This is a brief rundown of some beneficial and harmful aspects of Protozoa (animal-like protists) that may have direct or indirect economic effects.

1. SYED MUHAMMAD KHAN (BS HONS. ZOOLOGY)
pg. 1
ECONOMIC IMPORTANCE OF PROTOZOA
Protozoa are unicellular, eukaryotic, and animal-like protists. They are found everywhere, in
water, soil, and even on the bodies of organisms. They are of considerable economic value to
mankind. Based on their activities, they can be divided by the following two heads:
1. Beneficial Protozoa 2. Harmful Protozoa
BENEFICIAL PROTOZOA
Protozoa are useful to us in many ways, some of them are as follows:
1. FOOD: Protozoa provide food for insect larvae, crustaceans, and worms, which are taken by
large animals like fishes, lobsters, clams, and crabs, which are eaten by man. Thus they form
sources of food supply to man both directly and indirectly.
2. INSECT CONTROL: Several protozoa control harmful insects by persisting in their bodies,
they can be used in biological control of insects, i.e. Nosema locustae.
3. HELPFUL IN SANITATION: A large number of protozoa living in polluted water feed upon
waste organic matters and thus purify it. Many protozoa feed upon bacteria and play an
important role in the sanitary betterment and keeping water safe for drinking.
4. BUILDING MATERIAL: The skeletal deposits of protozoa (mostly foraminifera and
radiolarians) change into the limestone rock (after a lot of time). Limestone is provided by
such oceanic ooze, such as that of cliffs of Dover, which have played an important role in
the defense of England. Limestone-beds are used as building material, i.e. most of the
buildings of Paris and even the great pyramids of Egypt were constructed from limestone.
5. OIL EXPLORATION: Petroleum is of organic origin. The skeletal deposit of Foraminifera
and Radiolaria are often found in association with oil deposits, i.e. they help geologists and
petroleum scientists to locate oil.
6. SCIENTIFIC STUDY: The protozoans have been found as an ideal group of organisms for
cytological, cytochemical, physiological, biochemical, and genetic studies, due to their small
size, simple organization, quick reproduction and easy availability. Many protozoa are used
in biological and medical researches, i.e. Tetrachymena geleii is used in nutritional research.
The effects of various foods and poison have been investigated on this protozoan.

2. SYED MUHAMMAD KHAN (BS HONS. ZOOLOGY)
pg. 2
HARMFUL PROTOZOA
Protozoa can be harmful in the following ways:
1. WATER POLLUTION: Drinking water in natural conditions is made undrinkable by the
reproduction of some free-living protozoa in it. For example, Uroglenopsis brings flashy
odor like that of cod- liver oil and Peridinium emits smell resembling that of clam-shells.
2. KILLING OF ANIMALS OF FOOD VALUE: Dinoflagellates, when become abundant, are
responsible for turning the ocean red (red tides due to population explosion of
dinoflagellates). The water becomes foul and causes toxic reactions to mollusks like clams,
oysters, and mussels and they become unfit for being eaten by human beings.
3. DESTRUCTION OF WOODEN OBJECTS: Some flagellates like Trichonympha and
Colonympha live in the gut of termites and help in the process of cellulose digestion. In the
absence of these flagellates, the termites will die or change their diet. Thus such protozoa
indirectly help in the destruction of wooden articles and books.
4. REDUCTION IN FERTILITY OF SOIL: It has been observed that about 200-300 species of
protozoa are present in the soil. These protozoa feed on nitrogen-fixing bacteria and thus
reduce the fertility of the soil.
5. PARASITIC PROTOZOA: Many protozoa are parasitic to animals including humans and are
responsible for some of the most severe diseases known to mankind. Parasitism is an
association of two organisms in which one organism lives at the expense of the other giving
nothing in return. Some examples are:
 Parasitic Sarcodines: Sarcodines are also known as amoebae. There are two common
genera of parasitic amoebae: Entamoeba and Endamoeba, which live in the intestine of
man and other animals. One of the species of Entamoeba is known to be seriously
pathogenic: E. histolytica is responsible for amoebic dysentery or amoebiasis in man.
 Parasitic Sporozoans: The class Sporozoa is exclusively of parasitic protozoans. Though
most of sporozoans are harmless, yet some genera like Plasmodium, Eimeria, Isopora
and Babesia include pathogenic species.

3. SYED MUHAMMAD KHAN (BS HONS. ZOOLOGY)
pg. 3
1. Four species of Plasmodium, namely Plasmodium vivax, Plasmodium malariae,
Plasmodium ovale, and Plasmodium falciparum cause malaria (periodic chills and fevers)
in man.
2. Pathogenic species of Eimeria cause coccidiosis (intestinal infection, in severe cases
blood, may come out with diarrhea) in chickens and rabbits. Eimeria canis in dogs,
Eimeria felina in cats, Eimeria bovis in cattle, and Eimeria intricate in sheep and goats.
 Parasitic Ciliates: Balantidium coli is the only important ciliate pathogenic parasite. It is
found in the intestine of man and often in frogs.
 Parasitic Flagellates: Pathogenic parasitic flagellates include the genera Leishmania,
Trypanosoma, Histomonas, Trichomonas and Giardia.
1. Three pathogenic species of Leishmania have been known to cause severe disease in
man, i.e. leishmaniasis, Kala-azar, and Espundia (diseases that causes lesions on the
surface or inside the host’s body). These are transmitted by sandflies of the genus
Phlebotomus.
2. Parasitic species of the genus Trypanosoma cause the fatal sleeping
sickness/trypanosomiasis in mammals.
3. Trichomonas vaginalis is the causative organism of vaginal trichomoniasis or vaginitis in
human females. Trichomonas gallinae, a related species, is pathogenic in doves, pigeons
turkeys, and chickens.