BIOLOGY IN HUMAN WELFARE
An intimate association between two organisms of different species in which, one is benefited and the other one is often adversely affected is called parasitism.
The word parasitism derived from a latin word parasitos (para-at the side of; sitos-food or grain)which means one eating at another ones table.
The organism that obtains nourishment is called parasite (the gainer) and the organism from which the nourishment is obtained is called the host ( the loser).
Types of parasites:
Based on the interaction between the host and the parasite, various types of parasites are recognized.Someof them are
Ectoparasite:A parasite that lives on the surface of the hosts’s body is called ectoparasite.
e.g.Pediculus humanus capitis( Head lice ), Pediculus humanus humanus (body louce), Pithirus pubis( pubic hair)and itch mites on humans,
Tics on dogs,
Copepods on marine fishes, etc.
Endoparasite: A parasite that lives inside the body of the host is called endoparasite . Based on the place wherrer they live, they are again classified into three types, namely:
1. Cytozoic parasites(intracellular),
2. Histozoic parasites(intercellular),
3. Coelozoic paraites.
Cytozoic (intracellular)parasite-Tey live within the host’s cells.
e.g. Plasmodium vivax in man.
Nosema notabilis in Sphaerospora polymorpha.
Histozoic(intercellular)parasite-They live in between the cells of the tissues and organs of the host.
e.g. Wuchereria bancrofti in lymph tissue.
Enatamoeba histolytica in the intestinal wall.
Coelozoic parsite-They live within the cavities of the host’s body.They are called enterozoioc if they live in the alimentary canal.
e.g. Ascaris lumbricoides in large intestine.
Hyperparasite: It is a parasite which lives in/on the body of another parasite.
e.g. Nosema notabilis( a cnidosporan parasite ) lives in Sphaerospora polymorpha(also a cnidosporan parasite) which lives in the urinary bladder of toad fish.
Nosema notabilis- Sphaerospora polymorpha- toad fish
(Hyperparasite) (Parasite) (Host)
Facultative parasite: The parasite which can live in its host if it is available , but capable of living independently if its host is not available is known as Facultative parasite.
e.g. Micobacterium tuberculosis which cause tuberculosis in man is a facultative parasite.
Obligatory parasite: The parasite which depend on specific host throught life is called Obligatory parasite.
e.g. Taenia solium.
Intermittent parasite: They are not constantly associated with the host. They obtain nourishment from the host from time to time.
e.g. Bed bugs , leeches ,mosquitoes
Pathogenic parasite: They cause disease in main host.
e.g. Teania solium cause Teaniasis in man.
Plasmodium cause malaria in man.
Entamoeba histolytica cause Amoebiasis in man.
Non pathogenic parasite: Do not cause any disease in the host.
e.g. Taenia hominis inhabiting the intestine of man.
Monogenetic parasite: It is a paaite which completes its life cycle in only one host.
e.g. Entamoeba histolytica,
Ascaris lumbricoides, etc.
Digenetic parasite: It is a parasaite which requires at least two hosts to complete its life cycle.
e.g. Plasmodium vivax,