Parasite is any organism which derives nourishment and other benefits from the others.
Here the organism giving benefit is called host and the one receiving is called parasite.
The host is the loser while the parasite is the gainer.
Hence the host may be severely affected due to parasite.
Parasites are present in both plant and animal kingdom.
Few plants, microbes and many animals act as parasites.
A parasite can infect plant, animal or even microbe.
Many parasites causes severe diseases in humans.
Types of parasites
l. Ectoparasites: These are the parasites which live outside the body and derive nutrition. Ex: Head louse, Bed mites, leech etc. They do not cause severe diseases to humans but can spread diseases like plague and cause irritation to the body.
2. Endoparasites: These are the ones which live inside the host body. So they can be more dangerous and life threatening. Based on where they live inside the body, they are further classified as
a. Cytozoic parasites: These parasites live within the cells of host.
Ex: Malaria parasite resides inside the red blood cells and live cells.
b. Inter-cellular parasites: These parasites as the name indicates, live in between the spaces of host body cells.
Ex: Entamoeba hystolytica which causes diarrhea.
c. Coelozoic parasites: These parasites live in the body cavities. Ex: Tapeworms, hook worms live in the intestine of humans.
They derive the nutrition from the intestine and reside there for years together if untreated.
3. Obligate parasites: These parasites exist only as parasites. i.e. they can live only on other living organisms. Once they are out of the body of host, they die. Ex: HIV virus, tapeworms etc.
4. Facultative parasites: These parasites are organisms which can live as parasite and also without the help of host. Ex: Leeches, mosquitoes.
5. Hyper parasites: These are a special type of parasites. They are parasites which live on another parasite. Ex: Bacteriophage viruses like tobacco mosaic virus lives on bacteria like E-coli.
6. Pathogenic parasites: These are parasites which induce severe adverse effects on the host. They tend to release toxins or take up essential nutrients or bring about abnormal changes in the host body. Ex: Epstein bar virus infection in humans can lead to hodgkins lymphoma (a type of cancer).
7. Non-pathogenic parasites: These are the parasites which rely on the host body for nutrition and other requirements. But the host body is unaffected or very minutely affected by the parasite. Ex: tapeworms.
8. Intermittent parasites:These parasites rely on host only at time when nutrition is required.
They are not constantly attached to host. They visit the animal and leave often.
Ex: insects like mosquito, bed bug etc.
9. Monogentic parasites:These are the parasites which complete their life cycle in a single host. Ex: flatworms which are monogenetic flukes on fishes. The larvae are hatched into water and these larvae when get in contact with fish surface, they stick to them and never move.
10. Digenetic parasites:These are parasites which complete their life cycle in two hosts: Ex: malaria which lives in both mosquito and also humans. Tapeworm which live in pigs and humans.
They take up different morphological forms in different animals. The mosquito parasite exists as a cyst in mosquito before entering the human blood. Then in human blood it converts to another form called schizoat.
Parasites based on the organisms class
a. Plants: Few plants also act as parasites. Ex: Sandal wood tree. See parasitic plants for more details.
b.Bacterial: Many bacteria act as parasites and cause potential diseases Ex: Cholera bacteria.
c.Fungi: Fungi are multi-cellular organisms and some of them act as parasites:
d.Protozoans: These are single organisms: Ex: entamoeba.
e. Insects: Mosquitoes, lice, bed bugs.
f. Worms: Leeches.round worms, hook worms etc.