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Pathogens and Disease

Pathogens and Disease. IB Biology. What is a Pathogen?. Any microbes (organism or virus) that cause disease Including: Viruses Bacteria Fungi Protozoa Flatworms Roundworms. Viruses. Considered Non-Living Two Parts: A Capsid: protein coat A Nucleic Acid: DNA or RNA

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Pathogens and Disease

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  1. Pathogens and Disease IB Biology

  2. What is a Pathogen? • Any microbes (organism or virus) that cause disease • Including: • Viruses • Bacteria • Fungi • Protozoa • Flatworms • Roundworms

  3. Viruses • 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. Ebola HIV

  4. Virus Examples • HIV: Human Immunodeficiency Virus • Targets T-Cells (Immune Cells) • Influenza • Rhinovirus • Small Pox • Polio • Ebola, Marburg, Hantavirus • Herpes (different simplexes)

  5. Bacteria • 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 Escherichia coli Staphylococcus aureus

  6. 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)

  7. 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

  8. Protozoa • Protozoa are unicellular animal-like protists (motile) • Pathogenic examples include: • Giardia • Cryptosporidium • Trypanosoma • Many have insect vectors Giardia

  9. Flatworms • Flatworms belong to a group called platyhelminthes • Many are parasitic • Examples include: • Tapeworms • Flukes (liver fluke) • Schistosoma

  10. 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)

  11. Disease Transmission • Direct Contact: Person to person – communicable (mononucleosis) • Kissing • Shaking hands • Touching open wounds or sores • Sexual contact – body fluids

  12. 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)

  13. Disease Transmission Portals of Entry • Respiratory Tract – nose, mouth, lungs • Gastrointestingal Tract – throat, stomach, intestines • Mucous Membranes – nose, eyes, etc. • Penetration – bites, cuts, injections

  14. 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)

  15. 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

  16. 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

  17. 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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