Parasites are small organisms that live in or on another organism (called the host), obtain food at the expense of the host and cause some harm to the host. Parasites are adapted structurally to this mode of life. The chief reason for this type of association is nutritional.
Parasites could be microscopic, that is seen only with the aid of a microscope. e.g Entamoeba histolytica, Balantidium coli, etc. Macroscopic parasites on the other hand are large enough to be seen with the unaided eyes. e.g Ascaris lumbricoides, Taenia solium, etc
Parasites cause disease in man, some can be easily treated while others can't. Unlike predators or parasitoids, a parasite does not kill it's host. This is because the death of the host will ultimately lead to the death of the parasite within. Instead, it is the effect of the parasite's activity that results to complications in the host's system. This consequently leads to the death of the host.
The scientific study of parasites and their relationship with their host is known as Parasitology. The relationship or association between parasite and host is known as parasitism.
TAXONOMIC RANGE OF PARASITES
Parasitism occur in a wide range of organisms and taxonomic groups. They include animals, plants, fungi, protozoa, bacteria and viruses. For the sake of this Parasitology series, I shall be dwelling most on parasites of the Animal Kingdom.
TYPES OF PARASITISM
There are many types of parasitism. This is based on their size, characteristics and relationship with host.
- Ectoparasitism: These are parasites that stay on the outside of their hosts. e.g Fleas and Lice.
- Endoparasitism: These are parasites that stay inside of their hosts. e.g Plasmodium spp., Taenia spp., etc. Endoparasites can further be divided based on their location inside the host's body.
- Intracellular parasites: These are parasites that stay inside the cells of their hosts. They reside inside the tissues and muscles of man.
- Extracellular parasites: These are parasites that stay outside the cells of their hosts.
4. Obligate parasitism: These are parasites that must spend at least a part of their lives as parasites to survive and complete their life cycle. They have been well adapted overtime that they cannot live without their host. Many obligatory parasites have free-living stages outside their host, including some periods of encystation or staying within a protective egg-shell in the external environment.
5. Facultative parasitism: These on the other hand are normally not parasitic but for a time, can become parasitic when they are accidentally eaten or enter wound or other body orifice. Example is Strongyloides stercoralis which causes Strongyloidiasis in humans.
6. Microparasitism: These are parasites that are small enough not be seen with the naked eyes. To be seen, a light microscope must be used. They are generally unicellular e.g protozoan parasites.
7. Macroparsitism: These are parasites that are large enough to be seen with the human eyes.
8. Epiparasitism: An epiparasite is a parasite that parasitizes on another parasite. They are also called hyperparasites or secondary parasites.
9. Monogenetic Parasitism: These are parasites that require just an individual host to complete its life cycle. They are mostly parasites of amphibians and fish.
10. Digenetic Parasitism: These are parasites that require most than one host to complete their life cycle. For example, Plasmodium falciparum, the parasite that causes malaria, it requires a human and a female anopheles mosquito to complete its life cycle.
Next On This Series: Adaptation To Parasitic Life
Conclusively, parasitism is the most common type of symbiotic relationship in the animal kingdom, hence the need to study it. They are well adapted to survive in a single host through a process called Host Specificity.
0 Comments