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Pathogens and Disease IB Biology
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What is a Pathogen? Any microbes (organism or virus) that cause disease Including: Viruses Bacteria Fungi Protozoa Flatworms Roundworms
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Viruses Considered Non-Living Two Parts:
Ebola Considered Non-Living Two Parts: A Capsid: protein coat A Nucleic Acid: DNA or RNA Function: Reproduction (Replication, actually) Method: Hijack a living host cell and use it’s cellular machinery to replicate and build new virus particles. HIV
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Virus Examples HIV: Human Immunodeficiency Virus Influenza Rhinovirus
Targets T-Cells (Immune Cells) Influenza Rhinovirus Small Pox Polio Ebola, Marburg, Hantavirus Herpes (different simplexes)
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Staphylococcus aureus
Bacteria Escherichia coli Staphylococcus aureus Most are not pathogenic (major decomposers, major photosynthesizers, critical components for many ecosystems) All prokaryotic, unicellular Parasitic strains and those that produce toxic byproducts are pathogenic Most pathogenic varieties form colonies and can be grown on TSA plates
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Bacteria Examples Cocci: Staphylococcus (Staph), Streptococcus (Strep Throat) Bacilli: Escherichia coli (E. coli; 0157:H7), Bacillus anthracis (Anthrax), Clostridium botulinum (Botulism Toxin Producer) Spirilla: Campylobacter jejuni (causes diarrhea esp. in children), Helicobacter pylori (causes peptic ulcers)
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Fungi Decomposers that occasionally don’t wait until an organism is dead to feed on it Examples: Valley Fever (lung), Ringworm (skin), Athletes Foot (skin) Most are surface/epidermal, some (rarely) become invasive
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Protozoa Protozoa are unicellular animal-like protists (motile)
Pathogenic examples include: Giardia Cryptosporidium Trypanosoma Many have insect vectors Giardia
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Flatworms Flatworms belong to a group called platyhelminthes
Many are parasitic Examples include: Tapeworms Flukes (liver fluke) Schistosoma
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Roundworms Roundworms are nematodes that range in size from macroscopic to microscopic Many parasitic roundworms inhabit the intestines of a host organism Examples include: Pinworms like Enterobius vermicularis Hookworms like Necator and Ancylostoma Trichinella spiralis (larvae migrate to muscle)
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Disease Transmission Direct Contact: Person to person – communicable (mononucleosis) Kissing Shaking hands Touching open wounds or sores Sexual contact – body fluids
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Disease Transmission Indirect Contact:
Objects – doorknobs, telephones, ect... Air (tuberculosis) Food (botulism) Water (typhoid fever) Vectors Animal Bites – disease to organism to humans (rabies, West Nile virus)
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Disease Transmission Portals of Entry
Respiratory Tract – nose, mouth, lungs Gastrointestingal Tract – throat, stomach, intestines Mucous Membranes – nose, eyes, etc. Penetration – bites, cuts, injections
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Opportunistic Pathogens
MDR TB and Staph Infections Malaria (hiding in liver cells) HIV attacking T-cells and rapid mutation Influenza and Rhinovirus rapid mutation rate (flu shots every year)
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Prevention/Treatment Options
Antibiotics Attack existing bacterial infections only Began with Penicillin (1928 – Fleming) Resistance observed rapidly Overuse, Incompletion of Prescription, Livestock application Vaccinations Prepare an immune system in advance of a viral (usually) or bacterial infection (i.e. tetanus) Dead or inactive parts of a pathogen or synthetic
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HIV Blood-born pathogen Transmitted via:
Sexual Contact Used Hypodermic Needles Early Blood Transfusions (pre-testing) Uses only Helper T-Cells for replication Compromises Immune Response Rapidly mutates differently in each host Not a cause of death Subsequent infections finish off host
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Social Implications HIV in Sub-Saharan Africa:
22.5 million people living with it by 2008 1.7 million contracted it this year. 11 million orphans as a direct result Varies widely from country to country Impacts are widespread and threaten to hold up/roll back decades of progress/economic development Causes: poor education system (lack of basic understanding), lack of access to contraceptives, employment situations... Insult to Injury: lack of quality health care or testing, lack of funds for ARV drugs, poor sanitation (additional diseases)
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