The Biology of Disease Infectious Agents Modes of Infection Germ Theory of Disease Defense Against Disease

Disease Any change (other than an injury) that disrupts normal body functions Inherited/genetic Environmental factors Infectious agents (pathogens) Viruses Bacteria Protists Fungi Large parasites Prions* Incubation period 3-14 days http://en.wikipedia.org/wiki/Dengue_fever. http://www.rcsb.org/pdb/101/motm.do?momID=103

Miasma, curses, and more “As long as (individuals) believed that microorganisms could arise from nonliving substances, scientists saw no purpose in considering how diseases were transmitted or how they could be controlled.” - Black, 1996 http://upload.wikimedia.org/wikipedia/commons/9/92/Cholera_art.jpg

Germ Theory of Disease Refuted theory of spontaneous generation Infectious disease is caused by germs (L. “to beget”) or pathogens. http://jvi.asm.org/content/77/11.cover-expansion

Development of the Germ Theory of Disease Ignaz Semmelweis (1840s) Louis Pasteur (1860s) Joseph Lister (1860s) Robert Koch (1870s) Dmitri Ivanovsky (1890s) Development of the Germ Theory of Disease http://www.cdc.gov/features/handwashing/handwashing_a200px.jpg, http://www.accessexcellence.org/RC/AB/BC/images/lou_p.gif, http://news.bbc.co.uk/2/shared/spl/hi/pop_ups/06/magazine_local_treasures/html/1.stm, http://en.wikipedia.org/wiki/File:TB_Culture.jpg, http://www.extension.umn.edu/distribution/horticulture/dg1168.html

Pathogen What it is What it causes Viruses Bacteria Protists Fungi Noncellular particles that invade living cells AIDS, polio, smallpox, measles, colds, influenza, chicken pox, SARS, bird flu Bacteria Unicellular prokaryotes; from Domain Bacteria gonorrhea, botulism, pneumonia, strep throat, boils/acne, tuberculosis, meningitis, cholera, tetanus Protists Any eukaryote that is NOT a plant, an animal, or a fungus; from Kingdom Protista malaria, amoebiasis/amoebic dysentery, African sleeping sickness Fungi Eukaryotic heterotrophs w/ chitinous CWs; from Kingdom Fungi ringworm, athlete’s foot, San Joaquin Valley fever (lung disease), histoplasmosis Worms Parasitic animals from the phyla Platyhelminthes & Nematoda schistosomiasis, beef tapeworm Prions* Misfolded proteins that cause other normal proteins to misfold and cause widespread damage Mad-cow disease, Creutzfeldt-Jakob disease, scrapie

How do pathogens cause disease? Rapid multiplication interferes with normal cell function Destruction of body cells and tissues Production of poisons or toxins that kill cells or interfere with their functions http://www.morning-earth.org/Graphic-E/BIOSPHERE/Bios-Microbe-Image/M-Dfission.jpg, http://www.bioprepwatch.com/wp-content/uploads/2012/02/botulinum-toxin.jpg, http://www.trichinella.org/images/synopsis/21.1.jpg

Koch’s Postulates set of rules that is used to determine whether a specific pathogen is the cause of a specific disease Pathogen should always be found in the body of a sick organism and never in a healthy one Pathogen should be isolated and grown in pure culture When purified pathogens are placed in a new host, it should cause the same disease as in the first host When the infected pathogen is isolated from the new host, it should be identical to the original pathogen http://4.bp.blogspot.com/_xURh3pkJN6E/TOlmOYp_8FI/AAAAAAAAABA/IcD4KNRSt4k/s1600/Kochs%2BPostulate.jpg

Discovering the cause of Lyme disease Allen Steere (Yale University) Lyme, Connecticut Observations 39 children, several adults Pain, joint inflammation Summer-early fall Insect bite then expanding skin rash Problem What is causing Lyme disease? http://upload.wikimedia.org/wikipedia/commons/0/01/Erythema_migrans_-_erythematous_rash_in_Lyme_disease_-_PHIL_9875.jpg

Using Koch’s Postulates Skin rash linked to deer tick (Ixodes scapularis) bite Spiral bacteria (Borrelia burgdorferi) found in ticks B. burgdorferi found in patients with Lyme disease Hypothesis: B. burgdorferi causes Lyme disease Postulate 1 B. burgdorferi was grown in pure culture Postulate 2 B. burgdorferi introduced into lab mice caused them to develop symptoms similar to those of children Postulate 3 B. burgdorferi was obtained from sick mice Conclusion: B. burgdorferi is a pathogen that causes Lyme disease Postulate 4 http://commons.wikimedia.org/wiki/File:Ixodes_scapularis.png, http://www.lawestvector.org/LymeDisease.htm

Modes of Infection food- and water-borne ex. tapeworms, amoebiasis airborne ex. droplets of pathogens expelled into the air via coughing, sneezing, talking actual contact ex. common cold, STDs carriers/vectors: organisms that carry pathogens from person to person ex. mosquitoes, tsetse fly http://media.photobucket.com/image/vitruvian%20homer/austinheap/myspace/homer.gif?o=1

Two major types of defenses INNATE (NONSPECIFIC) IMMUNITY Rapid responses to a broad range of microbes ACQUIRED (SPECIFIC) IMMUNITY Slower responses to specific microbes External defenses Internal defenses Skin Mucous membranes Secretions Phagocytic cells Antimicrobial proteins Inflammatory response Natural killer cells Humoral response (antibodies) Cell-mediated response (cytotoxic lymphocytes) Invading microbes (pathogens)

Pathogen Awareness Project 3D model of a chosen pathogen that affects Filipinos (pref. recycled materials, NO STYRO!) Include a write-up with the following information on an A3 sized sheet: Characteristics of the pathogen Modes of transmission Incubation period Symptoms induced Prevention/cure Interesting trivia/statistics Due Oct 15th, 12NN CAMIA 1,2 – Virus 3,4 – Bacteria 5,6 – Large parasite 7,8 – Virus 9,10 - Bacteria CHAMPACA 1,2 – Virus 3,4 – Bacteria 5,6 – Large parasite 7,8 – Virus 9,10 – Large parasite