Intoduction To Parasitology Flashcards
Parasitology
-Study of parasites and their pathogenic effects.
-Deals with parasites that cause human infections and the diseases they cause.
-It involves the parasites, their hosts and the relationship between the two.
Main categories of parasitology
-Helminthology (Helminths)
-Entomology (Arthropods)
-Protozoology (Protozoa)
Protozoa
Single celled organisms
E.g. Giardia Lamblia
Helminths
Worms
E.g. Ascaris lumbricoides
Arthropods
Macro parasites. Things such as insects
E.g. Glossina morsitans
Parasite
A living organism which depends on another organism to survive. The other organism provides it with a shelter and food.
Host
Organism which harbours the parasite, providing it with food and shelter.
Types of hosts:
-Definitive: harbours the mature parasite and sexual reproduction of the parasite takes place in this host
-Intermediate: harbours parasite during periods of development and asexual reproduction of the parasite takes place in this host.
Multiple intermediate hosts may be required for certain parasites to complete different larval stages.
-Paratenic: intermediate host that is needed for the parasite to complete its life cycle. No development takes place though.
-Accidental: normally, this host is not the preferred host.
-Reservoir: harbours the parasite and acts as an important source of infection to other susceptible hosts.
E.g. dog is reservoir host of hydatid disease.
Habitat
The part of the host (definitive or intermediate) where the parasite lives and multiplies.
Some examples are: blood vessels, large intestines, muscles, lymphatics, etc.
Zoonosis
Diseases/infections which are naturally transmitted between vertebrate animals and humans
Vector
An agent/living carrier that transmits infection from man to man out from animal to man.
Vectors are usually arthropods.
Types of vectors
Biological (aka true vector): transmits the parasite from host to host and the parasite develops and multiplies inside this vector.
Mechanical: only concerned with transmission of the parasitic form of the parasite. Plays no role in the life cycle of the parasite.
Common symbiotic relationships
Commensalism: the parasite benefits but the host is neither harmed nor does the host benefit.
Parasitism: the parasite benefits at the expense of the host. The host does not benefit and is also injured in the process.
Mutualism: parasite and host metabolically depend on each other. One cannot live without the other.
Life cycle of parasites
Direct life cycle: parasite requires only Ine host to complete its development. E.g. entamoeba histolytica
Indirect life cycle: parasite requires more than host to complete its development. E.g. malaria parasite.
Sources of infection
Contaminated water and soil
Animals
Food
Self (auto infection)
Insect vectors
