreak”) Ex: Infl uenza Disease acquired by many people in a given area in a short time; spreads quickly Pandemic disease Worldwide epidemic gl obalscal el ike Covid, HIV/AIDS 12 Severity or Duration of A Disease Acute disease regarding symptoms everything is quickabout it.EX: Inl uenza Symptoms develop rapidly but the disease lasts only a short time Chronic/Persistent disease takes a l ong time for symptoms to devel op.EX: Tubercul osis Symptoms develop slowly Subacute disease Intermediate between acute and chronic Latent disease pathogen is dormant/inactive bc it hides in nervous system. Causative agent is inactive for a time, but then activates and produces symptoms EX: Shingles (herpes viridae, never goes away)-reactivation ofchickenpox 13 the human popul ation Herd Immunity Immunity where entire population is protected Accomplished through vaccinations How does this work? - If most of the population gets immunized  entire population is protected (including the healthy nonimmunized) Ex - Chickenpox, Measles no herd immunity Herd immunity 14 Extent of Host Involvement Local infection Typical l yskin infections.Pathogen doesnt spread. Pathogens are limited to a small area of the body Systemic (generalized) infection BC Pathogen spreads, usual l yspreads via bl oodstream. An infection throughout the body Which type of infection is worse? Systemic infection 15 Extent of Host Involvement Types of Systemic Infections Sepsis/Septicemia A) means "spread bybl ood" microbe or foreign particl e Uncontrollable spread of bacteria in the blood (blood infection)  types ofSepsis Life-threatening condition! 1 Bacteremia Bacteria in the blood 2 Toxemia Toxins in the blood 3 Viremia Viruses in the blood Mostl yel derl ypopul ation bc their immune system is weak 16 Extent of Host Involvement Primary infection Acute infection that causes the initial illness Ex - HIV weakens immune system so therefore a lot ofpathogens willtake advantage ofweakimmune system. Primaryinfection predisposes you to Secondaryinfection HIV l eads to AIDS-rel ated opportunistic infection. Secondary infection Caused by opportunistic pathogens after a primary infection Ex - AIDS-related opportunistic infections 17 Predisposing Factors Factors that make the body more susceptible to disease Examples: Gender Female= ovarian cancer;males = prostate cancer. Age Ex: Shingl es Lifestyle ex: IV drug users --cardio vascular disease Inherited traits Ex: Genetic diseases, diabetes Climate and weather Hot and rainywillhave a lot ofmosquitos = Malaria Poor sanitary conditions parasitic worm diseases 18 Development/Stages of Disease 1. Incubation period No signs & symptoms present; interval between initial infection and first signs & symptoms You are infected and the pathogen is stillgrowing 2. Prodromal period First time you start seeing symptoms Early, mild symptoms; short period after incubation 3. Period of illness Most severe signs & symptoms; start producing Ab’s 4. Peak of illness highest number ofmicrobes present can lead to period ofdecline, or death. Antibodytiter is the HIGHEST Leads to either: 1)period of decline or 2) death ofthe host 5. Period of decline Signs and symptoms subside pathogen number is decl ining 6. Period of convalescence/recovery patient feel s much better but the is highl yinfection asymptomatic/chronic carrier Body returns to its pre-diseased state 19 The Stages of Disease Peak of Illness THIS PIC ON EXAM Figure 14.5 (adapted figure) 20 Reservoirs of Infection where is the pathogen found (l ocation ofthe pathogen) Reservoir = continual sources of infection Three categories of reservoirs: 1. Human reservoirs can be broken down to Sick/Carrier OR Someone without symptoms Sick people or “carriers” with no signs & symptoms 2. Animal reservoirs pathogens that found in animals Ex: Bird fl u AKA Zoonotic transmission Zoonoses = ability to transmit pathogen from animals to humans 3. Non-living reservoirs non-l iving Contaminated inanimate objects: Ex -contaminated soil, air, water, food 21 pathogen from reservoir that transmitted to a host Transmission of Diseases Causative agents of disease can be transmitted from reservoir of infection to susceptible host ways oftransmission Three principal routes of disease transmission: 1. Contact transmission involves touching something that is contaminated 2. Vehicle transmission involves NON-LIVING thing 3. Vector transmission involves a LIVING thing 22 Contact Transmission touching something that is contaminated 1. Direct contact transmission - requires close association EX: Shaking Hands (touching) between infected person and susceptible host Im infected and touch an obj ect then you touch it and get infected 2. Indirect contact transmission - spreads to host by a contaminated door knob, spoons, contaminated non-living object called a fomite Ex: cel l phone etc 3. Droplet transmission - transmission via airborne droplets less than 1 meter Figure 14.6 23 Vehicle Transmission Transmission by a contaminated inanimate reservoir: 1. Airborne - transmission via airborne droplets more than 1 meter 2. Waterborne 3. Foodborne Figure 14.7 24 Vector Transmission creature l ike mosquitos, fl ees, rats.Theyhave pathogens either in them or Accomplished by arthropods loniving them Animals such as fleas, ticks, and mosquitoes Arthropods transmit disease by two general methods: 1. Mechanical vector transmission  Arthropod vector carries pathogen outside its body a fl yhas a pathogen on its feet, l ands on your  Called “passive transport” of pathogen Ex: food, you eat it and get the pathogen 2. Biological vector transmission  Arthropod vector supports life cycle of pathogen in its body  Pathogen transmitted via bites  Called “active transport” of pathogen 25 Healthcare-Associated Infections (HAIs) What is a HAI? An infection acquired in the hospital/clinical environment Affects 1 in 25 hospital patients 1.7 million per year infected; over 99,000 deaths (CDC 2020) Immuno- What are some common sources of HAIs? Improperly cleaned healthcare of pathogen settings Weakened immune status of the host immuno-compromised host Figure 14.9 - Chain of Infection Transmission of pathogens person to person transmission in medicalsetting 26 Healthcare-Associated Infections (HAIs) Common HAIs improper cl eaning of surgicalinstruments, skin etc Surgical-site infections ower respiratorytract infections Pneumonialcontaminated respiratorydevices C. difficile infections GItract infections---> pathogen Cl ostridium Difficil e Figure 14.10 - Principal Sites of Healthcare-Associated Infections 27 Microorganisms Involved in HAIs Skin cont.equipment 28 Emerging Infectious Diseases (EIDs) Contributing factors: Global travel Rapid urbanization Natural disasters Climate change Frequent gene mutations Developing drug resistance 29 Epidemiology rel ationship between popul ation and disease The study of where and when diseases occur and how they are transmitted in populations Al lcases added up -Prevel ance One year is Incidence Figure 14.11a 30 The Centers for Disease Control and Prevention (CDC) Collects & analyzes epidemiological information in the U.S. Morbidity number ofsickpeople  Number of people or incidence of a specific notifiable disease Mortality number ofdead people  Number of deaths from notifiable diseases Nationally notifiable infectious diseases  Diseases in which physicians are required by law to report occurrence to CDC 31 Al lSTD are national l y notifiabl e disease 32