1. Ciliophora
They are group of protozoa characterized by head like structure called cilium which is important in A – movement B - nutrition .
This parasite have two species :-
Balantidium suis infect the pigs .
Balantidium coli infect the human .
This disease is regarded as a zoonotic disease .
Disease : Balantidiosis
B.coli :- is the largest intestinal protozoa that effect human and can be seen macroscopically .

2. Morphology :- the parasite is observed in two stages only which are :-
A – trophozoite :-
1- Large size (40 µm to more than 70 µm) .
2- called the invasive stage .
3- ovoidal in shape .
4- covered by cilia & the anterior end are longer than the
posterior end .
5- in the anterior end there is mouth called cytosome .
6- the internal structures :-
A- have two nuclei , the macronucleus (the largest
one) & micronucleus (the smallest one ) .
B- the macronucleus is kidney or bean in shape .
C- the micronucleus is small spherical shape
located in the concavity of macronucleus .
D- have two secretory contractile vacuoles .
E- numerous food vacuoles .

3. B- Cyst :-
1- typically spherical in shape .
2- surrounded by thick wall (one or two layers ) by
encystation in small intestine to protect the parasite from
the host .
3- contain the macronucleus and contractile vacuoles are
visible in the cyst .
4- the cilia are undetectable , only the roots may present .

4. Multiplication :- occur by two method
1- Asexual type by binary fission .
2- Sexual type by conjugation .
Life cycle :- direct life cycle or simple life cycle that mean the parasite not need for intermediate host .
Mature cysts are passed with feces.
Transmission :- by ingestion of contaminated food or water (NOT in undercooked meat) with feces contain the mature cyst . 
Excystation occurs in the small intestine, and the trophozoites colonize in the large intestine.
Trophozoites undergo encystation to produce infective cysts.
Cysts are the infective stage of this parasite.