So protozoan parasites can be further classified
in a variety of ways. There can be amoebas for example.
Here is an example of an ameoba parasite
that causes disease of humans
This happens to be Entamoeba histolytica.
Amoeba of course move by extending pseudopods
and streaming their cytoplasm in the direction of the pseudopod.
Entamoebas are protozoan parasites that are amoebas. They
alternate between trophozoites which are in the form in the host
and the cyst form which is in the environment.
So again, a nice way of enabling passage of the entamoeba
from host to host, the passage occurs via the cyst
and the trophozoite grows in the host.
So that's Entamoeba histolytica.
Another classification of these protozoan parasites
is as flagellates.
Some of them have flagella that enable them to move in fluids.
An example of this is Giardia shown in this picture.
Typically, the protozoan parasites, that in fact,
the intestinal tract, that are flagellated
alternate between trophozoite and cyst forms.
But there's another category of this
flagellated protozoan parasites that infect the blood.
Those are transmitted by arthropods.
So these are Trypanosomes in the blood.
They don't alternate between two forms
as do the intestinal protozoan parasites.
These rather have one form but they're transmitted by arthropods
so that protects them outside of the host.
Then we have the ciliates. There are many ciliated protozoans
but only one of them is a human parasite.
And that's shown here in this photograph,
it's in the phylum Ciliophora and it's called Balantidium coli.
So this is the only ciliated protozoan parasite
known to cause disease in people.
As I said there are many many other ciliated parasites
but they are harmless.
This photo is actually quite nice because you can see
the tiny cilia around the entire organism
and these are constantly in motion
and they enable the organism to move.
And lastly, we hava category of what we call apicomplexans.
This is based on a morphological feature of this protozoan parasite.
And the epidemy of apicomplexan parasites
are the Plasmodium species which cause malarias.
And these are characterized by intracellular replication.