Download Disease causing organisms

Health and Disease
Objectives
To understand what is meant by
the terms health, disease,
pathogen and parasite
What is Health?
WHO definition of health:
A state of complete
physical, mental and social
well being NOT merely an
absence of disease
Well integrated into society
Suitably housed with
sanitation
Free from disease
Healthy Individual
Well fed with a
balanced diet
Happy, positive outlook
Able to perform normal
Physical and mental
tasks
What is Disease?
Disease is a malfunction of
body or mind which causes
symptoms that could be
physical, mental or social
Pathogens and parasites
• A Pathogen is a disease causing
organism which lives by taking nutrition
from a host and causing damage in the
process.
• A Parasite is an organism that lives in
(internal) or on (external) another host
organism causing it harm.
• All pathogens are parasites but not all
parasites are pathogens
For Example:
A head louse is
an external
parasite but is
not a pathogen
A tape worm is
an internal
parasite but is
not a pathogen
Norovirus is
an internal
parasite and
a pathogen
Disease can be caused by:
• Living organisms – infectious diseases
E.g. Tuberculosis
• Age induced
E.g. Alzheimer's
• Inherited
E.g. Cystic Fibrosis
• Environment
E.g. Allergies
Disease causing
organisms
(pathogens)
Bacteria
E. coli
Streptococcus
Salmonella
MRSA
Staphylococcus
Bacteria
Are small cells that reproduce rapidly (every
20 minutes in the right conditions). They
act by releasing toxins or damaging cells.
e.g. Vibrio cholerae (cholera),
Mycobacterium tuberculosis (TB)
Fungi e.g. Athletes Foot
Tinea pedis
Yeast
E.g.Thrush (Candida albicans)
Fungi
• Can live in the skin and send out branching
structures called hyphae. These are
reproductive structures which release spores
which can cause redness and irritation.
• E.g. Tinea (athlete’s foot and ringworm)
Ringworm – not actually caused
by a worm!
Viruses
HPV
Influenza
HIV
Meningitis
Norovirus
Herpes
Viruses
Cause many diseases by invading cells and
altering genes. They then cause the cell to
produce more copies of the virus. The host
cell eventually bursts releasing many new
viruses.
E.g. Tobacco mosaic virus (affects many
plants)
Electron microscope image
of TMV
Healthy and infected
plants
TMV is made up of a helix of over
2000 protein subunits
Protoctista
These are animal like organisms which enter host
cells and feed on their contents.
Plasmodium
falciparum
causes
malaria
Amoeba (Entamoeba
histolytica) causes
amoebic dysentery
Giardia lamblia
is the most
common cause
of diarrhea in
North America