What is the purpose of studying Parasitology?
The goal of studying parasitology is to control or reduce the parasitic diseases。
What are Parasites?
“all infections agents are parasites”
Introduction to medical parasitology
- Definition of Medical Parasitology
Human Parasitology (Medical Parasitology) is a branch of medical sciences dealing with the members of the animal kingdom living in and on the body of humans called parasites and with aspects of this host-parasite relationship.
This science includes the study of parasites vectors, reservoirs, hosts and all factors of an ecologic and epidemiologic nature associated with disease transmission and prevention.
-Medical Protozoology:Medical Protozoology deals with protozoa which are one-celled organisms.
-Medical Helminthology:Medical Helminthology deals with helminths which are worms.
-Medical Arthropodology:Medical Arthropodology deals with arthropods which are insects and their allies.
Evolution of parasitism – Life modes of organisms:
Certain relationship between different species of organisms has been established because of their “living together” (symbiosis) during the long history of their evolution.
Symbiosis:Symbiosis means literally “living together ” Any organism that spends a portion or all of its life intimately associated with another living organism of a different species is known as a symbiont , and the relationship is designated as symbiosis.
We will discuss three types of Symbiosis here:
Different forms of symbiosis may be distinguished on the basis of whether or not the association is detrimental to one of the two partners.
1. Commensalism:Commensalism,from the Latin for “eating at the same table”. Two organisms of different species live together, denotes an association that is beneficial to one partner and at least not disadvantageous to the other.
Pilot fish (Naucrates) and remoras are often cited as examples for commensalism.
A remora is a slender fish whose dorsal fin is modified into an adhesive organ that it attaches to large fish, turtles. The remora gets free rides and scraps, but it does not harm the host or rob of its food.
2. Mutualism:A special type of commensalism, known as mutualism, is seen when such association are benificial to both organisms.
Both partners benefit from the association:
A good example is the flagellates and its large herbivorous host animals. The flagellates have cellulases that catabolize cellulose into compounds the host can utilize and the flagellates cannot survive outside the host.
3. Parasitism:Parasitism, on the contrary, is a symbiotic relationship in which one animal, the host, is to some degree injured through the activities of the other animal, the parasite.
It is a type of association between two kinds of organisms, one participant, the parasite, lives in or on the body of the other, the host. The parasite is usually the benefited side, i.e. it obtains nourishment from the host, and the host is usually the injured side, it is usually damaged by the parasite.
The type of Parasite:
If a parasite are found upon the surface of its host, it is called an ectoparasite.
Parasite living within the host. May be disstinguished as endoparasite.
Parasitism as a way of life may be the only possibility for a given organism, or it may be but one alternative.
> Obligate parasite:
An organisms that can not survive in any other manner is called an obligative parasite.
> Facultative parasite:
A facultative parasite
is an organism that may exist in a free living state, or as a commensalism, and that if opportunity presents itself may became parasitic.
> Accidental parasite:
When a parasite enters or attaches to the body of a species of host in which it does not ordinary live.
> Permanent parasite:
A parasite lives its entire adult life within or on its host.
> Temporary parasite:
Some small organism, such as mosquitoes, feed on their hosts and then leave.
> Opportunistic parasite:
Some parasites, such as Toxoplasma gondii, usually live in human body and does not cause clinical manifestations ，but when the host’s immunity decreases, they reproduce abnormally and result in diseases.
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