Principles and Definitions (R and J
Chs 1 & 2)
• Parasitology is a division of Symbiosis two organisms living together.
• Categories of symbiosis are based on the
effects of one organism on the other.
Phoresis-2 organisms
traveling together
Mutualism- 2 organisms living
together in which both benefit
from the association; both are
metabolically dependent on one
another
Commensalism- Relationship
in which the symbiont benefits
from an association with a
host which is passive to the
relationship (not harmed or
benefited)
Parasitism- definitions:
• Original meaning from the Greek is a
relationship in which "one eats at another's
table or lives at another's expense.“
• R&J page 4 - "Parasitism is a relationship in
which one of the participants, the parasite,
either harms its host or in some sense lives at
the expense of the host.“
Entamoeba invadens
Entamoeba invadens
Parasitism- definitions:
• Noble and Noble – Parasitology: The Biology of
Animal Parasites
"Parasitism is an obligatory association between two
distinct species in which the dependence of the
parasite upon its host is a metabolic one involving
mutual exchange of substances."
Our Definition
Parasite-an organism which lives at least part of
its life cycle on or within another organism (the
host) upon which it is physiologically dependent
and to which it causes harm in some way.
In a parasitological or medical context, it is
restricted to animal agents, i.e., protozoa,
helminths, and arthropods.
Where are Parasites Found?
A brooding Glossiphonid leech
with its young feeding on my
wife’s leg!
Where are Parasites Found?
• Ectoparasite- a parasite which lives on the body
surface of the host.
Where are Parasites Found?
• Endoparasite- a parasite which lives within the
body of the host.
Definitions of Hosts
Many parasites have more than one host in their life cycle.
These hosts have different roles and are given specific
names.
Definitions of Hosts
Definitions of Hosts
• Definitive host – a host in which the parasite
reaches sexual maturity and undergoes
reproduction.
Definitions of Hosts
• Definitive host – a host in which the parasite reaches
sexual maturity and undergoes reproduction.
• Intermediate – a host in which the parasite
undergoes larval development but does not
reach sexual maturity.
Definitions of Hosts
• Definitive host – a host in which the parasite reaches
sexual maturity and undergoes reproduction.
• Intermediate – a host in which the parasite undergoes
larval development but does not reach sexual maturity.
• Paratenic host (Transport host) – a host in
which a parasite survives without undergoing
further development. A paratenic host
accumulates and maintains stages of a parasite,
and although beneficial, is not essential to the
life cycle.
Definitions of Hosts
• Vector- any agent, either animate or inanimate
(such as wind, water, or arthropod) that
transmits an infectious organism.
Definitions of Hosts
• Vector- any agent, either animate or inanimate (such as
wind, water, or arthropod) that transmits an infectious
organism.
• Biological Vector- a vector in which a parasite
lives or develops. The parasite undergoes
morphologic change and/or multiplication, and
the vector is usually essential for the life cycle.
Definitions of Hosts
• Vector- any agent, either animate or inanimate (such as
wind, water, or arthropod) that transmits an infectious
organism.
• Biological Vector- a vector in which a parasite lives or
develops. The parasite undergoes morphologic change
and/or multiplication, and the vector is usually essential
for the life cycle.
• Mechanical Vector- a vector which transmits a
parasite by mechanical means only. It may be
living or non-living and is not essential for the
parasite’s life cycle.
Host-Parasite Relationships
• Like other living organisms, parasites
have basic need in order to survive and
be successful.
Host-Parasite Relationships
•
•
•
•
Habitat or substrate
Energy source (food)
Reproduction of own kind
Dispersal
Host-Parasite Relationships
• Living animals present special problems
as habitats or environments.
Host-Parasite Relationships
• They move around and disperse
• They have non-specific defense
mechanisms
• They mount specific immune responses
• They age and change physiologically
• They die
Host-Parasite Relationships
• Some of the most important factors
influencing parasite transmission and
infection are related to host behavior.
Echinococcus Tapeworms
Echinococcus species
Echinococcus multilocularis
Echinococcus granulosus
Surgical removal of 3 unilocular hydatid cysts from
a Kenyan woman.
Host-Parasite Relationships
•
•
•
•
•
Innate behaviors
Learned behaviors
Ethnic and cultural practices
Local customs or habits
Religious practices
Your Areas of Responsibility
• Lectures
• Any specific assignments given
• A set of facts/info about selected species
of parasites (A-I)
9 topics
• A- Morphology (structure)-size
9 topics
• B- Taxonomy: Largely based on
morphology. Know where to place
organism in the scheme of things.
Phylum ????? (Sarcodina)
9 topics
• C – Life cycle, including the ontogenetic
(developmental) stages and their size.
9 topics
• C – Life cycle, including where found
environmentally.
Be more specific!
Habitat
9 topics
• C – Life cycle, including prepatent
period: The period of time from infection
of a host with a parasite until one can
demonstrate that the host is infected by
finding a stage of the parasite (cyst, egg,
larva, etc.) in or form the host.
9 topics
• D – Geographic distribution: Where in
the world would you find it?
Trypanosoma gambiense
9 topics
• E – Symptoms: Aspects which you
observe (headaches, fever, jaundice, etc.)
9 topics
• F – Pathology: Damage from infection.
Physical damage/changes done to body
which you can see. Otherwise know as
the consequences of the infection.
9 topics
• G – Diagnosis: How to look for the
parasite, where to look, and what do you
expect to see. Do not base on symptoms.
9 topics
• H – Epidemiology: How does it spread
thru a population?
9 topics
• I – Drug of Choice and Prognosis:
Treatment and what you expect to
happen/prospects.