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HLTH 101 Lecture Notes - Transmissible Spongiform Encephalopathy, Human Papillomavirus Infection, Intracellular Parasite

Health Studies
Course Code
HLTH 101
Glenn Ward

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HLTH 101 Fall 2010
Infectious organisms can be classified in a number of ways.
In this course, I have chosen to classify them according to their
size first, and then according to their taxonomic classification.
i. Subcellular Organisms
in fact, these are not technically organisms but are
complex microscopic agents that usually (but not
always) reside within living cells)
we’ll discuss two main types: viruses and prions
exist basically as RNA
DNA molecules (generally not
both) encased inside a coat of protein
about 1500 viruses have been identified (so far), only a
small number of which are believed to affect human
viruses have a simple existence outside host cells
they are obligate intracellular parasites, which
means that they must enter the host cell to
cells are susceptible to viral infection
even single celled organisms such as bacteria can
be infected with viruses (bacteriophages are
viruses that infect bacteria)
viral reproduction can damage the host cell
when the virus reproduces, the offspring viruses can
then invade a new cell and replicate, resulting in
damage to the new cell, etc.

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HLTH 101 Fall 2010
because of the ability of the virus to travel through the
body, there is a low association between the route of
entry and the tissue most affected by the virus
common diseases caused by viruses include:
i. common colds
ii. HIV (AIDS)
iii. influenza
iv. HPV (human papilloma virus)
v. herpes
vi. measles
prions are characterized as proteinacaous infectious
they lack DNA and RNA and consist mainly of protein-
like molecules
they appear to exist in all brains
their mechanism of action is still not well-
understood, but research suggests that prions are
susceptible to alterations in their shape or
if their configuration is altered, these altered
prions can reproduce and propagate throughout
nearby cells
this eventually leads to the death of neural cells
in which the prions reside
altered prions can be transmitted through food and
surgical instruments as infectious agents
rare diseases caused by prions:
i. transmissible spongiform encephalopathy
ii. CJD (Cruetzfeldt-Jakob disease)
iii. vCJD (form of CJD possibly associated with bovine

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HLTH 101 Fall 2010
spongiform encephalopathy [BSE]
ii. Unicellular Organisms
unicellular organisms are those that exist as single
as such, they are more complex that viruses and prions,
but are still relatively simple
however, they are highly specialized for life in their
respective environments
the two types of cellular organisms associated with
infectious disease are bacteria and protozoa
bacteria are unicellular prokaryotic organisms
structurally, they are highly adapted for survival
1) most (but not all) bacteria are enclosed in a
among other things, this capsule makes the
bacteria resistant to phagocytosis
the capsule also plays a role sometimes in the
virulence of the bacteria
2) all bacterial cell walls contain peptidoglycan (note
that some sources will refer the Archaebacteria as
an exception to this rule. While the cell walls of
Archaea do not contain peptidoglycan, it has become
common over the past decade to refer to them as a
prokaryote domain separate from bacteria. As they
are not known at this time to contribute to human
health problems, they will not be included in this
this substance provides rigidity and resistance to
it also determines the gram positive and gram
negative status of the bacterium (important for
determining appropriate antibiotic treatment)
3) some bacteria contain cytoplasmic organelles called
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