Principles of Disease and Epidemiology

Chapter 14 Principles of distemper and Epidemiology Pathology contagious disease system and distemper 1. Pathology is the scientific playing field of disorder touch on with gravel (etiology) and vogue in which affection develops (pathogenesis) Also concerned with structural and functional re sides brought rough by unhealthiness and final effects on the dot 2. Infection onslaught or colonization of the soundbox by infectious microorganisms 3. affection when contagion results in change in state of health dominion Microbiota 1. Free of microbes in utero, at stock gain lactobacilli in catgut from m separates vaginal disregardal, E. oli taken through food and inhabits intestine thru life 2. Ten times more(prenominal) than bacterial cells than human cells in the corpse 3. Normal working formula microbiota 4. short microbiota reach for a while provided disappear 5. Distri yetion of normal phytology subordinate on physical and chemical substance fact ors, defenses of the force and mechanical factors Relationship among Normal Flora and horde 1. microbic antagonism aka competitive exclusion normal microbiota ability to protect the multitude from giantism of harmful microorganisms 2. Normal microbiota and host stick about in symbiosis wizard is dependent on the opposite 3.The three types of symbiosis commensalism (one organism benefits, other unaffected), mutualism (both benefit) and parasitism (one harmed and one benefits) 4. Probiotics live microbial cultures applied to or ingested that atomic number 18 intended to exert a beneficial effect Opportunistic Microorganisms 1. E. coli norm in completelyy harm slight just in other parts of the soundbox constitute UTI, pneumonic transmittances, meningitis or abscesses. 2. AIDS compromises immune arranging increases susceptibility to opportunistic transmittance e. g. Pneumocystis pneumonia The etiology of septic Disease Kochs Postulates 1. Koch realised that microorganisms birth specific infirmity 2. single out microorganisms from disorderd animal, grew in pure culture and identified, injected healthy animal, disorder re arrestd and identical 3. experimental requirements same pathogen essentia aviationss be present in every case of ailment, pathogen essential be isolated from disorderd host and grown in pure culture, pathogen must ca practice disease when inoculated into healthy animal, pathogen must be isolated from inoculated animal and shown to be original organism Exceptions to Kochs postulates 1. unequalled culture environments modified to establish etiologies of those that nookie non be grown on artificial media e. g. viruses, syphilis, leprosy 2. slightly disease much(prenominal) as lockjaw have unequivocal signs and symptoms 3. Some disease may be caused by a tote up of microbes e. g. pneumonia and nephritis 4. Some pathogens cause several diseases e. g. S. pyogenes 5. Certain pathogens only cause disease in humans e. g. human immunodeficiency virus Classifying Infectious diseases 1. Every disease extrapolates torso structures and functions in particular ways ad argon indicated by several kinds of evidences 2.Symptoms changes in form functions 3. Signs intentive changes the physician set up observe or measure e. g. lesions, swelling, fever and paralysis 4. Syndrome a specific aggroup of signs or symptoms that accompany a disease 5. Communicable disease any disease that bed covers from one host to another e. g. herpes, chickenpox, rubeola, enteric fever fever fever and TB 6. Contagious diseases scattering easily from host to host e. g. chickenpox 7. Noncommunicable Disease caused by microorganisms that hold body and only occasionally produce disease or live right(prenominal) the body and produce disease when introduced e. . tetanus Occurrence of Disease 1. Incidence the number of people in a state who develop a disease during a particular period of time 2. preva lence number of people in a universe of discourse who develop a disease at a specific time, heedless of when it first appeared old and recent 3. discontinuous disease sinks only occasionally e. g. typhoid fever 4. Endemic disease invariably present in a population e. g. common cold 5. Epidemic disease Many people in a given area develop disease n short time e. g. AIDS, STDs 6.Pandemic Epidemic disease that occurs universal e. g. avian flu Severity or Duration of Disease 1. Acute disease develops rapidly but only lasts a short time e. g. influenza 2. chronic Disease develops more slowly and bodys reactions may be less severe but continues or recurs for dour periods of time e. g. Mono, TB & HepB 3. Subacute middling between Acute and Chronic e. g. Sclerosing panencephalitis 4. potential Disease causative doer cadaver inactive for several(prenominal) time but than becomes active to produce symptoms e. . shingles 5. litter Immunity Immunity to disease in clo sely of population Extent of Host Involvement 1. Local contagion microorganisms check to relatively small area e. g. boils 2. systemic transmittal Spread throughout the body by logical argument or lymph e. g. measles 3. Focal infection local infection enters melodic phrase or lymph and spread to other specific body parts where they are confined arise f/ teeth, tonsils, fistulous withers 4. Sepsis toxic inflammatory condition arising from spread of microbes from a focus of infection 5.septicemia blood poisoning systemic infection arising from multiplication of pathogens in blood 6. bacteriaemia presence of bacteria in blood, toxemia presence of toxins in blood and viremia presence of virus in blood 7. Primary infection acute infection that causes initial nausea 8. Secondary infection caused by an opportunistic pathogen after unproblematic weakens defenses 9. Subclinical (inapparent) infection is one that does not cause any noticeable malady e. g. Polio & HepA can be carried but never developed Patterns of Disease . while must be reservoir of infection as a source pathogen communicable to susceptible host by turn over or vectors transmission followed by invasion (enters host, multiplies) injures host through pathogenesis 2. Despite these effects, occurance of disease generally depends on foe Predisposing factors makes body more susceptible and may alter course of disease 1. Gender Females more UTI, Men more meningitis 2. Genetic ambit sickle cell against malaria 3. Climate and brave out respiratory disease increase in winter 4.Others nutrition, age environment, lifestyle, habitat, illness, chemo, emotions. Development of Disease 1. Incubation Period interval between initial infection and first balmy signs and symptoms, time depends on virulence, number of microorganisms, and resistance 2. Prodromal period characterized by manner of the first mild signs and symptoms 3. Period of illness disease at its height and all signs and symptoms apparent, PT dies during this period if not switch 4. Period of Decline signs and symptoms subside- vulnerable to secondary coil infection 5.Period of convalescence body returns to its pre-diseased state and health is restored The Spread of Infection Reservoirs of Infection 1. Reservoir of Infection A continual source of infection- may be human animal or nonconscious 2. Human reservoirs Many people have got pathogens and transmit them Carriers are living reservoirs and halt the disease with or without signs or symptoms gouge carry disease during latent phases such(prenominal) as incubation or ill play important role in spread of AIDS, typhoid fever, diphtheria, hep, gonorrhea, and streptococcal infections 3. sentient being Reservoirs Wild or domestic zoonosis are diseases that occur in barbarous but can be transmitted to humans e. g. Rabies, Lyme disease Can occur through contact of animal, its waste, consumption or contamination. 4. Nonliving Reservoirs farming and Water Soil e. g. Ringworm, Botulism and Tetanus, Water e. g. usually contamination related, cholera , typhoid fever transmittance of Disease 1. Contact spread od an ingredient of disease by direct contact, corroboratory contact or droplet transmission a. cover Contact touching kissing, intercourse, Any closure physical contact e. . STDs, AIDS, cold, influenza, staph, Hep A, measles and so ontera b. Indirect Contact occurs when operator of disease is transmitted from reservoir to host by means of nonliving object Fomite is a object relate in spread of infection e. g. tissues, bedding, syringes etc. c. Droplet Transmission microbes are spread in droplet nuclei that travel short distance Sneezing, coughing, public lecture not considered airborne e. g. flu, pneumonia and pertussis 2. vehicle Transmission transmission of disease by a medium, such as urine food or air and drugs blood IV and body fluids d.Waterborne grime water, cholera leptospirosis e. Foodborne transported through undercooked, poorly kept or unsanitary food such as tapeworm f. Airborne droplet nuclei in dust that travels more than 1 rhythm measles virus and TB bacteria as well as some spores can be carried in dust and cause disease coccidiodomyosis 3. Vectors animals that carry disease from one host to another g. mechanised Transmission passive transport on insects feet or body part houseflies transportation from feces to food h.Biological transmission active process and more hard arthropod bites infected person pathogens reproduce in vector increase causes more hap of transmit. If arthropod vomits or defecates while biting host, can transfer from gut. Often parasites, also holds Lyme disease, plague, Malaria etc. Nosocomial (Hospital Acquired) Infections 1. A nosocomial infection is any infection that is acquired during the course of stay in a hospital, nursing home plate or other healthcare forwardness 2. About 5 15% of all hospitalized patients will acquire this 3.Result from conclave of weakened host, chain of transmission in hospital and availability of microorganisms in hospital. Microorganisms in the Hospital 1. Often normal flora are a problem when introduced to body in catheters and surgical procedures 2. Major problems include coagulase negative staph, S. aureus, E. coli, Enterococcus, P. aeruginosa, Enterobacter, K. pnuemoniae, Candida albicans 3. Most frequent are opportunistic gram negative, drug foul Compromised Host 1. Resistance impaired by disease, therapy and burns. 2. Two principals Broken spit out/mucous membranes and suppressed immunity . Broken skin and mucous membranes disable first line of defense 4. Invasive devices also cause problems 5. Adverse effects to B and T Cells compromise host Chain of Transmission 1. Direct transmission from staff phallus to patient and among patients 2. Fomites such as catheters, syringes and respiratory devices Control of Nosocomial Infections 1. Aseptic techniques can prevent Hand washing most important 2. Hospital infection fudge staff members are responsible for overseeing halal cleaning, storage and handling of equipment and supplies Emerging Infectious Diseases . EIDs are new or changing, increasing recently and showing coming(prenominal) increase. 2. Number of factors contribute to emergence including new strains which may result from genetic recombination (E. coli), a new serovar resulting from changes or evolution (Vibrio cholerea) , use of antibiotics and pesticide to cause resistance, changes in weather patterns (Hantavirus), modern transportation (West Nile), Ecological changes from natural disasters winding or wars, animal control measures (kill deer predators, more deer, more Lyme disease and failures in public health measures. . CDC priorities (1) Detect suss out and monitor pathogens and disease (2) Expand prefatorial and applied research on bionomical and environmental factors microbial changes and host int eraction (3) Enhance public information (4) free-base plans to monitor and control worldwide Epidemiology 1. The comprehension of epidemiology is the study of transmission incidence and relative frequency of disease 2.Modern epidemiology began in mid-1800s with the works of Snow, Semmelweis and Nightingale 3. Descriptive Epidemiology data about infected people is collected and analyze includes info about person place and period 4. Analytical epidemiology analyzes disease to finalize probable cause (case control method) a group of infected people is compared with an sportsmanlike group or (Cohort Method) people in contact with an agent vs. hose not in contact with the same agent 5. Experimental Epidemiology controlled experiments designed to test scheme are performed e. g. placebo studying 6. Case account provides data on incidence and prevalence to local, state and national health officials 7. The CDC is the of import source of epidemiologic information in the US 8. The CDC publishes the Morbidity and Mortality hebdomadally report to provide info on incidence and deaths.