Transcript Medical Parasitology

LECTURE NOTES ON
GENERAL PARASITOLOGY
(An introduction)
Dept of Parasitology, Fac. of Medicine
Universitas Padjadjaran
Introduction to Medical
Parasitology
• Definition of Medical Parasitology
• Conceptions related to medical
parasitology
• Relationships between parasite and host
• The basic factors of transmission of
parasitic diseases
• The preventive measures of parasitic
diseases
What are Parasites
WHO GETS PARASITES ?
Why Do Parasites Matter
Disease and
Death
Zoonotic
Potential
Wealth Loss
Definition of Medical Parasitology
Medical Parasitology
Parasites
Parasitic diseases
Prevention
Transmission
Treatment
Diagnosis
Pathogenesis
Life Cycle
Morphology
Conceptions related to
medical parasitology
• Symbiosis
• Parasite and type of parasites
• Host and common type of host
• Life cycle and type of life cycle
Symbiosis
------The relationship beween two living
things (animals). Two living things live
together and involve protection or other
advantages to one or both partner.
• Commensalism
• Mutualism
• Parasitism*
Commensalism
------ Both partners
are able to lead
indepenent lives,
but one may gain
advantage from the
association when
they are together
and least not
damage to the other.
Fig. A female pea crab in the
mantle cavity of its mussel
host. The crab does not
damage the mussel and uses
its shell purely for protection
Mutualism
------ An association which is beneficial to
both living things.
Fig. A selection of ciliates from the rumen. The
rumen contains enormous numbers of ciliates that
break down cellulose in the feed.
Parasitism
------ An association which is beneficial to
one partner and harmful to the other
partner. The former that is beneficial to
is called parasite, the latter that is
harmful to is called host.
Human / Hookworm
Types of Parasites
• Ectoparasites
– Live on the outside or skin of
the host
– Usually insects or arachnids
(ticks, mites, or spiders)
• Endoparasites
– Parasites found within the body
of the host
– Can be in blood, tissue, or
gastro-intestinal tract
– Nematodes, Trematodes, Cestodes and
Protozoa
Ecto- & Endoparasitism
• Ectoparasites live on, but
not in their hosts (they
can nevertheless cause
severe illness). Ich a
protozoan ectoparasite of
the skin of a fish.
• Endoparasite live within
the body and tissues of
their hosts.
Trypanosomes (which
cause sleeping sickness)
within the blood of an
infected animal.
Infection & infestation
• Infectious diseases are caused by
transmittable parasitic agents
including bacteria, viruses, fungi,
protozoa and a variety of
metazoans commonly referred to
as helminths or worms
• Infection usually implies
replication of the agent resulting
in a growing number of
pathogens
• Infestation are characterized by a
constant number of pathogens.
Severity of disease often depends
on infection dose.
Is a mosquito a parasite?
• The border between
parasitism and micropredation is blurry
• Parasites usually live in a
very intimate relationship
with their host depending on
more than food from it
• The host is food source and
more or less permanent
habitat at the same time
• Many parasites show strict
specificity for a single host
METHOD OF/PORT OF PARASITE
ENTRY





Mouth
Skin penetration
Insect bite
Inhalation
Transplacental
(Congenital)




Transmammary
Sexual
Blood Transfusion
Tissue Transplantation
Hosts and life cycles
• The definitive host is by definition the one in
which the parasite reproduces sexually
• Additional hosts are then designated
intermediate hosts
• Host which actively transmit parasites to
humans are often called vectors
• In paratenic or transport hosts no parasite
development occurs
• Reservoir host are alternate animal host from
which the parasite can be transmitted to
humans (zoonosis) or domestic animals
• Accidental host, not suitable for parasite
development, but severe disease might ensue
nonetheless
Parasite life cycle
• Many animal parasites also have the potential to infect
humans
Life cycle and type of life cycle
• Life cycle : The whole process of parasite
growing and developing.
• The direct life-cycle : Only one host (no
intermediate host).
• The indirect life cycle : Life cycle with
more than one host (intermediat host and
final host).
PARASITE LIFE CYCLE
To study the parasite life cycle,
there is need to know :
 Source of infection (reservoir)
 Site/method of entry of parasite into the
host
 Physical changes of parasite occurring
inside the host
PARASITE LIFE CYCLE
The knowledge on life cycle is
needed in relation to :
 Treatment
 Prevention
 Control/eradication
PARASITE LIFE CYCLE
Reproduction may occur two ways :
 Sexual
 Asexual
In term of sexual organ, parasite may be :
 Hermaphrodite, or
 Sexually separate (male and female)
Parasite and the type of parasites
• Parasite: It is an animal that is dependent
on another animal (host) for its
survival.
• Type of parasites
Protozoa
Nematodes
Parasites Helminths Trematodes EndoCestodes
Arthropods ---------------- Ecto-
Endoparasite and ectoparasite
• ----A parasite which lives in or on the
body of the host is called endoparasite
(protozoa and heminthes) or ectoparasite
(arthropods).
Host and type of host
• Host : An organism that harbors the
parasite usually larger than the parasite.
• Intermediate host : The host harboring
the larvae or asexual stage of parasite.
• Final host : The host harboring adult or
sexual stage of parasite.
• Reservoir host : Animals harboring the
same species of parasites as man.
Potential sources of human infection.
Relationship (Effect) between
parasite and host
injure to
Parasites harbour in Host (animal or human)
to response immune produce
• Effects of the parasites on the host
• Effects of the host on the parasites
Effects of parasites on the host
• Depriving the host of essential substance
Hookworm Suck blood Anemia
• Mechanical effects of parasites on the host
Ascaris Perforate/Obstruction
• Toxic and allergy effect
E.h Proteolytic enzyme Necrosis
Parasite antigen Immune system
e.g Anaphylaxix
Immune response
Allergy/
Hypersensitivity
Effects of the host on the parasites
----The host can produce certain degree
resistance to parasites in human body or reinfection. The resistance (Immunity) is not
very strong. In general, It don’t wipe out
parasites completely, but may limit the
number of parasites and establish balance
with parasites.
• Innate immunity
• Acquired immunity
Innate immunity
• Barrier : Prevent parasites to invade in
certain degree. Skin/Mucous
membrance/Placenta.
• Acid in skin or stomach can cause
damage of the parasites.
• Phagocytosis of phagocyte.
----Non-specific/effective against a wide
range of parasitic infection/controlled by
genetical factors. But not very strong!
Acquired immunity
Mechanism : cellular and humoral immunity.
• Sterilizing immunity : Wipe out the parasites
completely, meanwhile get a long-term
specific resistance to re-infection. Rare!
• Non-sterilizing immunity : Wipe out most of
the parasites, but not completely. Common!
No parasite, no immunity!
The basic factor of transmission
of parasitic diseases
Parasitic diseases Infectious diseases Transmission
• The source of the infection
• The routes of transmission
• The susceptible host
----The combined effect of those factors determine
the dipersibility and the prevalence of the
parasites at a given time and place and regulate
the incidence of the parasitic diseases in certain
local population.
The source of the infection
• Patient : Persons who have parasites in
their body and show clinical symptoms.
• Carrier : Persons who have parasites in
their body, not show symptoms.
• Reservoir host : Animals that harbors the
same species of parasites as man.
Sometimes, the parasites in animals can
transmit into human.
The routes of transmission I
• Congenital transmission : From mother
to infant. Toxoplasmosis
• Contact transmission : Direct contact--Trichomonas vaginalis; Indirect contact--Ascaris lumbricodes
• Food transmission : The infectious stage
of parasites contaminated food / The
meat of the intermediate hosts containing
infectious stage of parasites.
The routes of transmission II
• Water transmission : Drink or contact the
water contaminated the infectious stage of
parasites.
• Soil transmission : Contamintion of the
soil by feces containing the certain stage of
parasites and this stage can develop into
stage.
• Arthropod transmission : Vectors of
certain parasitic diseases.
The susceptible host
----In general, most people is the
susceptible host (Why?). The parasite
reaching a susceptible host must gain
entrance and set up a favorable residence
in order to complete its life cycle and
cause the transmission of parasitic
diseases.
The avenues of invasion
• Digestive tract : Most common avenue of
entrance. (Food/ Water transmission)
• Skin : Infective larvae perforate skin and
reach to body and establish infection.
(soil/ water transmission)
• Blood : Bloodsucking insects containing
infective parasites bite the skin and inject
parasites into human blood. (Arthropod
transmission---malaria).
The prevention measures of the
parasitic diseases
• Controlling the source of the infection.
----Treatment of the patients, carriers and reservoir
hosts.
• Intervention at the routes of transmission
----Managing feces and water resource,controlling
or eliminating vectors and intermediate hosts.
• Protecting the susceptible hosts.
----Paying attention to personal hygiene, changing
bad eating habit, taking medicine.
Diagnosing Parasite Infection
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Direct observation
Blood antigen tests
Direct blood smears
Skin scraping
Fecal exam
Biopsy of tissues
Terima kasih ………………….
April
2005