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:
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

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

5. 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

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

18. 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)