1. Pathogens and Disease

2. What are pathogens?
A pathogen is an infectious agent (“germ”) that causes disease or illness in a host.
The host is the organism in which a parasite or pathogen does damage.

3. Key Terms
Parasite
Any organism that has a negative effect on another organism with which it has close contact.
All pathogens are parasites.

4. Key Terms Vector The item that transfers the pathogen to its host.
Vectors are “vehicles” that transport pathogens from one host to another.
Examples: water, blood, ticks, mosquitoes…

5. Key Terms Transmission
The passing of disease from an infected individual to unaffected individuals.
Passed by means of a vector.

6. Key Terms
Endemic
A common disease that occurs at a constant, but low, rate in a specific population.
Example: Malaria in Liberia (Africa) is said to be endemic, as it is at a low rate, but constant enough that is it expected that the majority of the population will contract it at some point in their life.

7. Key Terms
Epidemic
When an endemic disease occurs more frequently than expected, in a given area (i.e. Kingston) over a given time period.
Example: The flu would cause an epidemic if more than the usual number of people in a winter got the flu.

8. Key Terms
Pandemic
It is an epidemic of infectious disease that has spread over a larger area (continent, worldwide…).
Examples: HIV/AIDS since 1990, SARS and Avian Flu in the mid 2000s. Swine Flu in 2010.

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

10. Viruses Considered Non-Living Two Parts: Function: Reproduction
Ebola
Considered Non-Living
Two Parts:
A Capsid: protein coat
A Nucleic Acid: DNA or RNA
Function: Reproduction
Method: Hijack a living host cell and use it’s cellular machinery to replicate and build new virus particles.
HIV

11. Virus Examples HIV: Human Immunodeficiency Virus Influenza Polio Ebola
Herpes (different simplexes)

12. Staphylococcus aureus
Bacteria
Escherichia coli
Staphylococcus aureus
Most are not pathogenic
All unicellular
Parasitic strains and those that produce toxic byproducts are pathogenic

13. Bacteria Examples Streptococcus (Strep Throat) Escherichia coli
Bacillus anthracis (Anthrax),
Helicobacter pylori (causes peptic ulcers)

14. Fungi
Decomposers that occasionally don’t wait until an organism is dead to feed on it
Examples: Athletes Foot (skin)
Most are surface/epidermal, some (rarely) become invasive

15. Protozoa Protozoa are unicellular Pathogenic examples include: vectors
Giardia
Many have insect
vectors
Giardia

16. Flatworms Many are parasitic Examples include: Tapeworms
Flukes (liver fluke)
Schistosoma

17. Roundworms Roundworms 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)

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

19. 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)

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

21. 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)

22. 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