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Epidemiology and Disease Processes Chapter 17, examples from Chapter 19 Fields of Microbiology Epidemiology -- Population focus -- disease spread & containment Microbial pathology -- Disease focus -- ‘etiology’ of disease -- Biology of pathogen & effects on host
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Epidemiology and Disease Processes Chapter 17, examples from Chapter 19 Fields of Microbiology Epidemiology -- Population focus -- disease spread & containment Microbial pathology -- Disease focus -- ‘etiology’ of disease -- Biology of pathogen & effects on host Clinical Microbiology -- Patient focus -- ID of pathogen and treatment John Snow’s classic search for source of cholera – London, 1854 Germs Pathology
Roles of the the CDC Epidemiological studies the MMWR Notafiable diseases (see tables 15.3 & 15.4) Recommendations: antibiotics drugs vaccine The WHO based in Geneva, Switzerland Pathology
What are the clinical stages of a disease? Incubation Prodromal Invasive Acme Decline Convalescence Symptom can be: Acute Chronic Latent Pathology
What are disease ‘Reservoirs’? Nonliving (usually noncommunicable, opportunistic) tetanus fungi Living Animal (‘zoonotic’) (generally noncommunicable) rabies anthrax lyme disease Human (may be ‘contagious’) cholera Pneumonia HIV ‘Carriers’ (read essay about Typhoid Mary, p 376) Nosocomial Pathology
What are “modes of transmission:” The “Five F’s” A. Contact transmission Direct Contact transmission -- includes ‘aerosols’ -- respiratory infections Indirect Contact transmission involves ‘fomites’ Haemophilus B. Vehicular transmission (disseminates) water, food, dust cholera, salmonellosis C. Vector transmission Reservoirs, Vehicles and Vectors are not the same! Pathology
Case study: Lyme disease An “Emerging Disease” New Lyme, Conn, 1982 Borrellia burgdoferi White-tailed deer & mice Ixodes complex life cycle Pathology
Lyme disease, con’t Distibution Stages of disease Acute symptoms: “Bulls-eye rash” flu-like symptoms Chronic symptoms: arthritis neurological disorders etc Treatment antibiotics (yes and no) Pathology
Patterns of disease occurrence epidemic pandemic endemic sporadic cyclic Pathology
Case study: Tuberculosis -- A ‘reemerging’ disease Mycobacterium tuberculosis Intracellular pathogen lungs WBCs immune response granulomas Spread/control linked to clinical and social factors: 1) Diagnosis and treatment difficult 2) Slow growth 3) Poverty -- developed & developing nations 4) AIDS Pathology
What are the stages of an infection? Adherence Colonization Invasion 1. Adherence glycocalyx fimbriae receptors Pathology
Colonization and Invasion are often coupled Many ‘strategies’ Enzymes (‘virulence factors’) collagenase hemolysin streptokinase Phagocytosis Intracellular and extracellular infections collagenase hemolysin Listeria and actin tails Pathology
What causes the symptoms of infection? Altered physiology e.g., fever; lethargy; loss of appetite -- altered blood chemistry; -- effects on hypothalamus Immune responses – some damaging e.g., many diseases; tuberculosis, leprosy rheumatic fever, etc Pathogens’ damage to cells, tissues and organs Toxins Exotoxins Gram-Positive sp. proteins Secreted from cells Highly toxic, specific effects Endotoxins Gram-negative lipopolysacchrarides Less toxic, more general effects pyrogenic, hypotension Syphilis lesions in liver Pathology
Some Effects of Exotoxins 1) Cell destruction (hemolysins) 2) Hemorrhaging (anthrax, Streptococus toxins) 3) Effect intestinal function (enterotoxins) water balance (cholera toxin) 4) Nerve function (botulism & tetanus toxins) Anthrax lesion • Toxicity of Some ExotoxinsToxicity compared with: • Toxin Lethal Dose (mg) Strychnine Snake Venom • Botulism Type D 0.8 x10-8 (mouse) 3x106 times 3x105 X • Tetanus 4 x10-8 (mouse) 1x106 X 1x105X • Shigella Neurotoxin 2.3 x10-6(rabbit) 1x106 X 1x105 X • Diphtheria 6 x10-5(guinea pig) 2x103 X 2x102 X Pathology
Botulism and Tetanus Clostridium botulinum vs C. tetani obligate anaerobes Botulism food borne flaccid paralysis Tetanus soil borne rigid paralysis Scary tetanus picture? Pathology
A Botulism Case History Food risks Antitoxins Birds, Botox and Bioweapons… Pathology
Case study: Helicobacter pylori causes peptic ulcers Only discovered 1982 Dimorphic causes 60-80% of stomach ulcers 90% doudenal ulcers Stomach cancers Immune response plays important roles Good news: treatable Bad news: 25% in U.S. infected More bad news: antibiotic resistance is spreading Pathology
Gonorrhea agent Neiserria gonorrhoeae -- Gram-negative dipplococcus -- attaches via fimbriae Endotoxin Infection in males “thick, copious & yellowish” pus Pathology
Infection in females cervix fallopian tubes PID ectopic pregnancy neonatal prophylaxis epidemiology Pathology
A Souvenir of London Bought a souvenir in London got to hide it from my mum. Can't declare it at the customs, but I'll have to take it home. Tried to keep it confidential, but the news is leaking out. Got a souvenir of London. There's a lot of it about. Yes I've found a bit of London, and I'd like to lose it quick. Got to show it to my doctor, 'cos it isn't going to shrink. Want to keep it confidential, but the truth is leaking out. Got a souvenir of London. There's a lot of it about. by Procol Harum, 1973 ASoL Pathology
What causes the symptoms of Syphilis? Agent Treponema pallidum spirochete Stages of the infection Incubation Primary (1O) syphilis chancre (clinical latency) Secondary (2O) syphilis immune hypersensitivity (clinical latency/ recurrent 2O) Tertiary syphilis gumma lesions Pathology
Syphilis, con’t. Tertiary syphilis gumma lesions autoimmunity? Treatment Congenital syphilis Saddle nose Notched teeth Saber shin nose Pathology