Chapter 14 Principles of Disease and Epidemiology Lecture 20 EXAM 3 STUDY GUIDE o Pathology o Etiology o Infection Define pathology etiology infection and disease is the scientific study of disease is the cause of disease is the invasion or colonization of the body by pathogenic microorganisms or all of the body is not functioning normally o Disease occurs when an infection results in any change from a state of health part Define normal transient microbiota and opportunistic infections o Normal microbiota are microorganisms that establish more or less permanent residence in the body colonize but that do not produce disease under normal conditions months and then disappear a healthy person but may do so in a different environment may be present in the body for several days weeks or ordinarily do not cause disease in their normal habitat in o Opportunistic infections o Transient microbiota Compare commensalism mutualism and parasitism Commensalism only one benefits other is not harmed most microbes in our body Mutualism Both host and parasite could benefit from each other hermit crab Parasitism host is harmed microbes take advantage virus Understand Koch s postulates and the exceptions o Used the prove the cause of an infectious disease The same pathogen must be present in every case of the disease The pathogen must be isolated from the disease host and grown in pure culture The pathogen from the pure culture must cause the disease when it is isolated into a healthy susceptible laboratory animal The pathogen must be isolated from the inoculated animal and must be shown to be the original organism Exceptions Some microbes has unique culture requirements the bacterium causing syphilis has never been cultured on artificial media EXCEPTIONS Treponema pallidum causes syphilis but cant be plated Mycobacterium leprae causes leprosy and has never been grown on artificial media Some cant be plated some cause several disease conditions some pathogens cause different diseases also it would mean some people could be inoculated with infectious diseases Sometimes several different pathogens cause the same signs and symptoms Some pathogens cause several different disease conditions Pathogens that cause disease in humans and no other known host AIDS Some take years to develop HPV takes years to cause cancer due to mutations that must take place Understand predisposing factors for disease o A predisposing factor is one that makes the body more susceptible to a disease and may alter the course of the disease These are gender genetic background climate and weather inadequate nutrition fatigue age environment habits lifestyle occupation preexisting illness chemotherapy and emotional disturbances Define reservoir of infection o Reservoir of infection continual source of the disease organisms living organism or inanimate object that provides a pathogen with adequate conditions for survival and multiplication and an opportunity for transmission human animal or nonliving o Human Reservoirs can harbor pathogens and transmit to others Carriers have unapparent infections for which no signs or symptoms are ever exhibited Play an important role in the spread of diseases such as AIDs diphtheria typhoid fever hepatitis gonorrhea amoebic dysentery and streptococcal infections o Animal Reservoirs Both wild and domestic Diseases transmitted from animals to humans called zoonoses o Rabies lyme disease o Direct contact with infected animal o Directed contact with domestic animal waste o Contamination of food and water o By air hides fur or feathers o Infected animal products food o Insect vectors o Nonliving Reservoirs Soil and water o Fungi ringworm o Gastrointestinal diseases o Botulism tetanus Food that has been improperly stored or prepared salmonella Explain three methods of disease transmission Three principal routes contact vehicles vectors o Contact Transmission is the spread of an agent of disease by direct contact o Direct contact transmission indirect contact or droplet transmission agent by physical contact between its source and a susceptible host No intermediate object person to person is the direct transmission of an Touching kissing sexual intercourse Respiratory tract infections staph infections hepatitis A measles scarlet fever STIs AIDS o Indirect when the agent if disease is transmitted from its reservoir to a susceptible host by means of a nonliving object fomite Tissues towels bedding drinking cups toys money contaminated syringes AIDS Tetanus o Droplet microbes are present in droplet nuclei that travel only short distances Coughing sneezing laughing talking Not regarded as airborne Influenza pneumonia pertussis Vehicles transmission by an inanimate reservoir o Water food air o Blood other body fluids drugs o Waterborne untreated or poorly treated sewage Cholera o Foodborne incompletely cooked poorly refrigerated unsanitary conditions Food poisoning tapeworm o Airborne droplet nuclei in dust more than 1 meter Discharged from mouth and nose Measles tuberculosis Dust particles fungi spores Vectors animals that carry pathogens from one host to another o Arthropods o Mechanical transmission passive transport of the pathogen on the insect s feet or other body parts Contacts with host s food Houseflies Typhoid fever dysentery o Biological Transmission an active process Arthropod bites and infected person or animal and ingests some of infected blood fleas ticks mosquitoes Pathogens reproduce in the vector and increase the number of pathogens Some parasites reproduce in gut of arthropod passed with feces Defecates or vomit while biting potential host parasite can enter wound If parasites migrate to salivary glands of arthropod and directly injected into bite Define epidemiology o Epidemiology is the science that studies when and where diseases occur and how they are transmitted in populations Know the contribution of John Snow Ignaz Semmelweis and Florence Nightingale Epidemiology science that studies when and where diseases occur and how they are transmitted in populations o Relationship between human and agent o Epidemics o Occurrence distribution control and prevention John Snow mapped the occurrence of cholera in London o Concluded that contaminated water from the Broad Street pump was the source of the epidemic Ignas Semmelweis showed that hand washing decreased the incidence of perpetual fever o Mortality rate of babies delivered by medical students who had spent their morning dissecting
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