Transcript 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
Ebola
Considered Non-Living
 Two Parts:

A Capsid: protein coat
 A Nucleic Acid: DNA or RNA

HIV
Function: Reproduction (Replication, actually)
 Method: Hijack a living host cell and use
it’s cellular machinery to replicate and
build new virus particles.

Virus Examples

HIV: Human Immunodeficiency Virus

Targets T-Cells (Immune Cells)
Influenza
 Rhinovirus
 Small Pox
 Polio
 Ebola, Marburg, Hantavirus
 Herpes (different simplexes)

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

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)

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

Protozoa
Protozoa are unicellular animal-like
protists (motile)
 Pathogenic examples include:

Giardia
 Cryptosporidium
 Trypanosoma


Many have insect
vectors
Giardia
Flatworms
Flatworms belong to a group called
platyhelminthes
 Many are parasitic
 Examples include:

Tapeworms
 Flukes (liver fluke)
 Schistosoma

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)

Disease Transmission

Direct Contact: Person to person –
communicable (mononucleosis)
Kissing
 Shaking hands
 Touching open wounds or sores
 Sexual contact – body fluids

Disease Transmission
 Indirect
Contact:
– doorknobs, telephones, ect...
 Air (tuberculosis)
 Food (botulism)
 Water (typhoid fever)
 Vectors
 Objects
Bites – disease to organism to
humans (rabies, West Nile virus)
 Animal
Disease Transmission
Portals of Entry
Respiratory Tract – nose, mouth, lungs
 Gastrointestingal Tract – throat, stomach,
intestines
 Mucous Membranes – nose, eyes, etc.
 Penetration – bites, cuts, injections

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)

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
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
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)
