Introduction Flashcards
The relationship or interaction between two unlike organisms. Type of symbiosis depends on the positivity or negativity of the interaction between the organisms (symbionts).
Symbiosis
TYPES OF SYMBIOSIS
Commensalism
Mutualism
Parasitism
Phoresis
Two species live together and one species benefits from the relationship without harming or benefiting the other.
Commensalism (+/o)
Two organisms mutually benefit from each other.
Mutualism (+/+)
One organism, the parasite, lives off and benefits from a host, while causing it some harm.
Parasitism (+/-)
The smaller organism (phoront) is carried by the larger organism (host) but there is almost no/no interaction between the two.
*Phoresis (o/o)
derived from the phrase “to carry,” and that’s what the larger organism basically does.
*Phoresis (o/o)
Ex. of symbiotic relationship:
− Ex. Entamoeba coli in the intestinal lumen
Commensalism (+/o)
− Ex. of symbiotic relationship:
Termites and Flagellates (protozoa that inhabit the gastrointestinal tract) Flagellates help the termites
digest the wood through their cellulase.
Mutualism
− Ex. of symbiotic relationship:
The protozoan parasite Entamoeba histolytica,
which derives nutrition from the human host and causes amebic dysentery.
Parasitism
An area of biology concerned with the phenomenon of
dependence of one living organism on another.
Parasitology
Concerned primarily with parasites of humans and their
medical significance, as well as their importance in human
communities
Medical Parasitology
The study of parasites, their hosts, and their relationships
Parasitology
A public health concern, problem of developing societies
Medical Parasitology
Classification and Types of Parasites
Forms
Location
Behaviour?
Classification according to form
Protozoa (Single-celled)
Helminth (Multi-celled worms)
Classification according to location
Intestinal (Giardia)
Urogenital (Trichominas)
Blood (Plasmodium)
Tissue (Toxoplasma)
Classification according to Behavior
Endoparasite Ectoparasite Eratic Obligate Facultative Accidental Permanent Temporary/Transient Spurious Oviparous
A parasite which lives inside the host.
The presence of
such a parasite inside the host is also known as an
infection.
Endoparasite
Examples: tapeworms, hookworms, whipworms,
roundworms, giardia, coccidia, etc.
A parasite which lives outside the host. The presence of
such a parasite inside the host is also known as an
infestation.
*Have humans as their only host
Ectoparasite
Examples: head lice, ticks, fleas, etc.
A parasite which lives outside its usual habitat.
Erratic
Examples of Erratic parasites
Entamoeba histolytica (found usually in the intestines) which can move up to the patient’s liver or lungs
Ascaris lumbricoides, a roundworm, from the small intestines to other parts of the body
Paragonimus westermani, a lung fluke, which can reach the brain.
A parasite which requires a host for survival
Obligate
Examples: hookworms, Ascaris, and Trichuris.
splits time between being a parasite
and an environment-dwelling organism (free-dwelling
state). May become parasitic in nature when needed.
Facultative
Examples:
− threadworms (Strongyloides)
− Acanthamoeba sp.
− free-living Naegleria fowleri
A parasite which lives in a place where it doesn’t
usually live.
Accidental
▪ Examples include parasites that are usually found in
animals that made their way into humans.
A parasite that resides inside the host for the rest of its
life.
Permanent
Temporary/Transient
A parasite that uses the host for feeding or egg-laying
purposes only then leaves after a short amount of
time.
Examples: mosquitoes and bedbugs.
Spurious
A free-living parasite which passes through human
hosts without infection.
Oviparous
A parasite which can produce or lay immature eggs. These immature eggs lack larvae.
Examples: hookworms, Ascaris, and Trichuris.
Ovoviviparous
A parasite which can produce or lay mature / segmented / embryonated eggs.
Examples : Schistosoma sp, Clonorchis, Heterophyes.
Larviparous
A parasite which produces larvae in place of eggs.
Example: Trichinella spiralis.
Parthenogenetic
A female parasite which can self-fertilize.
Example: Strongyloides stercoralis.
Types of Host
Definitive or Final Host
Intermediate Host
Paratenic Host
Reservoir Host
A host which carries the mature parasite.
Stage at which
sexual reproduction of the parasite happens.
Definitive or Final Host
Humans are usually the final hosts. (they can be intermediate hosts too. see Plasmodium life span.)
A host that harbors or carries the immature, larval stage
of the parasite.
Also where asexual reproduction happens. Examples include animals, plants, insects.
Intermediate Host
Indirect life cycle
life cycle that contains intermediate host
Stage of the parasite that you would look for in the
specimen.
Diagnostic stage
The final host must obtain it in order for the infection
to happen.
Infective stage
Also known as the Transfer Host
Paratenic Host
Host wherein the parasite does not develop to later stages.
carries the larva stage and there will be
no further development stage.
Paratenic Host
Example: Wild Boars are the paratenic hosts of
Paragonimus westermani
Are primarily animal hosts.
able to continue the life cycle even with the absence of humans.
They can be a source of human infection.
Reservoir Host
Examples:
▪ Pigs are the reservoir hosts of Balantidium coli
▪ Field rats are the reservoir hosts of Paragonimus
westermani
▪ Cats are the reservoir hosts of Brugia malayi
Types of Vectors
Biological Vector
Mechanical / Phoretic Vector
Type of vector:
The parasite would be found inside the host
There would be physiologic changes in the parasite if it is
found inside this
Aedes Mosquitoes which are the vectors of Plasmodium. It can also be a vector of other parasites.
▪ Anopheles Mosquitoes are primarily thevectors of Plasmodium.
Biologic Vector
